Global warming is turning sex reversal in frogs into extinction risk, Pg2

Key Highlights:

• Global warming is increasing sex reversal in amphibians, posing a significant extinction risk.
• A study on agile frogs (Rana dalmatina) in Hungary found that excessive heat during the tadpole stage induces sex reversal.
• Genetically female tadpoles (XX) can develop into physically normal and fertile males (XX males) due to high temperatures.
• Sex-reversed males exhibit lower reproductive success in the wild and sire offspring that are more vulnerable to heat and infectious diseases.
• Computer models predict that these factors will lead to population declines and earlier extinctions for agile frogs, exacerbated by pathogens like ranavirus.

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Detailed Insights:

• Sex reversal, where an individual begins life as one sex and later switches or develops as another, is a well-documented phenomenon across the animal kingdom.
• Amphibians are the most threatened vertebrate group, with approximately 40% of species facing extinction risk.
• The research, published in Science Advances, highlights how environmental factors like temperature can override genetic sex determination in species like agile frogs.
• Female agile frogs often employ a "split clutch strategy," laying only a portion of their eggs with sex-reversed males, indicating a preference for sex-concordant mates.
• Offspring sired by sex-reversed males show a significantly higher rate of sex reversal (61%) compared to those from sex-concordant males (17%).
• Ranavirus, a highly pathogenic virus, further amplifies the threat by causing mass mortality events in amphibian populations, particularly in offspring of sex-reversed males.
• Small populations are especially vulnerable to these combined pressures, as the loss of even a few breeding females can severely impact reproductive capacity.
• The study underscores the urgent need for conservation strategies to incorporate the impacts of climate-driven sex reversal on species survival.

Scientific/Technical Concepts Involved:

• Sex Reversal: A biological phenomenon where an individual develops or switches to a sex different from its genetic sex due to environmental or internal factors.
• Genetic Sex Determination: The process where an individual's sex is determined by specific chromosomes inherited from parents, such as XX for female and XY for male.
• Environmental Sex Determination: The process where an individual's sex is determined by external environmental factors, such as temperature during embryonic development.
• Ranavirus: A genus of highly virulent viruses belonging to the Iridoviridae family, known to cause severe disease and mass mortality in amphibians, fish, and reptiles.