Trigonostomum, SCHMIDT, 1852

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 : 285-293

TRIGONOSTOMUM SCHMIDT, 1852

Trigonostomum Schmidt, 1852: 500 ; Graff, 1905:

73, 113; 1908: 2542; 1913: 302–303; Meixner,

1924b: 91–92, 96, 103; Luther, 1948: 36, 38;

Den Hartog, 1964: 373, t. 1; Ax, 1971: 146–

150, fig. 1. Vortex Schmidt, 1857: 352 , 356. Spiroclytus Schmidt, 1857: 352, 356; Claparède, 1863:

15. Orcus Uljanin, 1870: 19 . Kylosphaera Jensen, 1878: 16 , 36, 44–45. Hyporhynchus Graff, 1882: 336 . Hyporcus Graff, 1905: 73, 1910 ; 1908: 2542; 1913: 299. Woodshollia n.n. Graff, 1910: 947. Woodsholia Graff, 1911a: 198 ; 1911b: 61; 1913: 312. Woodsholia Graff, 1911b: 65 .

Diagnosis: Trigonostominae with anterior integumental invagination, connected with the body wall by several muscles. Pharynx situated anteriorly, strongly inclined forwards, with 11 radial muscles lengthwise and 24 in cross section. Paired testes at 50%, caudal to the pharynx.

Type species: Trigonostomum setigerum Schmidt, 1852

TRIGONOSTOMUM ARMATUM ( JENSEN, 1878) GAMBLE, 1900

( FIGS 5B , 8A , 9B , 10B; TABLE 1)

Alternative species name: trigonostomum-armatum

Kylosphaera armata Jensen, 1878: 7 , 12, 14, 17, 45– 47, t. 3, figs 14–22.

Hyporhynchus armatus Graff, 1882: 337 ; Gamble, 1893: 466–467; Attems, 1897: 228, t. 2, fig. 26.

Trigonostomum armatum Gamble, 1900: 813 ; Southern, 1912: 3, 9; Graff, 1913: 305–307, fig. 265; Southern, 1915: 34; Meixner, 1924b: 89, 94, 96, 99–100, 102; 1925: 256; Steinböck, 1931: 13, 23; Southern, 1936: 45, 57; Steinböck, 1938: 13, 22; Ax, 1952: 90– 91, fig. 1; Westblad, 1954: 9.

Known distribution: Norway ( Jensen, 1878; Graff, 1882; Westblad, 1954), English Channel ( Gamble, 1893), North Sea ( Attems, 1897; Meixner, 1924b, 1925), Ireland ( Gamble, 1893, 1900; Southern, 1912, 1915, 1936), Faeroe Islands ( Steinböck, 1931), Iceland ( Steinböck, 1938), Baltic Sea ( Ax, 1952).

New localities: Norway, Bergen, Karlsög, on algae, 9 July 1953 , Westblad (coll. SMNH). Norway, Trondheim, Munkholmen , in sand, 45–50 m deep, 22 July 1955 . Westblad (coll. SMNH). Norway, Leröy-Buröy , in fine-grained sand, 5–7 m deep, 1 August 1968 , Karling (coll. SMNH; type locality) . United Kingdom, Plymouth, Salcombe, Saltstone, on algae, 11 July 1949 , Westblad (coll. SMNH). Sweden, Gullmaren, Gåsövik, sheltered bay on brown algae, 19 August 2001 . France, Wimereux, Langue du Chien, on algae, 20 October 1999 . Curaçao (Dutch Antilles), Playa Canoa, on green algae, 10 December 1998 . Curaçao (Dutch Antilles), Dam di Cabicuchi , ‘Spaanse water’, on Turbinaria -like algae, 14 and 30 December 1998 and 5 January 1999 . Australia, New South Wales, Arrawarra, south of the marine station, on Sargassum sp. , 1 November 1997 . New Caledonia, Nouméa, Nouville, on algae in a lagoon, 10 August 2003 . South Georgia, Cumberland Bay, May Creek , on seaweed, 9 May 1902 (coll. SMNH).

Material examined: Several individuals studied alive. Neotype ( SMNH, no. 46427) from Norway. Whole mounts from France (1), Australia (1), New Caledonia (1), Curaçao (10) and South Georgia ( SMNH, no. 46448). Serially sectioned specimens from Sweden (3), Curaçao (1), Norway ( SMNH, no. 46425–6) and Plymouth ( SMNH, nos. 46419–20).

Diagnosis: Trigonostomum species with coiled copulatory organ, with one whole spire. Stylet 158–434 Mm long, enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage 50–149 Mm long, with two tubules, proximally curved over 270∞ and with straight distal part.

TRIGONOSTOMUM AUSTRALIS SP. NOV.

( FIGS 5D , 9D , 10D; TABLE 1)

Alternative species name: trigonostomum-australis sp. nov.

Holotype: Whole mount, Australia, Queensland, North Stradbroke Island, Point Lookout , algae in tidepool, 12 August 1996.

Other material: Observations on live material. Two whole mounts from Australia, New South Wales, Arrawarra , on Sargassum sp. , 28 August 1996 and 1 November 1997 .

Etymology: Reflects the species’ occurrence in the southern hemisphere.

Diagnosis: Trigonostomum species with coiled copulatory organ, with three whole spires. Stylet 414– 445 Mm long, enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage 34 Mm long, proximally curved over 270∞ and with straight distal section.

TRIGONOSTOMUM BREITFUSSI ( GRAFF, 1905) MEIXNER 1924

( FIG. 7E )

Alternative species name: trigonostomum-breitfussi.

Hyporcus breitfussi Graff, 1905: 112 , t. 3, figs 12–16; 1913: 301–302, figs 261, 262.

Hyporhynchus breitfussi Meixner, 1925: 256 .

Trigonostomum breitfussi Meixner, 1924b: 89 , 91–94, 96–99, 105, figs 3, 4; Steinböck, 1932: 309; Ax, 1952: 91–92, fig. 2; Westblad, 1954: 9; Armonies & Hellwig-Armonies, 1987: 104, table 5; Joffe & Kotikova, 1989: 70–72, 74–77, 79–82, figs 2, 3, 6 and 7.

Known distribution: Barents Sea ( Graff, 1905), Baltic Sea ( Ax, 1952), Greenland ( Steinböck, 1932), North Sea ( Meixner, 1924b, 1925; Ax, 1952; Armonies & Hellwig-Armonies, 1987), Norway ( Westblad, 1954).

New locality: Sweden, Gullmaren , Kristineberg, 23, 26 and 27 July 1932, Westblad (coll. SMNH; type locality) . Sweden, Gullmaren , on algae, 6 August 1945, Westblad (coll. SMNH) . Sweden, Gullmaren , Harpo Bedar, on red algae, 20 m deep, 7 August 2001 .

Material examined: Observations on live material from Sweden. Neotype ( SMNH, no. 47461). Two whole mounts ( SMNH, nos. 47462–3) and two serially sectioned specimens ( SMNH, nos. 47469–70) from Sweden.

Diagnosis: Trigonostomum species with copulatory organ ± 62 Mm long. Stylet ± 64 Mm long, proximally bent over, 180∞ and with a crest. Mantle with one blunt plate (shorter than the stylet), surrounds only the distal part of the stylet. Bursal appendage 20– 24 Mm long, proximally with a barrel-like casing and nine or ten distal tubes.

Remarks: The observation of Ax (1952) that there is only one plate-like structure instead of two ( Graff, 1905), surrounding the tubiform stylet, can be confirmed. This plate has a spine-like projection at its distal end, which lies close to the stylet but is displaced in highly squeezed animals ( Fig. 7E 1). The bursal appendage is short ( Graff, 1913 24 Mm; Ax, 1952: 20– 21 Mm), barrel-shaped and consists of nine, maybe ten, short tubes ( Fig. 7E 3 ).

TRIGONOSTOMUM CORONATUM ( GRAFF, 1882) GRAFF, 1913

( FIG. 7A )

Alternative species name: trigonostomum-coronatum Hyporhynchus coronatus Graff, 1882: 340 , t. 9, fig. 21. Hyporhynchus intermedius Attems, 1897: 228 , t. 2,

figs 22, 23.

Trigonostomum intermedium Graff, 1913: 308 , fig. 267; Meixner, 1924b: 96, 98; Southern, 1936: 45, 57.

Trigonostomum coronatum Graff, 1913: 307–308 , fig. 266; Meixner, 1924b: 96; Steinböck, 1933: 29.

Trigonostomum quadrifolium Riedl, 1954: 220–223 , figs 28, 29.

Known distribution: Madeira ( Graff, 1882), Irish Sea ( Southern, 1936), North Sea ( Attems, 1897), Mediterranean Sea ( Steinböck, 1933; Riedl, 1954).

New locality: France, Banyuls , Ile Gros, on algae left of the jetty, 23 June 2000 (type locality) .

Material examined: One specimen studied alive and mounted (neotype, LUC no. 228).

Diagnosis: Trigonostomum species with copulatory organ of ± 44 Mm. Stylet ± 70 Mm long, proximally bent over 90 ∞. Mantle split into three pointed plates, surrounding only the distal part of the stylet. Bursal appendage 78 Mm long, with proximal crown-like part and one terminal bent, striated tube.

Remarks: According to Graff (1882, 1913) the copulatory organ of T. coronatum consists of an inner and an outer tube. The inner tube is proximally bent and twice as long as the outer one, which forms a broad mantle around the distal part of the inner tube. These observations can more or less be confirmed on the specimen from Banyuls, although it was squashed and the copulatory organ was rather damaged. The bursal appendage consists of a crown-like proximal part, enveloped by the bursa, and a tubular distal part. The bursal appendage of the Banyuls specimen consists of a plate proximally carrying a crown-like part, which is enveloped by the bursa, probably consisting of four plates, which are proximally split. Distally, the bursal appendage forms two bent tubes. These tubes show an inconspicuous striation, giving the impression that they consist of a number of smaller tubules.

Based on this resemblance, the Banyuls specimen is placed within T. coronatum . However, two other species have the same structure of the bursal appendage - T. intermedium Attems, 1897 and T. quadrifolium Riedl, 1954 - although little is known of the structure of their copulatory organs. In T. quadrifolium the appendage carries only one tube ( Riedl, 1954), whereas the tube is apparently split into three tubules in T. intermedium ( Attems, 1897; Graff, 1913), of which no material was available. These species also differ in the number of plates forming the crown of the appendage: four in T. quadrifolium ( Riedl, 1954) and five in T. intermedium ( Attems, 1897: fig. 22; Graff, 1913) and T. coronatum ( Graff, 1882) . Based on the descriptions of T. intermedium and T. quadrifolium and our experience that the mentioned differences are often difficult to assess, we synonymise both species with T. coronatum .

TRIGONOSTOMUM DENHARTOGI ( KARLING, 1978) COMB. NOV.

( FIGS 8E , 11A )

Alternative species name: trigonostomum-denhartogi Proxenetes denhartogi Karling, 1978: 233 , figs 35, 36.

Known distribution: Bermuda ( Karling, 1978).

New localities: Kenya, Mombasa area, McKenzie Point, in shallow pool on seagrass, 30 September 1991. Curaçao (Dutch Antilles), Dam di Cabicuchi (‘Spaanse water’), on Turbinaria -like algae from exposed rocks, 14 December 1998. Curaçao (Dutch Antilles) ‘Spaanse water’, mixed sample of algae, 30 December 1998. New Caledonia, Nouméa, Nouville, on algae in a lagoon south of the asylum, 3 August 2003. New Caledonia, Nouméa, Anse Vata, on algae ( Ulva sp. and Enteromorpha sp. ) from a little estuary, 22 August 2003.

Material examined: Holotype (SMNH, no. 2965). Live material and five whole mounts, one from each new locality.

Diagnosis: Trigonostomum species with very complex copulatory organ, 106–121 Mm long. Mantle with numerous folds, rods and spines, one of which has a thread-like distal part. Stylet 61–66 Mm long. Bursal appendage with a straight initial part, 22–44 Mm long, and two heavily coiled tubes.

Remarks and additional data: Karling (1978) described this species from Bermuda based on one whole mounted specimen, but without observations of live animals. On the holotype, the anterior invagination (‘proboscis’) is not visible and Karling therefore did not observe this important feature. Based on the structure of the copulatory organ he reluctantly placed the species within Proxenetes Jensen, 1878 . He explicitly mentioned, however, that the bursal appendage was very unlike that of any other species of Proxenetes , where the bursal appendage consists of a split tube, surrounded by a ring. Observations on live material clearly show that this species indeed belongs to Trigonostomum , as it has the typical anterior invagination.

The specimens from Curaçao and New Caledonia are ± 0.8 mm long. The copulatory organ is of exactly the same structure as in the specimen from Bermuda ( Karling, 1978), consisting of an outer plate-like structure ( Fig. 11A 1: a) that forms a broad gutter enclosing several long rods ( Fig. 11A 1: e). One of these rods has a long distal thread-like point ( Fig. 11A 1: e1). A second, triangular, plate-like part ( Fig. 11A 1: d) surrounds the rods and carries three distal hooks ( Fig. 11A 1: a1, b and c). The length of the copulatory organ (excluding the thread-like tip) is 107–111 Mm ( Curaçao) and 109– 121 Mm ( New Caledonia), which is almost identical to that of the holotype (115 Mm: Karling, 1978). The exact number of rods could not be determined. The tubular stylet is only clearly visible in the New Caledonian specimens ( Figs 8E , 11A 3 ). It is 61–66 Mm long (n = 2) and rather broad, with a wide proximal funnel to which the mantle is attached. The bursal appendage of the specimens from Curaçao and New Caledonia clearly consists of two heavily coiled tubes and a proximal basal piece. This proximal part is 31 Mm and 44 Mm in the two specimens from Curaçao, 28 Mm and 36 Mm in the specimens from New Caledonia, and 22 Mm in the specimen from Bermuda ( Karling, 1978). Karling (1978) could not determine the exact number of coiled tubes in the Bermuda individuals.

TRIGONOSTOMUM FRANKI SP. NOV.

( FIGS 2 , 3 , 5A , 8G, I , 9A , 10A; TABLE 1)

Alternative species name: trigonostomum-franki sp. nov.

Holotype: Whole mount, Curaçao (Dutch Antilles), Dam di Cabicuchi (‘Spaanse water’), on Turbinaria - like algae from exposed rocks at the side of ‘Caracasbaai’, 14 December 1998 ( LUC no. 225).

Paratype: Whole mount, same data as for the holotype ( LUC no. 226) .

Other material: Observations on live material. Two whole mounts and one serially sectioned specimen from Curaçao ( Dutch Antilles ), ‘ Spaanse water’, mixed sample of algae containing mainly Caulerpa sp. and Halimedia gantia, 30 December 1998 . One whole mount from Florida ( USA), Fort Pierce, in fine detritus-rich sand between rocks, 16 November 1994 . Three whole mounts - Kenya, Mombasa area, Mc- Kenzie Point - on algae and seagrasses, 4 and 15 June 1987 and 27 September and 1 October 1991 . One whole mount from Tanzania, Zanzibar, Pete, on seagrasses, 16 August 1995 . Three whole mounts, New Caledonia, Nouméa, Nouville, on algae in a lagoon south of the asylum, 3 and 10 August 2003 . One whole mount, New Caledonia, Nouméa, Baie des Citrons, on algae in a lagoon, 8 August 2003 . Live observations from New Caledonia, Nouméa , Nouville, on algae covered with shells and sand on a reef in the western part of the Kuendu Bay, 16 August 2003 .

Etymology: Dedicated to Mr Frank Van Belleghem, who helped to collect the material on Curaçao.

Diagnosis: Trigonostomum species with moderately coiled copulatory organ, with 1 / 2 spire. Stylet 86– 111 Mm long, enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage 61–166 Mm long, with two tubules, proximally curved over 270∞ and with straight distal part.

TRIGONOSTOMUM GALAPAGOENESIS SP. NOV.

( FIGS 5E , 9E; TABLE 1)

Alternative species name: trigonostomum-galapagoensis sp. nov.

Trigonostomum setigerum Ehlers & Ax, 1974: 664– 666 , 668, fig. 13A- C.

Holotype: One micrograph (fig. 13C in Ehlers & Ax, 1974), Galapagos ( Ecuador), Santa Cruz, Bahía Academy ( Ehlers & Ax, 1974).

Etymology: The islands where the type material was found.

Diagnosis: Trigonostomum species with coiled copulatory organ, four whole spires. Stylet enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage coiled, with two tubules.

Remarks: Pigment spot rostrally, between the eyes (see Ehlers & Ax, 1974: fig. 13A). The length of both hard parts, copulatory organ and bursal appendage, could not be measured, because this species is only known from a micrograph of a live individual ( Ehlers & Ax, 1974: fig. 13), without a scale bar.

TRIGONOSTOMUM LILLIEI ( GRAFF, 1911A) MEIXNER 1924B

( FIG. 7D )

Alternative species name: trigonostomum-lilliei

Woodsholia lilliei Graff, 1911b: 61–65 , fig. 3, t. IV, figs 29–43; 1913: 312–314, figs 277–279; Meixner, 1924b: 91, 92.

Trigonostomum prytherchi Kepner, Ferguson & Stirewalt, 1941: 243–252 , figs 1–3, pl. 3.

Trigonostomum divae Marcus, 1948: 121–125 , 189, t. III, figs 13–18.

Trigonostomum lilliei Meixner, 1924b: 92 , 94, 96, 99, 102.

Known distribution: North American Atlantic coast ( Graff, 1911b, 1913; Kepner et al., 1941), Brazil ( Marcus, 1948).

New locality: Australia, New South Wales, Arrawarra , rocky tidepool at low tide, on brown algae, 29 August 1996 ; south of the marine station, mideulittoral, on Sargassum sp. , 1 November 1997.

Material examined: Observations on two live specimens, two whole mounts (all from Australia), the holotype of T. prytherchi , which is designated neotype (whole mount; SI-NMNH, Cat. no. 20593; Kepner et al., 1941) and Marcus’ (1948) material of T. divae (sections and whole mounts; SMNH, nos. 42204–8).

Diagnosis: Trigonostomum species with copulatory organ 42–46 Mm long. Stylet 40–57 Mm long, proximally bent over, 180∞. Mantle with one hooked plate (as long as the stylet) surrounds only the distal part of the stylet. Bursal appendage 95–98 Mm long, heavily coiled, consisting of one tube, which is distally split into five or six finer tubes.

Remarks and additional data: The stylet of the examined specimens is 40–57 Mm long (57 Mm in the holotype of T. prytherchi ; 40–43 Mm in Marcus’ material of T. divae , n = 2; 44–46 Mm in the Australian specimens, n = 2). The bursal appendage is a 95– 98 Mm long (n = 2). The bursal appendage could not accurately be measured in the second Australian specimen, or in Marcus’ material.

According to the description, including figures, of Kepner et al. (1941), it seems that they observed not one but three bursal appendages (including two smaller nonfunctioning appendages). These observations could be due to a misinterpretation of the serially sectioned material, because a thorough examination of the type material revealed only one bursal appendage.

According to Marcus’ (1948) drawings and description, the difference between T. divae and T. lilliei is the presence of only five tubes in the bursal appendage instead of six, a feature, which is often very difficult to assess. The overall construction of the bursal appendage of T. divae (i.e. the number and extent of coils) is identical to that of the Australian specimens. The bursal appendage of T. prytherchi is also identical in structure. The difference between T. prytherchi and T. lilliei would also be the ending of the prepharyngeal cavity in the ‘proboscis’ cavity as observed by Graff (1911b: fig. 31). According to Meixner (1924b) this feature is the result of the degree of contraction, and he therefore rejected the taxon Woodsholia . Because of these doubtful differences between these ‘species’ and the overall similarity in the structure of both the copulatory organ and the bursal appendage, we synonymise T. prytherchi and T. divae , with T. lilliei .

TRIGONOSTOMUM MESSOPLANOIDES ARTOIS ET AL., 2000

( FIG. 6B )

Alternative species name: trigonostomummessoplanoides

Trigonostomum messoplanoides Artois et al., 2000: 104–105 , fig. 1.

Known distribution: Weddell Sea, Antarctica ( Artois et al., 2000).

Material examined: Holotype ( LUC, no. 207).

Diagnosis: Trigonostomum species with stylet 225 Mm long, proximally bent over 270∞. Mantle with stylet 75 Mm long, flagelliform spine surrounding only the distal part of the stylet. Bursal appendage 22 Mm long, with a proximal ring and two distal tubes.

Remarks: The copulatory organ of T. messoplanoides resembles that of some species of Messoplana ( Artois et al., 2000) , for instance M. elegans ( Luther, 1948) Den Hartog, 1966 , M. helgolandica Ax, 1971 , M. pacifica Karling, 1986 and M. rugata Ehlers, 1974 . However, the presence of a ventral invagination clearly confirms that it is a species of Trigonostomum .

TRIGONOSTOMUM MIRABILE ( PEREYASLAWZEWA, 1893) GRAFF, 1913

( FIG. 7F )

Alternative species name: trigonostomum-mirabile

Hyporhynchus mirabilis Pereyaslawzewa, 1893: 267 , t. 4, fig. 27.

Trigonostomum mirabile Graff, 1913: 310–311 , fig. 273; Meixner, 1924b: 96, 98; Ax, 1959: 98–99, figs 80, 81; Mack-Fira, 1968: 179–180, figs 2–4; 1974: 249, 265, 273, 281, 284.

Proxenetes lictor Beklemischev, 1927: 190–191 , 203– 204, t. I, figs 8, 9.

Known distribution: Black Sea ( Pereyaslawzewa, 1893; Beklemischev, 1927; Ax, 1959; Mack-Fira, 1968, 1974); Sea of Marmara ( Ax, 1959).

New locality: Romania, Black Sea , Agigea, on Ceramium sp. , 26 September 1968, Mack-Fira (coll. SMNH; type locality) .

Material examined: Two individuals from Agigea (mounted on the same slide: SMNH, no. 47474). One of them designated neotype.

Diagnosis: Trigonostomum species with copulatory organ 72–74 Mm long. Stylet 83–84 Mm long, proximally bent over, 180∞. Mantle with two pointed plates (as long as the stylet) surrounds only the distal part of the stylet. Bursal appendage 66 Mm long, proximally with a barrel-like casing and ± ten distal tubules.

Remarks: The synonymization of Proxenetes lictor with T. mirabile was made by Ax (1959), but it was already recognized by Beklemischev in a personal note on the offprints of his article (see Ax, 1959).

TRIGONOSTOMUM NATASCHAE SP. NOV.

( FIG. 7G )

Alternative species name: trigonostomum-nataschae sp. nov.

Holotype: Whole mount, Kerguelen ( France, subantarctic territory), Port Raymond, tidepool with fine sand and silt, mixed with shells, 23 November 1992 ( LUC no. 227).

Other material: Observations on live material from Kerguelen.

Etymology: Dedicated to Mrs Natascha Steffanie, technical assistant at LUC, Diepenbeek ( Belgium).

Diagnosis: Trigonostomum species with copulatory organ ± 78 Mm long. Stylet ± 104 Mm long, proximally bent over, 180∞ and with a crest. Mantle with two blunt plates (shorter than the stylet) surrounds only the distal part of the stylet. Bursal appendage ± 65 Mm long, with proximal barrel-like part and very narrow tubules, forming two curved bundles of tubules distally.

TRIGONOSTOMUM PENICILLATUM ( SCHMIDT, 1857) MICOLETZKY, 1910

( FIG. 7C )

Alternative species name: trigonostomumpenicillatum

Vortex penicillatus Schmidt, 1857: 352 , t. 1, fig. 3.

Hyporhynchus penicillatus Diesing, 1862: 227 ; Graff, 1882: 341, t. 9, figs 15–20; Gamble, 1893: 467; Fuhrmann, 1898: 459; Gamble, 1900: 813; Meixner, 1925: 256; 1926: 577.

Trigonostomum intermedium n.n. Graff 1910: 4.

Trigonostomum penicillatum Micoletzky, 1910: 174 ; Graff, 1913: 308–309, figs 268–270; Southern, 1912: 3, 9; 1915: 34; Meixner, 1924a: 202–203; 1924b: 89, 92, 94, 96, 98, 99, 105; Southern, 1936: 45, 58; Westblad, 1954: 8; Den Hartog, 1964: 378; Ax, 1971: 216– 217, fig. 45.

Trigonostomum marki Graff, 1911b: 60 , t.4, figs 44, 45; 1913: 309–310, fig. 271; Meixner, 1924b: 96, 99.

Known distribution: North American Atlantic coast ( Graff, 1911b), French Atlantic coast ( Ax, 1971), English Channel ( Gamble, 1893), North Sea ( Graff, 1913; Meixner, 1924b), Ireland ( Southern, 1912, 1936), Norway ( Westblad, 1954), Mediterranean Sea ( Schmidt, 1857; Graff, 1913; Meixner, 1925, 1926) and Adriatic Sea ( Meixner, 1925, 1926).

New localities: Great Britain, Plymouth, 5 July 1949, Westblad (coll. SMNH) . France, Corsica, Ocellutia , large sandflat with coarse sand, 10–12 m deep, 19 October 1982 and 18 September 1983 . Italy, Sardinia, Porticciolo , on algae at ± 10 m deep, 14 August 1994 (type locality) . France, Banyuls, Ile Gros , on green algae near the jetty behind the station, 20, 22 and 23 June 2000 . Yugoslavia, Adriatic Sea, Dubrovnik , 24 June 1952, Westblad (coll. SMNH) . Bulgaria, Varna ( Black Sea ), on algae, 21 December 1953, Valkanov (coll. SMNH) .

Material examined: Observations on live material from Corsica, Sardinia and Banyuls. Neotype ( LUC no. 229) from Sardinia. One whole mount from Bulgaria ( SMNH, no. 47485) and serially sectioned specimens from Great Britain ( SMNH, nos. 47480–3) and Yugoslavia ( SMNH, nos. 47484). Seven whole mounts from Banyuls and three from Corsica.

Diagnosis: Trigonostomum species with copulatory organ 30–45 Mm long. Stylet 44–53 Mm long, proximally bent over 90∞. Mantle with three spiny plates, surrounds only the distal part of the stylet. Bursal appendage 60–70 Mm long, with a barrel-like casing and ± 12 distal tubules.

Remarks: According to Meixner (1924b), the bursal appendage of T. penicillatum partially consists of ± 26 fine rods. However, our observations on serially sectioned material of T. penicillatum (SMNH) revealed only 12 fine, slightly bent rods in the bursal appendage of a specimen from Plymouth, though more in the individuals in the whole mounts.

In 1897, T. intermedium was described by Attems, but the same name was used by Graff as a nomen nudum in 1910 for a species he later ( Graff, 1911b) described as T. marki . The structure of the bursal appendage of T. marki is identical to that of T. penicillatum ( Graff, 1911b, 1913). According to Graff (1913) the species differ in the structure of the copulatory organ. In T. penicillatum the organ has a stylet, enclosed by a mantle, which carries three plates; the same structure is described and drawn by Graff (1911b: 61, table 4, figs 44, 45; 1913: 309, fig. 271) for T. marki . T. marki is therefore synonymized with T. penicillatum .

TRIGONOSTOMUM SETIGERUM SCHMIDT, 1852

( FIGS 5C , 8B, D , 9C , 10C; TABLE 1)

Alternative species name: trigonostomum-setigerum

Trigonostomum setigerum Schmidt, 1852: 500 , t. 47, fig. 13; Diesing, 1862: 229; Graff, 1905: 113–114, t. 3, figs 17–21; Micoletzky, 1910: 173; Southern, 1912: 3, 9; Graff, 1913: 303–305, figs 263, 264; Southern, 1915: 34; Meixner, 1924a: 202–203; 1924b: 89, 90, 92, 93–94, 96, 99–101, 102, figs 1, 2, 5; 1925: 256; 1926: 577; Steinböck, 1933: 10–11; Southern, 1936: 45, 57; Meixner, 1938: 25, 114, fig. 23; Westblad, 1952: 30–31; Ax, 1959: 97; Riedl, 1959: 319–322, fig. 6; Den Hartog, 1964: 375; Karling, 1978: 231, figs 27, 28; 1986: 209–210, figs 39, 40, 47,48; Ax & Armonies, 1990: 100.

Trigonostomum setigerum setigerum Graff, 1905: 113 , t. 3, figs 19–21; 1913: 305.

Trigonostomum setigerum album Graff, 1905: 114 , t.3, figs 17, 18; 1913: 305.

Trigonostomum setigerum lunulatum Graff, 1905: 114 ; 1913: 305.

Spiroclytus nisus Schmidt, 1857: 356 , 365, t. 3, fig. 8; Diesing, 1862: 225.

Spiroclytus euryalus Schmidt, 1857: 356 , 365, t. 3, fig. 8.

Spiroclytus setigerus Claparède, 1863: 15 .

Vortex ornatus Uljanin, 1870 :, 18, t. 4, fig. 15.

Hyporhynchus setigerus Graff, 1882: 338–339 , t. 9, figs 6–14, t. 11, fig. 27; Pereyaslawzewa, 1893: 267, t.4, fig. 29, t. 10, figs 60a- e, 63d; Fuhrmann, 1898: 459; Sekera, 1901: 81; Sabussow, 1905: 488.

Known distribution: Mediterranean Sea ( Schmidt, 1852,, 1857; Graff, 1905; Sabussow, 1905; Micoletzky, 1910; Meixner, 1925; Steinböck, 1933; Riedl, 1959), Adriatic Sea ( Meixner, 1925, 1926), Black Sea ( Uljanin, 1870; Pereyaslawzewa, 1893; Graff, 1905; Ax, 1959), Sea of Marmara ( Ax, 1959), northern Atlantic Ocean ( Fuhrmann, 1898; Graff, 1905; Southern, 1912, 1915, 1936; Karling, 1978), North Sea ( Meixner, 1924b), southern Atlantic Ocean ( Westblad, 1952).

New localities: France, Corsica, Port de la station Stareso , on algae, 10 April, 9 May and 19 October 1982 ; Punta Reveletta , on algae, 11 May and 22 October 1982 . France, Banyuls, Ile Gros , on green algae near the jetty behind the station, 20–23 June 2000 . Greece, Perea , east side of the beach, coarse-grained detritus-rich sand mixed with shell gravel; on green and red algae, 22 July 2002 ; on green algae and seagrasses, ± 2 m deep, 31 July 2002. Greece, Nea Michaniona , flat exposed beach, on Enteromorpha sp. and seagrasses, 22 July 2002 . Greece, Aghias Triada , flat beach, on green algae and seagrasses ± 2.5 m deep, 22 July 2002 and 6 August 2002 (type locality) . Greece, Nea Fokea ( Kassandra Peninsula ), heavily exposed beach, on algae, 28 July 2002 . United Kingdom, Plymouth, Wembury , tidepool, 21 July 1949 , Westblad (coll. SMNH) . Kenya, Tiwi , on algae, 6 October 1991 .

Material examined: Several specimens studied alive. Neotype ( LUC no. 230) from Greece. Whole mounts from Banyuls (2), Bermuda ( SMNH, no. 46460), Corsica (5), Falkland ( SMNH, nos. 46429, 46430, 46440), Greece (26), Kenya (1), Plymouth ( SMNH, no. 46452) and South Georgia ( SMNH, no. 46448). Serially sectioned specimens from Falkland ( SMNH, nos. 46431– 9, 46441–4), Plymouth ( SMNH, nos. 46449–51), South Georgia ( SMNH, nos. 46445–7) and Greece.

Diagnosis: Trigonostomum species with coiled copulatory organ, with two whole spires. Stylet 284– 498 Mm long, enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage 64–161 Mm long, with two tubules, proximally curved over 360∞.

Remarks: Graff (1905, 1913) recognized three subspecies, based on the pattern of pigmentation: T. setigerum setigerum (with dorsal stripe), T. setigerum lunulatum (with a rostral spot between the eyes) and T. setigerum album (without pigmentation). The validity of these subspecies was questioned by Southern (1912). Observations on a large number of live animals from one population in Greece showed that the three subspecies occurred sympatrically and that the difference between these three is not always clear. For example, specimens with a rostral spot (T. s. lunulatum of Graff, 1905) showed a large variation in size of the spot, making the difference with T. s. album very small. There is also variation in the length and width of the dorsal stripe: some individuals have a short dorsal stripe, which is broader between the eyes, while in other specimens the dorsal stripe is long and very broad over its whole length, giving it a network-like appearance. Based on the occurrence of all forms in one population ( Greece, Thessaloniki), the lack of other distinctive features and the large variation of the three ‘forms’, the three subspecies are synonymized with T. setigerum .

TRIGONOSTOMUM SPINIGERUM SP. NOV.

( FIGS 8F, H , 11B )

Alternative species name: trigonostomum-spinigerum sp. nov.

Holotype: Whole mount, New Caledonia, Nouméa, Nouville, on algae in a lagoon south of the asylum, 3 August 2003 ( LUC no. 231).

Etymology: Refers to the spines on the mantle surrounding the stylet; spinigerum (L.) = prickly, spiny, thorny.

Diagnosis: Trigonostomum species with copulatory organ 61 Mm long. Stylet 57 Mm long, proximally bent over almost 90∞. Mantle surrounds the whole stylet and carries 8–10 small spines on the convex side. Bursal appendage ± 35 Mm long, proximally funnel-shaped with two heavily coiled distal tubes, very faintly striated.

Remarks: The bursal appendage is measured (and drawn) on the whole mount, in which it appeared extremely thin-walled. Therefore, the length (35 Mm) has to be interpreted as the minimum length. Furthermore, only one distal tube could be observed (two in the live individual), probably because both tubes are situated exactly above each other in the mounted specimen.

TRIGONOSTOMUM TORI SP. NOV.

( FIGS 5F , 9F , 10E; TABLE 1)

Alternative species name: trigonostomum-tori sp. nov. Trigonostomum setigerum Karling, 1986: 209–210 ,

figs 45, 46.

Holotype: One whole mount, USA, California, Pacific Grove ( SMNH, no. 46459; Karling, 1986).

Paratypes: Two whole mounts (SMNH, nos. 46457–8; Karling, 1986).

Etymology: Dedicated to Prof. Dr Tor G. Karling, who collected the material.

Diagnosis: Trigonostomum species with coiled copulatory organ, with five whole spires. Stylet 683– 853 Mm long, enveloped by the mantle over its entire length. Mantle distally split into two spiny plates with terminal hook. Bursal appendage 80–106 Mm long, with two tubules, proximally curved over 270∞ and with straight distal part.

TRIGONOSTOMUM VENENOSUM ( ULJANIN, 1870) MEIXNER, 1924 B

( 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 ).

TRIGONOSTOMUM WATSONI SP. NOV.

( FIG. 7B )

Alternative species name: trigonostomum-watsoni sp. nov.

Holotype: Whole mount, Australia, New South Wales, Arrawarra , on Pavonina -like algae in shallow tidepool between rocks near beach, 27 August 1996.

Paratype: One whole mount.

Other material: Observations on live material. Six whole mounts and six serially-sectioned specimens, Australia, New South Wales, Lennox Head , on beach with coarse sand and on algae in tide pool, 27 October and 1 November 1997 . One whole mount, Australia, New South Wales, Arrawarra , on Sargassum sp. in permanent pool, 27 August 1996 . One whole mount, Australia, New South Wales, Arrawarra, Mullaway headland, on algae in deep rock pools, 24 July 2003 . Two whole mounts, New Caledonia, Nouméa, Magenta , permanent pool near mangroves, on large algae covered with epiphytes, 22 August 2003 .

Etymology: Dedicated to Dr Nikki Watson, Armidale, Australia, who assisted with the collection of material at Arrawarra.

Diagnosis: Trigonostomum species with copulatory organ 28–36 Mm long. Stylet 29–41 Mm long, proximally bent over 90∞. Mantle with three spine-like plates surrounds only the distal part of the stylet. Bursal appendage 62–78 Mm long, with two coiled (more than 360∞) striated tubes.

Figures

Figure 2. Reconstruction on sagittal sections of the rostral body end from the left hand side (T. franki sp. nov.). Abbreviations: cbm, circular body muscles; dil1–2, dilators of opening of antero-ventral invagination; e, eye; ecm, external circular pharyngeal muscles; elm, external longitudinal pharyngeal muscles; i, antero-ventral invagination; icm, internal circular pharyngeal muscles; ig, invagination glands; ilm, internal longitudinal pharyngeal muscles; ir, integument retractors; lbm, longitudinal body muscles; m, mouth; pc, prepharyngeal cavity; pg, pharynx glands; ppt, pharynx protractors; prt, pharynx retractors; ps, pigment stripe; rm, radial pharyngeal muscles; rr, retractors of antero-ventral invagination.

Figure 3. Reconstruction on sagittal sections of the genital system from the left hand side (T. franki sp. nov.). Abbreviations: ba, bursal appendage; bs, bursal stalk; bu, bursa; cga, common genital atrium; cop, copulatory organ; ds, spermatic duct; fd, female duct; fg, female glands; gp, common genital pore; n, nucleus; od, oviduct; ov, ovary; rh, rhabdite; sd, seminal duct; vg, prostate vesicle; vit, vitellary; vs, seminal vesicle.

Figure 5. Schematic representation of the copulatory organ of the representatives of group 2, showing the different number of spires (dashed lines indicate the location of the mantle plates). A, T. franki sp. nov. (1/ spire). B, T. armatum. (11/ 2 2 spires). C, T. setigerum. (21/ spires). D, T. australis sp. nov. (31/ spires). E, T. galapagoensis sp. nov. (41/ spires). F, 2 2 2 T. tori sp. nov. (51/ spires).

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).

Figure 7. Copulatory organs and bursal appendages of the representatives of group 1B, A, T. coronatum: A1 copulatory organ; A2 bursal appendage. (from the neotype). B, T. watsoni sp. nov. B1, 2 copulatory organ; B3 bursal appendage (B1 from the holotype; B2, 3 from the paratype). C, T. penicillatum: C1 copulatory organ; C2 bursal appendage (from the neotype). D, T. lilliei: D1, 3 copulatory organ; D2, 4 bursal appendage. [D1, 2 specimen from Australia; D3, 4 specimen from the USA (neotype = holotype of T. prytherchi)]. E, T. breitfussi: E1 copulatory organ; E2 bursal appendage; E3 section through the bursa and the bursal appendage (different specimens from Sweden; E2, 3 freehand drawings). F, T. mirabile: F1, 2 copulatory organ; F3 bursal appendage (F1, 3 from the neotype; F2 from another specimen from the Black Sea). G, T. nataschae sp. nov. G1 Copulatory organ; G2 Bursal appendage (from the holotype).

Figure 8. A, rostral spot in T. armatum (whole mounted specimen from Curaçao). B, dorsal stripe in T. setigerum (whole mounted specimen from Greece). C, bursal appendage of T. tori sp. nov. (from the paratype). D, constricted distal tubes of bursal appendage (arrow indicates constriction) in T. setigerum (specimen from Bermuda). E, copulatory organ of T. denhartogi comb. nov. (specimen from New Caledonia). F, copulatory organ of T. spinigerum sp. nov. (from the holotype). G, habitus of T. franki sp. nov. (live specimen from New Caledonia). H, bursal appendage of T. spinigerum sp. nov. (from the holotype). I, head region of T. franki sp. nov. showing both epidermal and subepidermal pigment (live specimen from New Caledonia). Scale bars: A, B = 200 Mm. C-F = 20 Mm. H = 10 Mm.

Figure 9. Copulatory organ of the representatives of group 2. A, T. franki sp. nov. (specimen from Curaçao) B, T. armatum (specimen from Curaçao). C, T. setigerum (from the neotype). D, T. australis sp. nov. (from the holotype). E, T. galapagoensis sp. nov. (from the holotype; after Ehlers and Ax, 1974: fig. 13C). F, T. tori sp. nov. (from the holotype). Scale bars: A-D, F = 20 Mm.

Figure 10. Copulatory organs and bursal appendages of the representatives of group 2. A, T. franki sp. nov. A1, 3 copulatory organ; A2, 4 bursal appendage (A1, 2 from the holotype; A3, 4 from a specimen from Kenya). B, T. armatum sp. nov. B1, 3 copulatory organ; B2, 4 bursal appendage (B1, 2 specimen from France; B3, 4 specimen from Curaçao). C, T. setigerum: C1 copulatory organ; C2 bursal appendage (specimen from Kenya). D, T. australis sp. nov. D1 copulatory organ; D2 bursal appendage (from the holotype). E, T. tori sp. nov. E1 copulatory organ; E2 bursal appendage (from the holotype).

Figure 11. A, T. denhartogi comb. nov. A1, 3 copulatory organ; A2 bursal appendage (A1, 2 specimen from Curaçao; A3 specimen from New Caledonia). B, T. spinigerum sp. nov. B1 copulatory organ; B2 bursal appendage (from the holotype). Abbreviations: a-e, explained in text.