Sex change?

[Petter]

Hi,

Yesterday me and some other aquarists talked about whether some Malawi cichlids are able to change sex or not.

Some claims that Metriaclima livinstonii females are able to turn into males, if males are needed. Do you agree?

Are you aware of other Malawi cichlids with this capability?

Kindest
Petter

[Lisachromis]

I seriously doubt that female livingstonii are turning into males. I suspect that what people are seeing is young males that take a long time to show their true colours. The only cichlid I can come up with that changes sex comes from South America (Dicrossus sp.). Beyond that, I'm pretty much stumped. Anyone else?

[MatsP]

In general, fish that change sex are fish that commonly get isolated/caught in pools or puddles during dry season [typically live bearers, but I believe there are other fish that can also change sex in the same way]. I don't see the big Lake Malawi drying out sufficently to need this form of sex-change, so from this perspective it doesn't make sense.

--
Mats

[Philippe Burnel]

Don't forget that some marine fishes can change their sexe with age.
It seems that sexe can change in some Melanochromis spp and in some Victorian cichlids. Observations made by Fermon from the French Museum of Natural History but he never published anything about that.

[Greg Steeves]

Hello all

To my knowlege, sex change in Malawian mbuna has only been recorded by hobbyist observations in Melanochromis sp. I was unable to locate any firm scientific data when researching the subject a few years ago.

I think you are mistaken in your referal to Dr. Fermon's refrence. It was not sex change in Victorian cichlids he was reporting; it was an observation of duel gonads, male and female in single individual species of Neochromis greenwoodi (former Haplochromis sp. "velvet black") at Makobe Island.

If I am not mistaken, this is the reference:
L'éthologie
Auteur(s) : Fermon, Y.; Bigorne, Remy
IN : /Lévêque, Christian (ed.); /Paugy, Didier (ed.) - Les poissons des eaux continentales africaines : diversité, écologie, utilisation par l'homme
Source : IRD, Paris (FRA), 1999, p. 199-226, ill., tabl., phot.

Well documented and common in many reef fishes, protandry and protogyny, although suspected, remains unproven in Haplochromine cichlids.

[Esben]

I think, it is this link Petter is refering to:

http://www.panda.org/about_wwf/where_we ... change.cfm

If you look at George F. Turners comment here, it is also very interesting reading.

http://listserv.nic.museum/cgi-bin/wa?A ... &S=&P=1639


And try to look here also:
http://listserv.nic.museum/cgi-bin/wa?A ... &S=&P=2000

Esben

[Ken Boorman]

I'm sorry, but that first reference does nothing to substantiate the suggestion that cichlids change sex.
George kinda negates the suggestion too, while there is also nothing in the third reference either

Ken

[Don Hiatt]

I haven't heard of this in Mbuna, but I once read about sex change in South American Checkerboard Cichlids in National Geographic.

I found this paper online.

http://www.blackwell-synergy.com/doi/ab ... 05.00184.x

I don't find this suprising at all. Cichlids are Labroids.
Marine Wrasse (Labridae) and Damsels (Pomacentridae)
are also Labroids and many members of these families
change sex.

[Don Hiatt]

I saw Lisachromis mentioned Dicrossus.

[bob]

My two female dicrossus are still immature, and thus haven't changed sex.

However, if we look at this from an evolutionary point of view, we can say that dicrossus might have other reasons to change sex than being stuck in a hole. Although it may be that this genus was merely 1st to the punch other fish have had a long time to evolve too.

Heaps and heaps of marine fish change sex, and there is little reason for them to do this on the possibility that the sea might dry up. Most marine fish that do this live in harems and change sex when the dominant male is removed, and the top female changes, almost always within a week.

Great white sharks also change sex irresspective of both the above reasons to do so, and do at a certain time in their lives when they are old anough to be more useful to the species procreatively speaking, when they can have many young. And as we know from whale sharks, which can produce 60 two feet long youngsters, being a big female is a good thing.

Apistos often get stuck in the same kind of puddles as dicrossus, and I have never heard of them changing sex.


So why is it dicrossus? Why is it this one genus of three fish that change sex in the whole cichlid world of ~ 2000? Is it because of the challenges that these 3 species of fish faced that caused them to develop this ability, or is it that one fish (that looks like all of these fish in the genus put together) developed this ability and as such did not die out, but instead was successful enough to develop into three separate species, or was it a blend of the two, which is more unlikely.

So, the reasons for sex changes in any animal are varied, and it is likely that unless there is an outstanding reason for any animal to change sex, it is unlikely that they do.


BTW, to offer my opinion on malawi cichlids having this ability, I would definitely say it is more likely that they were just showing their true colours, so to speak. There is no huge reason for cichlids from malawi to do this