Disruptive coloration elicited on controlled natural substrates in cuttlefish,Sepia officinalis

Abstract

SUMMARYCephalopods are known for their ability to change camouflage body patterns in response to changes in the visual background. Recent research has used artificial substrates such as checkerboards to investigate some specific visual cues that elicit the various camouflaged patterns in cuttlefish. In this study, we took information from experiments on artificial substrates and assembled a natural rock substrate (fixed with glue) with those features that are thought to elicit disruptive coloration in cuttlefish. The central hypothesis is that light rocks of appropriate size, substrate contrast and edge characteristics will elicit disruptive camouflage patterns in cuttlefish. By adding graded light sand in successively greater quantities to this glued rock substrate, we predicted that disruptive camouflage patterns would be replaced by progressively more uniform patterns as the visual features of rock size, contrast and edges were altered by the addition of sand. By grading the degree of disruptiveness in the animals' body patterns, we found that the results support this prediction, and that there is a strong correlation between fine details of the visual background properties and the resultant body pattern shown by the cuttlefish. Specifically, disruptive coloration was elicited (1) when one or a few light rocks of approximately the size of the animal's White square skin component were in the surrounding substrate (dark rocks alone did not elicit disruptive coloration), (2) there was moderate-to-high contrast between the light rocks and their immediate surrounds, and (3) the rock edges were well defined. Taken together, the present study provides direct evidence of several key visual features that evoke disruptive skin coloration on natural backgrounds.