Comprehensive DescriptionRead full entry
“Spinther usarpia, new species
Record: 16:29 sta. 439 (1, TYPE).
Description: The body is depressed, oval to subspherical; length is 3 mm and width with parapodia nearly 3 mm; segments number 20. The ventrum is smooth (Fig. A). The dorsum is flat, has thick spines directed distally (Fig. B). The small, spherical prostomium is located between the notopodial ridges of the third setiger; the pygidium is terminal.
Neuropodia are most conspicuous on the ventral side, where each has a large, projecting falciger, and four or five embedded ones, in various stages of development. The shaft of these hooks is smooth, and the appendage sharply curved (Fig. C) and directed ventrally. Notosetae are much slenderer, occur in transverse rows on the dorsum. Each is entire, straight, and terminates distally in an unequally bifid tip in which the longer tooth is thicker than the other (Fig. D).
S. usarpia resembles S. alaskensis Hartman, 1948, from Alaska, in having similar setae; it differs in that it has a smooth ventrum. S. usarpia differs from S. arcticus (Sars) from the Arctic Ocean, in having only about 20 segments. The only other Spinther from the southern hemisphere is S. australiensis Augener, 1913, from southwestern Australia; in this the neuropodial hooks have an appendage with a large lateral tooth.
This is the first member of the family reported from Antarctica.
Distribution: Brabant Island, Antarctic Peninsula, in 128-165 m.”