Diagnosis: Probursa moei Corrêa, 1960 differs from its congener P. veneris in (1) the position of the ovaries (at the hind end of the pharyngeal cavity in P. veneris and about half-way along the cavity in P. moei), and (2) the presence of a genito-intestinal connection.
Habitus: The fully extended living specimen was about 5 mm long and 0.5 mm wide. The posterior end is obtusely pointed and the anterior end broadly rounded or truncate, with indistinct auricular protuberances. The dorsal body surface is brown, except for the margins and five pigment-free, mid-dorsal spots.
The pharynx lies in the posterior half of the body and is about one-fifth of the body length. The mouth opening is situated at the anterior end of the pharyngeal pocket.
The anterior ramus of the intestine reaches anterior to the eyes, without giving rise to preocellar diverticula. The first pair of postocellar diverticula curves anteriad, the branches extending beyond the level of the eyes. The posterior intestinal rami do not meet in the hind end of the body.
Male Reproductive System
The dorsal testes lie between the bases of the intestinal diverticula and extend from a short distance behind the brain up to the level of the copulatory apparatus. There are 6-8 testicular follicles on either side of the body.
The vasa deferentia unite to a an extra-bulbar common vas deferens, which penetrates the muscular penis bulb and opens at the tip of the intrapenial papilla. The latter is a short and broad cone, projecting into the proximal part of the ejaculatory duct. The intrapenial papilla is covered with a tall, infranucleated epithelium through which the abundant, coarse-grained and erythrophilous secretion of penial glands is dischaged into the proximal section of the ejaculatory duct. A much finer grained and lighter stained secretion is discharged into the ejaculatory duct, which is lined with an infranucleated epithelium. The distal section of the ejaculatory duct is surrounded by short and somewhat irregularly shaped septa, together forming a reticulated system of channels, thus canalizing the secretion of penial glands.
The cone-shaped penis papilla is covered with a flat, nucleated epithelium which is underlain with a thick, subepithelial layer of circular muscles and a well developed layer of longitudinal muscles.
Female Reproductive System
The ovaries are situated on either side of the pharyngeal cavity, near the middle of the latter, and lie medially to the ventral nerve cords. The oviducts run laterally to the ventral nerve cords and extend anterior to the ovaries. At the level of the male copulatory apparatus the oviducts gradually curve towards the dorsal body surface and, subsequently, unite to form an extremely short common oviduct. This common oviduct meets the anterior wall of the ventral, distal section of the bursal canal.
From the point of communication with the male atrium the bursal canal curves anteriad, runs dorsal to the male copulatory apparatus, and meets the copulatory bursa. The bursal canal is surrounded by a relatively thick layer of circular muscles. The bursa, which lies between the pharyngeal cavity and the male copulatory complex, is lined with tall cells and communicates with the gut.
Shell glands were not yet developed in the type specimen.
The vitellaria occur throughout the body length and are located laterally to the testes; the vitelline follicles occupy the entire space between dorsal and ventral body surface.
Each eye cup contains three retinal cells and is devoid of a lens.
Ecology and Distribution
At present P. moei is only known from its type locality, where it was collected from among marine algae growing on panels hung under a pier.
Material Examined, Type Material
U.S.P.: no. M1, sagittal sections on 4 slides.