A new approach to octopuses' body pattern analysis: A framework for taxonomy and behavioral studies*

Abstract

We systematically analyzed octopus body patterns, based on locations of chromatophore nerve projection, using a proposed new species in the Octopus vulgaris Cuvier, 1797 complex, Octopus insularis Leite and Haimovici, 2008. Although some taxonomic studies have used body patterns as characters to describe octopus species, a systematic analysis would provide detailed descriptions to assist reliable comparisons among species. This approach also links body patterns, behaviors, and underlying physiology of the chromatophore system. Body patterns were characterized by percent occurrence, areas of skin, and number of components in each. To verify the distribution of chromatic components, skin patterns, and colors among areas of the body, we ran a cluster analysis on occurrence of the components. We identified a total of 16 chromatic, 5 texture, 9 skin units, 6 colors, and 9 chronic body patterns. The cluster analysis showed twelve distinct skin areas of the components' distribution (expressive fields). Smaller fields were found in areas with complex patterns, especially around the eyes, while larger ones were found in areas with simple patterns. These findings differentiate between morphological and physiological units of the display system. The strong degree of similarity among photographs also supports previous taxonomic studies that pointed to morphological similarity within this species from the oceanic islands of northeastern Brazil.