Octopoda

Octopoda [äk′täp·ə·də]

(invertebrate zoology)

An order of the dibranchiate cephalopods, characterized by having eight arms equipped with one to three rows of suckers.

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Octopoda 

an order of marine cephalopod mollusks of the subclass Dibranchiata. Some zoologists consider the Octopoda to comprise only members of the family Octopodidae—the octopuses. The body is short and posteriorly oval; some species have one or two pairs of fins. The head is surrounded by eight long tentacles, or arms. (The term “Octopoda” came into use because the arms were formerly called legs.) In males, one tentacle (less frequently, two) has been modified into a copulatory organ, the hectocotylus. The arms are joined together by a thin membrane and are equipped with suckers. The body length, including the arms, ranges from several cm to 6 m.

Octopoda inhabit waters with a salinity of no less than 3 percent and are found at depths ranging from shallows to 8 km. The majority are benthic animals that use their arms for locomotion. Pelagic forms include some deep-water species and the Argonauta. Octopoda that inhabit shallows have an ink gland, which releases a cloud of inky fluid in defense against enemies. Deep-water Octopoda do not have an ink gland; some have organs of luminescence. Female Argonauta have a shell in which they nurture their developing young. All Octopoda are active predators. In turn, they serve as food for a number of marine mammals and fishes.

Of the approximately 200 species of Octopoda, about 30 are found in the USSR, in the seas of the Far East and in the northern Arctic Ocean. In a number of countries of South Asia, East Asia, and Southern Europe, Octopoda are used as food and are commercially valuable. A fishing industry for these mollusks is now being established in the USSR, in the seas of the Far East.

IA. I. STAROBOGATOV