Photo via Good Free Photos
How wasps help give figs that distinctive texture—no, not that way
I still remember what a revelation it was the first time I encountered a dried fig, having previously known that taste and texture only as a cookie filling. “Oh, so that’s where that flavor comes from!” Years later, when I tasted my first fresh fig, it was another epiphany, like eating a grape for the first time after only knowing of raisins. Figs are a terrific if under-appreciated fruit—delicious, high in fiber and a wide variety of nutrients, yet low in calories. But the fact that North American kids are far more likely to know about Fig Newtons than the actual fruit inside them may be the least surprising thing about figs. What’ll really blow your mind is how figs reproduce.
Fruits of Her Labor
First, let me back up a minute. Did I say the fig is a fruit? To be more precise, the fig is a syconium, a structure that contains hundreds of tiny fruits called drupelets (like the nodes of a blackberry), each of which hangs off a flower on the inside. So what we call a fig is sort of an inside-out bunch of flowers. Some of those flowers are male, and some are female; in order for pollination to occur, the pollen has to travel from the male flowers to the female flowers—a task often carried out by insects. In this case, the insect is a fig wasp (Blastophaga psenes), but its job is not as simple as flying into the small hole in the synconium (called an ostiole) and poking around. Oh no. We’re just getting started.
The female wasp enters the fig’s narrow ostiole, losing her wings and antennae in the process—meaning she’s stuck there. She spreads a bit of pollen around (more on where she got it in a moment), pollinating some of the female flowers and enabling them to mature. She then lays her eggs and dies, having lived a grand total of perhaps two days. The eggs hatch, and the baby wasps mate. (The males actually fertilize the females before the females even hatch—eww.) The males then tunnel holes through the skin of the fig, but because they never had wings in the first place, they can’t get very far before they die, and some of them in fact never leave the fig. The females, however, having hatched already fertilized, pick up some pollen on the inside of the fig, fly out, and pollinate other figs.
Now the cycle repeats: the fertilized female wasp carries some pollen from the fig in which she was born to another fig, lays more eggs, and so on. Ah, but I’ve glossed over some important details. The fig in which mama fig wasp lays her eggs has to be an inedible, male fig, also known as a caprifig, because the geometry of the inside of female figs interferes with egg-laying. But, because so many of the female flowers in the caprifig will have had eggs laid in them, they won’t be able to mature and form seeds. And seeds are, after all, the point of the process, because that’s where new fig plants come from (after the figs have been eaten and the seeds pooped out by various animals, obviously). The edible, female figs need to be pollinated in order to bear seeds, even though they don’t make a good spot for the wasp to lay her eggs. Fortunately for the fig (if unfortunately for the wasp), male and female figs look the same from the outside. So by the time a pollen-bearing female wasp has climbed inside a fig and lost her wings (making it her final resting place), it’s too late for her to realize her mistake. She’ll end up spreading pollen around those female flowers and dying—but without laying eggs.
I’m So Into You
Now, I know what you’re thinking: Hang on here, you mean to say that the only way an edible fig can mature and produce all those seeds that give it its distinctive texture is for a pregnant wasp to die inside it? Yeah, that’s pretty much it. But that doesn’t mean you’re eating the corpse of mama fig wasp, as such. The fig produces an enzyme called ficain that digests the wasp’s body and turns it (or most of it, anyway) into protein before the fig reaches maturity. (And in any case, nearly all figs sold commercially in North America are pollinated without the use of wasps, so it’s only something to think about if you’re elsewhere in the world, or eating a wild fig.)
All this is an example of what scientists call mutualism, in which two species are interdependent in a complex way. In this case, both fig and wasp need the other in order to reproduce. All of which makes it kind of funny that fig leaves are supposed to inhibit reproduction in a certain other species. (Tip: There are some fantastic videos about fig reproduction at Brain Stuff and Gross Science.)
Source: Interesting Thing of the Day