Featured Creature: Fig Wasp

Fresh, ripening fig.

Fresh, ripening fig.

Ever eat a fig; a nice, ripe, juicy fig? Then you have also eaten essence of fig wasp! The name Fig Wasp is actually a bit confusing as it can apply to several groups of wasps. Some of those groups are parasitic fig wasps that bore holes in ripening figs and so damage the crop. These are not the fig wasps I will be discussing in this Featured Creature. The fig wasps that I will be examining are a group of about 900 species of pollinating fig wasps in the subfamily: Sycophaginae. These are tinny wasps, with the larger females only getting to be about 2 mm long, are found all around the world and their influence on figs is huge!

Figs and Fig Wasps are so important that Kenya published a series of stamps in their honor.

Figs and Fig Wasps are so important that Kenya published a series of stamps in their honor.

The pollinating fig wasps are tightly linked mutualists with the figs they pollinate, a mutualism that has arisen over millions of years of evolution. Each species of fig wasp only pollinates one or two species of fig and each species or varietal of fig is only pollinated by one species of wasp. This makes the fig wasps incredibly important to figs, and also to the animals and economies that rely on figs. How this pollination occurs is the truly odd part and when we reach the end, you will see what I meant in the opening sentences about eating essence of wasp.

Black Figs.

Black Figs.

But first, a bit about figs and fig anatomy. Fig trees produce two types of figs: male figs called caprifigs which we do not eat, and female figs called edible figs which are what we do eat. Both types of fig are odd structures called syconia. The have the flowers on the inside which means that in order to reproduce pollen from the inside of a caprifig as to get to the inside of an edible fig. This is where the fig wasp comes in.

Male and female fig wasps hatch inside caprifigs. The males are blind and wingless and have only two jobs. One is to mate with the female wasps that hatched in the same caprifig. The other is bore tunnels through the tissue of the fig to the outside world. Once he has completed a tunnel, the male does not leave, but instead continues making more tunnels. He will spend his whole life in the one caprifig mating and making tunnels. The females have a bit more complex lives. After mating with one of the males who hatched in the same caprifig, they crawl out on of the

Female (left) and male (right) fig wasps.

Female (left) and male (right) fig wasps.

tunnels that the male made. In so doing, they brush against the male flowers on the inside of a caprifig and get coated in pollen. This means that when they emerge from the tunnel and fly away, they are carrying fig pollen with them. The female flies out in search of a fig to lay her eggs in. When she finds a fig, she enters it through a narrow passageway called an ostiole. The ostiole is so narrow that the walls scrap off the females wings and antenna. This means that a female wasp has only one chance to pick which fig to crawl into, since once she has crawled into a fig, she will never get out, dying inside her fig of choice.

Female fig wasp.

Female fig wasp.

But what happens inside the fig depends on whether the female wasp crawled into a caprifig or an edible fig! If she crawled into a caprifig, she finds the perfect environment to lay her eggs. The inside of a caprifig has flower parts that have a shape which perfectly matches the shape of a fig wasp egg. She will lay her eggs and die inside the caprifig. This is kind of a dead end for the fig life cycle since the male fig flowers have no use for the fig pollen the wasp is coated in. However, the fig wasp eggs will hatch in the safe space inside the caprifig and the fig wasp life cycle will continue.

Female fig wasp.

Female fig wasp.

This cycle has not yet included the figs we eat! So, what happens if the female fig was crawls into is an edible fig? In this case, she will find no place to lay her eggs. Female fig flower parts will not hold a wasp egg. This is kind of dead end for the wasp life cycle, but it is not for the fig. The female fig flowers inside the edible fig will accept the pollen that the female wasp is coated with. The female wasp will eventually starve to death in the edible fig, but the fig will grow and ripen thanks to the pollen she delivered. The fig will also secrete an enzyme called ficin which digests the body of the female wasp to be used by the growing fig. This is why you do not find a tinny wasp body in each fig you bite into. It has dissolved and been incorporated into the fig itself (This raises a question for the vegetarians reading this post: does eating a fig count as eating an animal?). Just a note of clarification in case anyone was wondering, the tinny crunchy things inside a ripe fig are fig seeds, not little bits of undissolved fig wasp.

Pretty wild, right? So next time to have a fig, or a fig newton, or some fig jam, or anything else with fig in it, think for a moment about the complex and interwoven lives of fig trees and fig wasps, and perhaps give a moment of thought to the female wasp who died inside the fig you are eating so that it could become the foods we enjoy so much.

Female fig wasp (Blastophaga psenes)

Female fig wasp (Blastophaga psenes)

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3 Responses to Featured Creature: Fig Wasp

  1. jeffollerton says:

    Most of the biology in here is correct and gives a nice introduction to the topic of fig-fig wasp interactions. But it’s not true to say that commercial figs are pollinated by these wasps; if they did the figs would be inedible as they’d be full of insects! In fact horticultural varieties of figs self pollinate to produce the fruit that we consume.

    Like

  2. Joost Peters says:

    Remember A.R. Wallace, saying as much as: nothing holding well for plants/animals in the wild will hold as well for their domestic lookalikes.

    Like

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