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This pelagic species occupies near-surface waters (at least at night) in the temperate regions of the world's oceans. The females are large with a mantle length up to 310 mm (Roper and Sweeny, 1976). The mantle is very muscular and the octopod, presumably, is an excellent swimmer. The ventral and dorsal arms are much longer than the lateral arms. Females of Ocythoe are one of the few known cephalopods with a true swimbladder (Packard and Wurtz, 1994) and the only known cephalopods that are ovoviviparous (i.e., give birth to live young that hatch internally) (Naef, 1923). A pair of water pores at the base of the ventral arms lead to extensive water-filled spaces between the eyes and arm bases. In subadult and adult females the ventral surface of the mantle has permanent ridges formimg a reticulate pattern. Males are dwarfs with a mantle length of about 30 mm.
Figure. Lateral view of a young female O. tuberculata, 71 mm ML, in a shipboard aquarium showing ridges and tubercules on the ventral half of the mantle. Photograph by U. Piatkowski, taken aboard the R/V G.O. SARS during the MAR-ECO expedition, 2004, at 50°N, 28°W.
An argonautoid ...
- with relatively arms II and III much shorter than arms I and IV.
- with reticulate ridge pattern on ventral surface of mantle in females.