Glow in the Dark Scorpions

Under UV light, scorpions are known to fluoresce. A few compounds have been identified in scorpions that are the root of this florescence, but it is not known why exactly the scorpions produce these compounds. Presumably, there is some sort of selective advantage to this florescence, or it is at least a byproduct of something else that confers a selective advantage.

Based on the work of Kloock et. al. (link to paper), it appears that this fluorescence has something to do with low-level UV light detection. Scorpions that underwent a treatment to remove the fluorescence properties seemed unable to detect the light. Individuals with the treatment were observed to behave differently under the same low UV light conditions as untreated scorpions, although curiously enough the type of behavior wasn't consistent between scorpions. In other words, ones with the treatment did different things than those without the treatment, but these things differed between individuals with the treatment (whew!).

Personally, I'm not 100% convinced of the results. The paper noted that the presented results were different from those of another paper, where the amount of UV light was so high that it likely caused the scorpions to avoid it altogether. Additionally, although it is completely possible that individuals with the treatment would exhibit different behavior, it seems odd to me that the behaviors differed.

Most importantly, the treatment itself, which batters the scorpions with light for weeks at a time, could be to blame for the differences. The authors acknowledged this, and presented an experiment to show that the eyesight of the scorpions was unaffected. This experiment showed there were no differences between treated and untreated scorpions in response to normal light as opposed to UV light. However, there still seems a possibility to me that there could have been retinal damage, but damage specific to the detection of UV. If a different protein or set of proteins is specifically responsible for detecting UV in the eye as opposed to normal light, then this is feasible. One of these proteins could have been degraded by the treatment, which would produce the same kind of results seen by the authors.

If time and money were not an issue, I think that a gene-knockout approach would be superior to the method used by the authors. By genetically preventing the scorpions from ever fluorescing, instead of relying on a post-fluorescence treatment, then it would be possible to make stronger conclusions about the results. However, this assumes that we understand at least part of the metabolism pathway involved in the production of the fluorescing compounds. Given that these compounds were all discovered within the decade (according to the paper), I might be getting ahead of myself here. It's one thing to know that an organism produces a given compound, and it's a whole other thing to know exactly how that organism produces the compound.

Even with all my criticism, I do think that the authors are on to something. They have provided enough evidence for me to think that their hypothesis is correct, though I would like to see additional experiments to help bolster it.