We Have Found A New Type of Sex Organ

Apr 17, 2014 • Research, Science


Nature defies our wildest imaginings, pushing the boundaries of what we know as possible. Most birds, for instance reproduce through the “cloacal kiss” a form of contact during which the male passes semen into the female through their cloacae, openings that functions for urination, defecation and sexual reproduction. But some other birds — like the ostrich and emu — have penises, though unlike human penises, these penises don’t become erect with blood, but with lymph, the milky fluid that is part of the lymphatic system. In some crocodilians, the female sex apparatus is so large, it is easy to confuse it with that of the male of the same species. In squid, the sperm travel into the female in a capsule that perforates the female body to deliver the sperm cells. Nature is a weird place and today, it got a little weirder.

Meet the Neotrogla, a class of insects found in caves in the area of Brazil. The females of this genus have neither a vagina nor a penis, but something completely different: a highly specialized organ that is used to penetrate the male, anchor in place and take both nutrients and sperm from him. The anchoring mechanism of the gynosome is so powerful that when scientists studying the insects tried to decouple a pair of mating specimens, the male was torn in half.

As Jason Goldman writes in an article about Neotrogla on io9, this isn’t the first time we have encountered a species that has a protruding, penis-like structure. He writes, “So-called ‘pseudo-penises’ are known in some other species, and they range from an enlarged clitoris in hyenas to enlarged labia in spider monkeys. But in each of those cases, the male must still penetrate the female during mating. In Neotrogla, the gynosome actually penetrates the male during sex — though the males still do the fertilizing.”

According to a study in Current Biology, these insects evolved this way because the female needs the additional nutrients provided by males when they pass along ejaculate (which researchers refer to as “seminal gifts”):

Due to the faster replenishment rate of gametes, males generally have higher potential reproductive and optimal mating rates than females. Therefore, sexual selection acts strongly on males, leading to the rapid evolution and diversification of male genitalia. Male genitalia are sometimes used as devices for coercive holding of females as a result of sexual conflict over mating. In contrast, female genitalia are usually simple. Here we report the reversal of intromittent organs in the insect genus Neotrogla (Psocodea: Prionoglarididae) from Brazilian caves. Females have a highly elaborate, penis-like structure, the gynosome, while males lack an intromittent organ. The gynosome has species-specific elaborations, such as numerous spines that fit species-specific pouches in the simple male genital chamber. During prolonged copulation (around 40 to 70 hours), a large and potentially nutritious ejaculate is transferred from the male via the gynosome. The correlated genital evolution in Neotrogla is probably driven by reversed sexual selection with females competing for seminal gifts. Nothing similar is known among sex-role reversed animals.

For a more accessible explanation of what researchers think led to the evolution of the gynosome, check out this article.

And for everyone that is describing this sex organ as a penis, please refer to this article.

Header image by Gonzales 2010.