Dear Isotope Geochemists,
In trolling through back emails, that I needed to attend to, the subject line “petroleum jelly” turned up. What in the heck are isotope geochemists doing with petroleum jelly? Well, my mind raced to ridiculous places—places where the minds of isotope geochemists
probably should not go! Especially when they are supposed to be working.
However, upon closer inspection, the message was even more “interesting”—petroleum jelly on ticks! Ugh. Years ago, my former Geophysical Lab Director Hatten S. Yoder, Jr., brought a bunch of ants into the lab for me to analyze. He was the Director, you
understand, well the former director, but a nice man, so I took the time to analyze them carefully. One of my colleagues remarked scornfully, “You’ll never get into the Academy if you spend your time analyzing ants.” Turned out he was right. I might draw the
line at ticks, though when I think about it--ticks feed on blood. We just analyzed some polar bear blood in the lab yesterday. (Do polar bears have ticks?)I can see food web and trophic discrimination concepts being challenged by the tick hypothesis, perhaps
resulting in new paradigms.
Seriously, I would attempt to wipe the petroleum jelly off of the ticks, as much as possible, using a kimwipe. According to Wikipedia, petroleum jelly is made of >25 C-hydrocarbons. Then I would rinse/soak the tick+petroleum jelly in dichloromethane: methanol
(9:1) for about 15 minutes. Look at the tick, the solution, and determine if you are damaging the tissue. Repeat if the solvent looks clear. You don’t want to over extract the tick, then you’d lose it’s lipids. As for picking off chitin, Arndt Schimmelmann
and others have shown that the d15N of chitin is very different from bulk tissue, because of isotope fractionation in making N-acetyl glucosamine. Stick with the whole tick tissue. (Yuck) Also, analyze a bit of the petroleum jelly itself. It might have a very
different d13C value that could be used to determine if it is still contaminating your samples. Last, with uncontaminated ticks, measure the C/N. Use that value in determining whether your petroleum jellied ticks might still have some petroleum jelly on them.
Do we need a tick isotope standard, like we have for leaves and collagen? I’ll stop now.
Are you analyzing the whole ticks or portions of the exoskeletal chitin?