Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): a-histological alterations in ovaries.

The present study investigated the gonads alterations of mature female Oreochromis niloticus caused by different concentrations (0, 40, 60, 100 µg/L) of 4-nonylphenol (NP) and also its effect on steroidogenesis. A tendency for a dose-dependent reduction in the gonadosomatic index, fecundity and oocytes diameter in the NP-exposed groups was observed. Histological examination revealed that NP impairs gonadal growth clearly shown in the oocyte development and differentiation. Also, the estrogenic activity of such NP was identified through 11-ketotestosterone, 17b-estradiol and vitellogenin which were affected significantly by the applied concentrations. The study indicates that NP has estrogenic potency-induced marked alteration in the sexual development including gonadal maturation, spawning time and egg production.

Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): b-histological alterations in testes.

The present study investigates the effects of different doses (0, 40, 60, 100 µg/L) of 4-nonylphenol (NP) on testis histology and sperms motility of mature Oreochromis niloticus. A tendency for a dose-dependent reduction in the gonado-somatic index (GSI) in the NP-exposed groups was observed. Histological examination revealed that high doses of NP (60 and 100 µg/L) cause hyperplasia of interlobular connective tissue components coincide with decrease in the size of seminiferous lobules and amount of lumen spermatozoa in comparison with the control and low-dose (40 µg/L)-exposed groups. In addition, within the seminiferous lobules, rupture of spermatogenic cysts, vacuolation and necrosis of primary spermatocytes due to damage of sertoli cells were clearly observed and lead to decrease in advanced spermatogenic cells. The highest dose caused significant decrease in the GSI associated with appearance of testis-ova (intersex) state. The percentage of abnormal sperms increased with increasing the dose of NP reaching to 96 % for those subjected to 100 µg NP/L, while it was only 11 % for the control group specimens. The study indicates that NP has estrogenic potency induced marked alteration in the sexual development including inhibition in testicular growth and deformation in the sperms.