Diagnosis: Procerodes australis Sluys, 1989a can be distinguished from all other southern hemisphere procerodids by the following combination of features: dorsally located testes, copulatory bursa, rather slender penis with highly developed penis glands.
Habitus: When the animals were prepared for sectioning apparently no particular attention has been paid to their external appearance. As the animals were together in the same jar with specimens of P. variabilis, it may be concluded that apparently they did not differ very much from this species. From the sections of the holotype it could be determined that this particular animal was about 5 mm long. No pigmentation could be discerned in the sections.
The anterior ramus of the intestine extends anterior to the eyes.
The pharynx measures between one-fourth and one-third of the body length and is constructed as follows: outer ciliated epithelium of about 2 µm, outer longitudinal muscle layer of 5.5 µm, outer circular muscle layer of about 20 µm, parenchymatous zone of 80 µm, inner longitudinal muscle layer of about 10 µm, inner circular muscle layer of about 45 µm, inner ciliated epithelium of 2 µm. The mouth opening is situated at the hind end of the pharyngeal pocket.
Male Reproductive System
The small, pear-shaped testes are situated dorsally, although some follicles occur half-way between the dorsal and ventral body surfaces. The follicles extend from just behind the ovaries into the hind end of the body.
In the pharynx region the vasa deferentia enlarge to form false seminal vesicles. The vasa deferentia penetrate the mid-dorsal portion of the penis bulb, narrowing considerably at the point of entrance. After having entered the penis bulb, the vasa deferentia expand slightly and then unite in the proximal portion of the penis papilla. The ejaculatory duct at first enlarges to form a seminal vesicle but, subsequently, narrows before opening at the tip of the penis papilla. Vasa deferentia and ejaculatory duct are lined with a cuboidal epithelium.
In the holotype the penis is folded inside the male atrium, whereas in the paratype the penis is very slender and is thrust out of the gonopore. Penis glands are highly developed, lying lie just outside the penis bulb. The glands discharge their secretion into the distal portion of the ejaculatory duct, where much densely staining secretion accumulates.
The lining epithelia of the male atrium and the penis papilla are underlain with a thin subepithelial layer of circular muscles and an equally thin layer of longitudinal muscles fibres. Ejaculatory duct and vasa deferentia are surrounded by a thin layer of circular muscles. The musculature of the penis bulb is only weakly developed.
Female Reproductive System
The paired, rounded ovaries are situated directly behind the brain and medially to the ventral nerve cords. The oviducts arise from the ventral surface of the ovaries and follow the course of the ventral nerve cords, running just dorsally to the latter. At the level of the female copulatory apparatus, the oviducts turn medially and unite to form a short common oviduct, which communicates with the diverticulum of the bursal canal.
Vitellaria extend from anterior to the ovaries into the hind end of the body. The main body of the vitellaria lies dorsally.
Procerodes australis is provided with a small, rounded or sac-shaped copulatory bursa which is lined with large, vacuolated cells. The rather wide bursal canal arises from the antero-ventral surface of the bursa and opens into the postero-dorsal section of the atrium. The nucleate lining of the bursal canal bears long cilia. Close to the bursa, a short and wide diverticulum arises from the posterior wall of the bursal canal. Extensive shell glands open into this diverticulum, which at its distal end receives the opening of the common oviduct.
Bursal canal and diverticulum are surrounded by a layer of circular muscles. The copulatory bursa is covered with a thin layer of interwoven muscle fibres.
The pigment cups house three retinal cells. There is no lens to the eyes.
Type locality: western beach of Peninsula Scott, Isla Navarino (55°16'S 69°49'W), Tierra del Fuego.
Material Examined, Type Material
The material examined consisted of two, already sectioned specimens which were collected on 10.02.1970 from the western beach of Peninsula Scott, Isla Navarino (55°16'S 69°49'W), Tierra del Fuego. The sections were made at intervals of 8um. Both series of sections suffer from the fact that part of the sections have been cut obliquely. With respect to the holotype the hind end was cut sagittally, but the front end more or less obliquely, whereas in the paratype most sections were cut in an oblique fashion.
The sample from which the specimens of Procerodes australis were obtained (NMC Acc. 70-27 F20), also contained a number of specimens of P. variabilis.