Fly Size Influenced by Mother's Previous Sexual Partner

Posted on October 4, 2014

Photo of Neriid flies

Researchers from the University of New South Wales in Australia say they have discovered an unusual way some traits are inherited in flies. They say they have found that the size of a fly offspring can resemble the size of the mother's previous sexual partner. This idea of telegony originated with Aristotle. It was discredited in the early 20th century, but the researchers say they have confirmed it exists in flies.

The researchers say the size of young flies is influenced not by the male fly that sires the offspring, but by the first male the mother fly mated with. The researchers think the effect is due to molecules in the seminal fluid of the first mate being absorbed by the female's immature eggs. This then influences the growth of the offspring of a subsequent mate.

The researchers produced large and small male flies by feeding them diets as larvae that were either high or low in nutrients. The researchers mated immature females with either a large or a small male. The mature females were then mated again with a large or small male. The scientists then studied and compared the offspring.

UNSW scientist Dr. Angela Crean says, "We found that even though the second male sired the offspring, offspring size was determined by what the mother's previous mating partner ate as a maggot."

Dr. Crean also says, "Just as we think we have things figured out, nature throws us a curve ball and shows us how much we still have to learn."

The study has generated a lot of articles about previous sexual partners and genetics in humans, such as this article in The Telegraph entitled, "Could previous lovers influence appearance of future children?" A Sydney Morning Herald story asks, "What if that sexual partner you'd rather forget remained forever a part of your life?"

This could be a horrifying prospect for some. Thankfully, there is no evidence this finding applies to any creatures other than flies. A research paper on the unusual discovery can be found here in Ecology Letters.

Photo: Russell Bonduriansky