Environmental estrogens and other endocrine-disrupting chemicals (EDCs) impact the reproductive health of fish in many aquatic ecosystems. Gonadal alterations and levels of sex hormones and vitellogenin, a family of glycolipoproteins that serve as precursors to egg yolk protein, are effective biomarkers of endocrine disruption. Although these biomarkers have been widely applied, their use in identifying EDC impacts in developing countries are lacking. Such is the case in Nigeria. This study investigated the endocrine and gonadal responses of a commercially important catfish, Chrysichthys nigrodigitatus, in Lagos and Epe Lagoons.
A total of 195 adult fish (Lagos: n = 105; Epe: n = 90) were collected monthly between November 2020 and May 2021. Blood plasma was extracted for analysis of vitellogenin protein and two sex hormones (testosterone and 17β-estradiol) using ELISA. Gonadal tissues were examined histologically. Fish muscle samples and sediment, also collected monthly, were analyzed for heavy metals (Hg, As, Cr, Cd) and harmful phthalates (DEHP, DBP, DEP) using atomic absorption spectroscopy. Physicochemical parameters, including pH, DO, Temp and EC, of both lagoons, were measured using a multiparameter probe.
Intersex conditions were observed in 3.81% of the C. nigrodigitatus from Lagos Lagoon (males: 50%; females: 50%) and 3.33% from Epe Lagoon (males: 33.3%; females: 66.7%). Gonadal alterations, including empty seminiferous tubules and distorted ovaries, were recorded in male and female fish, respectively, from both lagoons. Significantly higher testosterone levels (ng/µL) were observed in females (3.00 ± 0.71) relative to males (1.94 ± 0.48) from Epe Lagoon, but not from Lagos Lagoon. 17β-estradiol levels (ng/µL) were higher in females than in males in both lagoons. Vitellogenin (ng/µL) in male fish was statistically higher than those in female fish in both the Lagos (0.28 ± 0.08 versus 0.23 ± 0.02) and Epe (0.31 ± 0.03 versus 0.28 ± 0.05) lagoons.
Multivariate analyses revealed sex-specific patterns of metal uptake and positive relationships between sediment pH and metal and phthalate concentrations in both locations. These results indicate that C. nigrodigitatus populations in Lagos and Epe Lagoons experience endocrine disruption linked to exposure to environmental estrogens and other EDCs.