The finned octopods are of medium to large size (up to 1.5 m total length, although there is a photographic record of one estimated to be over 4 m in total length: Voss, 1988). The body is usually gelatinous and strongly foreshortened. The mantle opening is reduced and swimming via jet propulsion seems to have been abandoned. Fins are present and are the primary means of locomotion. The fins attach to and are supported by the internal shell which has an unusual consistency (i.e., cartilage-like structure) and an unusual shape (i.e., a U, V or saddle-shape). The arms have one series of suckers down the midline of each arm and a series of cirri along each side of each arm (i.e., two cirri per sucker). The cirri alternate with the suckers along the arm length. The web is usually well developed and may reach the tip of the arms. A hectocotylus is absent but the arms of some species exhibit sexual modification; enlarged suckers are the most common modification. The diameter of the largest of these suckers is a good external indicator for maturity in males of some species. The spermatophores have lost the entire ejaculatory apparatus and form sperm packets with an operculum (Villanueva, 1992). The eggs are very large and enveloped in a tough egg covering that is secreted by the oviducal gland. Where known, eggs are laid singly on objects on the ocean floor.
An octopod ...
- with fins.
- with cirri on arms.
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