Suctorial feeding in a deep-sea octopus as a means of niche partitioning (Cephalopoda: Octopodidae)

摘要

Molecular phylogenetic analyses indicate that two clades of deep-sea octopuses evolved at opposite ends of the earth to become globally sympatric. Coexistence of these overtly similar, but phylogenetically distinct octopuses requires some means of niche partitioning. To investigate details of feeding, the buccal complexes of specimens of each clade, Muusoctopus and Graneledone, were sectioned at 90A degrees to the radular ribbon. The buccal complex of Muusoctopus is the same as reported in Octopus; the radula and its bolsters extend the length of the buccal complex. In Graneledone, however, the radula and its bolsters are restricted to anterior half of the buccal complex. Posterior to the radular sac, a vertically oriented muscle, named here the buccal abductor, extends from the floor of the mouth to the base of the buccal complex. In Muusoctopus, the bolsters extend the radula to bring food into the mouth; the palps propel it to the esophagus. In Graneledone, although the bolsters extend the radula, contraction of the buccal abductor to expand the posterior mouth may be the primary food mover. The negative pressure differential created draws food into the mouth and to the entry to the esophagus. The buccal abductor may permit the ingestion of larger pieces of prey, as gut contents show. Its evolution may represent a key innovation that heightens deep-sea octopus diversity.