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Hatching annuals on command...
For those on the list interested in annuals,...
As the British Killifish Assoc. members amongst you may recall,
I predicted (1999 BKV-killi kontakt 27(5):115-127 and 2000 Killi-News
N° 416:63-72) that it would be possible
to hatch eggs of annuals on command rather than
applying an empiric incubation time that varied according to
the average length of the dry season in the fish's natural environment
The myth of eggs developing buried in the mud and waiting the first rain
to come in order for them to hatch has been proven wrong.
My theory that eggs of annuals will shortly after fertilisation go into
Diapause I (forced by anaerobic conditions prevailing in the bottom soil
where the eggs are being deposited) until such time that the first rain
of the new rainy season will push the resting primitive embryo (helped
in that by higher temperatures and availability of oxygen entering the
soil through micro faults in the substrate) to develop into a fully
developed embryo (with yellow iris) ready to hatch is in the process of
On 18th June 2000, I spawned N.virgatus in mud in which they were originally
collected. They should have been ready to hatch in Nov-Dec 00. When
inspecting them this morning (1 year + some days later), all the eggs
not sufficiently buried and exposed to the outside world were dead
and had collapsed. The 23 eggs that I managed to identify hidden deeper
in the wetted mud were all still in Diapause I. None showed any sign of
development. By wetting them this morning in order to inspect the eggs,
I simulated the first rain. This will (should) now force the primitive
Diapause I embryos to leave their resting phase and develop until the yellow
iris becomes visible. At that time they will enter Diapause II, waiting for
substantial rain to force them out and enter the big world. In nature, the
development from Diapause I to Diapause II or from primitive embryo to fully
developed embryo should not take more than a few days, a week at most (if
ambient temperature and humidity is high enough, e.g.. > 30°C and 80-90%
I will give them one month to develop (I have to go on assignment to Kenya
and Sudan) and will hatch them on my return.
I am convinced that it is the first rain that pushes the Diapause I
embryo to develop further into a Diapause II embryo, after an obligatory
resting phase of which the length is probably species specific, will also
to explain the mystery of the "resting eggs" ( = eggs still in Diapause I)
the belly sliders (= embryo's that stayed for too long in Diapause II,
too much of their meagre energy resources - hart beating, blood
We are a step closer to hatch annuals on demand.
I will keep you posted...
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