Remember that notorious scene from Alien? You know the one. But instead of just one alien organism bursting out of its host, picture hundreds, even thousands. That’s what happens when Copidosoma floridanum wasps mature, says Laura Corley, assistant professor of entomology. Admittedly, the bursting out is a bit less dramatic than in the movie, for the wasps’ caterpillar host is nothing but a dried out husk when they exit.
Corley studies C. floridanum because of its “fascinating biology.” Female C. floridanum lay up to 40 individual eggs, and each of those eggs develops into between 900 and 3,000 offspring. The offspring of any one egg will be either of two distinct castes—an asexual soldier or a sexual reproductive—even though all offspring share the same genes and the same environment during development, she says. And at least during the early part of the developmental cycle, some of the wasp larvae can switch castes in response to their environment.
“I want to know the ‘how’ for all of this,” says Corley. While there are a handful of other insect species in which one egg develops into more than one offspring, they usually average just eight to 40 offspring per egg.
C. floridanum are parasitoid wasps. They dine on their hosts’ fluids and tissue as larvae, pupate inside them, and leave. Their growth, proliferation, and development are synchronized with that of the host, which goes about its business while the wasp egg inside it proliferates. Eventually the wasp larvae consume the entire caterpillar, and its insides become dry enough for them to pupate within.
Corley currently is taking two research approaches to determine the “how.” She manipulates the host-parasitoid system in order to find the signals that enable an egg to respond to its environment. This work already has shown that while four percent of the offspring from one egg usually develop into soldiers, up to 24 percent may become soldiers when there is competition from another parasitoid species.
She also is looking at two interesting genes from drosophila, or fruit flies. One is involved in over-proliferation and the other, in the production of eggs and sperm. The former obviously applies to C. floridanum, the latter is something only its reproductive caste does.
The C. floridanum wasp is relatively simple as parasitoids go, says Corley. While not a useful biocontrol agent, as many parasitoids are, it provides a system for acquiring knowledge that should help with work on the more complex and potentially useful parasitoids.