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Sluys and Ball, 1989

Overview
Diagnosis : Jugatovaria spinosa Sluys and Ball, 1989 can be distinguished from other marine triclads by (1) the broad, muscular ducts arising from the anterior surface of the ovaries, communicating with sacs situated antero-medially to the gonads, (2) the presence of numerous sclerotized spines in the ejaculatory duct, and (3) by the lack of a copulatory bursa.
Habitus : Preserved specimens are 2.5-3 mm long and 1.25 mm wide. Front and hind end are rounded; the body margins run almost parallel. The anterior position of the small pharynx gives the animals a characteristic appearance: it looks as if they have a very long posterior part. The eyes are situated close together, at a short distance from the anterior margin. Preserved animals are unpigmented.

Alimentary System

The short pharynx lies in the anterior half of the body and measures between one-eighth and one-seventh of the body length. The inner circular muscle layer of the pharynx is much thicker than the outer circular muscle layer. The mouth opening is situated at the front end of the pharyngeal pocket.
The anterior ramus of the intestine extends between the eyes; it does not give off pre-ocellar diverticula, but its anteriormost portion may show a club-shaped expansion. Behind the eyes the anterior ramus gives off about 4, usually forked, diverticula. Each posterior ramus gives off about 15 lateral diverticula, which show either a simple or a more complex branching pattern. The posterior intestinal rami may also give rise to a few unbranched median diverticula. There are no commissures between the two posterior gut branches, and they do not meet in the hind end of the body.

Male Reproductive System
The small testes are situated between the bases of the intestinal diverticula. The follicles extend from directly behind the ovaries up to the level of the mouth opening. There are about 25 testicular follicles on either side of the body. The testes are principally situated ventrally, although an occasional large and oval-shaped follicle may extend to the dorsal body surface. Testicular follicles mostly occur with two or three together in a septum between two intestinal diverticula. In such cases the testes are not neatly arranged side by side, but more or less piled on top of each other. As a consequence, the uppermost follicles usually reach the dorsal body surface.
Behind the pharyngeal pocket the vasa deferentia enlarge to form false seminal vesicles. At the level of the penis bulb the ducts recurve and turn medially; their diameter decreases before penetrating the muscle layer of the penis bulb. Inside the bulb the vasa deferentia open into the dorsal portion of a large seminal vesicle. The latter communicates through a narrow opening with the lumen of the penis bulb. At the base of the penis papilla, this lumen communicates with the ejaculatory duct. Well developed penis glands, which lie outside the penis bulb, discharge into the lumen of the bulb. In the preparations examined the glands and their secretion stain dark red, but most of the epithelium lining the lumen of the penis bulb stains dark blue. A large portion of the lining epithelium of the ejaculatory duct is provided with numerous sclerotic spines. These spines are very slender, only their base being slightly broader, and the tips curve towards the tip of the penis papilla. The spines are packed close together, their tips reaching the center of the ejaculatory duct.
The penis bulb is well developed and surrounded by a layer of longitudinal muscle fibres. The penis papilla may either be a short, blunt cone or a broad rod-like structure of which the margins run almost parallel, only the base being slightly wider. In the last-mentioned case, the tip of the papilla is blunt. In the short cone-shaped papillae, the distal portion of the ejaculatory duct that is devoid of spines, is only very short. This situation obtains in the holotype and paratype V4076. In case of a rod-like, extended penis papilla this distal portion of the ejaculatory duct may be almost as long as the part containing spines; this is the case in paratypes V4075 and V4077.
The penis papilla is lined with a nucleate epithelium of which the basal surface, i.e. the basement membrane, follows an undulating course. Beneath the thin basement membrane lies a well developed layer of circular muscles, consisting of several rows of fibres. This layer is continuous with the thinner layer of circular muscles around the male atrium, and also with the thin layer of circular muscles that surrounds the distal portion of the ejaculatory duct, i.e. the part lacking spines. Entally to this circular muscle layer occurs a strongly developed layer of longitudinal muscles. This layer is continuous with the longitudinal muscles surrounding the penis bulb, and also with the longitudinal muscles around the ejaculatory duct. The epithelium lining the lumen of the penis bulb appeared not to be underlain by muscle fibres.

Female Reproductive System
The paired ovaries lie at a short distance behind the brain, medially to the ventral nerve cords. The oviducts arise from the latero-ventral surface of the ovaries. Another duct arises from the antero-dorsal surface of each ovary. The last-mentioned ducts are broad and lined with a low, cuboidal and nucleate epithelium, and they are surrounded by a thick circular muscle layer. The ducts curve ventro-medially and communicate with poorly defined sacs which lie antero-medially to the ovaries. These sacs are filled with loose parenchymatic tissue.
In following their course backwards, the oviducts stay laterally to the ventral nerve cords. Behind the gonopore the oviducts turn medially and unite to a common oviduct which opens into the female genital duct. It could not be decided whether the oviducts open separately into the posterior end of the female genital duct or unite into a common oviduct, since no transition between the latter and the female genital duct could be discerned. Both structures, presumed common oviduct and female genital duct, are lined with a nucleate epithelium which is devoid of cilia. The diameter of the female genital duct enlarges slightly at the point where welldeveloped shell glands open into the duct. These glands are for their greater part situated dorsally to the female duct. The female genital duct meets the rear wall of the atrium. Common oviduct, and the greater part of the female genital duct are surrounded by a weak layer of longitudinal muscles. The musculature of the anterior-most portion of the female genital duct appeared to be somewhat more developed in that there is also a thin layer of circular muscle fibres.
The vitellaria are well developed and extensive; they extend from the level of the ovaries into the hind end of the body.

Eyes
The eyes lack a lens. The material examined did not allow determination of the number of retinal cells.

Ecology
The type specimens were collected from a dead crayfish at a depth of 3 m.

Distribution
Type locality: Marion Bay, Yorke Peninsula, Australia. The species is known only from its type locality.

Material Examined, Type Material
S.A.M.: Holotype: V4074, Marion Bay, Yorke Peninsula, Australia, 3.01.1977, sagittal sections on 2 slides.
Paratypes: V4075, sagittal sections on 2 slides; V4076, sagittal sections on 2 slides; V4077, horizontal sections on 1 slide; V4078, transverse sections on 3 slides.

Jugatovaria spinosa