Drifting in the deep ocean, the vampire squid (Vampyroteuthis infernalis; pictured) has features of both octopuses and squid. Researchers have now worked out what and how this mysterious creature eats.

V. infernalis — which is related to octopuses and squid — has eight arms and, instead of the feeding tentacles used by squid to capture prey, has two long, retractile filaments. Hendrik Hoving and Bruce Robison at the Monterey Bay Aquarium Research Institute in Moss Landing, California, studied the feeding behaviour of V. infernalis using deep-sea video recordings, lab feeding studies and morphological examinations. They conclude that the filaments help the animals to capture food, which includes zooplankton, crustacean remains and even faeces.

Credit: MBARI

The filaments are homologous to the arms of octopuses and other cephalopods, although the creatures' feeding habits are very different, the authors suggest.

Proc. R. Soc. B http://dx.doi.org/10.1098/rspb.2012.1357 (2012)