Page 5 - TBAS-January-2021

TBAS January 2021 .................... -5-

Wet Season Actual African Pond Photo Dry Season
Ian Sainthouse, from England, Photos - Ian is a member of the our local Killifish Club!!

series of movements during which the fertilized egg is deposited on or into the
bottom substrate. There they remain in a state of suspended animation, with very
limited development activity, until the pool completely dries out. This quiescent
period is known as Diapause 1.
Initially, the deposited eggs are isolated from the atmosphere, first by the
water, and then by the uniformly solid substrate surface typical of the early stages
of the dry cycle. As the dry season deepens, the surface cracks, exposing the eggs
a mix of atmospheric gasses, fluctuations in temperature and increased levels of
light. These changing elements provide environmental
cues that impact the rate of development and the
onset and egress of the diapause stages. During this
dry cycle, the eggs experience periods of rapid
development, sometimes interspersed by one or
two additional diapause; diapause 2 and 3. Although
development appears to entirely suspend during
these diapause stages, metabolism is actively
Nothobranchius cardinalis regulated and organ genes developed that together

impart the ability of eggs to survive for extremely long periods of time, in some
species, many years.
But individual eggs do not respond
uniformly to these cues, and herein lies the key
to survival. Within a given clutch, some eggs
remain at one or another diapause stage, some
resume development at varying rates between
the diapause events, and others proceed directly
to the final pre-hatching stage. Because of this, Nothobranchius guntheri

To Table of Contents