Stressinduced inhibition of recruitment of ovaria

Authors: Ambarisha Chabbi C B Ganesh

Publish Date: 2012/04/17

Volume: 38, Issue: 5, Pages: 1521-1532

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Abstract

The tilapia Oreochromis mossambicus shows a short ovarian cycle of 24–26 days in nonmouthbrooding condition In this study the stripped female O mossambicus were exposed to repeated mild acute stressors such as handling chasing frequent netting and low water levels daily for a period of 26 days The follicular dynamics did not show significant difference during previtellogenic phase day 12 whereas the mean number of stage IV vitellogenic follicles remained significantly lower compared with controls at the end of vitellogenic phase day 18 The stage V vitellogenic preovulatory follicles were completely absent in contrast to their presence in controls prior to spawning day 23 The control fish spawned spontaneously after 24 days and entered mouthbrooding phase whereas those exposed to stressors did not spawn Furthermore the serum levels of estradiol E2 remained significantly lower concomitant with a significant increase in the serum cortisol concentration during vitellogenic and prespawning phase compared with those of the controls The LH cells in the PPD of the pituitary gland showed weak immunoreactivity through vitellogenic and prespawning phase in fish exposed to stressors indicating the diminished secretory activity in contrast to the intensely stained irmaterial in controls The study reveals the disruptive effects of aquacultural stressors on the spawning cycle through suppression of LH and E2 secretion along the pituitary–ovary axis The results suggest that the ovarian stress response depends on the phase of the cycle and that the interruption of the spawning cycle is due to inhibition of recruitment of preovulatory follicles in O mossambicus

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