Arizona Bark Scorpions
Over the past year I have worked on developing a research program involving scorpions in the Yuma area. The whole idea to pursue this topic was inspired by a student group presentation a few years ago in my biochemistry course. The group presented on the topic of black widow venom research into looking for components, if any, in the venom that could serve as safe and viable new sources of pesticides for the agriculture industry. Black widows are pretty much found all through the US so I thought what organism could we study that would be a niche that my undergraduate students could pursue at their own pace, contribute new information to the field, and be somewhat mysterious/exciting. The scorpion, of course!
UV light on scorpions
Growing up in Arizona we are told early on to watch out for the Arizona Bark scorpion because its sting is dangerous especially for the very young and old. Based on this presupposition we decided to go out into the desert, grab some scorpions, get venom, and develop an assay. The great thing about this area of research is that there is so much that can be discovered and determined. Plus the literature for scorpions in the southwest is pretty limited. So right off the bat my undergraduates were faced with ways to capture scorpions, house them, and to acquire venom.
Capturing scorpions is actually easier than we thought. Temperature and a UV light source are the key factors. They are typically really active at night than in the day – nocturnal. So on warm nights one can easily go out in the desert and find scorpions left and right – I wouldn’t recommend walking in sandals or other open-toed shoes. The UV light causes a particular molecule present in their exoskeleton (don’t know what it is but that is another question to study) to fluoresce (i.e. glow). Now keep in mind that under normal light conditions they are perfectly camouflaged with the ground, so if you switch your UV light to a normal light the scorpion becomes almost impossible to detect. To grab them we used long oversize tweezers or barbecue tongs and toss them into their own chamber/container. We found out early on that they are cannibalistic and need to be separated immediately otherwise all the big guys eat or kill all the small guys.
Venom extraction isn’t too difficult once a method has been worked out. One of my student researchers built from scratch a portable venom extraction device (i.e. it shocks the scorpions to get them to readily release their venom). One of the early things we considered was whether the scorpions needed to be anesthetized to keep them calm and to maintain a safe working area. In the end we decided it was just simpler and just as safe to tape down their claws and hold their tails with forceps. It was interestingly later discovered by my students that the device really only worked if the scorpions were sprayed with a saline solution – which provides better conduction of the current from the device. Questions my students are now looking at optimal rate of venom extractions and how much diet factors into venom production.
giant hairy
Barcoding and identifying scorpions in the area was more challenging than we initially thought. So most scorpions we were capturing looked like what we thought would be Arizona Bark scorpions (Centruroides sculpturatus or Centruroides exilicauda). As we discovered quickly the morphologies of the various species in the area are very similar especially if you don’t have a dissecting scope and a lethargic scorpion. We discovered quickly that the large ones we were getting (greater than 3 or so inches in length) appeared to match up best with Giant Desert Hairy (Hadrurus arizonensis) and possibly desert dune scorpions. This past year we had issues getting good clean DNA barcoding results. When we went back and investigated where there might be issues we found out that the paper we got the primers from had sloppily put together their methods area for their PCR (Valdez-Cruz et. al Biochimie 86 (2004) 387-396). I won’t go into the exact details of the information from that paper other than it was very sloppy and would only have been discovered by a reviewer had they actually BLASTed the PCR primers with the species.
Giant hairy found by co-worker
Resources are there if you know where to look. So scorpions are well studied but just don’t have the overwhelming literature and resources to start out working on them than compared to other organisms especially model organisms. The Biology of Scorpions by Gary Polis is an amazing resource. Unfortunately, Polis died in 2000 and really no one has put together as thorough a resource as he did. The book itself is out of print and costs about $300 to $700 to purchase a copy. Fortunately the NAU Cline library had a copy that we were able to borrow. We did come across a nice on-line resource called The Scorpion Files edited by Jan Rein out of Norway. This site provides a good database of North American scorpions. Interestingly enough through The Scorpion Files we came across information suggesting that the Arizona Bark Scorpion is not as lethal as thought due to possible issues with actually identifying the scorpion. The giant hairy had a higher LD50 than the bark?! Awesome.
Overall scorpions in Yuma have proved to be a great resource to do scientific research with undergraduate students. It provides them the opportunity to tackle difficult questions and to make discoveries that no one has reported yet.
One of our venom factories
Yuma Scientist 