First in situ observation of Cephalopoda at hadal depths (Octopoda: Opisthoteuthidae: Grimpoteuthis sp.)

Abstract

The Cephalopoda are not typically considered characteristic of the benthic fauna at hadal depths (depths exceeding 6000 m), yet occasional open-net trawl samples have implied that they might be present to ~ 8000 m deep. Previous in situ photographic evidence has placed the deepest cephalopod at 5145 m. The discrepancies between the two have meant that the maximum depth for cephalopods has gone unresolved. In this study we report on unequivocal sightings, by HD video lander, of a cephalopod at hadal depths. The demersal cirrate octopod Grimpoteuthis sp. was observed at both 5760 and 6957 m in the Indian Ocean. These observations extend the known maximum depth range for cephalopods by 1812 m and increase the potential benthic habitat available to cephalopods from 75 to 99% of the global seafloor.