Sorting millipedes with Jackson Means

guy in a lab
Jackson Means in the Marek lab holding a millipede habitat. Photo by Corrin Lundquist.

If you ask a fifth grader what they know about millipedes, you’ll likely get an answer that sounds something like, “millipedes are the same as centipedes” (they’re not), or, “millipedes have a million legs.” In reality, the leggiest millipede—or any animal, for that matter—only has 750.

If you thought like a fifth grader, you’re not alone.

“The thing about millipedes is that nobody has really worked on them at all,” said Jackson Means, a Ph.D. student studying entomology in the College of Agriculture and Life Sciences. “Our lab is the only one in North America that's dedicated to millipedes.”

Means works in the lab of Paul Marek, an assistant professor in the Department of Entomology in the College of Agriculture and Life Sciences. One of Dr. Marek’s main focuses is discovering and describing new species of millipede. By working in the lab and studying millipedes, Means has become an expert about an arthropod that very few know anything about.

What is known are the three characteristics that set millipedes apart from other arthropods like the centipede. First, they have four sensory cones at the top of each antennae; second, they have aflagellate sperm; and lastly what sets them apart from the centipede, disproving the fifth-grader preconception that they are the same insect, is that they have a different number of legs.

Millipede on a hand.
Iron worm millipede. Photo by Corrin Lundquist.

Millipedes have four legs per body segment, whereas centipedes only have two. Not only do millipedes have more legs, they can fit more legs into a smaller body. Millipedes are also detritivores, meaning they eat dead leaves, whereas most centipedes are carnivorous and feed on other insects.

What, then, eats a millipede?

“We assume it’s big birds, [but] we don't actually know who feeds on them,” Means admits. “I assume this because one, they have to be a visual predator because it's a bright color that's out during the day, and two, they have to be large enough to survive a cyanide dose and not die. One [species of millipede] Apheloria, actually produces enough cyanide to kill 18 pigeons, so it has to be a pretty big animal.”

Though Means is an expert now, he wasn’t always interested in pursuing science. He began his education at a small liberal arts school in Ohio with the intent to pursue film.

“They have this rolling admissions where you would go for your orientation on certain dates, and I was on the last date,” he said.

The film class he wanted was already full, so he was put into “Global Problems of the World Today,” a freshman seminar where they looked at a different global issue every class from air pollution to environmental dumping. Means was therefore exposed to all of these issues every day, making him attracted to the idea of “saving the world” from these problems, which led to his undergraduate focus in environmental studies.

As an undergraduate, he performed research which sparked a real interest in science and plants. After college, he worked at the Center for Historic Plants at Monticello, where the real stars were the insects, specifically, the assassin bugs.

“They’re super variable in their color, just really crazy looking, and they’re T-Rexes of the insect world. The big one is the wheel bug, and they actually have the worst bite in North America,” Means said, as he lit up. “Those are really fascinating [because] they were all over the place and I didn't know anything about them.”

This fascination soon developed into a passion for insects, which naturally led to an interest in pursuing a graduate degree. Virginia Tech was the first school he visited, and at the time he visited, he was interested in the plant pathology program. But then a spur of the moment decision on the car ride home to Keswick, Virginia, led him to accept a position as a honey bee researcher in a Master’s program.  

So how, then, did he make the transition from bees to millipedes?

“While I was doing my master’s, I got really into collecting insects and into taxonomy,” Means said. “That was just a hobby that I just got into because we didn’t have a taxonomist. The semester I got my master’s, we hired Dr. Paul Marek.”

Dr. Marek is a systematist who works to understand how different species are related to each other in terms of evolution. Systematics and taxonomy are closely related fields and often work in conjunction with each other, naming and describing new species and then determining where they fit evolutionarily.

In addition to learning about the arthropod as a whole, Means is also working on a revision of an entire genus of millipedes, Nannaria. “The Nannaria revision [will] be equal parts describing species and trying to understand why there's so much gonopod variation.” Gonopods are the male sexual organ in millipedes and evolve from a set of legs. Females have membranous sacs called cyphopods.

“Traditionally it's always been thought of as lock and key, basically the gonopods are the key, and the cyphopods are the lock. The problem with that is that the key is variable and the locks are the same on everybody.” Part of the Nannaria revision will be trying to figure out why gonopods change shape between species in the first place. Some theories point to female selection and others point to the genes.

The second part of what Means is working on is trying to figure out why another species, Appalachoria, has so much color variation. “I'm figuring out areas of high and low color variation, so someone in the future could do predator studies, because we think it's related to predators. If there's a high predator pressure, then you think there would be a pressure to not vary from that color, because it's a warning signal, and if you vary from it, you might get eaten. If there's low predator pressure, you can be any color you want.”

The third aspect of Means’ thesis is a paper that establishes that the range for a specific millipede. The Laurel Creek millipede occurs in a less than a half km squared (0.48 km2) strip vertically down Laurel Creek on the Blue Ridge Parkway, and nowhere else in the world.

The work is essential, especially in southwestern Virginia, where mountaintop removal is a common method of coal mining. When a mountaintop is removed, an entire species could have been wiped out without ever having been named or studied.

“The big problem is that with a lot of these millipedes, they live in just that one spot," said Means. “We want to avoid what's called anonymous extinction, which is where something goes extinct before we've ever named it or described it, it doesn't exist yet.”

Means began his journey to becoming a millipede taxonomy expert by first developing a passion for science that funneled into classifying millipedes, but this certainly isn’t the only thing that sustains him. He finds the feeling he gets when he discovers something like a new species is one of the big motivators to keep researching the leggy arthropod.

“I just find them fascinating and that people haven't really looked at them, and I think they deserve, just like any other group of animals, to be studied and understood.”

Article by Corrin Lundquist while participating in ENGL 4824: Science Writing in Spring 2017 as part of a collaboration between Fralin and the Department of English at Virginia Tech.