[1] The species of this genus show distinctive characteristics among the class Cephalopoda, including an oval shaped body compressed along the longitudinal axis, a gelatinous consistence and a large interbarachil web.

[4] Other distinctive features include the presence of two small fins on the mantle, an internal U-shaped shell that has a groove along its outer surface.

[1] Since, previous captured specimen of O. agassizi, that were found in the Mediterranean have been accredited to O. calypso, and is now believed to be the sole Opisthoteuthis species in the area.

The most important prey items for Opisthoteuthis calypso include benthic gammarid, amphipods, and polychaetes of the epibenthic fauna (those which live on or just above the bottom sediments).

This decrease in energy usage is attributed to the reduction in locomotion needed with the visually instigated predator-prey relationship in the light-limited habitat they live in.