Mysterious Morphology: An Investigation of the Octopus Keel and Its Association with Burrowing

The octopus keel is a trait that has been hypothesized to be connected with burrowing in octopuses, but has never been explored in any detail. This research aimed to test for anWe investigated the association between these two traits phylogenies using two approaches independent sets of methods. First, we examined phylogenetic correlation between presence of a keel and known burrowing behavior in incirrate octopuses.by using a phylogenetic approach, benthic octopuses as a group were examined for known burrowing and the presence of a keel to determine whether an evolutionary relationship exists between these traits. Second, burrowing and non-burrowing captive Muusoctopus leioderma were evaluated for keel prominence to determine whether the keel is lost more rapidly in non-burrowing individuals. Pagel’s test for the coevolution of binary characteristics showed the model of best fit for the resulting phylogenetic tree to be one of evolutionary interdependence, and that non-burrowing Muusoctopus leioderma lost their keels over time, while burrowing individuals maintained their keels. Together, these results indicate the keel may be a trait associated with burrowing in octopuses.