Novel, complex burrow structure and burrowing behavior of the mud-dwelling octopus Octopus minor (Sasaki, 1920)

The strategies employed by octopuses for predator avoidance and escape, which are adapted to their structurally simple habitat, have been the subject of much research. In the present study, the shapes and structural characteristics of Octopus minor's burrows were investigated and the burrowing behavior was also observed to reveal the dynamics of burrow formation. From 2012 to 2017, 85 plasticized cement burrow models were measured. The burrow, a complex project, includes 7 interconnected structural parts: digging holes (DH), digging channel (DC), horizontal channel (HC), lounge (LG), breathing channel (BC), breathing holes (BH), and breathing hole heap (BHH), with each part having its own cross-sections of special shape and size. The diameters of all parts were very significantly different and had extremely significant correlations with other factors, except for the weight of the occupants. The burrows have 1-2 DHs, 1-4 BHs and 1 BHH, with DHs and BHs distributed at opposite ends of the burrow. The burrows were categorized into 7 types according to the number of DHs, and burrows with 2 BHs accounted for a distinct type. The diameters of LG, DC and HC and the occupants' weight decreased as the number of BHs increased. The process of excavating a burrow involved 5 steps: creating a DH, inserting arms into the DH, burrowing, excavating the BC, and creating the LG. Abandoned burrows could be reoccupied by other octopuses, regardless of whether they were larger or smaller than the previous occupants. As an adaptation to structurally simple environment, O. minor seems to use a particular skill in digging more complex burrows as shelters.

Automated summary

This study investigates the burrowing behavior and structural characteristics of Octopus minor's burrows. The burrow consists of 7 interconnected structural parts, each with its own unique shape and size. The burrows were categorized into different types based on the number of breathing holes, and it was found that the diameter of the burrows and the weight of the occupants decreased as the number of breathing holes increased.