Pseudoceros bimarginatus Meixner, 1907
The diagnostic characters for this species are the color and color pattern which is white with three marginal bands: yellow, black and orange, and the presence of spermiducal bulbs or vas deferens dorsally directed.
External morphology: white or cream dorsal surface with three marginal bands in the following order from the inner to outer: yellow-green, black and an orange rim. In some worms there is also a fine median white line that ends before the posterior margin. On the ventral side is pink-orange with the three marginal bands. The pseudotentacles are formed by simple folds of the anterior margin. Presence of a cerebral cluster formed by about 30 to 40 eyespots and the marginal eyes can’t be detected because the presence of the intense black band. Ruffled pharynx with folded lateral branches.
Internal anatomy: The male apparatus is formed by the spermiducal bulbs dorsally directed and a rounded seminal vesicle connected to a coiled ejaculatory duct. The prostatic vesicle is small and oval. The penis stylet is short. The female system is characterized by a wide antrum with a short and muscular vagina surrounded by the cement glands.
This specis has been found in Heron Islands, Central Great Barrier Reef in Australia, and also has been reported for Somalia and Philippines.
This species was found moving on the boulders or sand at the reef crest.
The location of the type material is unknown but there is a whole mount and a set of serial histological sections of this species deposited at the Queensland Museum in Brisbane, Australia.
This species was described by Meixner (1907) from the original descriptions made by Gravier, possibly based on preserve animals. Stummer-Traunfels (1993) figured the same species but it was not named. Subsequently, Hyman (1954) described this species as P.corallophilus based on one preserve and immature specimen. Finally, Newman & Cannon (1994) re-described this species based on living worms and fresh material. Their description differs slightly from the original description, probably as a result of the examination of preserved animals made by Meixner (1907). They included this species in the group 2 characterized by the presence of marginal bands, according to the categories based on the color patterns (Newman & Cannon 1994). P. gamblei and P. heronensis resemble this species but the color of the marginal bands is a distinctive character for P. bimarginatus, and P. confuses has an extra black marginal band. The vivid orange, black and yellow color suggests an aposematic coloration.
Pseudoceros corallophilus Hyman, 1954