Liquid sand burrowing and mucus utilisation as novel adaptations to a structurally-simple environment in Octopus kaurna

Cephalopods are often celebrated as masters of camouflage, but their exploitation of the soft-sediment habitats that dominate the ocean floor has demanded other anti-predator strategies. Previous research has identified a small number of cephalopods capable of burying into sand and mud, but the need to directly access the water column for respiration has restricted them to superficial burying. Here, we report on the first known sub-surface burrowing in the cephalopods, by <em>Octopus kaurna</em>, a small benthic species that uses advanced sand-fluidisation and adhesive mucus for sediment manipulation. This burrowing strategy appears linked to easily fluidised sediments as shown in experimental trials in three size-grades of sediment. While the selective pressures that drove evolution of this behaviour are unknown, its identification enriches our understanding of the possible life-history traits and functional role of mucus in other benthic octopus species living in soft-sediment environments.