Autophagy in Octopus

Automutilation, specifically of the arms, is well known in some octopod species. It occurs in two forms, autotomy and autophagy. Autotomy of an arm is achieved by breaking off at a predetermined site, or by biting off by the animal itself. Biologically, autotomy is a meaningful behaviour. It is well known, e.g. in male Argonauta during reproduction; it has also been described in several octopod species as a survival strategy. Autophagy, in contrast, is more puzzling; it is distinct from cannibalism because the animals eat (parts of) their own arms. This paper is based on 161 cases of autophagy in Octopus vulgaris. Although the data are still limited, they indicate that autophagy is not caused by hunger or stress, but is an infectious, deadly disease. Incubation time is between one and two weeks; death occurs 1–2 days after autophagy starts. Some data suggest that autophagy is caused either by a (so far unknown) substance released by the animal itself or, more likely, by viruses or bacteria; these, in turn, seem to affect the nervous system. Stress (often thought to be the reason for autophagy) may contribute to it but it is not its primary cause.