irouping reduces the metabolic demand of a social squid

摘要

Many squids are social cephalopods and demonstrate exceptionally high metabolic rates. However, all prior investigations of metabolism in social cephalopods have utilized individual animals. We measured oxygen consumption of the social squid Doryteuthis opalescens both in groups and with solitary individuals to examine the influence of grouping on energy demand and performance under hypoxic conditions. On average, the presence of conspecifics reduced routine metabolic rate by 21% but did not influence the critical oxygen partial pressure below which a stable rate of oxygen uptake is not maintained. In addition, displays of chromatic behaviors associated with relaxation were observed more frequently in groups, whereas behaviors associated with stress or vigilance were observed more frequently in solitary individuals. We hypothesize that through a potential reduction in energy consumption, grouping may be relevant in allowing social squids to exploit habitats with marginal oxygen availability that may impose a physiological constraint.