Ball, 1977 (Incertae Sedis)
Overview
Diagnosis: Dinizia (?) sanctaehelenae Ball, 1977 can be distinguished readily by its curved female genital duct, into which the oviducts open separately, and by the absence of a copulatory bursa.
Habitus: Preserved specimens up to 3.25 mm long and 0.75 mm wide. The body margins run parallel, while hind and front end are broadly rounded. A slight constriction occurs in front of the eyes and sets off the somewhat narrower head from the rest of the body. Pigmentation absent.
Alimentary System
The anterior ramus of the intestine extends anterior to the eyes but does not give rise to pre-ocellar diverticula. Behind the eyes the anterior ramus gives off about four irregularly branched or unbranched diverticula. The two posterior rami give rise to short lateral diverticula, as well as to medially directed diverticula. The two rami meet in the hind end of the body.
The pharynx lies in the posterior half of the body, its root being situated at about 60 % of the body length from the front end (Ball 1977a). The inner circular muscle layer of the pharynx exceeds the outer one two or three times in thickness. The mouth opening lies at the hind end of the pharyngeal pocket.
Male Reproductive System
The rather large testes are situated ventrally but their dorsal portion extends well beyond the mid-line of the body. There are about 4-7 follicles on either side of the body. The testicular follicles extend from some distance behind the ovaries to the root of the pharynx.
Anterior to the root of the pharynx the vasa deferentia enlarge to form greatly expanded false seminal vesicles which, posterior to the root of the pharynx, narrow to broad ducts. At the level of the gonopore these ducts turn dorso-medially and unite just dorsally to the penis bulb to form a short common section. The latter communicates with a seminal vesicle which lies within the penis bulb and empties into the ejaculatory duct. The last-mentioned duct is lined with a cuboidal, nucleate epithelium which bears cilia. The seminal vesicle is lined with a tall, and also nucleate, epithelium. Ejaculatory duct and seminal vesicle are surrounded by a layer of circular muscles.
The penis bulb is rather large and well muscularized. The penis papilla is a narrow cone with a blunt tip, covered with a nucleate epithelium which is underlain with a layer of circular muscles and a layer of longitudinal muscles, respectively. These muscle layers are continuous with those surrounding the atrium. The male atrium provides just enough room to house the penis papilla.
Female Reproductive System
The paired ovaries are small, rounded follicles which lie at a short distance behind the brain, dorsally to the ventral nerve cords. The oviducts arise from the ventro-lateral surface of the ovaries and run dorso-laterally to the ventral nerve cords. At the level of the mouth opening the ducts curve dorso-medially and open separately into the end of the female genital duct. The dorsal section of the female genital canal runs more or less parallel to the body surface but then the canal curves anteriad, meanwhile increasing in diameter, and meets the male atrium and the gonopore. The female genital duct is histologically distinguishable in that, in contrast to the oviducts, it has an infranucleate epithelium bearing long cilia. The duct is surrounded by a layer of circular muscle fibres.
Shell glands could not be discerned in all specimens, but when present, they discharge their secretion into the female genital duct (Ball 1977a), the openings of the glands piercing the wall of the duct over its entire length.
The vitellaria extend from the level of the ovaries to the hind end of the pharyngeal pocket and, when fully developed, occupy the entire space between dorsal and ventral body surface. In the front end of the body the vitellaria are situated laterally to the testes.
Eyes
The eyes possess a distinct lens, according to Ball (1977a), but I have been unable to discern lenses in the specimens examined.
Ecology
The species is known only from freshwater habitats on St. Helena. Here it has been collected from the perched water tables or from other freshwaters.
Distribution
Type locality: Rose Hill, St. Helena. The species is known only from the type locality.
Material Examined
M.R.A.C.: Paratypes: 33.930, transverse sections on 3 slides; 33.339, sagittal sections on 2 slides; 33.927, sagittal sections on 1 slide; 33.340, sagittal sections on 1 slide; 35.385, sagittal sections on 1 slide; 33.930, transverse sections on 2 slides; 33.930, sagittal sections of 4 specimens, each series mounted on a separate slide; 33.930, 2 whole mounts, each on a separate slide.
Private collection I. R. Ball: Paratypes: 33.339-1, Rose Hill, St. Helena, April 1967, sagittal sections on 1 slide; 33.339-2, transverse sections on 5 slides.
Type Material
M.R.A.C.: Holotype: 33.928, Rose Hill, St. Helena, April 1967, sagittal sections on 1 slide. Paratypes: 33.930, transverse sections on 3 slides; 33.339, sagittal sections on 2 slides; 33.927, sagittal sections on 1 slide; 33.340, sagittal sections on 1 slide; 35.385, sagittal sections on 1 slide; 33.930, transverse sections on 2 slides; 33.930, sagittal sections of 4 specimens, each series mounted on a separate slide; 33.930, 2 whole mounts, each on a separate slide.