Trigonostomum venenosum, (Uljanin, 1870)

Willems, Wim R., Artois, Tom J., Vermin, Wouter A. & Schockaert, Ernest R., 2004, Revision of Trigonostomum Schmidt, 1852 (Platyhelminthes, Typhloplanoida, Trigonostomidae) with the description of seven new species, Zoological Journal of the Linnean Society 141 (2), pp. 271-296 : 292

TRIGONOSTOMUM VENENOSUM ( ULJANIN, 1870)

MEIXNER, 1924B

( FIGS 1 , 6A )

Alternative species name: trigonostomum-venenosum

Orcus venenosus Uljanin, 1870: 19 , t. 2, fig. 5.

Hyporhynchus venenosus Graff, 1875: 419 ; 1882: 341; Pereyaslawzewa, 1893: 265, 266, t. 4, fig. 28; Attems, 1897: 227, t. 2, figs 24, 25.

Hyporcus venenosus Graff, 1905: 110 , t. 3, figs 9–11; Southern, 1912: 3, 8–9; Graff, 1913: 299–301, fig. 260; Southern, 1915: 34; Meixner, 1924b: 91, 92; Southern, 1936: 45, 57; Meixner, 1926: 577.

Trigonostomum venenosum Meixner, 1924b: 89 , 92, 94, 96, 99, 102; 1925: 256; Steinböck, 1931: 12, 23; 1938: 12–13, 22; Ax, 1959: 98, figs 78, 79; Mack-Fira & Cristea-Nastasesco, 1971: 225, 227, figs 5, 6; Mack-Fira, 1974: 249, 265, 273, 281–282, 284.

Known distribution: Iceland ( Steinböck, 1938), Ireland ( Southern, 1912, 1936), Faeroe Islands ( Steinböck, 1931), North Sea ( Attems, 1897; Meixner, 1924b, 1925), Mediterranean Sea ( Graff, 1882; Meixner, 1926), Adriatic Sea ( Meixner, 1926), Black Sea ( Uljanin, 1870; Pereyaslawzewa, 1893; Graff, 1905; Ax, 1959; Mack-Fira & Cristea-Nastasesco, 1971; Mack-Fira, 1974).

New localities: Sweden, Gullmarsfjord, Gåsövik , among algae, August 1945, Westblad (coll. SMNH) . Norway, Bergen, Bay south of Tyssöy , stones, gravel, algae and fine shell-sand, 5–8 m depth, 29 July 1968, Karling (coll. SMNH) . Norway, Bergen , sound between Leröy and Buröy; sand and mud, 5 m depth; 1 August 1968, Karling (coll. SMNH) . France, Corsica, Port de la station Stareso, on algae, 6– 4 m deep, 9 May 1982 and 12 March 1983, Martens; Bay of Calvi , 11 April 1984 and 26 March 1985 . Italy, Sardinia, Porticello , about 0.2–1.5 m deep, on Vaucheria -like algae on rocks, 14 August 1994 . France, Banyuls, Ile Gros, on green algae near the jetty behind the station, 22–23 June 2000. Kerguelen , Port Couvreux , bay at the right, green algae, 25 November 1992 .

Material examined: Several specimens studied alive. Neotype ( SMNH, no. 47499). Whole mounts from Sardinia (2), Corsica (4), Banyuls (3), Kerguelen (6), Norway ( SMNH, nos. 47496–8) and Romania ( SMNH, no. 47500–1). Two serially sectioned specimens ( SMNH, nos. 47493–4) from Sweden.

Diagnosis: Trigonostomum species with copulatory organ 74–130 Mm long. Stylet 117–194 Mm long, proximally bent over 270∞. Mantle with one pointed plate, surrounds only the distal part of the stylet. Bursal appendage ± 54 Mm long, with a proximal ring and two distal tubes.

Remarks and additional data: The length of the stylet shows large variation between the populations of Banyuls (117–124 Mm; n = 2), Sardinia (148– 156 Mm; n = 2), Corsica (165–179 Mm; n = 2) and Kerguelen (157–194 Mm; n = 3). The stylet resembles that of some species of Messoplana (e.g. M. elegans Luther, 1948 ; M. helgolandica Ax, 1971 ; M. pacifica Karling, 1986 ; M. rugata Ehlers, 1974 ).

Figures

Figure 1. Habitus of live animal (Trigonostomum venenosum). Abbreviations: ac, apical tuft of cilia; b, brain; ba, bursal appendage; bu, bursa; cop, copulatory organ; e, eye; gp, common genital pore; i, antero-ventral invagination; m, mouth; ov, ovary; ph, pharynx; rg, rostral rhabdite glands; t, testis; vg, prostate vesicle; vit, vitellary; vs, seminal vesicle.

Figure 6. Copulatory organs and bursal appendages of the representatives of group 1A. A, T. venenosum: A1, 3 copulatory organ; A2, 4 bursal appendage. (A1, 2 specimen from Norway, neotype; A3,4 specimen from Sardinia). B, T. messoplanoides: B1 copulatory organ; B2 bursal appendage. (from the holotype; after Artois et al., 2000).