University of Toronto Magazine University of Toronto Magazine
Winter 2006

Dangerous Liaisons

Zoologist Maydianne Andrade makes an intriguing discovery about the bizarre mating habits of redback spiders

Zoologist Maydianne Andrade
Zoologist Maydianne Andrade
UTSC zoology professor Maydianne Andrade (MSc 1995) remembers the first time she witnessed the brutal mating ritual of Australian redback spiders, a close relative of the black widow. It was 12 years ago and Andrade, a graduate student, had been at the lab all night watching the spiders’ extended courtship. Then the main event happened: the male deliberately positioned himself over his lover’s fangs – while still copulating – and was soon consumed. “I ran around the department in a sort of eureka moment,” she says. Andrade and her research colleagues had heard about the bizarre cannibalistic act, but she was the first in her lab to witness it.

This fall, Popular Science magazine named Andrade, 36, one of its “Brilliant 10” young scientists in North America. In 1996, her pioneering work on redback spiders’ mating habits was published in the prestigious journal Science. While other scientists had proposed that the males sacrificed themselves to literally feed their future offspring, Andrade proved that their suicidal behaviour is in fact an act of self-interest, allowing them to copulate for longer and fertilize more eggs. Male redbacks greatly outnumber females and only 10 to 20 per cent live long enough to find a willing mate, so any opportunity to spread their genes is worth dying for.

One of Andrade’s most recent discoveries is that male redbacks actually break off their copulatory organs in females to prevent other suitors from usurping their paternity. “This is about the power and elegance of natural selection to create these amazing behavioural strategies that you would just never predict,” she says.

Andrade currently has between 1,500 and 2,000 redbacks in her University of Toronto at Scarborough lab, along with a few pet tarantulas. In an adjoining workspace, her husband, Professor Andrew Mason, studies hearing systems in the parasitic fly and acoustic signalling in insects such as crickets and spiders. Not surprisingly, their three-year-old daughter “likes creepy-crawlies,” although spiders were an acquired taste for Andrade. “I wasn’t phobic as a child,” she says, “but I wasn’t a big fan.” Today, though, she can’t imagine ever getting bored with the eight-legged creatures. “Even now, they’re always surprising me.”

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