ScienceShot: Eunuch Spiders Are Better Fighters

Helen Fields is a freelance science writer based in Washington, D.C.

Mating never has a pretty ending for the male Nephilengys malabarensis orb-web spider. After sex, either the female eats him, or he jettisons one or both of his palps, the organs he uses to deliver sperm (red arrow, above). But these unfortunate eunuchs have one thing going for them: they're great fighters, battling any other males that try to horn in on their mate. To find out why, researchers removed one or both palps from male spiders, then put each arachnid in a plastic box and poked it with a paintbrush whenever it stopped moving. Intact spiders were able to rouse themselves and keep going for, on average, about 15 minutes. Half eunuchs lasted about a third longer, and full eunuchs made it 80% longer than an intact male, the team reports online today in Biology Letters. So what's the secret? Spiders without palps weigh 9% less than intact spiders, write the researchers, so their fighting prowess might just come down to the fact that they have fewer body parts to lug around.

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Posted in Plants & Animals