Scilliijortex phytophilus, Faubel & Warwick, 2005

Faubel, A. & Warwick, R. M., 2005, The marine flora and fauna of the Isles of Scilly: Free-living Plathelminthes (‘ Turbellaria’), Journal of Natural History 39 (1), pp. 1-45 : 36

ScilliIJortex phytophilus gen. et sp. nov.

( Figure 8A, B )

Material examined

HOLOTYPE: Site 7: two specimens in squash preparation, stored on CD-ROM: 2003.5.22.5; whole mount slightly squashed WM: 2003.5.22.5.

Etymology

The specific epithet refers to the phytal habitat in which specimens were living (from Greek, phyton 5plant and philos 5specially favoured).

Description

Length of body squashed 1.7 mm, fore-end slightly tapering to a pointed tip, rear end rounded. Colour dark dirty grey with transparent areas marking the locations of the pharynx and genital organs. With a pair of crescentic eyes; lateral eyes very close to each other. Eyes 204 M m distant from anterior margin. Epidermis with numerous small rhabdites. Pharynx doliiformis small, 290 M m long, mouth of pharynx 100 M m caudal to eyes, distal pharynx bordered with tiny papillae. Hind body end provided with four very large caudal glands with inner thread-like structure up to 120 M m long.

Reproductiυe system. Common gonopore in rear body leading into a voluminous genital atrium. Gonopore and distal atrium surrounded by cement glands. Testes paired, behind pharynx. Vasa deferentia join testes with paired seminal vesicles. The male copulatory apparatus consists of paired seminal vesicles and a prostatic vesicle bearing a coiled stylet. The prostatic duct and the ejaculatory duct openings obviously independent from each other but very close to each other in the genital atrium. The paired seminal vesicles combine to a common ejaculatory duct; the distal part of which increases gradually in sclerotization of the walls forming distally a collar-like border. The spherical prostatic vesicle, 140 M m in diameter and provided with a thick muscular wall, opens distally into a proximally coiled stylet making one and a third turns. The stylet is tapering distad starting at the end of the first proximal third of the twisted part. The distal part of the stylet is straight, about 100 M m long and provided with a short distal hook-like bend at an angle of about 90 °. The stylet resembles the penis stylet of Pogaina annulata Ax, 1970 .

The female gonads are paired germovitellaria. The vitellogenous part is located dorsolaterally and extends from somewhat anterior of the testes to the level caudal of the seminal receptacle. The distal ovarial parts lie immediately in front of the seminal vesicle. Female ducts, i.e. oviduct and uterus, could not be discerned and traced to the common genital atrium.

Discussion

According to Luther (1962), the characters of paired gonads and common genital atrium in the caudal body-half refer Scilliυortex phytophilus to the family Provorticidae . The Provorticidae are additionally characterized by a more or less combined seminal and prostatic vesicle. The family is subdivided into the subfamilies Provorticinae Meixner, 1926 (paired vitellaria, seminal and prostatic vesicle side by side), Kirgisellinae Luther, 1962 (paired vitellaria, seminal vesicle proximal of prostatic vesicle) and Haplovejdovskyinae Luther, 1962 (single testis and germovitellar, paired vasa deferentia). Based on the characters given, Scilliυortex phytophilus differs from the known species of the subfamilies of the Provorticidae in the character combination of paired germovitellaria and separate seminal and prostatic vesicle with excreting ducts which separately open into the common genital atrium. A special feature is that both ducts are provided with sclerotized elements and enter independently from each other into the genital atrium. This character combination is unique within the Provorticidae and the other families of the order. Consequently, we have to establish a new family or at least a new subfamily within the Provorticidae . However, we must desist from this because of the absence of serial sections for the final resolution of the exact relations of the male ducts and their entrance into the genital atrium.

Figures

Figure 8. Scilliυortex phytophilus gen. et sp. nov. (A) Dorsal view in squash preparation; (B) sclerotized male stylet. Polycystis sp. (C) sclerotized male stylet. Scale bars: 250 Mm (A); 50 Mm (B); 10 Mm (C).