Mature, living specimens up to 650 µm long and 150 µm wide (Figs. 1A, 2). Preserved specimens contracted to approximately 360 µm long and 140 µm wide (Figs. 1B, 3). Body cylindrical. Anterior and posterior ends rounded. Body color yellow by transmitted light. Epidermis completely ciliated. Many large rhabdoid glands present; mostly concentrated at anterior end (Figs. 1, 2). Musculature with circular muscles that encircle the body along entire length of animal; straight longitudinal muscles present between frontal organ and anterior edge of mouth; longitudinal-cross-over muscles (fibers with a longitudinal orientation anteriorly, but bend medially to cross diagonally) present in both dorsal and ventral body wall; anterior end with ventral diagonal muscles positioned between outer circular and inner longitudinal muscles (Fig. 3A) Frontal organ well developed; cell bodies of frontal glands positioned ~100 µm behind frontal pore (Fig. 1B, 2B). Mouth opening on ventral surface, middle of body. Digestive central syncytium extends from posterior end of frontal glands to level of seminal vesicle. Ovary presumed to be unpaired, ventral; no more than two eggs—positioned medially—discernible in live and sectioned material (Figs. 1, 2A, C). Testes paired, dorsal, compact; separate from ovary. Testes extend anteriorly to level of mouth and posteriorly to male copulatory organ. Common gonopore on ventral surface opens anteriorly to sperm-filled seminal vesicle composed of thin layer of muscle and surrounded on ventral and posterior sides by several conspicuous nuclei (Figs. 1B, 2B, 3B). Gonopore opens posteriorly to ill-defined, weak-walled vagina that runs anteriorly over dorsal side of seminal vesicle to sperm-filled seminal bursa; bursa with well-developed bursal wall (Figs. 1B, 2B).[From Hooge MD, Eppinger N (2005): 2-6]
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