Ms. K,
Great looking site. Some time I'll have you tell you a hissing cockroach story.
We have a couple of teaching resources on our Understanding Evolution site that deal specifically with stomatopods. If you don't already know about them, you might want to check them out.
http://evolution.berkeley.edu/
To try to answer your question about O. scyllarus color change, let me first say that there have been no formal studies on this such as there have been on P. ciliata and N. wennerae. We do know that some of background color change is ontogenetic. The species specific color markings such as the carapace spots, uropods, antennal scales, etc. stay pretty much fixed. Juveniles often have a light golden or almost yellow general background color (30-50mm). This gradually darkens as they grow to a more olive base. You may also notice that juveniles have fairly pronounced spots down each side of the body, one on each plurite. At a little over 100-110 mm this species reaches sexual maturity. Females remain olive or brown while some males develop the green background color. This becomes more prominent the large males become to the point that every very large male that I have seen (160 mm+) is bright green. I might add that some very large females become a bit more green - but never the bright emerald green of the males.
That said, there certainly appears to be some underlying genetic variation, particularly in the color of juveniles. I some locations they are much more yellow than at others and this does not seem to vary with habitat.
However, nutrition and habitat also play a major role. Animals kept on a poor diet often "fade" and take on a grayish cast. This can be reversed by providing a varied diet of live shrimp, annelids, etc. (I have no idea what specific classes of nutrients are required, but carotinoids seem to be important.) Spectral quality and light intensity are also factors that affect O. scyllarus, although certainly not as much as in gonodactylids. Dim, bluish light promotes darker colors, this has not been examined systematically. Substrate color also seems important. Keeping animals on white sand certainly promotes a lightening of body color, although again this takes a long time and a few molts.
One final observation. Long ago I noticed that O. scyllarus in tanks with lots of green and brown algae developed richer colors than those held in clean tanks. I assumed that it was color matching, but now it appears that this is more likely to occur if the stomatopods are eating live snails and crabs that graze on the algae. I assume that they are ingesting a broad diversity of nutrients when they consume their prey that have fed on the algae. As a university animal facility, we are frequently inspected to maintain the health and welfare of our animals. While technically stomatopods and cephalopods aren't covered by USDA regulations, I was more than once told that I had to clean up my "dirty" stomatopod tanks because they were overgrown with algae. I have finally convinced the campus vets that at least some kinds of algae are good for stomatopods.
Roy
I love seeing them in classrooms.
