Does anyone have a solid theory regarding the distinct coloration in juvenile Zebra sharks? The juveniles are striped, whereas the adults are spotted. As far as I know, no data is published on their habitat differences explaining color. A yellow-lipped sea krait, Laticauda colubrina is present in much of the S. fasciatum range. Could mimicry of this venomous reptile be a relevant explanation? This is already performed by several octopus species to my knowledge.
Image links:
http://www.fishbase.org/images/species/Stfas_j1.jpg
(S. fasciatum juvenile)
http://upload.wikimedia.org/wikipedia/commons/thumb/0/01/Laticauda_colubrina_%28Wakatobi%29.jpg/490px-Laticauda_colubrina_%28Wakatobi%29.jpg
(L. colubrina)
Hi Leon, I think you need to turn to the terrestrial literature and look at theories for the evolution of striped colouration there. While I don't think you can rule out mimicry of venemous sea snakes, I would suggest that camoflage from predators is a more appropriate explanation for striped colouring in juvenile Stegostoma. The stripes basically help to break up the outline of the individual so it blends in better against disrupted or heterogenous backgrounds. The development of so-called shark proof wetsuits has made heavy use of stripes, so perhaps stripes are really great for helping to avoid large predators. You might be able to find some information on why they used striped neoprene to help you with your question.
Interesting! I've been down this path a little while, but abondoned it when the recent study on zebra striping (linking equid striped patterns with horse fly abundance) was published. I've tracked swimming Laticauda while diving and their patterns are truly mesmerizing, it is hard to see how they might offer a chance to blend though since the pattern is indeed very contrasting. I will look into it more! Although I sound doubtful, I think your interpretation is great, and probably closer to reality than mine.
Cheers!
I'm not sure it is about being able to blend in, rather that the stripes break up the outline of the shark. It would be interesting to do some trials with model sharks of different colours/stripe combinations to see if there are differences in how the models are approached by predators. If there was total avoidance of the true colouration by predators, it would provide strong evidence for your mimicry explanation. Any chance you could do such a thing?
interesting question and system! Can these sharks change color or are the stripes fixed in the young?
You may want to ask Karen Cheney, Bristol University, Australia, about this. She is an expert on marine mimicry
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