Stylochus ellipticus ( Verrill, 1873 ) Hyman, 1939

Bulnes, V. N., Faubel, A. & Park, J. - K., 2005, Two new marine species from South Korea with remarks on the family Stylochidae (Acotylea, Polycladida, Plathelminthes), Journal of Natural History (J. Nat. Hist.) 39 (23), pp. 2089-2107 : 2095-2097

Stylochus ellipticus ( Verrill, 1873) Hyman, 1939

( Figure 2F )

Planocera elliptica Girard 1850, p 251 .

Planocera nebulosa Girard 1853, p 367 .

Stylochopsis lateralis Girard 1893, p 194 –195.

Stylochopsis littoralis Verrill 1873, p 632 , Plate 19: Figure 99.

Stylochus littoralis: Lang 1884, p 453 .

Eustylochus ellipticus: Verrill 1892, p 467 , Plate 40: Figure 2 , Plate 41: Figures 1, 1a , Plate 42: Figures 1, 1a .

Eustylochus meridionalis Pearse 1938: 73 , Figure 25.

Stylochopsis ellipticus: Faubel 1983: 73 .

Material examined

Voucher specimen. No. 2947, one sagittally sectioned specimen, locality: east coast of USA, deposited in MNHV.

Morphological notes

In the following, only morphological characters which deviate from the description of Hyman (1939, p 130–134) are added or re-described.

Reproductive system. Male genital system with dorsal testes follicles. Vasa deferentia ventral, coiling alongside pharynx, and becoming spermiducal bulbs just before joining the seminal vesicle. Spermiducal bulbs and seminal vesicle distinctly separate, therefore, a tripartite, anchor-shaped vesicle not present as developed in Imogine Girard. Seminal vesicle tapering gradually caudad into the distal ejaculatory duct beyond the prostatic vesicle. Roundish oval prostatic vesicle with finger-like extensions (polyglandular type). Extra-vesicular glands arranged radially at a short distance from the muscular wall of the prostatic vesicle ( Figure 2F ). The prostatic duct joins the ejaculatory duct at the base of the penis papilla. A solid, pointed plug of mucus lying distally just at the tip of the penis papilla, simulating a short, pointed sclerotized process (cf. Hyman 1939); however, a true stylet is absent.

Ovaries arrranged ventrally; female genital organs as described by Hyman (1939).

Remarks

Stylochus ellipticus has had a diverse taxonomic history, being shuffled among four genera in the past 150 years. In 1873, Verrill described Stylochopsis littoralis , a synonym of S. ellipticus , as monotypic member of the genus Stylochopsis Verrill, 1873 . More recently, Hyman (1939, 1940) re-described Stylochus ellipticus (Girard) , emphasizing the identity of the structure of the male copulatory organ with the structure of the other species of the genus Stylochus . However, unlike other species in the genus, S. ellipticus was described as possessing a stylet. Meixner (1907), however, did not describe a stylet, and we did not find any in the voucher specimen. Evidently, Hyman misinterpreted the accumulation of hardened mucus solidifying during histological procedure at the tip of the penis papilla as stylet. Therefore, on the absence of a stylet, the monotypic genus Stylochopsis Verrill, 1873 has to be rejected and Stylochopsis ellipticus is referred to the genus Stylochus .

Figures

Figure 1. Diagrammatic reconstruction of types of prostatic vesicles of Stylochidae. (A) Monoglandular type; (B) polyglandular type.

Figure 2. Diagrammatic reconstruction of prostatic vesicles of Stylochidae. (A) Cryptostylochus coseirensis (Bock) after Meyer, 1921; (B) Imogine nebulosa (Girard); (C) Imogine oculifera Girard; (D) Stylochus alexandrinus Steinböck; (E) Stylochus frontalis Verrill; (F) Stylochus ellipticus (Verrill).