Anemonefish reproduction affected by chemical pollutants

Anemonefish reproduction has been greatly affected by chemical pollutants being dumped in the ocean by humans, a new study has found.

The study raises concerns over the huge negative impact of the chemical pollution happening across the world with the study showing how chemicals can affect the reproduction in common anemonefish Amphiprion ocellaris. The endocrine disrupting chemicals can obstruct normal reproduction in animals, researchers have said.

Bisphenol A and 17a-Ethinylestradiol (EE2) are two common chemicals of this nature. BPA is an endocrine disruptor and is found in a lot of different plastics like water bottles and EE2, commonly found in birth control pills, enters into the ocean from human waste and wastewaters of manufacturing plants and hospitals.

A. ocellaris live in small groups with one alpha female, one beta male, and lower ranking non-reproductive males. Their sex is not genetically programmed and, instead, is dependent on environmental cues: A male transforms into a female if the female is removed from the group or if males are paired together.

The researchers paired sexually immature, male fish and fed them twice daily with normal food, food containing BPA, or EE2. There were 9 pairs of fish per group and they were monitored for six months. The amount of BPA and EE2 were determined based on the environmental concentrations of these chemicals.

The researchers found that fish that were fed BPA had no testicular tissue, lower androgen levels, just like female fish, and increased expression of genes in the brain that are responsible for feminization. Surprisingly, although females tend to be more aggressive, BPA decreased aggression in these fish. In contrast, the effects of EE2 were similar, but less pronounced.

It is still unclear how BPA is exerting its effects. In other studies BPA was thought to bind to estrogen receptors. However, since EE2 is an estrogen mimic and had subtle effects, the researchers believe that BPA has other additional effects. “BPA could be affecting other hormone receptors or interfering with androgen signaling. It could be a mix of different effects and we don’t know yet,” one of the researchers said.

The study “Impact of bisphenol-A and synthetic estradiol on brain, behavior, gonads and sex hormones in a sexually labile coral reef fish” was published in Hormones and Behavior and can be found at https://doi.org/10.1016/j.yhbeh.2021.105043. The work was supported by the National Institute of Environmental Health Sciences.

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