EFFECT OF COMBINED THYROXINE AND CORTISOL TREATMENT ON HATCHING OF EGGS, POST-EMBRYONIC GROWTH AND SURVIVAL OF LARVAE OF HETEROPNEUSTES FOSSILIS
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Abstract
In order to record the effects of thyroxine and cortisol (individual/
combined) on hatching, post-embryonic growth and survival of larvae of
Heteropneustes fossilis, newly fertilized eggs were given bath immersion
treatments of L-thyroxine (T4; 0.05 mgfl), cortisol (0.50 mgll) and T4+ cortisol
(0.05 mgll +0.50 mgfl) for 15 days. Hatching of eggs, growth and survival of the
larvae improved significantly (P < 0.001) in the hormone treated groups as
compared to those of control. The frequency of deformities was reduced in
the combined hormone treatment group. The present observations suggest
that the advanced digestive function probably induced by T4+cortisol
treatment might have resulted in improvement in food utilization during the
critical phases of first feeding and promoted vital developmental processes
resulting in uniform growth, decreased mortality, better survival and
transformation of larvae to juveniles. This combined hormone therapy appears
to have practical utility in fish hatchery practice for better success in larval
rearing.
Keywords: Thyroxine (T4), cortisol, larvae, survival, growth,Heteropneustes
fossilis