Life Lines by Dr. Dolittle

Sponsored by the American Physiological Society

Rising water temperatures masculinizes Nile tilapia


Image of a Nile tilapia by Bjørn Christian Tørrissen via Wikimedia Commons 

Nile tilapia, Oreochromis niloticus, is a species of freshwater fish native to Egypt and Africa. Global warming has the potential to significantly impact this species as water temperatures above 32 to 36.5 degrees Celsius can induce young fish (10-30 days after fertilization) that are genotypically female to become masculinized. Moreover, a recent study published in PLOS ONE showed that some young fish choose to visit warmer waters.

A new study published in the Physiological Genomics was designed to try to figure out how temperature affected changes in the expression of genes in the brains of these animals. The researchers were able to identify 16 genes that were either increased or decreased in the brains of heat-exposed female fish. In fact, the changes in these genes were similar to normal levels found in genetically male Nile tilapia. Just why these fish evolved to increase male populations with rising temperatures is not known.


Nivelle R, Gennotte V, Kalala EJK, Ngoc NB, Muller M, Melard C, Rougeot C. Temperature preference of Nile tilapia (Oreochromis niloticus) juveniles induces spontaneous sex reversal. PLOS ONE. 2019

Zhao Y, Mei Y, Chen HJ, Zhang LT, Wang H, Ji XS. Profiling expression changes of genes associated with temperature and sex during high temperature-induced masculinization in the Nile tilapia brain. Physiological Genomics. 51(5): 159-168, 2019.


Categories: Climate Change, Environment, Reproduction and Development

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