Some girls: only females hatch from the eggs of sea turtles due to warming

The discovery, made by an international group of researchers on the territory of the Great Barrier Reef, revealed another victim of global warming. This is a green sea turtle (Chelonia mydas), in a population of which after 20 years there will not be a single male and which, most likely, will die out if there are no positive changes on the planet.

The thing is that the sex of future offspring in some reptiles depends on the ambient temperature at which the embryos develop. This phenomenon is called the temperature determination of sex. By it is meant the development of the sexual characteristics of the future organism under the influence of a certain temperature. Similar features are characteristic of all alligators and crocodiles, most sea and land turtles, as well as for some lizards.

Briefly, this process is as follows. The female lays eggs on the shore, burying them in soil or sand. In the embryo, both male sex hormones (androgens) and female hormones (estrogens) are initially present. The special enzyme P450 aromatase, which is also present in the embryo's body, is able to convert androgen to estrogen, and its activity directly depends on the ambient temperature. Each reptile species has its own narrow temperature range at which these transformations occur or do not occur.

The green sea turtles, which live in the northern part of the Great Barrier Reef off the coast of Australia, have found disturbing effects of exposure to too high temperatures in the region. Among young individuals capable of breeding, males are only 0.2%, all the rest are females. Among the newly hatched cubs, the situation is approximately the same: 99.1% are females. Only the adult generation has a slightly more optimistic sex ratio: 13.2% of males in this group.

Large-scale studies were conducted by the Australian branch of the World Wide Fund for Nature in collaboration with American scientists. Such a situation, according to experts, will lead to the fact that after 20 years the population of these turtles in the northern part of the Great Barrier Reef, numbering about 200,000 individuals, will consist exclusively of females.

It turns out that some reptiles, like no other, depend on the ambient temperature. The slightest temperature deviation from the norm during the incubation period leads to the appearance of same-sex offspring. Based on this, interesting assumptions about the extinction of dinosaurs made by Ferguson and Joanen are based (Ferguson, Joanen, 1982). Biologists suggested that a similar dependence could exist in dinosaurs, which so quickly and massively disappeared from the face of the Earth. For the death of such an extensive group of reptiles, according to biologists, most likely, no global cataclysm was needed, just a simple change in air temperature by several degrees was enough. Thus, in a short period of time, a same-sex population could be formed, incapable of further reproduction and survival.