Deception in the dark—an ethogram of Callistoctopus furvus

Résumé fourni par la source

ABSTRACT Callistoctopus furvus (the “eastern” or “sand octopus”) is a relatively unstudied species of medium-large nocturnal octopus inhabiting shallow coastal areas of the tropical western Atlantic. To aid in field identification, promote further study of this species and enhance the understanding of skin patterning and behaviour in nocturnal shallow-water octopuses, we composed an ethogram of C. furvus from photographs and 3.11 h of video collected of wild individuals in the natural environment. We catalogued two colours, 17 static chromatic components, six groups of skin patterns (divided into 16 subpatterns), three textures, 10 postures and 11 behaviours. Photographs and videos of C. furvus from other geographic areas could be classified using this ethogram, supporting its validity for the study of C. furvus throughout its geographic range. We also described eight features that can be used to differentiate C. furvus from co-occurring octopods through observation alone: strict nocturnality, brick red incorporated into most skin patterns and rows of regularly spaced white spots that are always at least faintly visible on the arms, a polka-dotted deimatic pattern, large “U”-shaped papillae on the mantle, six distinct mantle shapes, a shallow arm web, the execution of very few “parachute attacks” and a tendency to enter existing holes or bury itself in response to disturbance. Notable features include the use of at least one “dynamic” chromatic component, a putative masquerade as algae, and potential mimicry of trumpetfish or cornetfish. Greater observation and study of C. furvus and other octopods from a diversity of habitats, latitudes and temporal niches will enhance our understanding of how these factors have shaped the use of colours body patterning and behaviour of this unique group of molluscs.

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