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Wikipedia:Signatures

Signing your posts on talk pages, both for the article and non-article namespaces, is required, since it facilitates discussion by identifying the author of a particular comment. Other users can then navigate to a talk page and address their comments to the specific, relevant user(s). Discussion is an important part of collaborative editing, because it helps all users to understand the progress and evolution of a work.

Signatures are added automatically when using the reply tool or new topic tool. When editing in source text mode not using these tools, they must be added manually, which can be done by typing four tildes or clicking the signature icon  in the edit toolbar.

Comments posted on user talk pages, article talk pages and other discussion pages must be properly signed. Signature use that is intentionally and persistently disruptive may lead to blocks.

When editing a page, main namespace pages (which are all Wikipedia articles) be signed, because the content is a shared work, based on the contributions of many people, and one editor should not be singled out or "credited" above others.

Purpose of signatures
Signatures on Wikipedia identify you as a user and your contributions to Wikipedia. They encourage civility, collaboration, and communication by identifying the author of a particular comment and the date and time at which it was made. Because of that, having an uncivil signature (especially one that makes any kind of personal attacks toward someone else) is prohibited and, in some cases, the user will be blocked from editing until the signature is changed. In most cases, anything that is not allowed as an account's username (in whole or in part) is also not allowed to be in a signature either.

Furthermore, signatures also serve a technical purpose: various user scripts and talk-page archiving bots, including lowercase sigmabot III, rely on their timestamps to know when to archive old threads. It's because of this that it's also important to not change the timestamp of any signatures, as doing so can lead to stale threads persisting longer, and after they would've otherwise been archived.

When signatures should and should not be used
Any posts made to any type of discussion page signed (this does not include adding WikiProject boxes and other such administrative templates). Note that, as stated below, if you choose to edit those kinds of pages without logging in, then you should still sign your posts—regardless of whether or not you have an account. Edits to articles be signed, as signatures on Wikipedia are not intended to indicate ownership or authorship of any article. Instead, the page history identifies who made edits. Signatures do not translate from  in edit summaries. In other instances, and when posts be signed, specific instructions are provided to specify this on the specific page. Files that are used in articles, including image and sound files, should also not contain any signatures.

How to sign your posts
When using the reply tool or new topic tool, the software will automatically sign your post. (If you type a signature anyways, it will remove the duplicate.)

Standard signature
There are three ways to sign your posts manually:

 * 1) At the end of your comments simply type four tildes (~), like this:.
 * 2) If you are using the edit toolbar option (by default, it appears above the edit box), click the signature icon OOjs UI icon signature-ltr.svg to add two hyphens and four tildes like this:.
 * 3) Use the reply tool or new discussion tool that are available as beta features in your user preferences. Both of these features will automatically insert a signature, without needing to add any wikicode.

The four tildes will be automatically replaced with your signature after you have published the changes, as follows:

Since typing four tildes adds the time and date to your resulting signature, this is the preferred option for signing your posts in discussions.

Note that if you choose to contribute without logging in, regardless of whether you have an account, you must still sign your posts. In this case, your IP address will take the place of a username, and will link to your contributions history. Your IP address will look like something similar to 192.0.2.213 or 2001:DB8:CEEE:21B:DB60:07FE:4277:63FF.

If, for some reason, you are not getting the above results when signing, see the SineBot Frequently Asked Questions for tips.

Using three tildes
Typing three tildes results in the following:

However, since this does not date-stamp your signature, you may wish to sign this way only when leaving general notices on your user page or user talk page. This is also a convenient shortcut (rather than typing out the full code) when you want to provide a link to your user page.

Using five tildes
Typing five tildes will convert to a date stamp with the current date and time, without adding your signature, like this:

In general, when communicating with others, you should use one of the previous options and not only a timestamp. There are exceptions to this: such as when requesting assistance from the Third Opinion project, the requested format for signing is the five tilde signature, to slightly help improve neutrality from the responding volunteer. A timestamp may also be used when updating one of your submitted posts on a talk page by appending  to your already existing signature.

In some templates, this is the preferred way to add the date.

Customizing your signature
Every editor's default signature (as defined by MediaWiki:Signature) will display when  is typed. This looks like:

Example (talk), 29 July 2024 (UTC)

Unregistered users, or users not logged in, may choose to manually sign with a pseudonym or tag (e.g. anon.), as their IP address will be stored in the page history. If you choose to sign your posts in such a way, you must still finish your signature with four tildes (such as ) to help aid others with reading the thread easily, and with communicating back with you.

Customizing how everyone sees your signature
Registered users can customize their signatures by going to Special:Preferences and changing the field "Signature". This changes the signature that is left when you enter  into discussions. It can be used to sign your posts with a nickname, or with custom formatting, or both.

This technique only applies where you have left your signature onto a page while logged into your account. It also doesn't affect how your username appears in your watchlist, in any logs or page histories, or where someone else has added a link to your user page in a discussion. Modifying your signature in your user preferences will only apply to the future signatures that you leave moving forward. Since adding  to discussions simply results in those characters being replaced by your signature before the edit is saved, any existing signatures that you've left on previous or existing discussions will not be automatically updated or changed.

Treat as wiki markup
If you do not check the "Treat the above as wiki markup" box, the exact content you enter will be used as your signature. For example, if User:Example had set their signature to read, thereafter the signature (generated when they mark a post with  ) would be:

NICKNAME  (talk), 29 July 2024 (UTC)

If you do check the "Treat the above as wiki markup" box, you can describe your signature using "raw" wikitext (such as and wiki-markup ) which will be substituted unchanged when you sign your posts. If User:Example had set their signature to read, the signature generated by   would be:

Ex@mplet@lk, 29 July 2024 (UTC) In this case, you are responsible yourself for linking to your user page (e.g. User:Example).

To visibly include the pipe or equals  characters in your signature, you must escape them, or they will break templates unexpectedly when your signature is present. To escape the  symbol, use the following special code:   (including everything from the ampersand to the semi-colon). To escape the  character, use.

Putting two or more exclamation points in a row in your signature can break tables in which your signature appears. Use  as a substitute in order to avoid having two exclamation points in a row.

Customizing how you see your signature
To change how your signature appears to you, e.g. to make it easier to spot, without affecting how it appears to other users, you can create a personal CSS style sheet. For example, to display your username in bold white text on an orange background (like Your username ), add the following to Special:MyPage/common.css, replacing Your username with your actual username:

When you use this technique, bright colors can help you to more quickly scan long pages that contain, including Talk pages, page histories, your watchlist, and if anyone links to you in a discussion. Colors to use for this can be researched via the Web colors article, and you can update your common.css file at any time to modify the display style.

Guidelines and policies
Because these signatures are seen by everyone, be aware of the guidelines and policies summarized below:
 * A customised signature should make it easy to identify your username, but this is not required.
 * Do not impersonate other users.
 * Do not use images, transcluded templates, Lua modules, parser functions, TemplateStyles or external links in your signature.
 * A distracting, confusing, or otherwise unsuitable signature may adversely affect other users. For example, some editors find that long formatting disrupts discourse on talk pages, or makes working in the edit window more difficult.
 * Complicated signatures contain a lot of code ("markup") that is revealed in the edit window, and can take up unnecessary amounts of narrative space, which can make both reading and editing harder.
 * Always keep the time/date-stamp: these are used by bots to determine when a discussion is eligible to be archived.

Syntax guidance
If you attempt to save a signature with certain types of errors, you will see an error message. These errors can be a little tricky to diagnose, but here are some tips:
 * Each opening tag must have a corresponding closing tag. Example: each needs a matching . This applies to   and   markup as well.
 * Tags must be "nested" correctly. Example:, not.
 * If an opening tag appears within a wikilink, it must be closed within a wikilink. Example:, not.
 * Your signature must include a link to your user page, talk page, or contributions. At least one of the three must be on the same Wikimedia project as the page where the signature is used. (This is a technical requirement enforced by the MediaWiki software.)

Signature forgery
Impersonating another editor by using their username or signature is forbidden. Altering the markup code of your signature to make it look substantially like another user's signature may also be considered a form of impersonation. Editing the code of your signature to link it to another editor's user page is not permitted. It is also ineffective, as the change log of the page records the IP address and (if applicable) username of all editors; as such, any impersonators can easily be caught if the signature in the diff view differs from the editor's default signature. While not an absolute requirement, it is common practice for a signature to resemble to some degree the username it represents.

If you encounter a user whose signature is disruptive or appears to be impersonating another account, it is appropriate to ask that user to consider changing their signature to meet the requirements of this policy. When making such a request, always be polite, and assume good faith; do not immediately assume that the user has intentionally selected a disruptive or inappropriate signature. If are asked to change your signature, please avoid interpreting a polite request as an attack. Since the success of Wikipedia is based on effective teamwork, both parties should work together to find a mutually acceptable solution.

Appearance and color
Your signature must not blink, scroll, or otherwise cause inconvenience to or annoy other editors. For guidance on how to use color and other effects to customize the appearance of your signature, see this tutorial.
 * Avoid markup such as and (or more) tags (which enlarge text); this is likely to disrupt the way that surrounding text displays.
 * Do not add line breaks, which can also negatively affect nearby text display. The use of non-breaking spaces or  to ensure that the signature displays on one line is recommended.
 * Be sparing with subscript and superscript. In some cases, this type of script can also affect the way that surrounding text is displayed.
 * Do not make your signature so small that it is difficult to read.
 * As some users have vision problems, be conscious of color and contrast issues. If you use different colors in your signature, please ensure that the result will be readable by people with color blindness, defective color vision, and other visual disabilities.
 * Do not include horizontal rules ( or ).
 * Do not include s because those cause the surrounding text to make a new line.

Signature formatting has been the subject of numerous Requests for Comment, and has also resulted in some very heated debates by some of the editors involved, and on both sides of the discussion. When dealing with potentially problematic signatures, simply being polite is often sufficient and can prevent the situation from escalating into a dispute.

Borrowing designs
Editors do not own the design of their signature and cannot prohibit others from borrowing it. However, because signature customization is intended in part to make it easier to tell editors apart, it is considered good practice when borrowing a signature design to change the color or another design element.

Font tags
 tags were deprecated in HTML4 and are entirely obsolete in HTML5. This means that the popular browsers may drop support for them at some point. Wikipedia is already preparing for this by delinting code project-wide through Linter, and by disallowing obsolete tags in new signatures. When support is finally dropped, the tags will be ignored in all existing signatures; any properties such as color and font family will revert to their default values. For this reason, it is recommended that you use tags and CSS properties instead. For usage examples, see. You may request additional coding assistance at Help desk.

When you change your signature, it does not affect signatures that you used on pages in the past. Therefore, if you currently use  tags in your signature, switching to tags now will reduce the number of your signatures (including those in the archives of talk spaces) that will render incorrectly after the browsers drop support for . Moreover, refactoring old signatures from you and other users (including in archive pages) by changing tags to  tags can help prepare the project for this eventual loss of support.

Images
for the following reasons.
 * Excessive or large images can cause issues for users on low-performance devices.
 * A new image can be uploaded in place of the one you chose, making your signature a target for possible vandalism.
 * They make pages more difficult to read and scan.
 * They make it more difficult to copy text from a page.
 * They are potentially distracting from the actual content.
 * Images do not scale with the text, making the lines with images higher than those without them.
 * They clutter up the "file links" list on the respective image's page every time one signs on a different talk page.
 * Images in signatures give undue prominence to a given user's contribution.

Unicode symbols (including emoji) may be used in your signature, as long as the signature complies with the other guidelines on this page.

Length
The limit is 255 characters.

Extremely long signatures with a lot of HTML/wiki markup make page editing and discussion more difficult for the following reasons:
 * Signatures that take up more than two or three lines in the edit window clutter the page and make it harder to distinguish posts from signatures.
 * Long signatures give undue prominence to a given user's contribution.
 * Signatures that occupy more space than necessary in the edit box displace meaningful comments, thus forcing editors to scroll when writing their replies.
 * The presence of such long signatures in the discussion also disrupts the reading of comments when editors are formulating their replies.

The software will automatically truncate both plain and raw signatures to 255 characters of in the Signature field. If substitution of templates or another page is used, please be careful to verify that your signature does not violate the 255-character length limit when the templates are expanded, as the software will not do this automatically.

Unclutter signature minimiser
If you prefer not to see other users' custom signatures, you can use the custom JavaScript module Unclutter. By default, Unclutter scans non-special non-article pages for timestamped signatures, wraps them up and replaces with a text of the form:

 * — Example (annotation) (talk • ctb • act • [ log] • sig)

This technique displays the actual username to you and is extensively configurable. It doesn't affect how anyone else sees the signatures. See User:Kephir/gadgets/unclutter for more details.

While this script works in practice for most signatures found on the English Wikipedia, there are several unavoidable limitations which make Unclutter fail to recognise every possible signature. Signatures which violate policies laid out on this page may not be recognised. Unclutter is not an excuse to violate or decline to enforce the signature policy.

Using custom CSS
It's also possible to use your personal common.css style sheet to override the formatting of other users' signatures.

This allows you to decide how links to user pages should be displayed to you when you are logged-in. For example, you could highlight Your username in bold reversed mauve and Other signatures in normal mauve. This approach works by reversing a variety of commonly used signature formatting techniques, but it doesn't attempt to replace the text content of the signature. For example, if  has customized their signature to read Ex @ mple, changing the formatting would display Ex@mple rather than their actual name Example.

No other users will see your custom effects. You can remove or modify them at any time by changing the instructions in your style sheet. The change will apply to all pages regardless of how old they may be. For an example stylesheet, see User:Pointillist/reformat-signatures.css.

Internal links
Signatures must include at least one direct internal link to your user page, user talk page, or contributions page; this allows other editors easy access to your talk page and contributions log. The lack of such a link is widely viewed as obstructive.

If, while making modifications, you accidentally disable this link, see Help:How to fix your signature. When you insert your signature on your talk page or user page, a link to that page will appear black, bold and inactive, so test your signature elsewhere, such as the sandbox.

Disruptive links
It is better to put information on your user page rather than in your signature. Brief additional internal links are generally tolerated when used to facilitate communication or to provide general information, but undesirable if seen as canvassing for some purpose.

Do not place any disruptive internal links (especially when combined with custom formatting, for example CLICK HERE!!! ) in your signature.

Transclusion of templates (or other pages)

 * Transclusions of templates, Lua modules, parser functions, and TemplateStyles in signatures (like those which appear as,  ,   or  ) are forbidden for the following reasons:
 * Certain automated scripts (bots) are used to automatically archive particularly active talk pages. These bots read the source of the talk page, but don't transclude templates, and so don't recognize the template as a signature.
 * Signature templates are vandalism targets, and will be forever, even if the user leaves the project.
 * Signature templates are a small but unnecessary drain on the servers. Transcluded signatures require extra processing—whenever you change your signature source, all talk pages you have posted on must be re-cached.
 * User mention notifications will not work if the mentioning user's signature is contained in a template.
 * If you try to use a transcluded signature, it will automatically be converted to.
 * Substitutions of templates in signatures is permissible but discouraged, as the template that is substituted may be vandalized without the user knowing.
 * Users who choose to substitute their signature are to be  of their signature whenever they sign.
 * Substitution must not be used to circumvent the normal restrictions on signature content, including the use of images, obnoxious markup, or excessive length.

Simple text signatures, which are stored along with the page content and use no more resources than the comments themselves, avoid these problems.

Categories
Signatures must not contain categories. Categorizing talk pages by who has edited them is unhelpful, and the same information can be found by using your contributions list. Many of the various edit counting utilities also provide this data.

Non-Latin usernames
Users with usernames in non-Latin script writing systems are welcome to edit Wikipedia. There is no requirement that usernames must be in English or that Latin script characters must be used. However, such usernames may appear illegible to other contributors to the English Wikipedia, and not every user's keyboard or input device may have immediate access to non-Latin characters. In addition, sometimes certain characters may not display correctly. As a courtesy to other contributors, and to avoid possible confusion or mis-identification, users with such usernames are encouraged to consider providing a Latin-character transliteration of their username as (at least part of) their signature. For an example, using the signature Παράδειγμα/Paradigma for User:Παράδειγμα.

A signature consisting of, or ending with, characters from a right-to-left script will appear (in modern browsers) when viewing pages as
 * --DD ,HH:MM NAME Month YYYY (UTC)

e.g.,
 * --29, שֵׁם July 2024 (UTC)

and similarly misordered text in the edit box. Adding a left-to-right marker symbol, at the end of the raw signature (HTML code: ), will resolve this. Or, if you include both Latin and a right-to-left script, such as Hebrew or Arabic, in your signature, consider putting Latin second, where it will be directly next to the timestamp.

Dealing with unsigned comments
The templates unsigned and unsigned IP can be used at the end of an unsigned comment to attach the username or IP to the comment. None of these templates automatically populates (fills in) the username or IP of the poster or the time of the post. That information is best copied from the history page and pasted into the following templates. All of the unsigned templates must be substituted.

The templates unsigned2 and unsignedIP2 do almost the same as unsigned and unsigned IP when used with two parameters, but the ordering of the parameters is reversed. The resulting display is the same. These templates may be useful when copying and pasting from the edit history, where the timestamp appears before the username.

The template xsign is a wrapper for unsigned and unsigned IP that will parse the username and date string copied and pasted directly from the edit history. The resulting display is the same.

It is also a good idea to notify users, especially new users, that they should sign their comments. You may use the template uw-tilde on the user's talk page or one of the welcome messages for new users.

Also, the template undated can be used at the end of comments where the user gave their username but no timestamp:

Automatic adding of signatures
The bot SineBot signs comments on talk pages and pages in Category:Non-talk pages that are automatically signed, for unregistered users and users who have fewer than 800 edits. To re-enable autosigning of your unsigned comments, you can place YesAutosign on your user page or user talk page.

Dealing with problematic signatures
Wikipedia's Username policy describes accepted practices and behavior in naming and operating a user account on Wikipedia that apply to both usernames and signatures. A purpose of your signature is to identify you as a contributor. If your signature is unnecessarily confusing, editors may request that you change it. Our guidelines for talk page usage also permit editors to change signatures that contravene this guideline back to the standard form. An editor with a confusing signature may be blocked sooner than usual for other inappropriate behavior such as disruption or vandalism, if their confusing signature contributes to the disruption.

Signatures that link to, but do not display, the user's username (for example by signing with a nickname, as in User:Nickname or Nickname ) can be confusing for editors (particularly newcomers). The actual username always appears in the page history, so using just the nickname on the relevant talk page can make your signed comments appear to be from a different person. Alternatives include changing your username and including your account name in addition to the username, e.g., in the form User:Example/Nickname.

The timestamp must adhere to the system-generated format and must not be customized. This is necessary for clear communications and for archiving bots to function correctly. Timestamps that are customized may be considered disruptive and editors using them may be blocked accordingly.

Persistent failure to sign after being reminded may become disruptive and be subject to sanctions.

History
UseModWiki, the wiki software in use on the English Wikipedia from its inception to 25 January 2002, did not have markup to create a signature, so signatures had to be made manually where desired. (c.f., for example, several such signatures in this diff et al.) The modern tilde feature was a part of the earliest MediaWiki coding from mid-2001; the original developer of MediaWiki, Magnus Manske, intended it to resemble scribbled physical signatures like that of his father. Images in signatures have been banned since 2006, but had been discouraged beforehand.

The concept of signing one's contributions to the main namespace has also not always been here. The first ever revision to the page WikiPedia, from 15 January 2001, indicated that "You can [write an article] anonymously or give yourself credit," and indeed several pages from early 2001 have signatures at the end of them, such as here and here.

title: Wikipedia:Signatures


text:
Wikipedia talk:Signatures

Draft message to be sent out to users with invalid signatures
...is at User:HouseBlaster/sandbox. Comments welcome. House Blaster  (talk · he/him) 22:16, 31 January 2024 (UTC)
 * I adapted a message that a few of us have been using for three years or so. It has worked well; I have had a number of comments thanking me for the detailed instructions or saying that they worked. – Jonesey95 (talk) 22:44, 31 January 2024 (UTC)
 * Thank you! The new version suggests that a replacement signature is provided, but that is not the case. If someone wants to go through and do that for all 300+ people on the list, be my guest. Otherwise, I think it be changed to say (in kind language) "either figure out how to fix your signature on your own or ask for help". House Blaster  (talk · he/him) 22:50, 31 January 2024 (UTC)
 * I've gone ahead and ✅ the above. does it look alright to you? House Blaster  (talk · he/him) 00:58, 1 February 2024 (UTC)
 * Good catch. The message looks great now. I used to provide fixed custom signatures for each editor when I delivered this message. See this talk page for an example. We're not going to do that with this message. How was the list of editor recipients created? I'm curious about the criteria. Also, does the "Learn more" button appear automatically for editors who have an invalid signature, even before they click Save? – Jonesey95 (talk) 01:49, 1 February 2024 (UTC)
 * The list was created at T356168 (with a massive thank you to !). The button appears automatically. House Blaster  (talk · he/him) 01:54, 1 February 2024 (UTC)
 * Thanks. I poked around that task and some of its links, but I was unable to find a set of criteria that were easy for me to parse. I did a bit of spot-checking, and I didn't see any errors. I was expecting there to be a lot more than 300 active editors with font or tt tags in their sigs. We'll see. We may need to repeat this process once every month or two for a while; infrequent talk-page posters appear on and disappear from the toolforge signature report. – Jonesey95 (talk) 02:13, 1 February 2024 (UTC)
 * The list comes directly from MediaWiki; if they are not on that list they either have not edited a discussion in the past three months or they do not have an invalid signature. I know some people create a template and use that instead the standard ~~~~; their signatures are not technically "invalid". House Blaster  (talk · he/him) 02:15, 1 February 2024 (UTC)
 * if there are no further objections, would you be able to send out the message to everyone at User:HouseBlaster/invalid signatures? House Blaster  (talk · he/him) 23:25, 1 February 2024 (UTC)
 * Yes, but I will be away from Wikipedia for the next couple of days. Please ping me again on Sunday or Monday. Thanks. – Jonesey95 (talk) 02:39, 2 February 2024 (UTC)
 * would it be easier if I ask at WT:MMS? House Blaster  (talk · he/him) 02:40, 2 February 2024 (UTC)
 * That would be fine with me. You might also mention that this message will need to be re-sent (to smaller groups of editors) every month or two for a while. – Jonesey95 (talk) 02:49, 2 February 2024 (UTC)

it shouldn't need to be resent, because in a month all of those editors with invalid signatures will no longer have invalid signatures. House Blaster  (talk · he/him) 02:50, 2 February 2024 (UTC)
 * The change has been deployed :) House Blaster  (talk · he/him) 21:07, 5 March 2024 (UTC)
 * Hooray! I look forward to not seeing font tags in newly posted signatures. – Jonesey95 (talk) 21:47, 5 March 2024 (UTC)

Bot incorrectly notified me
I fixed my signature months ago. -- Zac  Bowling  (user|talk) 04:50, 3 February 2024 (UTC)
 * , unsurprisingly, bots are imperfect. Express your concerns to the bot operator. Cullen328 (talk) 04:52, 3 February 2024 (UTC)
 * Also, telling a bot to go away (begone) is ineffective. They do not respond to random editor comments. Cullen328 (talk) 04:59, 3 February 2024 (UTC)

Guidelines and policies
At present there are two policies on this page addressing the same thing: There was a RfC in 2021 which closed with the consensus against signatures being required to correspond exactly to usernames and no consensus to require that signatures be easily recognizable to a new user as referring to the username they link to.
 * A customised signature should make it easy to identify your username.
 * It is common practice for a signature to resemble to some degree the username it represents.

The two conclusions from the RFC were: It seems only the second guideline (above) adheres to this consensus, so the obvious solution is to remove the first one. However when I tried to do this it was undone by another editor. So I'm bringing the discussion here. Thanks. WikiMane (TP2001) (talk) 14:29, 15 April 2024 (UTC)
 * "There is significant opposition to the point where it is clear there is a consensus that signatures are not required to display someone's username in its entirety, without changes."
 * "There is therefore no requirement that signatures be easily recognizable to a new user as referring to the username they link to."
 * , why did you reimplement your disputed edit before getting any responses to this question? – Jonesey95 (talk) 21:02, 15 April 2024 (UTC)
 * Because I'm a naughty Wikipedian :-P Note that actually it wasn't the same edit, I moved the second point to more prominence because I reached out to the editor who undid my edit on their talk page... and they refused to discuss their edit, which led me to think they hadn't even read the whole list before undoing the original change I made. WikiMane (TP2001) (talk) 10:04, 17 April 2024 (UTC)
 * I note the second conclusion also states I would add that the existing advice on the subject could be worded more strongly regardless of it not being a hard requirement. I don't think we need both of the bullets, but it would be reasonable for someone to support stronger language in the merged version. Anomie⚔ 11:24, 16 April 2024 (UTC)
 * Do you have a proposal? It seems hard to find wording that is both strongly suggestive to new users but also won't be used as a cudgel by other well-meaning editors. WikiMane (TP2001) (talk) 10:09, 17 April 2024 (UTC)
 * Maybe "A customised signature should make it easy to identify your username, but this is not required."? 🤷 Anomie⚔ 11:51, 17 April 2024 (UTC)
 * Yeah, I think that works. Do we keep the second point, too? WikiMane (TP2001) (talk) 16:34, 17 April 2024 (UTC)
 * I'd have just one bullet point, with the footnote from the second existing bullet included. Anomie⚔ 21:49, 17 April 2024 (UTC)
 * Agreed. Although just thinking about this with fresh eyes, what's wrong with: "It is common practice for a signature to resemble to some degree the username it represents, but it is not required."? Do you think it's too soft? WikiMane (TP2001) (talk) 21:13, 20 April 2024 (UTC)
 * That is too soft. One reason people opposed requiring signatures to match user names is that a significant number of excellent editors started years ago with a user name that no longer appeals and they have signatures that don't draw attention to it. This guideline/policy is mainly for the future and newer editors should be encouraged to have comprehensible signatures. The fact that the policy does not say "a signature must match the user name" is sufficient leeway for cases like yours. You have "TP2001" in the signature and that's fine. Johnuniq (talk) 02:02, 21 April 2024 (UTC)
 * Ok, updated with @Anomie's suggestion. Thanks! WikiMane (TP2001) (talk) 20:59, 21 April 2024 (UTC)

Government Sites like Texas.Gov are Free-Use
You recently erroneously deleted a whole page I created due to "Copyright Infringement" because I copied the text from the site, which is allowed in Texas. Texas allows free-use of the Government site content like the one I used and you were outside your lane deleting the whole thing. It was an award and I copied the EXACT Qualifications for the awards, the same way we post US Military Awards and qualifications here. We don't edit them or change them we post exactly how DOD/or the Branch lists it.

Please un-delete my page as you're incorrect. TheNathanMuir (talk) 18:22, 19 July 2024 (UTC)
 * this is the talk page for discussing improvements to the page Wikipedia:Signatures. You should probably ask the person who deleted that page. -- Red rose64 🌹 (talk) 22:06, 19 July 2024 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Wikipedia talk:Signatures


text:
Talk:William Tecumseh Sherman

Semi-protected edit request on 15 November 2023
The opening paragraph opines negatively on the supposed scorched earth strategy General Sherman employed against the confederate states in open rebellion against the union. It should be rewritten without this pro-confederate bias. For example: “General Sherman used tactics that, while extreme, were permissible under the law of war as it was read at the time. While controversial, his strategies were critical in ensuring a Confederate surrender, reunification of the Union, and a lasting peace.” 100.16.234.26 (talk) 09:13, 15 November 2023 (UTC)
 * Red information icon with gradient background.svg Not done: please provide reliable sources that support the change you want to be made. •C y b erw o l f• talk? 15:36, 15 November 2023 (UTC)

Grammar Correction
The sentence: “According to historian John D. Winters's The Civil War in Louisiana (1963), at this stage Sherman…” should be updated to: “According to historian John D. Winters' The Civil War in Louisiana (1963), at this stage Sherman…” 2600:100B:B021:7805:1881:D5D6:2196:4E74 (talk) 09:51, 25 February 2024 (UTC)

Grandchildren
Joseph M. Sherman is a Great Great Great Great Grandchild 74.74.77.165 (talk) 01:45, 28 March 2024 (UTC)

Page number error in cite note #237
The citation states that, in addition to the book cited, the quote can also be found on page 262 of volume 17 of "Papers of Ulysses S. Grant". I have checked the source, which can be accessed for free here, and have tracked the quotation in question down to page 162 (going by the printed-in page numbers). I believe this is a simple typo and should be edited to read "162" instead of "262".

In case the page citation numbers should change, I am referring to section that says: 'In 1867, he wrote to Grant that "we are not going to let a few thieving, ragged Indians check and stop the progress" of the railroads.' L. Ron Musk (talk) 02:54, 27 June 2024 (UTC)

title: Talk:William Tecumseh Sherman


text:
Jellyfish

Jellyfish, also known as sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.

Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae. These then disperse widely and enter a sedentary polyp phase which may include asexual budding before reaching sexual maturity.

Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.

Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.

They are also used in cell and molecular biology research, especially the green fluorescent protein used by some species for bioluminescence. This protein has been adapted as a fluorescent reporter for inserted genes and has had a large impact on fluorescence microscopy.

The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.

Names
The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish".

A group of jellyfish is called a "smack" or a "smuck".

Definition
The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:

"Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked]."

The Merriam-Webster dictionary defines jellyfish as follows:

"A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells."

Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.

The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with "???" on the following cladogram of the animal kingdom:

Medusozoan jellyfish
Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.

Taxonomy
The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.

The four major classes of medusozoan Cnidaria are:

 * Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.
 * Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.
 * Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.
 * Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.

There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.

Fossil history

Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is Burgessomedusa from the mid-Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead.

Anatomy
The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal. The mesoglea is 95% or more composed of water, and also contains collagen and other fibrous proteins, as well as wandering amebocytes that can engulf debris and bacteria. The mesogloea is bordered by the epidermis on the outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.

On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate the fluid in a regular direction.

The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.

Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.

In many species of jellyfish, the rhopalia include ocelli, light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.

Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.

Box jellyfish eye
The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.

Evolution
Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.

Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.

Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans) and other light-guided behaviors responsive to the intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis. Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes.

The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics. Critically, the visual systems of box jellyfish are responsible for guiding multiple tasks or behaviors in contrast to less derived visual systems in other jellyfish that guide single behavioral functions. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate.

Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution. The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.

Utility as a model organism
Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.

Characteristics
Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems. There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.

Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.

Box jellyfish have multiple photosystems that comprise different sets of eyes. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.

Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless, it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.

Comparison with other organisms
Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.

Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.

The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.

All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.

Evolution as a response to natural stimuli
The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.

Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance, and in fact, species with more complex habitats exhibit faster rates. ''Ch. bronzie'' inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and ''Ch. fleckeri'' are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive. Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.

Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). The upper lens of ''Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora'' (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to ''Ch. bronzie'' as it is to species in more obstacle-filled environments. Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.

Largest and smallest
Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 m in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.

The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 mm to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools; many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.

The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting. The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m in bell (body) diameter and about 200 kg in weight, with average specimens frequently reaching 0.9 m in bell diameter and about 150 kg in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m.

The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm wide, and four thick, "strap-like" oral arms extending up to 6 m in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.

Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters). Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).

Life cycle
Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae. In some species certain stages may be skipped.

Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day; in many instances this is at dawn or dusk. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.

The planula is a small larva covered with cilia. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles. The polyps resemble those of closely related anthozoans, such as sea anemones and corals. The jellyfish polyp may be sessile, living on the bottom of boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial. Most polyps are only millimetres in diameter and feed continuously. The polyp stage may last for years.

After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish. The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp. A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.

Lifespan
Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.

An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula, might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.

Locomotion

Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals. They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.

Diet
Jellyfish are, like other cnidarians, generally carnivorous (or parasitic), feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth. Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.

A few species such as Aglaura hemistoma are omnivorous, feeding on microplankton which is a mixture of zooplankton and phytoplankton (microscopic plants) such as dinoflagellates. Others harbour mutualistic algae (Zooxanthellae) in their tissues; the spotted jellyfish (Mastigias papua) is typical of these, deriving part of its nutrition from the products of photosynthesis, and part from captured zooplankton. The upside-down jellyfish (Cassiopea andromeda) also has a symbiotic relationship with microalgae, but captures tiny animals to supplement their diet. This is done by releasing tiny balls of living cells composed of mesoglea. These use cilia to drive them through water and stinging cells which stun the prey. The blobs also seems to have digestive capabilities.

Predation
Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins. Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds. In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.

Symbiosis
Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish. The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.

Blooms
[[File:Jellyfish population trends by LME.jpg|thumb|Map of population trends of native and invasive jellyfish.

Circles represent data records; larger circles denote higher certainty of findings.

{{legend|#E51A1D|Increase (high certainty)}}{{legend|#F1A341|Increase (low certainty)}} {{legend|#4DAF4A|Stable/variable}}{{legend|#377CB5|Decrease}}{{legend|#CCCCCA|No data}}]]

Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration. Currents collect jellyfish together, especially in years with unusually high populations. Jellyfish can detect marine currents and swim against the current to congregate in blooms. Jellyfish are better able to survive in nutrient-rich, oxygen-poor water than competitors, and thus can feast on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are able to survive in warmer waters. Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so-called because they are hypoxic (low in oxygen). This in turn kills fish and other animals, but not jellyfish, allowing them to bloom. Jellyfish populations may be expanding globally as a result of land runoff and overfishing of their natural predators. Jellyfish are well placed to benefit from disturbance of marine ecosystems. They reproduce rapidly; they prey upon many species, while few species prey on them; and they feed via touch rather than visually, so they can feed effectively at night and in turbid waters. It may be difficult for fish stocks to re-establish themselves in marine ecosystems once they have become dominated by jellyfish, because jellyfish feed on plankton, which includes fish eggs and larvae.

As suspected at the turn of this century, jellyfish blooms are increasing in frequency. Between 2013 and 2020 the Mediterranean Science Commission monitored on a weekly basis the frequency of such outbreaks in coastal waters from Morocco to the Black Sea, revealing a relatively high frequency of these blooms nearly all year round, with peaks observed from March to July and often again in the autumn. The blooms are caused by different jellyfish species, depending on their localisation within the Basin: one observes a clear dominance of Pelagia noctiluca and Velella velella outbreaks in the western Mediterranean, of Rhizostoma pulmo and Rhopilema nomadica outbreaks in the eastern Mediterranean, and of Aurelia aurita and Mnemiopsis leidyi outbreaks in the Black Sea.

Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).

Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers. Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment. Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.

During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms. Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton. Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition. The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.

These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries. Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water. Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.

Jellyfish form a component of jelly-falls, events where gelatinous zooplankton fall to the seafloor, providing food for the benthic organisms there. In temperate and subpolar regions, jelly-falls usually follow immediately after a bloom.

Habitats

Most jellyfish are marine animals, although a few hydromedusae inhabit freshwater. The best known freshwater example is the cosmopolitan hydrozoan jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some jellyfish populations have become restricted to coastal saltwater lakes, such as Jellyfish Lake in Palau. Jellyfish Lake is a marine lake where millions of golden jellyfish (Mastigias spp.) migrate horizontally across the lake daily.

Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.

Some species explicitly adapt to tidal flux. In Roscoe Bay, jellyfish ride the current at ebb tide until they hit a gravel bar, and then descend below the current. They remain in still waters until the tide rises, ascending and allowing it to sweep them back into the bay. They also actively avoid fresh water from mountain snowmelt, diving until they find enough salt.

Parasites
Jellyfish are hosts to a wide variety of parasitic organisms. They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish.

Fisheries
Jellyfish have long been eaten in some parts of the world. Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.

Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.

Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.

Products
Aristotle stated in the Parts of Animals IV, 6 that jellyfish (sea-nettles) were eaten in wintertime in a fish stew.

In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia. Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.

Traditional processing methods, carried out by a jellyfish master, involve a 20- to 40-day multi-phase procedure in which, after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing makes the jellyfish drier and more acidic, producing a crisp texture. Jellyfish prepared this way retain 7–10% of their original weight, and the processed product consists of approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.

In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.

Biotechnology

Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.

In 1961, Osamu Shimomura extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa Aequorea victoria, while studying photoproteins that cause bioluminescence in this species. Three decades later, Douglas Prasher sequenced and cloned the gene for GFP. Martin Chalfie figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien later chemically manipulated GFP to produce other fluorescent colors to use as markers. In 2008, Shimomura, Chalfie and Tsien won the Nobel Prize in Chemistry for their work with GFP. Man-made GFP became widely used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene, making a fusion of the normal protein with GFP attached to the end, illuminating the animal or cell reveals what tissues express that protein—or at what stage of development. The fluorescence shows where the gene is expressed.

Aquarium display
Jellyfish are displayed in many public aquariums. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible. Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it. As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.

Stings
Jellyfish are armed with nematocysts, a type of specialized stinging cell. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, but only some species' venom causes an adverse reaction in humans. In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.

The effects of stings range from mild discomfort to extreme pain and death. Most jellyfish stings are not deadly, but stings of some box jellyfish (Irukandji jellyfish), such as the sea wasp, can be deadly. Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava.

Vinegar (3–10% aqueous acetic acid) may help with box jellyfish stings but not the stings of the Portuguese man o' war. Clearing the area of jelly and tentacles reduces nematocyst firing. Scraping the affected skin, such as with the edge of a credit card, may remove remaining nematocysts. Once the skin has been cleaned of nematocysts, hydrocortisone cream applied locally reduces pain and inflammation. Antihistamines may help to control itching. Immunobased antivenins are used for serious box jellyfish stings.

In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps by pressing fresh leaves on the skin with quick results.

Mechanical issues
Jellyfish in large quantities can fill and split fishing nets and crush captured fish. They can clog cooling equipment, having disabled power stations in several countries; jellyfish caused a cascading blackout in the Philippines in 1999, as well as damaging the Diablo Canyon Power Plant in California in 2008. They can also stop desalination plants and ships' engines.

title: Jellyfish