High temperature treatments induce germ cell loss in gonads of vertebrate animals, including fish. It
could be a reliable source for induction of sterility if the treatments led to a permanent loss of germ cells.
Here we report that heat treatment at 37C for 45–60 days caused a complete loss of germ cells in female
Nile tilapia,Oreochromis niloticus, and that sterility was achieved in fish at all stages of their life cycle.
Unlike previous observations, germ cells did not repopulate even after returning them to the water at
control conditions suggesting permanent depletion of germ cells. Gonadal somatic cells immunopositive
for 3b-hydroxysteroid dehydrogenase (3b-HSD) were clustered at one end of the germ cell depleted
gonads close to the blood vessel. Serum level of testosterone, 11-ketotestosterone, and 17b-estradiol
was significantly decreased in sterile fish compared to control. Body weight of sterile fish was higher than
control fish at the end of experiment. Our observations of increased growth and permanent sterilization
in the high temperature-treated fish suggest that this method could be an appropriate and eco-friendly
tool for inducing sterility in fish with a higher thermal tolerance