Why Warmer Water Leads to Male Offspring -- If You're a Fish

Why Warmer Water Leads to Male Offspring -- If You're a Fish - Yahoo! News:

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To a list that includes extreme weather patterns and disappearing polar bears, you can add another dispiriting effect of climate change: too many males. Three years ago, Francesc Piferrer and other scientists working at Barcelona's Institute of Marine Sciences proved that rising water temperatures caused some species of fish to produce a disproportionate ratio of males to females. Now, Piferrer and his team have gone on to discover something of a mechanism behind that imbalance.

Most fish species don't have the x and y chromosomes that differentiate the sexes in humans. In fact, at least 40 species of fish -- as well as many reptiles -- are more dependent on temperature than genes when it comes to separating the boys from the girls. In these TSD ( temperature-dependent sex determination) species, the sex of offspring is fixed by temperatures experienced during embryonic development. In the 2008 study, Piferrer's team showed that in a species like the Atlantic silverside, a water temperature increase of 4 degrees Celsius could result in a population that was 98% male.