About 10 years ago, I had quite a scare when my high school biology teacher warned us away from figs because their insides were crawling with wasps. Some internet research revealed that this claim was only partly true, so I continued along my fig-consuming way without thinking much more of it.
That is, until today, when we published a paper titled “Moving your sons to safety: galls containing male fig wasps expand into the centre of figs, away from enemies,” which made me look deeper into this symbiotic relationship – and now I’m eager to share all the creepy crawly details I found.
The short story is that fig wasps lay their eggs inside the fruit, where they hatch and mate. The female then crawls out of the fig, through a tunnel chewed by the male, and eats her way into a new fig to lay her eggs. In the process, she loses her wings and antennae and dies, trapped, inside the new fig, which she has also pollinated.
As for the caveats: there are also species of self-pollinating figs, which do not require the wasps, and species of parasitic fig wasps that game the system, taking advantage of the figs as incubators without doing their pollination duty. (I’m still not sure which ones make it to the supermarket though.)
Today’s paper explores some of the differences in egg-laying behavior between pollinating, symbiotic wasps and non-pollinating, parasitic wasps. Non-pollinating wasps not only take advantage of the fig, but sometimes also kill the larvae of pollinating wasps. In response to this threat, it appears that pollinator wasps have developed some defense mechanisms, including the location and sex ratio of eggs laid, the authors report.
Wasps aside, I also learned a surprising piece of information about figs themselves. They are not fruits, but are actually something called an “inflorescence,” or a cluster of flowers. It’s just that the flowers are hidden on the inside: each crunchy little seed in a fig represents one flower. To make it more complicated, there are three different types of flowers: male, short female, and long female. Female fig wasps can only reach and lay their eggs in the short female flowers, so the long female flowers are left to develop fig seeds, allowing both the fig and the wasp to prosper.
Image source: Mundoo via Flickr