Chemical pollutants disrupt reproduction in anemonefish

Date:
December 5, 2021
Source:
Carl R. Woese Institute for Genomic Biology, University of Illinois
at Urbana-Champaign
Summary:
Ocean pollution is unfortunately becoming more commonplace,
raising concerns over the effect of chemicals that are leaching
into the water.

In a new study, researchers have discovered how these chemicals can
affect the reproduction in common anemonefish Amphiprion ocellaris.



FULL STORY ========================================================================== Ocean pollution is unfortunately becoming more commonplace, raising
concerns over the effect of chemicals that are leaching into the water. In
a new study, researchers have discovered how these chemicals can affect
the reproduction in common anemonefish Amphiprion ocellaris.


========================================================================== Endocrine disrupting chemicals -- which interfere with how the body's
hormones work -- can obstruct normal reproduction in animals. 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.

"In Indonesia, for example, there are beautiful coral reefs found below a
lot of garbage, so anything that enters the water is affecting the fish,"
said Jose Gonzalez, a former undergraduate researcher in the Rhodes group.

"There have been previous studies that have established that these
pollutants tend to feminize animals like freshwater fish, rats,
mice, and even humans," said Justin Rhodes (GNDP), a professor of
psychology. "However, no one has studied their effects on a fish whose
sex is totally determined by the environment." 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.

"We looked at these fish specifically because they can transition
from male to female helping us understand how BPA and EE2 can affect reproduction," said Sarah Craig, an undergraduate research assistant in
the Rhodes group.



==========================================================================
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.

"Since these fish are able to change their sex, we looked at different indicators such as behavior, gene expression in the brain, and hormone
levels," said Abigail Histed, an undergraduate research assistant in
the Rhodes group.

"Interestingly, other than behavior, we found a feminizing effect in all
the other categories." 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.

"In nature, the females are very aggressive and do not tolerate the
presence of other females," Rhodes said. "We discovered that although
BPA is feminizing the gonads, the fish are not that aggressive and can
live with each other. These results suggest that the feminization in the
brain occurs independently of gonadal hormones." 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," Rhodes said.

The implications of the findings, however, are clear. "These fish can
only change their sex from male to female. If BPA is turning them female
in the wild, they can't go back to being a male and that can influence
their population numbers," Gonzalez said.

The researchers are interested in investigating the effects of EE2
further.

Specifically, they would like to use higher concentrations of EE2 because
they are concerned that the administered levels were not high enough. They would also like to follow the fate of these fish for longer since the
fish normally take more than six months to mature completely.

"A longer time frame would be better to compare the degrees of
feminization with BPA compared to natural feminization. Maybe they do eventually fight and kill each other and it's something we missed with
a shorter time frame," Rhodes said.

========================================================================== Story Source: Materials provided by Carl_R._Woese_Institute_for_Genomic_Biology,_University of_Illinois_at_Urbana-Champaign. Original written by Ananya Sen. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jose A. Gonzalez, Abigail R. Histed, Ewelina Nowak, Dominica
Lange, Sarah
E. Craig, Coltan G. Parker, Achint Kaur, Supriya Bhuvanagiri,
Kevin J.

Kroll, Christopher J. Martyniuk, Nancy D. Denslow, Cheryl
S. Rosenfeld, Justin S. Rhodes. Impact of bisphenol-A and synthetic
estradiol on brain, behavior, gonads and sex hormones in a sexually
labile coral reef fish.

Hormones and Behavior, 2021; 136: 105043 DOI:
10.1016/j.yhbeh.2021.105043 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211205111707.htm

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