Re: Temp vs. sex ratio

["V Kutty" <kutty@earthlink.net>]

Helen Burns wrote:
> The recent postings regarding temperature vs.sex ratios has got me
thinking,
> could this apply to other species.
> The reason I am interested in this particularly is that my wild pair of
> Crenicichla regani Santarem have successfully produced two broods
recently.
> The first young (5th Aug) are now 2"TL and to me they all look like males
> but perhaps they are too young to sex out, I'm not sure.  The second brood
> (5th Sept) are still with the parents and if things go like they have they
> may be thinking of spawning again anytime in the following 10 days.
> As dwarf pikes share the same habitat as some species of Apistogramma it
may
> be that temperature can play an important factor in the sex ratio of dwarf
> pikes also.  My breeding tank is pH6.5 and the temperature was 30c.  Due
to
> the unusually hot weather we have had the temperature in the tank was high
> despite the heaterstat being set at 26c.  Any advice would be welcome
> Helen.

Hi Helen,

This stuff is really interesting!  You're right about these dwarf pikes
sharing habitats with many Apistos and there may be temperature related
sex-ratios happening here.  The 4°C difference between the two spawns may
make a difference - they would with Apistos.  These pikes all look like
males when they are young and start developing dorsal spots at 6 months or
so.  From the size of your 2-month old juveniles, I'm guessing you feed your
fishies very well and the females may start showing dorsal spots at 4-5
months age.

As far as I know, no one has done the "Romer study" with pikes.  My
suggestion is to keep the two batches separate and see what happens.  The
parents'll probably produce a couple of more broods before they tire of
breeding or of each other, so may be you could turn up the heater a little
higher this time or lower it to 24°C.   Keep us posted.

Vinny







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