Meeting Abstract
Octopuses possess many interesting morphological features that enable them to both avoid predation and successfully hunt prey, such as neurally controlled skin camouflage, an ink sac, a raptorial beak with a radula, and eight muscular hydrostat arms with intricate rows of suction cups. Our study focuses on the arms, which are incredibly flexible, and capable of regrowth after catastrophic injury. In other invertebrates, functional specialization has resulted in the differential scaling of morphological traits. Octopuses appear to show little functional specialization in their arms other than the male’s hectocotylized arm. However, since the arms in front of the head are usually the first to be exposed in agonistic and defense postures, we hypothesized that the scaling patterns of arm growth would not be isometric. We therefore predicted that the left and right front arms (L1 and R1) would exhibit allometric growth compared to the other arms on each respective side. We measured arm lengths of museum specimens of Octopus bimaculatus across a size range, and quantified truncation and regrowth in previously injured arms. Our preliminary data suggest that arm growth is allometric, but the pattern is not bilateral: L1 of uninjured octopuses grew at a faster rate than other arms on the left side, while R1 grew slower than the rest of the arms on the right. Additionally, the left arms incurred over 50% more injuries, and greater proportions of the left arms were truncated. This lateralization was unexpected, as our specimens were collected from a wide geographic area, but may be partially due to a male’s need to protect his hectocotylized arm. Future behavioral work is needed to determine whether octopuses favor one side over the other in antipredator displays.
