Fatty Pheromones

A new class of pheromones, triacylglycerides, helps male fruit flies mark their mates to deter rivals.

Jul 1, 2014
Rina Shaikh-Lesko

SCENT OF A MALE: A male fruit fly ignores a female (lower right) smeared with a male pheromone, and mates with an untreated female (left). NATIONAL UNIVERSITY OF SINGAPORE, JACQUELINE S.R. CHIN

EDITOR'S CHOICE IN BIOCHEMISTRY

The paper
J.S.R. Chin et al., “Sex-specific triacylglycerides are widely conserved in Drosophila and mediate mating behavior,” eLife, doi:10.7554/eLife.01751, 2014.

The suspicion
Animals often relay sexual messages through pheromones, typically small, volatile organic molecules. In recent years, Joanne Yew at the National University of Singapore and others had spotted triacylglycerides (TAGs)—compounds usually found in fatty tissue—on the exterior of fruit flies, a pattern hinting that they might be pheromones.

The scrutiny
In Yew’s latest study, her team found TAGs on a dozen desert-dwelling Drosophila species—including 13 different TAGs on two species alone—by using a mass spectrometer with a fine-point laser trained on the flies’ cuticle surface. “They’re secreted in just one region—the anogenital region—on males,” says Yew, and they increased in concentration as the flies reached sexual maturity.

The mating game
After observing that males snub freshly mated females—and finding TAGs on those females’ abdomens—Yew’s team dusted one of two females with TAGs and found that a male fly chose the untreated one, suggesting that the molecules act as pheromones. The researchers speculate that males mark females with TAGs when they mate, rendering them unattractive to subsequent suitors. “I’d like to know more details about how the triacylglycerides are doing what she’s saying they’re doing,” says geneticist Joel Levine of the University of Toronto, Mississauga. “How are they sensed by the male? How are they transmitted to the female?”  

The implication
TAGs are heavier than many known pheromones, suggesting that other pheromones may have been overlooked because of their size. “You’re missing a big piece of the puzzle if you’re not detecting these heavy chemicals,” Yew says.