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Lizard can switch from female to male before birth, but not vice versa

Some offspring of the noticed snow skink, a lizard present in Tasmania, are born anatomically male however are genetically feminine


1 June 2022

A noticed snow skink

Donovan Klein / Alamy

A lizard from Tasmania is the primary non-egg-laying animal recognized to typically change sexes earlier than start, relying on the encircling temperatures.

Some egg-laying fish, frogs and reptiles hatch with male sex organs and female chromosomes, or vice versa, when the eggs are uncovered to environments which are very warm or cool, indicating that their intercourse modified throughout incubation.

Now Peta Hill on the College of Tasmania and her colleagues have discovered the identical is true of the spotted snow skink (Carinascincus ocellatus), a lizard present in Tasmania that provides start to dwell younger.

The researchers trapped 100 newly pregnant feminine noticed snow skinks at completely different altitudes in Tasmania and positioned them in particular person terrariums of their laboratory.

Two teams of 20 skinks had entry to a warmth lamp over a part of the terrarium for both 4 or 12 hours a day, creating temperature zones starting from 20 to 37°C and falling to round 10°C when the lamp was off. The remaining three teams lived in managed temperatures of both 33°C, 29.5°C or 26°C for eight hours a day and 10°C for the opposite 16 hours.

The researchers sexed every new child skink by analyzing its intercourse organs within the first month of life. Additionally they assigned genetic sexes by sequencing DNA taken from the animals’ tails.

All of the skinks with feminine intercourse organs had XX chromosomes – that means there have been no male-to-female modifications. Nevertheless, 7 per cent of the 423 new child skinks had male intercourse organs and XX chromosomes.

These skinks had been principally present in litters within the cooler terrariums and born to females from decrease altitudes. Particularly, 20 per cent of the offspring with male intercourse organs and XX chromosomes had been born to females from low altitudes that had been within the 26°C terrariums or provided solely 4 hours of warmth lamp per day. That was the case for less than 2 per cent of the offspring born to females from low altitudes stored in hotter situations.

The findings are “putting” not solely as a result of they’re seen in a live-bearing reptile, but in addition as a result of the phenomenon is so one-sided, says Benjamin Geffroy on the French Institute for the Exploitation of the Sea in Montpellier, who wasn’t concerned within the examine.

Even so, that could be defined by a era impact, says Geffroy. Skinks with male intercourse organs and XX chromosomes – “XX males” – can develop up as practical grownup males and may mate with XX females, he says. However as a result of they lack a Y chromosome, all of the pair’s offspring could be XX.

“I discover it actually attention-grabbing that we will clarify the… bias towards females in heat situations, if we contemplate that some XX males reproduce with XX females, resulting in extra genetic females within the second era,” he says. An extended examine over a number of generations may assist help the idea, says Geffroy.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2022.0689

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