Propylene glycol – a useful capture preservative for spiders for DNA barcoding

The usefulness of propylene glycol as capture preservative in pitfall traps, with the aim of using the captured spiders for DNA barcoding, was tested. For this purpose a laboratory experiment on the conserving and/or denaturing effect of propylene glycol on mitochondrial DNA (COI) was set up. For the experiment 110 specimens of the common and abundant wolf spider species Pardosa lugubris were manually captured, killed and incubated from one to four weeks in either pure or watered propylene glycol or 70 % denatured ethanol. Rates of successful sequencing, following a standard protocol, did not differ between samples incubated in propylene glycol and in the more commonly used ethanol. Thus, within four weeks, propylene glycol did not significantly denaturize mitochondrial DNA. In two field studies, pitfall traps with propylene glycol captured more spiders than traps with acetic acid. The effect was significant only in one of two field trials, but then consistent at three different sites and the three dominant spider families. Based on these results and our operating experience, we recommend propylene glycol as a capture preservative for (pitfall) traps to obtain specimens for DNA barcoding identification