Phaenocora gracilis (Vejdovsky, 1895) Graff 1909

Phaenocora gracilis (Vejdovský, 1895) Graff, 1909

(Figs 13A, 15G)

Derostoma coecum partim Fuhrmann 1894: 276 –281, Figs 48–56, Vejdovský 1895: 127; Fuhrmann 1900: 730; Sekera 1904: 440, 441; Hofsten 1911: 39, 46; Cognetti de Martiis 1916: 200; Luther 1921: 16.

Derostoma stagnalis e.p. Fuhrmann 1900: 730; Dorner 1902: 493.

Derostoma stagnale Sekera 1904: 440, 441; Hofsten 1911: 39, 46.

Phaenocora stagnalis Hofsten 1907: 550; Graff 1909: 93, 95, Fig. 188; Hofsten 1911: 38 –39; Hofsten 1912: 627, 676, 678; Meixner 1915: 538, 541; Luther 1921: TextFig. 26f; Wilhelmi 1913: Figs 9, 85.

Phaenocora coeca Hofsten 1911: 38 –39; Hofsten 1912: 627, 676, 678.

Derostoma coecum partim Fuhrmann 1894 only Fig. 52 with certainty; Gilbert 1935: 361.

Derostoma gracile Vejdovský 1895: 114, 128, plate 6 Figs 41–43; Dorner 1902: 493; Sekera 1904: 440, 442–443.

Phaenocora gracilis Graff 1909: 93 –94, Fig. 190; Hofsten 1911: 37 –38, 44–46, TextFigs 11–12, Hofsten 1912: 582, 627, 678; Graff 1913: 134, Fig. 144; Nasonov 1919: 621, 633, 635; Luther 1921: 4; Sekera 1930: 100; Gilbert 1935: 284, 320, 330, 332, 355, 359, 361, 364, 369–370, TextFigs 3Ca, 3Cb, tables 1, 2; Beauchamp 1936: 150; Marcus 1946: 71 –72, 80–82, 164, 166; Marcus & Marcus 1959: 19.

Phaenocora cf. gracilis Beauchamp 1934: 209.

Phaenocora gracile Gilbert 1935: 343; Weise 1942: 145.

Known distribution: Münchenstein near Basel (Switzerland) (Fuhrmann 1894); mud from pond at Klecany near Prague (Czech Republic) (Vejdovský 1895); Former East Prussia (i.e. roughly Latvia and Lithuania) (Dorner 1902); Switzerland, Bohemia (Czech Republic), former East Prussia, Russia (Graff 1913); Bulychevo (Russia) (Nasonov 1919); source of Tchiera Midjina, 700 m south of Novi-Pazar (Serbia) on the road towards Osoje, at 540 m altitude (Beauchamp 1934); vicinity of Berlin (Germany) (Weise 1942).

Material examined: None.

Diagnosis: Animals about 1.5 mm long, but can be up to 2.5 mm. Visible eyes absent. Body pigmentation diffuse reddish. Zoochlorellae absent. Male copulatory organ of the duplex-type IIIA. Penis papilla with a thickening, which is probably an increased part of its sclerotised wall. Female genital system of the AGLOBULATA - type or the UNIPUNCTATA - type.

Remarks: Vejdovský (1895) described the caudal body end as trilobed. However, according to Hofsten (1911) these lobes may have been caused by contraction of the specimens.

The presence of a burso-intestinal duct was not described, but Gilbert (1935) assumed its presence based on the description by Vejdovský (1895), according to whom the proximal part of the intestinal bursa forms a long channellike blind sac. This indeed suggests that a burso-intestinal duct might be present (Fig. 15 G: el).

It was complicated to appoint a valid name to this species. It was originally described as Derostoma coecum Fuhrmann, 1894. However, the name D. coecum was already used by Ørsted (1843) for another species (see Graff 1882: p. 371). Graff (1882) doubted the validity of Derostoma coecum Ørsted, 1843 as a species and stated that Ørsted’s (1843) illustration and description could also refer to a macrostomid. Nevertheless, it is the senior synonym and an available name. Being the junior name, D. coecum Fuhrmann, 1894 could no longer be used for this species and therefore Fuhrmann (1900) proposed a replacement name: Derostoma stagnalis Fuhrmann, 1900. In 1911, Hofsten stated that he had examined six serially-sectioned specimens of Phaenocora coeca = stagnalis (sic.). He mentioned that this was the original material of Fuhrmann (1894). Hence, according to articles 72.1.1 and 72.7 of the ICZN (1999), these six sectioned specimens constitute the type series, and collectively they constitute the name-bearing type of both D. coecum Fuhrmann, 1894 and D. stagnalis Fuhrmann, 1900. Hofsten's (1911) study of these specimens showed that they actually represent two distinct species. Two specimens have a penis papilla without spines, which were considered P. stagnalis (Fuhrmann, 1900) by Hofsten (1911), who further stated that it is identical to P. gracilis (Vejdovský, 1895). Being the senior synonym, P. gracilis (Vejdovský, 1895) has priority and is the valid name for this taxon. The two specimens studied by Hofsten (1911) constitute the type series, but we were not able to trace them.

The four other specimens studied by Hofsten (1911) have a penis papilla with spines. Hofsten (1911) identified these four specimens as P. clavigera Hofsten, 1907.