The mimic octopus: a master of disguise

By Camille Martens

The mimic octopus, Thaumoctopus mimicus, is the first known cephalopod species to not only perform mimicry of a poisonous species, but also the only animal to quickly interchange morphs of many different species, specialized for any given threat (Norman et al. 2001). Also known as the long arm octopus, the mimic was only recently discovered in 1998 in the waters off Sulawesi, Indonesia (Norman et al. 2001). This octopus’ habitat consists of shallow open, sandy plains with minimal reef and coral cover, leaving the cephalopod highly exposed and vulnerable to predation (Norman et al. 2001; Hanlon et al. 2008).

Its odd foraging behaviour is what first caught the eye of biologists, also the first of its kind to emerge during the daylight in spite of the presence of large predators (Norman et al. 2001). It was first found swimming with all its tentacles trailing behind, head flattened, and eyes positioned, creating the shape of what is now interpreted as the impersonation of the poisonous sole (Baker 2010). The mimic would then approach burrows and tunnels, reaching its long arms underground for food (Norman et al. 2001). The shape shifting is not the only amazing feat by the mimic; it also imitates behaviour specific to the sole, rippling its ‘body’ in short quick bursts over the sandy floor (Norman et al. 2001; Hanlon et al. 2008).

Thaumoctopus mimicus portraying the first discovered impersonation, the poisonous sole, swimming with all its tentacles trailing behind its head in a teardrop shape. Photo by Klaus Steifel. Licensed under the Creative Commons Attribution-NonCommercial 2.0 Generic license.

Biologists can only guess what the camouflage is alluding to by investigating common species in the area, but it is said that the mimic has 13 species up its long sleeve (Hanlon et al. 2008). By swimming with its tentacles splayed out, it seems as though it is trying to mimic the spines on the fins of the poisonous lionfish; with six tentacles in a tunnel and two splayed out lengthwise it looks to be a venomous banded sea-snake, both species common in the Indonesia waters that are its territory (Norman et al. 2001). While swimming high in the water it looks as though it may be a jellyfish, and while lying sessile on the ocean floor with its arms floating, it looks as if it’s an anemone -two possible interpretations that are still up for debate (Norman et al. 2001; Hanlon et al. 2008). Thaumoctopus mimicus is incredibly intelligent and will morph into certain species dependent on which predators are passing by as it forages; for example, in the presence of damselfishes, the mimic has been observed impersonating a sea snake, its known rival (Norman et al. 2001).

Mimic octopus spreading its tentacles in what is interpreted as impersonating a poisonous lionfish. Photo by Steve Childs. Licensed under the Creative Commons Attribution 2.0 Generic license.

Thaumoctopus mimicus is unusual in many ways, and crypsis (changing colour to camouflage themselves into the background of reefs) is no exception; a common trait to cephalopods, but this octopus also changes to dark colours and bold patterns in an instant, what some scientists think may even attract other species (Baker 2010).

It is still unknown whether T. mimicus is itself a poisonous species; making the difference whether it is Batesian or Mullerian mimicry that this species performs (Baker 2010; Norman et al., 2001). Also undetermined is whether this trait of advanced polymorphism is learned or an innate knowledge they are born with (Baker 2010). This master of camouflage is one of a kind, and there is certainly reason behind its impersonations that we have only just begun to understand. A fairly recently discovered species, much more research is needed on the mimic octopus and its bizarre behaviour, but finding the subjects might prove harder than expected.

References

Baker, B. 2010. Unusual adaptations: evolution of the mimic octopus. BioScience. 11: 962.

Hanlon, R. T., Conroy, L., and Forsythe, J. W. 2008. Mimicry and foraging behaviour of two tropical sand-flat octopus species off North Sulawesi, Indonesia. Biological Journal of the Linnean Society. 93: 23-28.

Norman, M. D., Finn, J., and Tregenza, T. 2001. Dynamic mimicry in an Indo-Malayan octopus. Proceedings of the Royal Society B: Biological Sciences. 286: 1755-1758.