Gypsy Moth Caterpillar (Lymantria dispar) ©Pawel Bieniewski
This week, a very knowledgeable and friendly, past-technician visited the university to train me in a some new techniques, as well as familiarize me with techniques I had seen but was not very familiar with. There were some long days and nothing seemed to work quite like we wanted (the themes of the week were: hindsight is 20/20 and everything takes longer than you expect the first time). Despite these small setbacks, I learned a LOT! Some of the techniques we went through were: freezing and thawing cell lines, ways to determine the titre of a virus (we did plaque assays and endpoint dilutions), infecting cell lines with baculovirus, obtaining virus from cells and caterpillars, dissecting caterpillars and recognizing organs, the function of the LdMNPV (Lymantria dispar multicapsid nuclear polyhedrosis virus) the baculovirus we are studying, and I got to show off my cool new skill of operating the TEM microscope to view some of the virions.
Gypsy Moth were introduced to Massachusetts in 1869 by those who were trying to crossbreed it with the asian silkworm, which was not thriving in the North American climate. Lacking natural predators, the gypsy moth quickly spread through the Eastern coast and have had a few major outbreaks leading to tree defoliation, especially in Pennsylvania (where I now live and work!). I have heard that in years where the outbreaks are bad, when the gypsy moth larvae hatch they literally rain from the sky (the neonates engage in a behavior called ballooning which is when they let out a thread of silk and let the air carry them, this is an attempt to spread out the population and reduce competition for food and space).
BEWARE ZOMBIE CATERPILLARS! Not exactly, but close enough :). It is both cool and a little unnerving...the baculovirus we are studying causes changes to the egt gene (the gene that involves climbing behaviors) in the infected larvae to make the larvae crawl up the tree when they are about to die from the virus and then the caterpillar bursts open and spreads the virus over the widest possible area to increase virus proliferation...very cool, but weird...
Other neat things: gypsy moth females are really large and flightless and thus the males have plumose antennae (the really fluffy feathery antennae in the second picture) which help them catch the pheromones of the females and track them down!
One last thing I learned about some caterpillars (gypsy moth is one) in the entomology course I am sitting in on to learn more about insects, which are more amazing the more I learn about them, is that some plants when stressed by the damage caused by feeding caterpillars release a chemical which attracts a parasitoid wasp, which comes and lays an egg in the caterpillar. This egg grows and uses the caterpillar as a food source until it is ready to hatch and then it breaks out of the caterpillar (killing it) and continues on its way. This is the plant's natural pest control. Awesome, if a little grisly, right?!
What About You? What is your favorite insect and why? Do you know something cool about insect behaviors or illnesses? Feel free to ask any questions you might have about gypsy moth as well, I will do my best to answer them.