Saturday, April 19, 2008

Brainless but not clueless

photo of Eisenia foetida from our worm bin

Ah! The all hail the lowly earthworm! You may already know that they're master composters, but did you know that they also have some remarkable abilities in the sack (so to speak)? Red worms, like many other worms, are simultaneous hermaphrodites, which means that they have functional male and female reproductive organs at the same time. The sperm recipient also has the ability to store sperm. Sperm storing is remarkably common in the animal kingdom, and has led to some amazing innovations in sperm sorting (on the ladies' end) and sperm removal (on the male's end).

The May 7, 2008 issue of the Proceedings of the Royal Society of London. Series B has a paper by Alberto Velando et al. addressing this very issue in Eisenia andrei, a close relative of the red wiggler in your compost bin. Check it out:

Brainless but not clueless: earthworms boost their ejaculates when they detect fecund non-virgin partners.

From their abstract:
we performed a double-mating experiment to determine whether earthworms (Eisenia andrei) detect the mating status of their partners and whether they respond by adjusting their ejaculate. We found that earthworms triplicated the donated sperm when mating with a non-virgin mate. Moreover, such increases were greater when the worms were mated with larger (more fecund) partners, indicating that earthworms perform a fine tune control of ejaculate volume.

Way to go guys! Brainless but not clueless indeed.

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