My Research: Biomechanics of insect sex

Mammalian sex that we’re all familiar with is amazingly simple. You have a gaping vagina to be penetrated by a shaft-shaped penis. Sure, there are variations on the theme, but it all boils down to that.

On the other hand, the mechanics of most insect sex is more complicated, since the penile and vaginal apparatuses are composed of multiple interlocking parts. Besides studying the structure of the reproductive parts (which is species-specific most of the times), looking at how sex actually proceeds is also a legitimately interesting question.

Of course, for the most part, insects are too small to film having sex close-up without very good video equipment or high-speed cameras. So what needs to be done is close observation and behavioural recording, then standardised interruption to discern what is courtship and foreplay, and what is actual mating movements.

The way to do this is simple: observe a couple copulating completely and record all the distinct phases and movements (e.g. thrusting, leg tapping on abdomen, antennal touching). Then have more pairs copulate, and interrupt at each phase you identify by pulling the male away. Immediately anaesthetise both male and female and put them under the stereoscope and check the status of the genitals. If there is sign of opening or entry, then check for ejaculate in the female by dissecting her.

This may all seem like much work for nothing but satisfying a juvenile sense of humour. But such research forms the basis of studies on sperm storage and sperm competition, which then informs the study of sexual selection. My interest here extends to endemism.

As I make clear here, I consider Cypriot endemics to have evolved due to geographical isolation and rampant microevolution rates driven by geology. But there is also reason to suspect that the isolation may not just be geographical, and that it is in fact impossible for sister insect species from the mainland and from Cyprus to mate because of changes in primary sexual characteristics, i.e. the shape and mechanics of the genitals. It’s certainly common enough for this to happen in insects, and linking it with my master scheme provides another interesting dimension – I’ve concentrated so far on linking genotypical changes with gross morphology, but the same can be done with genotypes and sexual morphology. This line of research will involve attempting to mate subspecies from the mainland with the endemic Cypriot subspecies.

I will be concentrating on beetles since I’m most familiar with their genitals.

One further potential, if I ever get access to a 3D printer, would be to do 3D models of the genitals, then print them out and play. But this  would be speculation until actual observed evidence of how sex actually proceeds.

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