Hot or cold –
We’re figuring out the genes that let reptiles use temperature to determine sex.
John Timmer – Apr , (2: 645 pm UTC
There’s a global pandemic happening on a scale that hasn’t been seen in roughly a century. So we decided it would be the perfect time to talk about turtle sex. Not turtles having sex, which is undoubtedly an interesting geometry problem, but rather the process by which turtles develop as male or female.
That process is interesting because it seems, at least from our XY chromosomal perspective, to be a bit haphazard: turtles and many other reptiles determine their sex based on ambient temperature. In elevated temperatures, most of the eggs will develop as female; at lower temperatures, most of the eggs will develop as males. We don’t really know how they register the temperature and somehow translate it to a complex program of anatomical development. But a new paper in Science fills in some of our gaps.
Sex, of the less interesting sort
(This is ignoring all the many things that can happen during this process and produce a non-binary result.)
Despite that seemingly rigorous requirement, biology has found a bewildering variety of ways
Compared to chromosomes, which are pretty stable, it’s hard to see how temperature can work to set a binary state. Turtle eggs are left in the environment, where the temperatures vary over time. That variation occurs over the long term, as incubation may take place during changing seasons; medium term, due to day-to-day changes in temperature; and short term, with temperatures rising in the morning and falling at night. Somehow, all that has to be converted to a reasonably binary decision. For turtles, that conversion occurs in a way that does have some strong parallels to humans. The signal is read by cells that go on to form the animal’s gonads, which go on to produce hormones that direct the turtle’s development.
Obviously, understanding this pathway isn’t going to help us cure cancer or anything like that. But it is an intriguing example of how a variable environmental signal can be converted to an essentially permanent alteration in gene activity — something that seems to happen in humans, such as when they’re subjected to persistent stress. And as climate change begins to alter the temperatures of turtle habitats, understanding this pathway could potentially inform conservation approach. So it isn’t exactly esoteric science for science’s sake, either. (Science) , . DOI: / science.aaz (About DOIs
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