Category Archives: Science

Shaving your legs to deter ticks

Colin Purrington Photography: Green steps &emdash; girl-with-shaved-legsPeople shave their legs for a variety of reasons: to look younger (artificial neoteny), to look less like men, to show off tattoos, to show off muscle definition, to improve athletic performance (less drag, plus fools brain into thinking you’re going fast), to facilitate post-accident wound cleaning (cyclists), and because shaved legs induces a pleasurable sensory overload (at least to some). But can shaving also protect you from ticks? I became curious this week after watching a tick crawl up my leg (photograph below). I was really surprised to discover that no experiments on this topic have been done, but did succeed in finding three relevant snippets on the internet (two from mountain bikers, one from cross country runner):

“One thing that helps is shaving your legs. Not a foolproof way but I would say it reduces them critters by 80%, maybe more. I noticed that when my wife and I were out and she had none, I had around 14 that day.” source

“As an experiment I shaved my legs before riding point to point at lbl with KRS and a few others. It was tick season. After 40+ miles of riding I had 1 tick on my sock. Along the way KRS pulled OVER 15 ticks. We rode the same route at the same pace. I’ve kept the hair off ever since.”  source

“I’d say its mostly impractical. Although, I know many trail runners (including myself sometimes in the summer) do it to prevent ticks from attaching.” source

But, hey, maybe the anecdotes are just that, and hairy legs actually deter ticks in some way. 

Colin Purrington Photography: Spiders and ticks &emdash; American dog tick (Dermacentor variabilis)

But it makes sense that shaving would deter ticks. The first is obvious: ticks can grip hair, so if you are hairless (and are wearing shorts, skirt, or kilt), they can’t climb as fast (they are headed for your groin, by the way). The second is that you if you have hairless legs you can most likely better feel them crawling up your legs. I.e., all eight of their legs are touching your skin’s sensory array (or all six of their legs if they are larvae). The third is that when you remove all your leg hair you are removing a lot of sensory distractions caused by wind (experiment on swimmers), and thus you can zero in on things crawling on you. Indeed, all of these mechanisms might touch on why we evolved to be relatively hairless in the first place

So about the experiments that need to be done …

An easy way to assess would be to count numbers of ticks on a group of people out for a walk, some of whom shave. But at least in the United States, that would break down to men versus women, and males smell worse than women and thus might attract more ticks, regardless of hirsuteness. And men are usually larger, so there’s the surface area thing that goes against us, too. So it would be far better to recruit a group of hairy-legged women and ask them to shave just one leg, then march around a field known to have ticks. Participants would tie white bandanas around their upper thighs to arrest the ticks before they got too intimate, then count tick numbers. But finding enough women who don’t shave might make the protocol hard to follow (again, at least in the United States). So perhaps using a group of guys would be more feasible. An ideal group might be a men’s college swim team right before the season begins. Just ask the coach to donate their legs for science. Would be an easy publication for a day’s work, and the experiment would be crazy photogenic. Plus great team-building exercise. Would get the college on the evening news I’m sure. 

A simpler design might be to just have a motivated group of people (perhaps students in a field ecology course?) conduct tick races on shaved, unshaved legs. You just need to start them on the ankles and have participants hold still while the ticks make their ascents. That would be equally photogenic and fun, I think. And to get at the perception part, you could have blindfolded participants that would be asked to identify location of ticks crawling up legs (with controls being placement of non-ticks on ankles, perhaps).

The proposed experiments might seem horrific, but just the for record, I once swam around the edges of a small pond just to see how many leeches would attach to me. I recall that my father challenged me, and that we were going to see who could win. I don’t remember who ended up with more. (Yes, that was a nerd x testosterone interaction effect.)

If somebody does go ahead and conducts this experiment — and if the effect is huge (my guess) — the next step would be to alert the folks at the CDC so they could add a shaving recommendation to their tick page. The reaction to that would be entertaining.

Posted in Biology, Education, Gardening, Photography, Science | Tagged , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

Golden-backed snipe fly

Here’s a male golden-backed snipe fly (Chrysopilus thoracicus). The species is strangely understudied. For example, the adults don’t seem to feed, or at least do so very rarely or in complete privacy. I’ve read about them eating aphids, but that’s secondhand at best. The family (Rhagionidae) is full of predaceous members, so it’s certainly possible, but it’s still odd that we don’t really know for sure, and there should be at least a single photograph of them eating something. I wish somebody would PCR their gut contents to settle the issue. Not much is known about the larvae (image), either, other than that they can mature in rotting logs (Johnson 1912). 

Colin Purrington Photography: Insects &emdash; Male Chrysopilus thoracicus on leaf

I’ve photographed this insect twice before. One was floating on top of water, the other was sporting a severely dented eye. They are easy to photograph because they refuse to budge even when the lens gets within centimeters.

 Colin Purrington Photography: Insects &emdash; Golden-backed snipe fly (Chrysopilus thoracicus)

Colin Purrington Photography: Insects &emdash; Golden-backed snipe fly (Chrysopilus thoracicus) with dented eye

Snipe flies (Rhagionidae) are so named because their unfurled probosces resemble snipes (long-beaked birds in the Scolopacidae). Not everyone buys that naming explanation, though. Some insist it’s because of their agile, predaceous habit (i.e., they are good at sniping).

Posted in Biology, Photography, Science | Tagged , , , , , , , , | 1 Comment

Conference poster full of tips for creating conference posters

In case you need a quick guide to making a conference poster, here are two versions of my poster of poster tips. They have content overlap, so just choose the layout that pleases you. More details below the images.

Poster example (Colin Purrington's)Advice on designing scientific posters

Both posters are descendants of a document I created circa 1997 for my evolution students at Swarthmore College. The bottom one is available as a PDF if you want to print an actual poster of it — which I highly recommend if you are assigning a poster project for your class (students don’t like reading the website, below).

My full tips are at Designing conference posters. I created the website for my students, too, but eventually made it public in case it might help make the world’s poster sessions more enjoyable and their posters easier to understand. Please share with your friends.

Posted in Education, Science | Tagged , , , , , , , , , , , , , , , | 4 Comments

Pyractomena borealis

Pyractomena borealis (Lampyridae) exploring the surface of trees on a warm winter day in February. The third photograph shows how they can retract their head under the carapace like a turtle. At first I thought they might be foraging — they are highly predaceous, and hunt slugs and earthworms (in packs!) by first injecting them with paralytics. But they might have just been looking for a place to pupate, because it’s time for that. Adults will emerge sometime in early Spring to be the first fireflies in the area. The larvae are bioluminescent, too. The hypothesis about why the larvae glow is that it evolved first as an aposematic trait in larvae, warning mice and toads of the presence of lucibufagins, steroidal toxins in the hemolymph. It’s thought that the adult habit of using flashes is secondarily evolved, millions of years after the larvae evolved the ability to glow. The ability of larvae to glow even predates the origin of the Lampyridae, I gather. For more enlightening details, see Branham and Wezel (2003)Stanger-Hall et al. (2007), and Martin et al. 2017.

Colin Purrington Photography: Insects &emdash; Pyractomena larva

Colin Purrington Photography: Insects &emdash; Pyractomena larva

Colin Purrington Photography: Insects &emdash; Pyractomena larva

Posted in Biology, Photography, Science | Tagged , , , , , , , , , , , , , , , | Leave a comment

Green slime mold

Plasmodial slime molds (class Myxogastria) come in many colors (yellow, purple, orange, blue, red), but rarely in green, so this find at a local park intrigued me. I found it February 23 under the bark of a decaying pine tree in Springfield, Pennsylvania. There were no fruiting bodies. 

I’m curious what species it is (let me know, if you know, please), but would love to know why it’s green. Here are three possibilities (I have more, if they fail): (1) the slime mold has formed an association with an algae or cyanobacteria, (2) the green pigment replaces the yellow pigment under some conditions, and (3) this is a species of slime mold that’s green but not frequently encountered so not part of books and online keys. The latter two are most likely, but the first was interesting to consider … see below if you have a few minutes.

Colin Purrington Photography: Slime molds &emdash; Green slime mold

(1) In regards to algal associations, I looked into this option first because the green appeared so exactly like that of alga. Of course, I’d never, ever heard of algal/myxomycetes symbiosis, so I looked into this possibility very, very quietly so people wouldn’t spew coffee out their noses. But I eventually found an article on the topic (Lazo, W. 1961.Growth of green algae with Myxomycete plasmodia. American Midland Naturalist 65:381-383). Here’s the summary from his abstract:

“Three species of Chlorella were able to enter into full associations with Physarum didermoides and Fuligo cinerea, forming green plasmodia in which the algae multiplied in light.”

The above association was under special laboratory circumstances, however, notably using slime molds that he’d purged of their bacterial partners with antibacterials. But even though the conditions might seem artificial, I suspect slime molds have a built-in ability to purge themselves (and surrounding substrate) of bacteria. And algae are easily found growing in soil and on dead trees, so it’s very likely that slime molds and algae come into contact in the wild regularly. And algae (or at least some species like Chlorella) can grow heterotrophically in the dark (e.g., on sucrose) and still remain green. This latter fact is important because I found this slime mold under rather thick bark, and I doubt it received any appreciable light. 

Indeed, some plasmodial slime molds appear to even specialize on the algal biofilms growing on wood (reviewed in Smith 2007). One mentioned by Smith is Barbeyella minutissima, which I Googled and found this:

“In addition to liverworts, Barbeyella is found socialised with monocellular algae. It is assumed that the protoplasmodium phagocytizes either the algae or the bacteria on their surface.”  — Global Fungal Red List Initiative

Smith also mentions that a Didymium iridis plasmodium harbored an alga (Trebouxia sp.) for months in a laboratory culture (Keller and Braun 1999; I couldn’t obtain to read).

So if the above scenario does occur, perhaps it’s similar to the trick noticed in some Dictyostelium spp. (cellular slime molds, in the class Dictyostelia), which known to carry around bacteria, which they can release onto substrates that are favorable for bacteria (i.e., they farm). 

Anyway, I don’t have a microscope to examine the slime mold for algae or cyanobacteria, so the above is just mere speculation. I suppose I could spray it with a good herbicide, but that’s seems cruel.

(2) The green color might simply be a pigment change. I don’t know much about myxogastrid pigments, but apparently moisture, light, starvation and other environmental factors all cause color changes. But I could find only a few papers discussing a green pigment. Here’s the best line from one of them:

“The yellow pigment of P. polycephalum has been found to be an excellent natural pH indicator (Seifriz & Zetzmann, 1935). In a neutral medium, the natural indicator is yellow, in an alkaline medium it is bright green, and in an acid medium it is deep reddish orange.” Seifriz and Russell (1936) [emphasis added]

[The citation of the referenced paper, which I couldn’t obtain in full, is Seifriz, W., and M. Zetsmann. 1935. A slime mould pigment as indicator of acidity. Protoplasma 23:175-179.]

The above fact is really interesting, but don’t know why a decaying pine log would become alkaline. I couldn’t find any good research on the topic, but perhaps I missed it.

The more interesting scenario is that a pigment gene is mutated. Mutations happen, though it’s rare enough that I don’t think it’s likely. 

(3) It’s of course most likely that there’s a species of green slime mold and I’m simply ignorant of its existence. Maybe it’s not even a slime mold.

(4) Or it could be oobleck


Some more pics:

Colin Purrington Photography: Slime molds &emdash; Green slime mold plasmodia

Colin Purrington Photography: Slime molds &emdash; Green slime mold

 

Posted in Biology, Photography, Science | Tagged , , , , , , , , , , , , , , , , , , | 2 Comments