Itaipusa renei, Reygel, Patrick C., Willems, Wim R. & Artois, Tom J., 2011

Reygel, Patrick C., Willems, Wim R. & Artois, Tom J., 2011, Koinocystididae and Gnathorhynchidae (Platyhelminthes: Rhabdocoela: Kalyptorhynchia) from the Galapagos, with the description of three new species, Zootaxa 3096, pp. 27-40 : 33

Itaipusa renei n. sp.

( Fig. 4 )

The pharynx is situated at ± 50%. It does not show any peculiarities in comparison with other species of Itaipusa or Koinocystididae in general (for a detailed account see Meixner 1925 and Karling 1954, 1980). A pharynx mouth sphincter could not be observed. Oesophageal glands are prominent.

Male and female gonads are paired. The two oval testes are situated dorso-laterally at both sides of the pharynx. The kidney-shaped ovaries lie dorso-laterally at ± 70%. The vitellaria extend from the pharynx to the common genital atrium. The common genital pore, situated at ± 90%, opens into this atrium, which can be expanded or contracted and folded in several directions. It is surrounded by an outer longitudinal and an inner circular muscle layer, the latter one becoming weaker towards the genital pore. The most distal part of the atrium is lined with a nucleated epithelium, which lowers to become a membranous epithelium more proximally. In all studied specimens sperm are present in the proximal part of the atrium. Dorso-caudally the common atrium is connected to a copulatory bursa, which is filled with degenerating sperm. The bursal stalk is lined with a dense and thickened basement membrane (pseudocuticle) and filled with sperm. It is surrounded by strong circular muscles, which form a very large symmetrical sphincter ( Fig. 4 E: sph2), situated somewhat distally from the entrance of the bursa. In an immature specimen, the developing bursa appears as an eosinophilic globular structure packed with many round nuclei and clearly discernable cells. In adult specimens the bursa shows some flattened nuclei and a central area filled with a patchwork of dense and clear areas.

The male copulatory organ ( Fig. 4 D, also indicated on Fig. 4 E) is situated dorsally in most sectioned specimens with its proximal part pointing rostrally. It enters the common genital atrium from the left hand side, in between the female system and the uterus. The copulatory organ basically consists of an asymmetrical bulb surrounded by a muscular septum that consists of strong inner circular muscles and weak outer longitudinal muscles. The paired, elongated seminal vesicles are lined with a low, nucleated epithelium and surrounded by a circular muscle layer that runs somewhat spirally. The vesicles fuse just outside the septum, and the ejaculatory duct enters the copulatory bulb accompanied by several gland necks of the extra-capsular prostate glands. The bulb is partly filled with prostate ducts with coarse-grained basophilic secretion. This secretion is discharged into a flattened cup-like structure, surrounding the pore of the ejaculatory duct, which is surrounded by weak longitudinal muscles. This cup-like secretion area ( Fig. 4 D: y) is surrounded by circular muscles and opens through an orifice into the male genital atrium. Next to this orifice, the male atrium forms a large diverticulum, which is armed with many, small (± 3 µm long), pointed spines. This diverticulum, therefore, can be considered as an armed cirrus, although it is not directly connected to the ejaculatory duct. At one side, this cirrus incorporates a fine-grained eosinophilic secretory area ( Fig. 4 D: x). Its small gland necks are continuous with the basophilic prostate ducts surrounding the ejaculatory duct. They penetrate the wall of the cirrus at the side facing the centre of the copulatory bulb, forming an eosinophilic secretion structure, which bulges out of the wall. This secretory area extends from the proximal point of the cirrus towards the cup-like structure mentioned above. The circular muscles of the copulatory bulb continue in the circular muscles of the diverticulum, which also shows an outer layer of prominent longitudinal muscles on its dorsal side. The most distal part of the male genital duct is surrounded by inner circular and outer longitudinal muscles, and lined with a pseudocuticle. It also contains two hollow, smoothly-curved, blunt hooks (± 50 and 80 µm long; Fig. 4 B, 4D: h). The smaller hook possesses a well-developed basal ring. The exact position of the hooks could not be determined in the sectioned specimens. They are not connected to any muscular structure.

Two short oviducts, which are lined with a low, anucleated epithelium and surrounded by longitudinal muscles, connect the ovaries to the female duct. The oviducts can be closed by a weak distal sphincter. In between the two oviducts the common vitelloduct opens into the female duct through a weak sphincter. This female duct is swollen and filled with sperm, functioning as a seminal receptacle. It is lined with a nucleated epithelium and surrounded by circular muscles over its whole length, accompanied by an external layer of longitudinal muscles at its most distal part. The duct opens into the common genital atrium from the dorsal side and can be closed by a strong symmetrical sphincter ( Fig. 4 E: sph1). Close to the opening of the female duct into the atrium, a large bundle of glands is present, containing small, fine-grained basophilic glands surrounded by larger, fine-grained, eosinophilic ones.

The uterus is lined with a high, nucleated epithelium and is surrounded by longitudinal muscle fibres. In its proximal part a small, weak sphincter is present. It is provided with two types of glands. The first type contains a fine-grained eosinophilic secretion, whereas the second type is situated just distally of the first type and contains a coarse-grained basophilic secretion.

Figures

FIGURE 4. Itaipusa renei n. sp. A, general organisation (from a live specimen). B, hooks (from a live specimen). C, habitus of retracted individual. D, reconstruction of the male genital system (from the holotype). E, reconstruction (from the holotype) of the atrial organs from the right hand side; the position of the male system is indicated in dashed lines.