Effects of nonylphenol, bisphenol A, and their mixture on the viviparous swordtail fish (Xiphophorus helleri)

A number of fish species have been used for studies on endocrine disrupting chemicals (EDCs). However, despite the widespread use of oviparous fish, r elatively little attention has been given to viviparous species. This study investigated the effects of EDCs in a viviparous fish and examined the pos sible usefulness of the fish as an alternative model for the studies on EDC s. Swordtails (Xiphophorus helleri) were exposed to nonylphenol (NP), bisph enol A (BPA), and their mixture. Both short-term (3-d) and relatively long- term (60-d) exposures were carried out using adult male and 30-d-old juveni le fish, respectively. Following the short-term exposure, both NP and BPA c aused vitellogenin mRNA expression. Flow cytometric analysis and terminal d eoxynucleotidyl transferase assay on the testes of treated fish indicated r eproductive damage. Histopathological analysis found degenerative and necro tic cells in seminiferous tubules following the exposure to 100 ppb NP. The testes with lesions were also associated with highly suppressed spermatoge nesis. Following the long-term exposure, both NP and BPA exposures signific antly affected the growth of swordtails. In all cases, the results showed t hat the mixture was always more potent than a single chemical and that swor dtail fish can be a useful model for the study of endocrine disruptors.