title: Gonado-histopathological changes, intersex and endocrine disruptor responses in relation to contaminant burden in Tilapia species from Ogun River, Nigeria.
abstract: In the present study, we investigated the occurrence of intersex condition, histopathological changes in the gonad and endocrine disruptor biomarker responses in Tilapia species (Tilaipia guineensis, Sarotherodon galileaus and Oreochromis niloticus) along the Ogun River, Nigeria. The study sites covered a length of 320 km and a total of 1074 tilapias were collected from three sampling sites (Abeokuta, Isheri and Ikorodu) with different degrees of anthropogenic contamination. Samples were also collected from an upstream putative control site (Igboho) along the Ogun River. Hepatic transcript levels for vitellogenin (Vtg), zona radiata (Zrp) and aromatase (cyp19a1) were analyzed using real-time PCR. Gross gonadal morphology revealed a 24% prevalence of intersex showing visible testis and ovary in phenotypic females (25.4%) or males (74.6%). The intersex condition paralleled histopathological changes (ovotestis or testis-ova) in the gonads of female and male fish, respectively. Plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), 11-ketotestosterone (11-KT) and estradiol-17β (E2) were measured using enzyme immunoassay, showing that male fish from downstream of the control site had significantly higher plasma E2, LH, and FSH concentrations compared to females. Similarly, Vtg, Zrp and cyp19a1 mRNA was significantly higher in males, compared to females. Analysis of contaminants showed the presence of 15 PCB congeners, lindane and dieldrin, and 4-iso-nonylphenol (4-iso-NP) and 4-tert-octylphenol (4-tert-OP) in fish muscle and sediment samples from Ogun River. Principal component analysis (PCA) revealed site and sex relationships between measured biological responses to groups of environmental contaminants, showing that the endocrine disruptive responses in fish were associated with biota and sediment contaminant burden. In addition, strong positive correlations were observed between male fish and Zrp, cyp19a1, E2, LH, FSH, PCBs, 4-iso-NP and 4-tert-OP, suggesting possible feminization effects of these contaminants on the male. In female fish, PCBs, 4-iso-NP and 4-tert-OP showed positive relationships with 11-KT and gonadosomatic index (GSI), suggesting masculinization effects by these contaminants. Overall, our findings demonstrate a causal relationship between endocrine disruption and contaminants burden in Tilapias species from Ogun River.
authors: Department of Zoology, University of Ibadan, Ibadan, Nigeria.
authors: Oju R
authors: OR
authors: Ibor
authors: Department of Zoology, University of Ibadan, Ibadan, Nigeria.
authors: Aina O
authors: AO
authors: Adeogun
authors: Department of Veterinary Microbiology and Parasitology, University of Ibadan, Ibadan, Nigeria.
authors: Olusegun A
authors: OA
authors: Fagbohun
authors: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, N-7491, Trondheim, Norway. Electronic address: arukwe@bio.ntnu.no.
authors: Augustine
authors: A
authors: Arukwe
mesh_terms: D000818:Animals; D023681:Cichlids; D003906:Developing Countries; D017753:Ecosystem; D052244:Endocrine Disruptors / Q000032:analysis*; D004958:Estradiol / Q000032:analysis; D005260:Female; D005843:Geography; D006066:Gonads / Q000187:drug effects; D006728:Hormones / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009549:Nigeria; D010053:Ovary / Q000187:drug effects; D010636:Phenols / Q000032:analysis; D011078:Polychlorinated Biphenyls / Q000032:analysis; D015995:Prevalence; D025341:Principal Component Analysis; D045483:Rivers; D013737:Testis / Q000187:drug effects; D013739:Testosterone / Q000031:analogs & derivatives; D017210:Tilapia / Q000502:physiology*; D014819:Vitellogenins / Q000097:blood; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D052244:Endocrine Disruptors; D006728:Hormones; D010636:Phenols; D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone; D011078:Polychlorinated Biphenyls; C041594:4-nonylphenol; C105260:4-tert-octylphenol; C003600:11-ketotestosterone
keywords: Contaminant burden; Endocrine disruption; Intersex; Nigeria; Ogun river; Tilapia species