The only time I have seen the black spots on the legs was from mites having caused the joint to become black by eating the rest of the limb from the inside. It sort of appears as though it has rotted. I treated mine for mites and it stopped. They did regain the ability to use the leg again, though it was not until the last molt. I have one adult who it happened to and he can't use it at all, though he wont molt again either. NOTE: I have only seen this black occurance at the joints.
I did notice that once a leg ceases to move, the scorpion tends to pass away very shortly thereafter. I had one that had been unable to move the right rear leg for about a year (the longest lived in this shape I have found). He showed up the other day upside down and yes...gone with the wind. I have also noticed that I have not had this occurance in any desert or scrubland scorpion species, but rather the high humidity, rainforest only. Do you think this could perhaps be caused by something in the humidity levels or have you noticed this tendency in deserts/scrubland scorps as well? If it is with the humidity levels, as I have noticed, I'll probably drop humidity some with raises only for breeding periods to see if this lengthens the lifespan of the scorps in question. As it seems, the past year, I have kept some P. imperator at nearing 65% humidity (incl. the one recently deceased). Others that died sooner had humidity in the 80s range. I can hardly imagine an environment that consistently stayed at that sort of humidity level. I think it would be virtually impossible. Even for Southern Africa, considering the temp changes that occur there. I would suspect the humidity to drop by at least 10-15% during the winter.
Funny you should mention that ED. I have only had it happen with desert species. I lost two of my 3 H.arizonensis this way and 2 of my M.martensii this way. I have been just assuming that it is more common when the scorpion gets old for them to injure their leg. The M.martensii are buthids so of course don't live as long in the first place. The H.arizonensis who knows how old they were. They did last longer than the M.martensii with the same type of injuries though.
Interesting theories though. Anyone else who has kept a number of species notice anthing similar to what Ed and I are seeing?
Last year I had something mysterious happen to many of my desert species, including several Hadrurus, Androctonus, Parabuthus, Opistophthalmus and Vaejovis. I can't say the syptoms were exactly as you're describing, but some did seem to lose the ability to move some of thier limbs. They also seemed to lose control of their muscles and seemed to twitch uncontrolably. Normally, I would chalk this up to exposure to some sort of toxin, but my many desert (and other) tarantulas, non-desert scorpions, and a selection of other arthropods including mantids (whom I normally consider to be the most delicate) are kept in the same area, fed the same prey, and watered with the same water were uneffected. My best guess is that my scorps developed some type of fungal infection in my basement (where the collection was moved last year) that only attacked the desert scorps.
That seems most interesting, Wade. I am curious of what may be causing these things to occur with scorpions. Also, I have only noticed it to have the initial symptoms and occurance possibly being prone to attack them during warmer months as well. I have not noticed it being present until the warmer months arrive. Perhaps it could be a contrast in humidity level and temp or simply the change being too rapid and the legs, being small portions, not having the opportunity to adjust? I know the symptoms I had occur have never happened to a scorp I raised, but rather the scorps I have purchased as adults. It might be that they combination of the two cause a slow rotting at the joints, much similar to wood. I wonder if there might be a way to prevent this occurance, as there is in wood. All of my scorp's tanks slowly increase and decrease in humidity and temps to compensate during the specific times of year. Perhaps this could be the cause that I haven't had the symptoms in my scorps which I raised. Ideas?
If I recall correctly, the last scorp I had which suffered from these symptoms, also had the same leg begin to narrow, and it seemed that it hollowed out as well, at least by glace through a microscope.
The scorpions that I had that got the loeg problems and eventually died did not start out with the black spot at the joint. I first noticed a problem as the leg didn't move as smoothly as it should. The problem progressed until the leg no longer moved but had to be dragged. Eventually the joint where the limb ceased to move turned black and the scorpion died shortly(relative to the species) after that. That is the reason I assumed thay had gotten old or had injured the leg. On the scorps where I noticed this, the leg was the only injury until shirtly before death(days to weeks) they began to slow down and eventually died.
Hmmm... Mine didn't have the black spots upon purchase either, though the first sign I noticed with mine was the joint having a slight darker tint in time and eventually, the leg ceasing to be operative. I noticed it took mine anywhere for two-three months before the leg was unable to move and had to be dragged. The always had slight movement of the leg afterwards, though it was only the joint before the black spot. Like I said, the scorp who recently passed away, lived for about a year after the leg was unable to move. Mine appeared to slow down as well and seemed to become much more docile and easily picked up with little or no struggle. Then again, it may be old age, but I don't see how. I currently have a couple H. spiniferis young which also have the spots and are quite thriving in their 75 gal habitat with complete use of all limbs.