![]() ![]() That is, they weren’t until the discoveries of Afrotrogla and Neotrogla. Male bush crickets in Australia transfer nutrients to the females during copulation: At times of the year when food availability is more constrained, females court the males when that’s not the case, traditional sex roles dominate.īut usually those reversals weren’t known to extend to genitalia. In some species of birds, for instance, skewed sex ratios cause females to court multiple males and control territories. These strategies can be stood on their head, however, when the limiting resource instead lies with the males. Throughout nature, male genitalia also often have structures like spines that can prevent a female from breaking away or a competing male from gaining access to her. Meanwhile, males will try to make themselves appealing - to as many mates as possible - with showy displays (like the male peacock’s tail) or by defeating rivals or offering females “nuptial gifts” of nutrients from their own bodies. Typically, females will tend to be picky about their mates to avoid wasting precious eggs. Because of that asymmetry, which leaves females with the more limited reproductive resource, the sexes can find it advantageous to pursue different breeding strategies, and that conflict lays the foundation for sexual selection, an important mode of natural selection. In evolutionary terms, it’s gametes, not genitals, that define sex: Males make numerous small, mobile sperm, while females produce a smaller number of larger, far more metabolically expensive eggs. In doing so, they’ve also challenged our conceptions about what it means to be male and what it means to be female, and witnessed just how flexible and innovative nature can be. Evolutionary forces seemed to favor these structures so much that they emerged independently in two lineages of the barklice, the Neotrogla in South America and the Afrotrogla in Africa.Īs scientists have sought to gain a better understanding of how the structural reversal arose in these barklice, they’ve had the opportunity to test the universality of sexual selection theory, explore the selection pressures on sex roles and assess the major, often overlooked part that environment and ecology play in the evolution of genitalia. Now, the story has developed even further: It turns out the gynosome evolved not once, but twice, as described recently in Biology Letters. The finding not only piqued widespread interest (and amusement - the team was awarded a comedic Ig Nobel Prize in 2017), but also led to a debate about whether the scientists involved were correct to refer to the structure, called a gynosome, as a “female penis.” (Some experts, for instance, disagree with that characterization because the gynosome collects sperm rather than delivering it.) Moreover, complementary changes in the genitalia of the males had left them with a small pumping mechanism inside a membranous “vagina-like” cavity. ![]() It didn’t just look like a penis but acted like one, too: a penetrative organ the female insects used to anchor themselves to their mates during copulation. For the most part, though, certain genital morphologies are associated with males, others with females.īut in 2014, a tiny insect called the barklouse broke even that rule when researchers reported that the females of all four species of a genus found in the caves of Brazil had a penis. Nature is full of strange reproductive organs with unusual uses. Female cabbage white butterflies have a hinged jaw inside their genital tract. The male seahorse has a brood pouch that receives his mate’s eggs for fertilization and in which he nurtures the resulting offspring until birth. They’re also among the most diverse, arrayed in all shapes and sizes, adorned with spines, hooks and even teeth. Genitals are among the fastest-evolving features in the animal kingdom. ![]()
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