Mother knows best: a fatty acid is the key to making sexy sons

A parasitic wasp laying her eggs. Image via Wikipedia.

In honor of Mother’s day (I know, I’m a day late), I thought I would share a story about moms that help their sons get dates, by making sure they eat the right food growing up. The moms I’m talking about are female parasitoid wasps (Nasonia vitripennis).

Male parasitoid wasps attract females by releasing a special pheromone. But what determines the sexiness of the signal? According to new research (link here) from Birgit Blaul and Joachim Ruther at the University of Regensburg, the food that mom lays her eggs in is the deciding factor.

Nasonia life cycle. Image via Biologycorner.com

Parasitoids lay their eggs in the pupae of other insects. While the unsuspecting fly (or other insect) is undergoing metamorphosis, a female parasitoid wasp can come along and lay her eggs inside of it, where they will hatch and develop, eating up the fly in the process. So, the developing parasitoid larvae don’t have any choice when it comes to food. If mom doesn’t pick the best fly pupa for her babies, they’re out of luck.

According to the new research (published online in the Proceedings of the Royal Society, Biological Sciences), females can detect levels of a fatty acid called linoleic acid (LA) in insect pupae. Virgin females (which produce only sons) prefer to lay eggs in host pupae that are high in LA. LA is an essential fatty acid, meaning the wasps have to eat it because they can’t make it themselves.

So what’s the advantage of getting more LA?

The researchers showed that LA is a precursor of the male sex pheromone. Males that grew in high LA hosts made more of the pheromone and attracted more virgin females than males grown in low LA hosts. That means a decision made by mom, when the male was still an egg, affected how sexy he was later on.

You might wonder why the pheromone, which is made from LA, is so sexy to females. Sexual selection theory predicts that when females choose males based on a signal, like this pheromone, it should be related to how ‘fit’ the male is in order for the preference for the signal to keep being passed on to further generations of females.

The researchers went on to show that sexy males (the ones that grew up on high LA diets) were also the more fertile males. High LA males made three times as much sperm as their low LA counterparts.

Mom picks the best food for her sons, her sons grow up to be sexy and mate with lots of females, and those females will produce daughters that are attracted to sexy males. And so, the cycle continues.

By the way, if you want to see some awesome Nasonia pics, check out the Werren lab website.