Trigonostomum coronatum
Creators: name: Willems, Wim R.
name: Artois, Tom J.
name: Vermin, Wouter A.
name: Schockaert, Ernest R.
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabditophora
Rhabdocoela
Trigonostomidae
Trigonostomum
Trigonostomum coronatum

description: 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.
description: Published as part of 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, pp. 271-296 in Zoological Journal of the Linnean Society 141 (2) on pages 286-287, DOI: 10.1111/j.1096-3642.2004.00124.x, http://zenodo.org/record/4634553