In contrast to other members of the Drosophila family, the spotted-wing fly D. suzukii deposits its eggs in ripe fruits. Biologists from Ludwig-Maximilians-Universitaet (LMU) in Munich, Germany, have now elucidated the sensory basis of D. suzukii’s ability to exploit a novel ecological niche. Unlike most species of the genus Drosophila, which deposit their eggs in fermenting fruits, D. suzukii lays its eggs in ripe fruits. This apparently minor difference in behavior can have catastrophic consequences for commercial fruit-growers, and has made the species into a crop pest--for the puncture made by the female's ovipositor facilitates infections, while the hatched larvae feed on the fruit pulp. As a result, these infestations cause enormous damage to soft-fruit crops, such as cherries, raspberries, grapes, and strawberries. LMU biologists led by Professor Nicolas Gompel, in a collaboration with the groups of Dr. Benjamin Prud'homme (CNRS, France) and Professor Ilona Grunwald Kadow (Technical University, Munich), have begun to explore the genetic basis for this unusual egg-laying behavior. Their findings were published online on March 9, 2017 in Current Biology. The article is titled “Evolution of Multiple Sensory Systems Drives Novel Egg-Laying Behavior in the Fruit Pest Drosophila suzukii.” The researchers combined behavioral tests and genetic methods to determine how the closely related Drosophilid species D. melanogaster, D. biarmipes, and D. suzukii go about choosing the ideal nursery for their brood, each in their own way. The experiments showed that, in the search for egg-laying sites, the flies respond to the texture of the fruit, to the chemical composition of the surface and to characteristic odor compounds. In other words, they use the senses of smell, touch, and taste. D.
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