Nephasoma (Cutlerensis) rutilofuscum (Fischer, 1916)
This species has a rusty red color and no hooks on the introvert. Introvert is five to six times the trunk length. The posterior part of the trunk sometimes appears pointed and grooved resembling a caudal “shield” as in Aspidosiphon, but this appearance varies with degree of body wall contraction. The posterior end can also be smooth and round. Another character that distinguishes this species from other Nephasoma is the tentacle array of about 30 slender tentacles, in a dorsal zone covering an area like a fingerprint part of a human finger.
External anatomy
(From Cutler & Cutler 1979)
The introvert is about five to six times the length of the trunk, and its distal half loses the coloration gradually becoming whitish.
No hooks are present on the introvert.
The tentacles are about 30. They are slender and unbranched tentacles and they are localized in a dorsal zone on the distal introvert covering an area like the fingerprint part of a human finger. Few tentacles surround the mouth at the end of the introvert.
The cylindrical trunk is 2-15 mm long, and has a rusty red color (irregular white patches can be present in adults animals). Posterior end can be smooth and round or sometimes appears pointed and grooved resembling a caudal “shield” as in Aspidosiphon, but this appearance varies with degree of body wall contraction.
Internal anatomy
(From Cutler & Cutler 1979)
The trunk body wall has a continuous longitudinal muscle layer.
One pair of long and thin ventral retractor muscles, attached to the trunk body wall on either side of the nerve cord in the posterior fifth of the trunk.
Two short nephridia unattached to the trunk wall open to the exterior, anteriorly to the anus.
Intestine is loosely coiled, and is not attached to the posterior end of the trunk.
The anal region of the rectum is anchored to the trunk body wall by a well-defined wing muscle.
Western Indian Ocean, from 1-1560 m (Cutler, 1994).
This species was found inside coral rubble (Fischer, 1916). Cutler and Cutler (1979) reported this species from medium sand to clay sediment.