Halloween is just around the corner, but it seems like some members of the animal kingdom have already started playing ghoulish tricks on one another.
Scientists recently discovered something that was causing European gypsy moth caterpillars to behave very strangely. The caterpillars were infected by a deadly baculovirus, and with their last bits of strength, they did something that would be out of the question if they were healthy: they climbed out onto the very highest leaves of their tree in the middle of the day.
There, their diseased bodies split open, raining infected caterpillar guts onto the leaves and branches below. The death ritual is so bizarre, that scientists started using the term ”tree top disease” to describe the virus that caused it.
In a recent issue of Science magazine, researchers reveal the cause of this odd final act: a specific viral gene that drives infected caterpillars to die in a way that offers the best potential for spreading the virus that killed it…just like a zombie (ScienceDaily).
The virus “ends up using just about all of the caterpillar to make more virus, and there are other genes in the virus that then make the caterpillar melt. So it becomes a pool of millions of virus particles that end up dropping onto the foliage below where it can infect other moths that eat those leaves,” study co-author Kelli Hoover told National Geographic.
According to researchers, this discovery provides evidence that genetic characteristics of the host help determine a parasite’s effect on its behavior.
Because the baculovirus that causes this strange behavior only affects invertebrates, scientists think that it could be a useful tool in controlling invasive caterpillar populations like the gypsy moth.
A healthy gypsy moth caterpillar feeds at night and either hides in a tree’s bark crevices during the day or climbs down the tree to the soil to avoid predators. For the virus behind tree top disease, there is a significant advantage to a caterpillar dying in the middle of a leaf within the canopy of the tree rather than in a crevice. The dead caterpillar liquefies, releasing millions of virus particles into the environment where they can spread throughout the tree and contaminate other gypsy moth larvae. This virus is specific for the gypsy moth, and consequently will not impact any other insect, animal, or plant in the treatment area. (ScienceDaily)
The Northern Research Station and the USDA Animal and Plant Health Inspection Service (APHIS) are partners in producing the virus for states, the National Park Service and other agencies to use to control gypsy moths.
Image Credit: Flickr - GollyGForce