Umbraculum umbraculum

Order : NOTASPIDEA
Superfamily : TYLODINOIDEA
Family : Umbraculidae

DISTRIBUTION
Widespread in tropical to warm temperate Indo-West Pacific.

A primitive notaspid, with a large external shell covering the dorsum. The shell, as in these photos, is usually covered with encrusting plant and animal growths. The body is circular, with large pustules. Even when crawling the animal does not elongate and the position of the head can only be determined by the tubular rhinophoral tentacles which extend out from beneath the shell. Below these tentacles the body is split by a “mid-anterior cleft” in which the permanently protruded penis sits and the mouth opens. The radula is very broad with many small rasping teeth. Umbraculum umbraculum is a sponge feeder, and has been recorded on a number of different species of the Demospongia, including Tethya spp., Aaptos aaptos, Ancorina alata, and Plakina trilopha. The proboscis does not avert, so in feeding, the anterior cleft must be spread open so that the mouth can be pressed against the sponge colony.