Altered development and reproduction in western mosquitofish (Gambusia affinis) found in the Hanxi River, southern China

Abstract

The current study investigated the development and reproductive health of western mosquitofish (Gambusia affinis) in the Hanxi River, which has been heavily contaminated by municipal wastewaters from towns in Dongguan of southern China. Western mosquitofish collected from four study sites, Songmu (SM), Yangwu (YW), Hengli (HL), and Zhangcun (ZC) of the Hanxi River, as well as a reference site (LX) of the Liuxi River, were dissected and analyzed for development parameters (total length, wet body mass, liver mass, gonad index, and population composition), reproductive parameters (oocyte count and weight of females, and sperm count and viability of males), and morphology (anal fin in males and females, and hemal spines in males). With the exception of the origin site (SM), mosquitofish from the Hanxi River exhibited significantly decreasing development and reproduction levels. Significant correlations were found for the collected mosquitofish between the morphological and reproductive indexes (ratio of perpendicular distance to tip to vertical distance from the tip on the 16th hemal spine) versus the sperm count of males; ratio 16P:16D versus sperm viability of males; segments of anal fin ray 3 versus oocyte count of females; and segments of anal fin ray 3 versus average oocyte mass of females. The results demonstrated that both male and female mosquitofish in the Hanxi River were affected by the discharged wastewaters, as reflected in their morphological changes in comparison with those of mosquitofish from the reference site.