This species belongs to the cirrate octopods, distinguished by fins used for swimming, an internal shell (to which the fins attach) and cirri, paired filaments or papillae, on each sucker. Like other species in the Stauroteuthidae, S. syrtensis has a u-shaped internal shell, and secondary webbing that connects the arms to the primary web. This allows the arms to move inwards towards the mouth without collapsing the large bell-shaped web of skin that forms around arms. The web covers nearly two thirds of their total length ending at sucker 25, with each arm bearing between 55 to 65 suckers. The average arm length is about 70-85% of its total length with total lengths ranging from 280-500mm.
The body of these animals is soft and gelatinous, and is often heavily damaged in trawls and collections. It is often found hanging in the water with its webbed arms forming a bell shape. There are large glands near the mouth that may produce mucous to trap small prey animals.
Males have sexually dimorphic suckers. The first 8 suckers are barrel shaped, suckers 9 to 22-25 are enlarged and pointed. Suckers 9 to 12 are very closely packed and suckers 13 to 18 are the largest with a diameter of about 6.5 mm. Females have smaller suckers with suckers 1 to 3 as the largest with a diameter of 2.2 mm. Suckers 1 to 4 are very tightly packed, but suckers 5 to 24 are well separated. In both sexes, the suckers diameter decreases dramatically after sucker 25 nearing where the web ends. Both male and females have three kinds of suckers, proximal, mid arm, and distal. This sexual dimorphism in the size and shape of the suckers is unique to the species, and is probably related to sperm transfer or other reproductive activity.
Range length: 280 to 500 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently