Reef Fish May Switch Their Offsprings' Sex as Temperatures Rise

Oceans are continuing to warm, which means that fish on tropical reefs have to adapt to new changes and temperatures. Now, scientists have discovered that when early reef fish parents develop at elevated temperatures, they can adjust their offspring's sex through non-genetic and non-behavioral means.

"Understanding the ability of species to respond and cope with rising environmental temperature is key to predicting the biological consequences of global warming," said Jennifer Donelson, lead author of the new study, in a news release.

When temperatures warm, a type of sex bias occur; temperature essentially determines the likelihood of whether offspring are male or female.

"The research findings are significant because global warming poses a threat to species with temperature-dependent sex determination (TSD), such as reptiles and fish, potentially skewing the sex-ratio of offspring and, consequently, breeding individuals in a population," said Donelson.

The researchers found that even relatively small increases in developmental temperatures, of just 1.5 degrees Celsius, can reduce the proportion of female offspring by more than 30 percent. However, this female sex ratio of offspring was restored when parental fish were reared at this temperature for their entire life and for two generations.

With that said, only partial improvement in the sex ratio occurred at 3 degree Celsius above average conditions, even after two generations. This, in particular, suggests that there's a limit to transgenerational plasticity.

"Previous research has focused on the changes to the timing of breeding and mothers behaviorally altering the location of their nest to compensate for warming," said Donelson. "The novelty of our study was using a multigenerational (three generations) rearing design to ask questions about non-genetic and non-behavioral parental effects to sex determination."

Currently, the researchers aren't sure how coral reef fish manage to engineer these adjustments. Research is ongoing, but it does show that the fish can cope with warmer temperatures to some extent.

The findings are published in the journal Global Change Biology.

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