Some blog posts are pretty easy to write, as I am pretty certain that I know the answers to the problems I present. Of course, as a scientist, I realize that time might prove me wrong, but as far as I believe I have a reasonable explanation, I am fine with that. Others are harder, much because I really do not have a clue where to start the explanation. One of the things I often think about while diving (and actually also on land) is the weird notion of family wide camouflage adaptations. It wouldn´t per se be weird if a genus or even a family of animals with a common ancestor (well, that would be the definition of a family or a genus!) with propensity for using camouflage as a strategy to evade predators just continued using that strategy It would´t be weird, at least as long as they keep using the same model, despite evolving into different species (with model I mean the subject that is mimicked in order to achieve camouflage). The different scorpion fish do just that, all mimicking debris strewn on the sea floor. As you probably understand, I wouldn´t be writing this post if there were no exceptions to the scorpion fish strategy.
Three different cases of the problem I described above comes to mind. First of all, juvenile spade fish are all mimicking more or less unpalatable items. The problem is that the items they are mimicking are as diverse as leaves, flatworms and crinoids! The second example are the pygmy sea horses, which all are excellent mimics, but of very different models, such as sea fans, hydroids and something small and yellow (I really have no idea what H. pontohi wants to look like!). Finally we have the ghost pipe fish, mimicking drifting algae, crinoids and Halimeda algae. In all three cases, different species within a genus or family use camouflage but are all adapted to widely different models. And in all three cases, their common ancestor probably had a specific model.
Why is this so weird? After all, choosing a mimic and resembling it enough should be straightforward. However, it is hard to explain how species already adapted to a specific model changes model completely. How for example, does one go from mimicking a flatworm to mimicking a leaf (or the other way around, if that is the case)? And how does one go from mimicking sea weed to mimicking Halimeda algae (or, again, the other way around, but you get the point)?
Honestly I have no idea, but this will absolutely be the subject of a heated lunch discussion with the evolutionary ecologists at my department once I get back from Lembeh. Stay tuned!
