Saturday, September 12, 2009

Antifreeze and Rancid Snails

I should probably issue an advisory with this entry. I thought about including images, but they would be too graphic even for mature audiences. Suffice it to say that science is often (maybe even usually) a dirty, toxic business. I learned that in a convincing fashion over the last two weeks or so while I was processing raw pitfall trap samples.

You may recall that when I first began work here at the University of Massachusetts I was sorting pitfall trap samples from the 2008 field season. This year’s traps were even greater in number since the students sampled two watersheds instead of one. Last year’s samples had already been placed in alcohol, and were about as “clean” as one could expect. My task over the past couple weeks was to render this year’s specimens workable.

Scientists using pitfall traps face several challenges. First, you need to be able to kill the trapped animals quickly, before they can maul each other. Second, you need a fluid that will not readily evaporate over the trapping period. The trapping interval in this case was one week. The solution, in a literal sense, was propylene glycol.

Propylene glycol is the major ingredient in antifreeze. One of the problems with it is that it is a sweet substance that is attractive to vertebrates like raccoons and other wildlife. While antifreeze was once dyed green, it is now often dyed pink so as to help discourage its consumption. Another problem with this compound is that it has a really corrosive effect on some invertebrates. Beetles trapped in the pitfalls often begin to disarticulate. Snails and slugs quite literally melt. You can only imagine the putrification factor. Actually, you can’t imagine that.

My supervisor is a graduate student who is simply amazing. She has a great deal of responsibility, but never asks anyone to do something she wouldn’t do. So, she cleaned the samples from one watershed, and I cleaned the samples from the other. Neither of us ever ended up passed out, or throwing up all over everything. Quite a feat, especially considering that ventilation in the lab leaves something to be desired, and the odd salamander or frog that was accidentally trapped only amplified the odor. The worst was a long-tailed (or “masked”) shrew, Sorex cinereus, that just about brought me to tears and seriously threatened to initiate my gag reflex.

Still, the slug slime was probably the most aggravating, not as much for the smell, but for the fact that it blocked the screen of the sieves we were using to filter the specimens from the antifreeze solution. Pouring out a sample with slugs meant you had debris everywhere, not concentrated in the center of the sieve where you wanted it.

The protocol was to check to make sure the label inside the container (urine specimen containers, how appropriate) matched the label on the outside. Then you wash the label over the sieve and set it aside. You pour the contents of the container into the sieve, and then rinse it gently with water from a squeeze bottle. Next, you invert the sieve, give it a sharp tap to dislodge as many specimens as possible into a bowl, and rinse the rest off with 70% ethanol (ethyl alcohol). Lastly, you pour the contents of the bowl back into the container (after rinsing the container). Did I mention that small quantities of detergent are also used to break the surface tension of the liquid agent in pitfalls? Some samples contained enough suds to do a load of laundry.

Ah, but that is all behind us now, and I can hardly wait to get a better look at the actual specimens. The pitfall traps were done a week later than last year’s traps, and the difference was quite dramatic. All the spiders in this year’s samples were much, much larger than those in last year’s! More beetles, too, it would seem. Now, if I can just get all my food to stop smelling like rancid snails….


  1. Ewww. And interesting as well. Sometimes I'm glad my science is mostly digital, with the occasional exuviae thrown in to liven things up.

    I wouldn't mind some pictures, but no Smell-o-vision, please....

  2. Hmm, not exactly the best thing to read around dinnertime. But having picked up numerous empty beer bottles with dead,decaying slugs and even some dead shrews,I know what you are talking about. It sticks with you.

  3. I would sooner drink a pink liquid than a green one. I guess I just don't get how that's supposed to discourage anyone (especially a color-blind pet) from imbibing the propylene glycol. Which incidently, I happened to find on the ingredient list of some pancake syrup last week! Perhaps HFCS isn't sweet enough?

  4. Um, I think I'll postpone lunch for a bit while I wait for the mental smell to dissipate.

  5. LOL! Sincerely sorry, folks, but thank you for the empathy, Kirk; Nice piece of trivia on pancake syrup, sort of, Jomegat. I'll make it up to all of you shortly:-)


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