If you give a male worm an option between food or mating, he'll choose sex over a snack. The nematode C. elegans, a very small species of worm often used as a model organism in genetic research, will "abandon food to search for mates" say biologists at the University of Rochester in New York and Brandeis University in Massachusetts on Thursday.
To produce offspring, male nematodes need to mate with the other worm sex (who are hermaphrodites, not female). In a series of tests reported in the journal Current Biology, male worms in a petri dish would cross a through a ring of food to mate with hermaphrodites living in the middle. The hermaphrodites, who can reproduce without copulation, appeared content to remain in the middle of the dish and munch on food.
Getting from research in nematodes to ramifications in us takes a bit of swinging through evolutionary branches. (About three-quarters of human genes have homologous genetic information in the worms.) But the biologists say their findings have wider implications for sex differences across the animal kingdom.
"While we know that human behavior is influenced by numerous factors, including cultural and social norms, these findings point to basic biological mechanisms that may not only help explain some differences in behavior between males and females, but why different sexes may be more susceptible to certain neurological disorders," says Douglas Portman, a professor at the University of Rochester, in a statement. Parkinson's disease, for example, is more prevalent in men.
With a tweak to a single cell, the scientists could alter the animal's behavior. The researchers tuned the ability of the male worms to follow the scent of food, and found that a heightened sense of smell meant males were more likely to chase after food than another worm. The study adds to a growing body of knowledge regarding gene expression in different sexes, which, Portman says, "influence differences in behaviors - and in disease susceptibility - between the sexes."
And for some species, like bonobos, food and sex come hand in hand, regardless of sex. As primatologist Frans de Waal wrote for Scientific American, regarding his observations at the San Diego Zoo in the early ‘80s: "As soon as a caretaker approached the enclosure with food, the males would develop erections. Even before the food was thrown into the area, the bonobos would be inviting each other for sex: males would invite females, and females would invite males and other females."