The present study was conducted to determine the effect of some organophosphorus insecticides (dimethoate and malathion) on the reproductive performance, hormonal levels and growth performance of the female and male Nile Tilapia; Oreochromis niloticus. The experimental fish were kept in well prepared fiberglass tank and were fed a diet containing dimethoate or malathion at concentration 1.6 and 0.17 mg/kg, respectively for 120 days. Treatment with dimethoate and malathion resulted in a significant (P <0.05) decrease in absolute fecundity, sperm motility, live-dead ratio and increased sperm abnormalities compared to the control group. Nonetheless, there was not a significant effect neither on semen pH, sperm cell concentration or compiled growth exponent; condition factor (K). Gonadosomatic index (GSI) was significantly (P <0.05) decreased in both dimethoate and malathion male treated groups. On the other hand, GSI treated was significantly (P <0.05) low in female tilapia fed a diet containing dimethoate. Although dimethoate noticeably increased plasma testosterone and estradiol 17β hormones, malathion decreased both sex steroids in treated male tilapia as compared with control. Histopathological examination revealed testicular degeneration, pyknosis of spermatocytes nuclei and complete absence of germ cells lining seminiferous tubules. The ovaries showed presence of multiple atretic oocytes with oocyte necrosis embedded in the ovarian interstitial tissues and decrease of vitellogenic oocytes. From these results we can can conclude that, even though long exposure to pesticides has not effect on the growth performance of O. niloticus, it interferes with both male and female fecundity through hypothalamic-hypophyseal-gonadal axis and/or the pathological alternation of gonadal morphophysiology. |
