Mating mites caught in sex switch-up

U. MICHIGAN (US) — A 40 million-year-old moment of passion between two mites—preserved in Baltic amber—offers evidence that the females were clearly in control.

In a paper published March 1 in the Biological Journal of the Linnean Society, researchers at the University of Michigan and the Russian Academy of Sciences describe an extinct mite species in which the traditional sex roles were reversed.

In the species Glaesacarus rhombeus, the male lacked the specialized organs for clinging to females that are seen in many present-day mites. The female, however, had a pad-like projection on her rear end that allowed her to control the clinging. A remarkably preserved copulating pair of mites found in amber gave researchers a glimpse at how the apparatus worked.

Structures found in some living mites also show evidence of female control over mating, says Pavel Klimov, an associate research scientist at the University of Michigan Museum of Zoology. “Some lineages have developed female copulatory tubes that function like a penis.”

Top view of the mating mites. (Credit:Ekaterina Sidorchuk)

Klimov says the female’s ability to partially or completely control mating “is in contrast to the present-day reproductive behavior of many mite species where almost all aspects of copulation are controlled by males.” In mites, as in other animals including humans, the battle of the sexes has been raging throughout evolutionary history. Each gender struggles to get the upper hand to assure that their interests are protected.

In the case of mites, males benefit from coercing females to mate and making sure no other males mate with them. Harassing reluctant females, guarding females before and after mating, and fighting off competing males are typical behaviors.

Females, on the other hand, gain an evolutionary advantage if they have some control over matters of mating.

This allows them to choose superior males to mate with, while rejecting losers (who may be, however, extremely adept at coercing females), and it spares them the wear and tear of being subjected to harassment, guarding, and frequent copulation.

Klimov’s coauthor, Ekaterina Sidorchuk, is a researcher at the Paleontological Institute of the Russian Academy of Sciences.

The research was funded by the National Science Foundation and the Russian Ministry of Education and Science.

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