This particular specimen was stranded at Bokbaai on the West Coast in March 1986. It was a male with a mantle length of 790 mm and weighed 18 kg. The specific name is derived from the rhomboid shape of the fins, which are characteristically as long as the mantle. Much information concerning the diamond squid comes from Japan, where it is well known to fishermen by various names such as barrel squid, box squid, sleeved squid, umbrella squid and red squid. In late autumn and winter the diamond squid is quite common in the Sea of Japan, when it is caught by commercial fisheries and is often found stranded, especially after rough weather.
Japanese data indicate another point of interest.
There is apparently a case to be made for diamond squids occurring in pairs, because a pair of squids is caught more often than a single individual, and the catch of more than three squids at a time is quite rare. Whether each pair consists of a male and a female is not known. When the mantle is cut open it becomes quite obvious that diamond squids must be extremely powerful swimmers. The thickness of the mantle musculature shown here is some 46-49 mm. Swimming by jet propulsion is accomplished by drawing water into the mantle cavity on either side of the head then, by contracting the mantle muscles, forcing the water out through the funnel.