Effects of tributyltin on gonad and brood pouch development of male pregnant lined seahorse (Hippocampus erectus) at environmentally relevant concentrations.

The male pregnancy of seahorses is unique, but their reproductive response to environmental disturbances has not yet been clarified. Tributyltin (TBT) is known to have an endocrine disrupting effect on the reproductive system of coastal marine organisms. This study evaluated the potential effects of exposure to environmentally relevant concentrations of TBT on the development of gonads and brood pouch of the lined seahorse (Hippocampus erectus). Physiological, histological, and transcriptional analyses were conducted, and results showed that high levels of TBT bioaccumulation occurred in male and female seahorses. TBT led to ovarian follicular atresia and apoptosis with the elevation of androgen levels, accompanied by the induction of genes associated with lysosomes and autophagosomes. Comparative transcriptional analyses revealed the likely inhibition of spermatogenesis via the suppression of cyclic AMP and androgen synthesis. Notably, the transcriptional profiles showed that TBT potentially affects the immune system, angiogenesis, and embryo nourishment of the brood pouch, which indicates that it has negative effects on the male reproductive system of seahorses. In summary, this study reveals that environmental levels of TBT potentially affect the reproductive efficiency of seahorses, and may ultimately lead to a reduction in their populations in coastal environments.