A deep-sea octopus (Graneledone cf. boreopacifica) as a shell-crushing hydrothermal vent predator

The gut contents of a female specimen of Graneledone cf. boreopacifica coll ected from the caldera wall of Axial Volcano, near an active hydrothermal v ent in the Northeast Pacific Ocean are reported. At least 30 individual gas tropods and 46 individual polychaetes are represented in the gut contents b y hard parts. Shell fragments and shells removed from the gut allow ready i dentification of the gastropods Provanna variabilis and Lepetodrilus fucens is, both of which are known only from North Pacific hydrothermal vents. Jaw s of polychaete worms are identified as those of the nereidid, Nereis pisce sae, and the predatory polynoids, Levensteiniella kincaidi and an unidentif ied species in the subfamily Branchinotogluminae. Not only was a considerab le volume of prey hard parts ingested, the gastropod shells had been crushe d before being ingested. The large size of the beaks in this genus of octop us and the increased area they offer for insertion of the superior mandible muscle, the prime mover in beak closure, support the hypothesis that these beaks exert sufficient force to crush the gastropod shells. Although cepha lopods had been reported to be absent from hydrothermal vents, the data pre sented here demonstrate that not only do they occur in vent habitats, they actively prey on vent fauna.