Whole-body cortisol was measured by radioimmunoassay from spawning for
various periods up to 188 h post-spawning in 5 different broods. Fert
ilized eggs contained varying levels of cortisol (0.62-2.25 ng/g wet w
eight; designated ''C-0'') that presumably originated from the mother.
These levels declined as embryogenesis proceeded. The rate of decline
(0.056 +/- 0.004 ng/g/h) was fairly constant and was independent of C
-0. The decline continued up to about 4 h post-hatching (around 20 h p
ost-spawning) when cortisol reached minimum levels. Soon after attaini
ng the minimum, the levels started rising steadily to reach values as
high as 6.10 ng/g by 180 h post-spawning. The rise is presumed to be a
result of cortisol production by the larvae. The onset of this rise i
s much earlier than that reported in other species; it is also earlier
than the first immunohistochemical evidence for the activity of the p
ituitary-interrenal axis, at around 40 h post-spawning.