Sexual Prime Peaks When Males "Smell" Mates, Spider Study Shows

June 16, 2006

For male Australian redback spiders, life is about sex and death. If they are lucky, the former is part of the latter—female redbacks eat their male mates during copulation.

But death comes first for 83 percent of the males, according to research.

To boost their chances at successfully fathering offspring, the male spiders can adjust how quickly they mature, depending on how many mating prospects are nearby, said Maydianne Andrade, a zoologist at the University of Toronto at Scarborough in Ontario, Canada.

"The male wants to be the first one to reach the female, but he also has to survive the arduous trip to find the female," she said.

The males mature more quickly when they smell that ample females are close by. But when pickings are slim, they bide their time to bulk up for an extended journey in search of sex, Andrade explained.

She and graduate student Michael Kasumovic reported their research in the April issue of the journal Current Biology.

Jutta Schneider is a biologist at the University of Hamburg in Germany who studies reproductive behavior in spiders. She says the finding is exciting and important.

"Surely most animals use external cues to adjust timing of breeding and migration and other major occasions in their lives," she said in an email.

"But the nice thing with the redback males is that they appear to flexibly adapt growth and maturation to expectations of fitness rewards."

Sexual Cannibalism

According to Andrade, Australian redback spiders—members of the black widow family—are ideal models for testing theories of sexual competition and selection.

(See a photo gallery about spider sex.)

Continued on Next Page >>




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