Trigonostomum, SCHMIDT, 1852, SETIGERUM 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 : 284-285

IDENTIFICATION KEY

1. Copulatory organ 106–121 Mm long and very complex, consisting of a gutter-shaped plate, enveloping a bundle of rods, of which one has a long thread-like distal tip; stylet funnel-shaped, ± 65 Mm long; bursal appendage with initial straight part (22–44 Mm long) and two heavily coiled distal tubes. (Figs 8E, 11A) .................................... T. denhartogi comb. nov.

- Copulatory organ ± 60 Mm long; stylet bent over 90∞, surrounded by the mantle that has 8–10 small spines at the convex side and with broad distal plates and spines distally (Fig. 11B4); bursal appendage with two broad, highly coiled tubes (Figs 8F, H, 11B) ........................................................................................................................... T. spinigerum sp. nov.

- Copulatory organ otherwise................................................................................................................................................2

2. Proximal part of the stylet curved over 90-270∞ and surrounded by the mantle only in its distal part. (Figs 4B, 6, 7)..........................................................................................................................................3

- Copulatory organ spirally coiled over 360∞ or more (except in T. franki , where it is coiled over 180∞); stylet surrounded over its whole length by the mantle, latter mostly wrinkled and split distally into two narrow, spiny plates with a terminal hook; bursal appendage consisting of two tubes (coiled over 270-360∞), with a straight distal part; animals with dorsal stripe or rostral spot or without pigmentation (Figs 4C, 5, 8A, B, G, I, 9, 10)..............................................................................................................................................7

3. Stylet long and narrow with a proximal turn of 270∞; mantle forming a narrow ring and carrying a long and slender spine; bursal appendage with two tubes, proximally with a ring (Fig. 6)...............................................................................................................................................................4

- Stylet broad, proximally curved over 90∞ or 180∞; mantle split into one, two or three plates (Fig. 7)........................................................................................................................................................................5

4. Copulatory organ consisting of a ± 225 Mm long slender stylet; mantle with flagelliform spine (± 75 Mm); bursal appendage ± 22 Mm long (Fig. 6B)................................................................... T. messoplanoides

- Copulatory organ 74–130 Mm long; stylet 117–194 Mm long; mantle with a straight spine of 70–78 Mm; bursal appendage ± 54 Mm long (Fig. 6A)..................................................................... T. venenosum

5. Stylet bent over 90∞, mantle split into three pointed plates:

* Copulatory organ 30–45 Mm long; stylet 44–53 Mm long; bursal appendage 60–70 Mm long, with a proximal barrel-like casing and ± 12 tubules, diverging distally (Fig. 7C)........................ T. penicillatum

* Copulatory organ 28–36 Mm long; stylet 29–41 Mm; bursal appendage 62–78Mm long, consisting of a short funnel-shaped proximal part and two coiled (>360∞) tubes, all with a faint striation (Fig. 7B) ...................................................................................................... T. watsoni sp. nov.

* Copulatory organ ± 44 Mm long; stylet ± 70 Mm long; bursal appendage ± 78 Mm long, with a proximal part, shaped like a clover leaf, and one to three distal bent tubes with a fine striation (Fig. 7A) ......................................................................................................................... T. coronatum

- Stylet bent over 180∞; mantle with one or two plates.......................................................................................................6

6. Mantle split into two plates, stylet with spoon-like terminal opening (Fig. 7F1, 2, G1) (note that the copulatory organ of T. franki may easily be confused with this type):

* Plates of the mantle blunt and shorter than the stylet; copulatory organ ± 78 Mm long; stylet ± 104 long, proximally with a crest; bursal appendage ± 65 Mm long, curved proximally over 270∞, with proximal barrel-like part and a bundle of very narrow, faint tubules, which form two bundles distally (Fig. 7G) .............................................. T. nataschae sp. nov.

* Plates of the mantle pointed and at least as long as the stylet; copulatory organ slender, 72–74 Mm long; stylet 83–84 Mm long; bursal appendage ±66 Mm long, with a proximal barrel-like part and ± 10 distal tubules (Fig. 7F) ................................................................. T. mirabile

- Mantle with only one plate (see Fig. 7D1, 3, E1):

* Plate of the mantle as long as the stylet and ending in a little hook; copulatory organ 42–46 Mm long; stylet 40–57 Mm long; bursal appendage 95–98 Mm long consisting of a coiled tube, which distally splits into five to six tubules (Fig. 7D) .................................................................................................................................................................... T. lilliei

* Plate of the mantle blunt and shorter than the stylet; copulatory organ ± 62 Mm long; stylet ± 64 Mm long, proximally with a crest; bursal appendage 20–24 Mm long with proximal barrel-like part and ±10 distal tubules (Fig. 7E) .............................................................................................................................................................. T. breitfussi

7. Copulatory organ 86–111 Mm long, proximally bent over 180∞ and continuing in a straighter part, where the two spiny plates are; bursal appendage 62–166 Mm long, coiled over 270∞; animals mostly with dorsal pigment stripe (Figs 5A, 9A, 10A)............................. T. franki sp. nov.

- Copulatory organ with 1-5 complete spire(s) of 360∞, continuing in a straighter section, where the two spiny plates are situated (Fig. 5B- F):

* Copulatory organ with one spire, 158–434 Mm long; bursal appendage 50–149 Mm long, coiled over 270∞ (Figs 5B, 9B, 10B) ..................................................................................... T. armatum

* Copulatory organ with two spires, 284–498 Mm long; bursal appendage 64–161 Mm long, coiled over 360∞ (Figs 5C, 9C, 10C)......................................................................................................... T. setigerum

* Copulatory organ with three spires, 414–445 Mm long; bursal appendage ± 34 Mm long, coiled over 270∞ (Figs 5D, 9D, 10D) ........................................................................................ T. australis sp. nov.

* Copulatory organ with four spires (Figs 5E, 9E).................................................................. T. galapagoensis sp. nov.

* Copulatory organ with five spires, 683–853 Mm long; bursal appendage 80–106 Mm long, coiled over 270∞ (Figs 5F, 9F, 10E).................................................................................................... T. tori sp. nov.