Suicide Wasps and Fig Pollination — Chromatography Investigates

Those crunchy bits you find when eating figs — they’re dead insects right? Unfortunately — or fortunately if you like figs — this belongs with the information we file under urban myth, alongside the alligators in New York’s sewers and saying ‘candyman’ five times.

But millions of years of evolution has created a fascinating relationship between figs and wasps — one that is only now being unravelled and the power of chromatography is playing its part. Let’s take a look at mutualism, dioecious and wasp suicide in the world of figs.

Figs and wasps — symbiosis in action

The lives of figs and fig-wasps cannot be separated with each species of fig needing a species of wasp to reproduce — they are the fig’s only pollinator and the wasp needs the figs as they are the wasp’s only source of food and shelter. A relationship like this is known as mutualism — a mutual dependence between two species that is necessary for their well-being. Figs and fig-wasps have evolved together for millions of years and this has resulted in life-cycles that are closely entwined — if a little strange and devious.

The female wasps lay their eggs inside the figs — but to confuse the matter there are two types of figs. Caprifigs are an inedible fig containing the male flower parts that are perfect for wasps to lay their eggs in. These eggs develop into larvae and then male and female wasps. The male wasps job is to dig escape tunnels so that the female wasps can escape — taking pollen with them.

If a female enters an edible fig — she’ll find nowhere to lay her eggs and won’t be able to leave as she probably lost her wings and antenna when she entered the fig. The good news is that the fig has been pollinated and so will produce lots of seeds and juicy figs for us to eat. And don’t worry, the fig takes care of the wasp by producing an enzyme that dissolves the wasp.

But if the edible fig is such a disastrous end-point for the fig-wasp — why do they choose to go there?

Dioecious and devious figs

There are over 800 different fig species and the figs we eat are but one species. Edible figs are dioecious — which means that male and female flowers are on different trees or plants. So how does the female fig attract fig-wasps to a certain death — suicide wasps if you like.

A recent paper published in Nature Scientific Reports could have found the answer — chemical mimicry. A team of international researchers used gas chromatography – mass spectrometry to analyse the VOCs from both male and female fig flowers and found that the female flowers can mimic the scent of the male flowers and attract fig-wasps to an almost certain pollination death. As discussed in the article, Trace Level VOC Analysis in Different Sample Matrices GC-MS is an ideal technique for VOC analysis.

Fig biscuit anyone? Mmm… Crunchy.

Image from Wikimedia commons