Nematoplana martensi, Curini-Galletti & Oggiano & Casu, 2002

Curini-Galletti, M., Oggiano, G. & Casu, M., 2002, The genus Nematoplana Meixner, 1938 (Platyhelminthes: Unguiphora) in eastern Australia, Journal of Natural History 36 (9), pp. 1023-1046 : 1035-1036

Nematoplana martensi sp. nov.

(gures 3, 4A, 8F)

Material examined

HOLOTYPE: Australia, Queensland, Green Island , intertidal in medium to coarse coralline sand (September 1993), whole mount (lactophenol): G211823 . PARATYPES: same data as holotype, one whole mount (lactophenol) (G211824); one specimen sagittally sectioned (G211825) .

Etymology

The species is dedicated to Paul M. Martens (Hasselt, Belgium), in recognition of his contribution to the knowledge of the Proseriata .

Description

Animals colourless, comparatively rather large: the holotype is about 5 mm long; paratype G211824 is over 7 mm long. Anterior end elongate, provided laterally and terminally with sensory bristles. Posterior end with few adhesive glands. With two pigmented eye-spots, enclosed within the brain capsule. Epithelium entirely ciliated (cilia ranging from 2 to 3 Mm), with non-depressed nuclei. The distal edge of the epithelial cells appears strongly eosinophilous. Subepidermal longitudinal musculature well developed on the ventral side.

The gut extends posteriorly nearly to the caudal tip of the body, and, anteriorly, to just behind the brain. The pharynx (gure 4A) is located in the posterior fth of the body. It is very short and collar-shaped. Its epithelium has depressed nuclei, and is ciliated except for a small area at the distal tip, where few pharyngeal glands discharge. The nuclei of these pharyngeal glands are located well outside the pharynx itself. Pharyngeal cilia are about 1.5 Mm long. No oesophageal area could be seen. With subepidermal, longitudinal external and much weaker, inner circular musculature. The pharyngeal cavity is narrow, and opens to the outside through the mouth. The epithelium of the pharyngeal cavity is unciliated, with non-depressed nuclei.

Male genital organs. Numerous testes irregularly arranged laterally among vitellaria, in front of the pharynx. The copulatory organ consists of a single seminal vesicle, and a bulb provided distally with a stylet. The seminal vesicle is narrowly elongate, and provided with a thick coating of circular musculature. The spermiducts enter the vesicle anteriorly. In one of the specimens (G21182 4) sperm was not visible in the seminal vesicle, which was apparently degenerating. The seminal vesicle enters the bulb at its proximal base. The bulb is ovoid in shape (about 70 Mm high and 34 Mm wide in the holotype). It is lined with a thick coating of circular musculature, and provided with numerous prostatic glands, some of which have their nuclei outside the bulb itself. The stylet is thin and diaphanous, shaped as an elongate truncated cone, slightly in ated proximally. It is about 40 Mm high in the holotype, with a proximal opening 17 Mm wide, and a distal opening 9 Mm wide. Stylet of paratypes G211824 and G211825 are larger (respectively 60 Mm and about 55 Mm in length). The distal opening is minutely denticulate, and provided with a spike, about 6 Mm long in the holotype, and about 9 Mm in G211824. Due to the diaphanous condition of the stylet, this spike is di cult to see in xed mounts. In living animals, it is apparently held in the sagittal plane, since it could only be seen during torsions of the caudal part of the body. The male antrum opens to the outside through a narrow male pore, which is located close to the mouth.

Female genital organs. With two ovaries, consisting of one mature oocyte each, laterally in front of the pharynx. Vitellaria stretch from behind the brain to in front of the ovaries. The oviducts fuse at the level of the copulatory bulb into a common female duct, which is lined by an unciliated epithelium with non-depressed nuclei, and opens to the outside through a female pore, surrounded by numerous, long female glands, posterior to the male pore.

Discussion

The species is characterized by its stylet, shaped as an elongate, truncated cone, provided distally with a spike, and lacking an apophysis. Such morphology is unique in the genus, and allows immediate discrimination. Nematoplana pullolineata Tajika, 1979 has a tubular stylet without apophysis; the tube is however slightly recurved, with both openings markedly oblique, without a distal spike, and its distal opening is not denticulate. Furthermore, the species is provided with a cephalic gut and chorda intestinalis ( Tajika, 1979).

The stylet of N. martensi is unusual in being very thin and diaphanous, and easily deformable. This, together with its diOEerential degree of maturity, may account for the remarkable diOEerence in size among holotype and paratypes.