PROFILE OF CORTISOL DURING THE ONTOGENY OF THE ASIAN SEA-BASS, LATES-CALCARIFER

Whole-body cortisol was measured by radioimmunoassay from spawning for various periods up to 188 h post-spawning in 5 different broods. Fertilized eggs contained varying levels of cortisol (0.62-2.25 ng/g wet weight; 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 post-spawning) when cortisol reached minimum levels. Soon after attaining 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 is much earlier than that reported in other species; it is also earlier than the first immunohistochemical evidence for the activity of the pituitary-interrenal axis, at around 40 h post-spawning.