First record of potential Batesian mimicry in an elasmobranch: juvenile zebra sharks mimic banded sea snakes?

Various forms of mimicry have been recorded in a large number of marine fishes; however, there have been no records of mimicry for any elasmobranch species. We propose that the distinctly banded neonates of the zebra shark (Stegostoma fasciatum) are Batesian mimics of banded sea snakes (Elapidae). Observations of banded juveniles of S. fasciatum swimming close to the surface strongly resemble banded sea snakes in colour and body form as well as the undulatory swimming movements. Sea snakes are venomous and are known to defend themselves against predators. Although several shark species prey on them, most species appear to avoid sea snakes as prey items. Juvenile S. fasciatum possess a very long, single-lobed caudal fin that remarkably resembles the broad, paddle-like tail of sea snakes. This may be an adaptation enabling this species to mimic sea snakes, at least in the earliest life stages. There is a need for empirical testing of the hypothesis that juvenile S. fasciatum is a true example of Batesian mimicry, but here we provide evidence that suggests this may be the first example of mimicry in an elasmobranch species.