Tuesday, 6 September 2011

A Strange Place for a Centipede

I had an unexpected encounter with a centipede today around lunchtime. I walked into the restroom and glanced down at the floor, where I found an inch-long centipede....and I was pretty excited. Unfortunately, it was dead, probably due to being stepped on. If nothing else though, that made collecting it easy for me. Have you ever tried to catch a fleeing centipede? They're ridiculously fast and not an easy catch.

After putting it in a plastic bag for safekeeping and eating some lunch, I headed off to the lab, grabbed my centipede ID guide, and threw it under a microscope.

It's a little intimidating, measuring out to about an inch long.

Earlier this summer, I attended an advanced naturalist workshop at the Edge of Appalachia preserve in West Union, Ohio that focused on the centipedes and millipedes (and isopods), which gave me the skills I needed to tackle Myriapoda identification. It was led by Bill Shear, from Hampden-Sydney College in Virginia, and boy did he know a lot about the Myriapods. He was kind enough to hand out some ID guides, which is what I've been using since then to figure out what all these leggy creatures are.


I'm always impressed with what I see when I put a centipede under the microscope. There are so many little structures that you completely miss out on until you magnify them, and they're super interesting. It's almost like you're looking at an entirely new animal.

That's a lot of legs. Centipedes have one pair per segment, while millipedes have two pairs per segment.

This centipede has 15 pairs of legs, and even more antennae segments--more than 35 (I haven't been able to get a final count yet). Not all of its legs are there: a good number broke off, including some of the posterior legs, which are important for identification purposes. An interesting fact: centipedes always have an odd number of leg pairs.

A close-up of the centipede's maxillipeds, which have fangs on the end of them that inject venom. You can see an oval outline on the left side of the maxilliped, which I believe is the centipede's venom gland.

Centipedes are predators: they're quick, and they also have fangs. These fangs are found at the end of the centipede's maxillipeds, which are actually a pair of modified legs (whoa!). The venom glands are contained within these maxillipeds, and work in short order to paralyze and kill its prey. Generally, a bite from a centipede from North America won't hurt too much since they're relatively small compared to a human. But there are some species in the southwestern United States and Mexico that are more dangerous, such as those in the genera Bothropolys, Lithobius, and Neolithobius, which are large centipedes.

The fangs and coxosternal toothplates, with teeth.

Due to the rough shape this centipede was in when I found it, I haven't been able to nail down its ID further than Family Lithobiidae. Currently, family designations for the Order Lithobiomorpha are in flux, with only two families officially recognized--Lithobiidae and Henicopidae. There's definitely room for improvement, and the group is waiting for someone to tackle it.

 Ventral view of the centipede, with coxal pores circled.

An interesting part of centipede anatomy (and a useful characteristic for identification) are the coxal pores, located at the bases of the posterior legs. These pores are connected to coxal glands, which are used for nitrogenous waste excretion.

Make sure to be on the lookout for centipedes and millipedes where ever you are: once you start looking, you'll start seeing them everywhere. The world of the Myriapods is surprisingly vibrant: chemical defenses, parental care, and even bioluminescence characterize many species. It would be a shame to ignore it.

References:

Shear and Weaver. 2007. Keys to the Centipeds of Virginia and Adjacent Regions.