Re: Temp and sex ratios

[jonathan <fung@is2.dal.ca>]

I am currently working on a thesis titled
Investigation of behaviour and environmentla sex determination in
Apistogramma borellii (Cichlidae) 

and I shall publish it when it is complete. General trend in most
(not all) developing Apistogramma spp. broods appears to yield more
females at higher pH (near 7.2) and more males at lower pH (near 6).
Temperature appear to have an effect where higher temperatures (near
29 C) yield more males while lower temperatures (near 23 C) yeild more
females. However, I suspect that the relationship between temperature and
sex determination may be indirect. Perhaps it is related to rate of growth
or embryonic development as Apistogramma borellii fry grow painfully slow
(for my thesis) at 23 C.

Published sources on environmental sex determination so far include 

Romer, U. and W. Beisenherz. 1996. Environmental determination of sex in
     Apistogramma (Cichlidae) and two other freshwater fishes (Teleotei).
     J. Fish. Biol. 48: 714-725.

Rubin, D.A. 1985. Effect of pH on sex ratio in Cichlids and a Poecillid
     (Teleostei). Copeia. 1: 233-235. 


-------------------------------------------
Jonathan Fung... Reef Geek
Dalhousie University Honours Marine Biology
Aqua Creations Inc. Assistant Manager
writer for Marine Fish Monthly 
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On Thu, 8 Feb 2001, David Sanchez wrote:

> Could anyone tell me where, on-line if possible, I could find the the paper
> done on Apistos and the relationship Temperature has on their sex ratios?
> 
> Thanks in advance
> 
> David Sanchez
> 
> 
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