Home Science Reef fish can change their offsring’s sex as oceans warm

Reef fish can change their offsring’s sex as oceans warm

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With the changes in climate as a result an ocean temperatures rise, fish are
adapting in unexpected ways to give their offspring the best chance for
survival.

Image: JamesDPhotography / Flickr

Reef fish have to spend their whole lives in
warmer waters. A new study by researchers at the University of Technology, Sydney (UTS),Australia
show that reef fish can arbitrarily adjust the sex of their offspring.
Interestingly, this isn’t the result of genetic factors or changes in
behaviour, the researchers say. 
The team’s research, which have been published in the journal Global Change Biology,
suggest the mechanism for determining the sex of offspring is switched
on in the very early development of a fish, and is not necessarily
triggered by exposure to warmer water.

“Understanding the ability of species to respond and cope with rising
environmental temperature is key to predicting the biological
consequences of global warming,” said lead author and UTS Chancellor’s
Postdoctoral Research Fellow Dr Jennifer Donelson. 

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, Dr
Donelson said.
The UTS:Science researchers studied the Spiny Chromis, Acanthochromis polyacanthus,
photographed below, which lives in coral reefs in the western Pacific
Ocean, in places like Indonesia and northern Australia. They looked at
multiple generations of the fish to see how they responded to varying
temperature increases – both when they were born into these waters, and
when they were exposed to warmer waters later in life. 
 
The researchers showed that even relatively small increases in
developmental temperatures, just 1.5 degrees Celsius above average
summer temperatures, can reduce the proportion of female offspring by
more than 30 per cent. However the female sex ratio of offspring was
restored when parental fish were reared at this temperature for their
entire life and for two generations.

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“However, only partial improvement in the sex ratio occurred at 3.0
degrees Celsius above average conditions, even after two generations,
suggesting a limitation to transgenerational plasticity when the
developmental temperature is too hot,” Dr Donelson said.

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

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