37.4 Saturday, Jan. 5 The costs and benefits of losing an arm: autotomy in the octopus Abdopus aculeatus ALUPAY, J/S*; CALDWELL, R/L; Univ. of California, Berkeley; Univ. of California, Berkeley firstname.lastname@example.org
Animals have evolved a diversity of defense mechanisms including cryptic and startling displays and flight responses to escape their predators. Arguably one of the most extreme tactics is autotomy, the voluntary shedding of a limb or body part. This behavior is beneficial in the immediate escape of the animal and leaves behind a potential distraction for the predator. However, organisms may incur long term costs to activities where the lost limb played a vital role. Reptiles, echinoderms, and arthropods are known to lose specific body parts and provide evidence for increased survival in autotomizing individuals. Several studies in these skeletalized taxa have also shown that autotomy decreases locomotor performance. We studied a soft-bodied organism, Abdopus aculeatus, an octopus known to autotomize and regenerate its arms. More than 50% of the 48 individuals observed in the Philippines were found with one or more arms lost or regenerated. Additional arms were autotomized in the lab and were found moving and suctioning to surfaces for up to three minutes without stimulation. Stimulated arms continued to move for more than one hour, attaching to surfaces at the base and repeatedly curling at the tip. These results suggest that autotomized arms have evolved behaviors that distract the predator as the octopus escapes. Preliminary locomotion studies also suggest that there is no difference in the kinetics of how autotomized and intact individuals move. However, the type of locomotion and gait patterns may differ depending on the number of arms that are lost. With these data, more quantitative analyses of the costs and benefits of autotomy may be determined along with a better understanding of the evolution of this mechanism in octopuses.