Giant sperms come in small packages

Belonging to the species Zorotypus impolitus and commonly known as ground lice or angel insects, the Zoologgers are just a few millimeters long, look like termites and spend their lives in rotting wood, where they feed on fungi. What Mother Nature has seriously messed up here is the Zoologger's reproductive system, giving this very tiny insect a single huge sperm, that's almost its own size, to ensure the continuity of its species.

The Zoologgers are winged insects. However, where most winged insects deposit their sperm directly into the female genital opening, or as Romano Dallai, University of Siena said, "In general it is copulation," the Zoologgers act as an exception.

When Dallai and his colleagues monitored the mating and reproduction process of these Zoologgers in their lab, they were surprised to note that the male Zoologgers didn't bother to place the sperm into the female Zoologger's genital tract.

"This is the first time we have described external transfer of sperm in a Pterygote insect," Dallai explains.

Other than the normal copulation, winged insects demonstrate a different behavior of mating and reproduction wherein the male insect would place his sperm on the soil, after which, the female insect would pick it up, and then reproduce.

The Zoologgers, however, seem to be much more evolved - the female approaches the male and strokes him with her antennae; if the male decides to mate, he moves behind her, performs a simple dance, walks backwards and forwards while moving and vibrating his antennae, and then slips underneath the female for a few seconds, attaching a spermatophore to the female's abdomen.

"It [the sperm package] is the smallest we have seen in all insects," Dallai said. Other species usually make spermatophores upto 2 millimeters across, whereas that of the Zoologger is just 0.1 millimeters across; and that's where the surprise lay - dissecting the spermatophore, Dallai discovered, to his amazement, the longest sperm ever in insects - a single sperm around 3 millimeters long.

This particular reproductive behavior is quite surprising, since the males would want to maximize their chances of fertilizing the female's eggs, which is not so easy with a single sperm that's as long as the female itself!

Dallai speculates that this giant sperm may have something to do with outcompeting the other males. "The sperm is so large, it can fill the space in the female's [genital tract]," he explains. This sperm actually plugs the female's genital tract, so that no other male could mate with her. Smart move!

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