Video shoot #2

Our second attempt at capturing high speed video of the stinging motions went far better than our first attempt. We managed to capture relatively high consistency in the stinging motions in only seven ten-second runs with few hiccups. We did encounter one problem, but also fixed a former one.

First, the new problem. There was what looked like a piece of dust on the lens, but was discovered to actually be on the CCD. This was fixed by cleaning the CCD with compressed air.

Second, the fixed former problem. Originally, we put the scorpion on ice to make them docile, but this resulted in a long warm-up period. This time we managed to secure the scorpion without cooling it first. This was slightly more difficult than before, but eliminated the warm-up period, thus allowing us to start shooting earlier.

I uploaded the best of the videos to YouTube:

Here are some pictures:

More notes on scorpion keeping

It rained last night and I noticed a large increase in the activity of the two captive scorpions. They appeared restless and agitated; they must have been able to sense the moisture in the air.

Mirror box v2 test

After having redesigned the trigger mechanism in the mirror box (see Revised trigger mechanism) John and I tested it on one of the two remaining scorpions.

It performed better than expected, getting us a sting 100% of the time. Because of my confidence in the new trigger, I have scheduled another video shoot for this Monday (July 30). Here are some pictures of the test:

 

Revised trigger mechanism

After the almost complete failure of the original trigger mechanism, some revisions were in order (see Video shoot #1 for the issues).

As mentioned in Revised trigger mechanism design and scorpion habitat, the scorpions responded violently to being brushed or poked with a paintbrush (I assume because of the large number of contact points from the bristles). Therefore I decided to scratch the foam and pushrod design and switch to a paintbrush on the end of a swingarm. Here are the designs and pictures:

Because the electronics were unchanged, all I had to change in the code was the behavior of the servo in the Arduino IDE, and the commands in the Processing IDE. Here are is all the new code:

Version 1.8 (click to view, right click and “Save Link As..” to download) of my Arduino software takes commands via serial as usual, but instead of only being able to write the received angle to the servo, it can now receive “activate” and “retract”, which cause the servo to vibrate and stop respectively.

Version 1.8 (click to view, right click and “Save Link As..” to download) of my Processing code still allows for angles to be assigned to various buttons, but now also has two new buttons: Activate and Retract. Here’s a screenshot of the GUI (some buttons are currently unused):

MRI imaging

Today John and I took the scorpions to St. Joseph’s hospital for the MR (magnetic resonance) imaging.

After considering various ways to kill the scorpion we had selected to image (subject cannot move during imaging), I decided to have the scorpion anesthetized so that it would be easier to handle, then made an incision across its back, right behind the eyes to sever the spinal nerve. We then proceeded to place the dead scorpion in a 50mL vial filled with water and insert it into the MR machine.

Because of the tendency of the scorpion tail to bend, we had some difficulties getting a clear image. We decided that, as we were primarily concerned with getting images of the structure of the tail, to remove it an image it alone (because the tail is not very wide we could put it in a much smaller vial, thus keeping it straight). This improved our images but lead us to discover that we were not getting a strong enough signal from the internal structures of the tail. This was due to the fact that an MR machine sees hydrogen atom nuclei (protons), and as our subject was suspended in water, we were getting a large signal from the water surrounding the tail, thus masking the weaker signal originating from the tail itself (akin to taking a picture of something with the sun behind it). To fix this we switched the water for a perfluorinated fluid (a hydrocarbon-like molecule where all hydrogen atoms have been replaced with fluorine) atoms that does not have a magnetic signal.

After all of this we were finally able to get a clear image. The high resolution scanning was started with an estimated time until completion of six and a half hours.

Notes on scorpion keeping

Given that my first group of scorpions did not fair well in captivity (dying or acting very lethargic) I have been closely observing my new group and have noticed that when fed crickets until they will eat no more (rather than giving them a cricket on regular intervals (one or two days) as with the first group), the scorpions remain very active and healthy in appearance.

Revised trigger mechanism design and scorpion habitat

After the unsuccessful video shoot on July 9, it is clear there need to be some revisions:

• Use a paintbrush attachment as paintbrushes seem to be quite good at provoking a sting (as mentioned in the Mirror box construction post).
• If the scorpions remain oblivious to paintbrush strokes/pokes use electrical shocks in tandem with the paintbrush strokes/pokes in order to cause the scorpion to associate contact with the paintbrush with electrical shocks. The director of my project, Dr. Stephen Helms-Tillery has assured me that this method is quite affective for getting subjects to be more aggressive towards something (in this case the paintbrush).

As for the scorpions, it has proven difficult to keep the them alive (at least in their small, separate containers). After mentioning this to Dr. Steven Helms-Tillery he agreed to take a few of the scorpions and put them in a proper aquarium.

Third successful night scorpion collecting

It had rained the previous day and night, and given that my last successful search was the day after a rain I decided to search again tonight. Although the weather was not hot (the scorpions prefer hot nights) I found three good sized giant desert hairy scorpions in a short time. Two were very large and one was large enough to keep.

Given that now both my successful searches have been conducted after rainfall I can at least conjecture that the activity of the giant desert hairy scorpion is increased by rainfall (all of my searches on nights not after rainfall have been unsuccessful).

Video shoot #1

Today we attempted to take the high speed video (250 fps) and encountered several problems.

First, we had to put the scorpion on ice to get it to stop moving. This works very well and does not seem to injure the scorpion, but it does take a very long time for the scorpion to warm up sufficiently to sting anything (about 30 minutes). This is a problem because the we only have access to the camera for a limited time. Second, the scorpion would not respond to the soft foam trigger with more pinching. Only irritating it with a pen on its head or back would induce a sting. And finally, we had a slight issue with camera view and depth of field. The high speed camera did not have a very wide angle so it had to be moved several feet away from the box. This caused us to lose some depth of field, but eventually we got an acceptable view.

Notes:

I have several thoughts on the issue of the scorpion not stinging. The first is that scorpions are nocturnal. This may cause them to be lethargic during the daytime. If this is the case, we may have to do the video shoot in the evening or night (from my observation in the wild, the giant desert hairy scorpion becomes active right after nightfall, or at about 9:30 during the summer). Another possible cause for the scorpion’s lack of aggression towards the foam block could be due to how it is chilled before being placed in the harness. Although, as I mentioned above, it the icing does not seem to harm them in the long term, it does seem to sap their energy right afterwards. This could possibly be some type of temperature shock. However, we have little choice in the matter as handling a live and warm giant desert hairy scorpion is quite difficult. The last, and possibly most likely reason for the scorpion not stinging the foam is that the giant desert hairy scorpion has very large pedipalps (claws). For most scorpions (not all!) the general rule is that the larger the pedipalps, the weaker the venom. This is because a scorpion with large pedipalps is able to subdue its prey with its pedipalps alone, where as a scorpion with smaller pedipalps must rely more on its venom (and example being the giant desert hairy scorpion (large pedipalps, mild venom) versus the Arizona bark scorpion (tiny pedipalps, most venomous scorpion in North America). Therefore, the reason for our giant desert hairy scorpion not stinging is because it instinctually relies more on its pedipalps than stinger (as noted above, it would pinch the foam block, but not sting it). If this is the case, we must find some means of stimulus that startles it enough to provoke a sting.

Mirror box construction

Today, John and I constructed the mirror box and trigger mechanism.

The wood was precut to spec (see Initial mirror box design), so all we had to do was drill and countersink the wholes. After finishing the woodwork, we then had to figure out how to mount the mirrors at 45 degrees. I suggested using 90 degree corner brackets and bending them to 45 degrees. This worked very well. We then attached the mirrors to the brackets with velcro for easy removal. Next I attached the restrainment mechanism I had prototyped earlier (see Initial restrainment mechanism design) with hot glue to the bottom of the mirror box. We then attached the servo and pushrod and connected all the electronics (see Initial sting-trigger mechanism design). After finishing all this we tested it.

Result:

Although the entire system (mirrors, electronics, etc.) ran without a glitch, there was one issue: The scorpion would not sting the foam block. When tickled with soft foam or a paintbrush however, the scorpion responded by stinging it violently.

Modifications to be made:

Switch out the hard foam for soft foam, and if that doesn’t create a stinging response, try a paintbrush (entire physical setup will have to be changed for paintbrush, which is why I chose to try soft foam first).