In San Francisco, I saw this fish:

enter image description here

and quoting the aquarium's page:

Part of the wrasse family, the California sheephead is a protogynous hermaphrodite. Simply put, all sheepheads are born as females, but eventually transform into males. Due to hormonal changes triggered by environmental and social cues, this fish can go from a reproductively-functional female to a fully-functional male.

I have never heard of something like this for any organism. Is this behavior unique?

But the real biology question is why they do that and not simply retain one gender throughout their life? In other words, what's the evolutionary advantage of such a weird approach?

  • 5
    $\begingroup$ This is not the only organism that does that. See en.wikipedia.org/wiki/Sequential_hermaphroditism. The wikipedia page also mentions some reasons for why such a phenomenon happens. $\endgroup$
    Commented Sep 21, 2016 at 7:15
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    $\begingroup$ What you see is what you get (aka @WYSIWYG), would you like to post an answer? :) $\endgroup$
    – gsamaras
    Commented Sep 21, 2016 at 17:38
  • 1
    $\begingroup$ I get what you say (:P) but I'll be merely repeating what is written in wikipedia. You can actually wait for a better answer. There are people here who would know about this topic better than me. $\endgroup$
    Commented Sep 21, 2016 at 17:41
  • $\begingroup$ @WYSIWYG I only know because I had worked on such an editor when I was in Switzerland! :) Anyway, nobody seems to be able to answer, thus I would tell you to think twice for whether you should be posting an answer or not! If a better answer arrives later, trust me, I will check it up! ;) $\endgroup$
    – gsamaras
    Commented Sep 22, 2016 at 22:31
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    $\begingroup$ @WYSIWYG You're probably better for judging this than me (you're a mod), but I'd say your WP link with a brief summary would be sufficient for now, and if a better answer does come along, we'll respect it as well. $\endgroup$
    – Harris
    Commented Sep 23, 2016 at 20:38

1 Answer 1


This is an interesting question. This strategy is common among wrasses, but the Labridae is a rather huge family. I found this article here that I think may help answer your questions: http://faculty.sites.uci.edu/johncavise/files/2011/03/299-SexDev-herms.pdf

  • $\begingroup$ Please don't simply link to sources, but provide a summary or direct quotation of the relevant part as well. $\endgroup$
    – iayork
    Commented Jan 4, 2018 at 15:12
  • $\begingroup$ That's silly, why write a summary of exactly what the paper says. $\endgroup$
    – user31589
    Commented Jan 5, 2018 at 12:30
  • $\begingroup$ Because links die or change; because you could be pointing to anything; because people shouldn't have to read a full paper to find one minor point from it; because the guidelines explicitly say to do it ("Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline.") $\endgroup$
    – iayork
    Commented Jan 5, 2018 at 13:36
  • $\begingroup$ No. They're guidelines, not requirements, so lay off. He can click the link or not, no one else has provided an answer since 2016. I won't argue with you further. $\endgroup$
    – user31589
    Commented Jan 6, 2018 at 16:06

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