Trichodrilus moravicus Hrabě, 1937

Rodríguez, Pilar & Fend, Steven, 2025, Contributions to the knowledge of the genus Trichodrilus Claparède (Lumbriculidae, Clitellata) with the description of new groundwater species from Spain, Zootaxa 5711 (1), pp. 57-78 : 70-73

Trichodrilus moravicus Hrabě, 1937

( Figures 8A–C , Table 3)

Trichodrilus moravicus Hrabě, 1937: 3 , 20. Hrabě 1938: 73, fig. 1–8 (partim); 1942: 28; 1960: 265; 1981: 107, 108, table 19(3). Dumnicka 1995:19; 2000: 359, 385, tables 7–10; 2014:18, tables 1 & 2. Dumnicka & Galas 2017: table 1. Dumnicka et al. 2020: 7, fig. 5, table 3.

Lectotype: NMP Trichodrilus moravicus Hr 1007 -2( IV) (#11) NMP P6 j-20/89/144, sagittal sections, mature, with egg sac.

Type locality: Říčka River , Moravian Karst , Czech Republic, about 10 km from Brno (https://mapy.cz/ s/narozularu). Hrabě’s collection was sampled from several sites in a section of the Říčka river , near Pekárna ( N49.24305, E16.74583), Netopýrka and Ochozská Caves ( N49.24444, E16.74944), Brno District, separated about 300 m (coordinates from Timm & Abarenkov, gbif.org). The lectotype is from site B described in Hrabě 1938: 80, Dr. P. Dolejs, pers. comm .)

Paralectotypes: NMP P6 j-20/89/144. Hr 1006: not fully mature, unmated individual in histological sections (#1); two immature, whole-mounted individuals (#2). Hr 1007-2 (#4, #6) whole mount, mature, unmated, no egg sac. Hr 1007-2 (#8, #14) sagittal sections, mature, unmated, no egg sac. Hr 1015 transverse sections, mated individual (#17). Hr 1015-2 (#19) 1 immature, whole-mounted individual. Three sites located 10 km of Brno, Moravian Karst, Czech Republic .

Description (based on four mature individuals from the NMP type material from Říčka River, mated or unmated but with sperm in male funnels and long sperm sacs). Small worms, body diameter in X 0.21–0.31 mm. Prostomium round. Clitellum not well separated from adjacent segments, but with thicker epidermis: to 14 µm high in X– XIII, vs. 5–10 µm in anterior segments. Secondary annulation from III. One pair of male pores in X (in IX in one of the examined individuals) behind and in line with ventral chaetae, one pair of female funnels in 11/12 and two pairs of spermathecae, in XI and XII, behind in line with the ventral chaetae. One pair of chaetae per bundle, simple pointed; in the anterior body segments, dorsals somewhat smaller than or equal in length to ventrals (dorsals 60–78 µm, ventrals 68–82 µm in Hr 1007-2c (#6); dorsals 83–96 µm, ventrals 85–106 µm in Hr 1015-2 (#19).

Pharynx in segments II and III, with a well-developed dorsal pad. Pharyngeal glands from V to the anterior part of VIII. Chloragogenous tissue from segment VII. First nephridia in VII. Sperm sacs only developed backwards to XI–XV, no egg sacs. Two pairs of testes (segments IX and X) and one pair of ovaries (segment XI).

Semiprosoporous male duct. Atrium petiolate, with a round ampulla and a well-defined duct ( Fig. 8A ), its total length about half the body diameter. Round to oval ampulla (74–122 µm long, 53–91 µm Ø), atrial duct 33–51 µm long, 20–27 µm Ø, roughly cylindrical or slightly conical, narrowed to the pore (to 12–17 µm). Atrial musculature ≤ 2–3 µm thick, epithelium with glandular, nucleated cells, 10–18 µm high. Prostate glands in clusters, to 80–94 µm high. One pair of vasa deferentia joins medially or subapically to atrial ampulla ( Fig. 8B ), the posterior one crossing septum 10/11 and forming a short loop in segment XI.

Spermathecal ampullae 100–247 µm long and 60–130 µm Ø, in the same segment as the corresponding pore, or crossing to the following one. Long spermathecal ducts, about 105–160 µm long, 15–30 µm Ø, with a small distal widening, that in mated specimens can form a small vestibule containing sperm ( Fig 8C ).

Remarks. The species name was made available in a key to species of Trichodrilus ( Hrabě 1937: 20) , but the formal and detailed description is in Hrabě (1938). The description of T. moravicus was based on several populations, but mainly from two sites: the Říčka River and in the Býčí Skála Cave, in the Czech Republic. Hrabě (1938) reported differences in size (number of segments and body diameter) and the study of the type series from the NMP showed additional morphological differences between these populations. Most interesting was the difference in the position of the junction of the vasa deferentia to the atrial ampulla, subapical in specimens from Říčka R. vs. basal in specimens from Býčí Skála. This fact has led us to review the diagnosis of T. moravicus and to evaluate two options to deal with this problem:

1) To amend the description of T. moravicus , considering that these characters are variable for the species;

2) Not to modify the original description, so that T. moravicus shows the subapical junction of the vasa deferentia, which occurs in the type series from Říčka River. This option implies the proposal of a new identity for Hrabě´s population in the Cave Býčí Skála, mostly based on the different position of the vasa deferentia junction, but also considering the differences already evident in the original description.

We have taken the second option. This meant the designation of a lectotype for T. moravicus from the Říčka River , since all specimens from Říčka River and Cave Býčí Skála were syntypes, due to the lack of original type designation. We chose a specimen consistent with the original description of the species, with junction of vasa deferentia and atrium clearly visible. The present description, based on the revision of the type material from Říčka River , fits the original descriptions by Hrabě (1938) where the junction of vasa deferentia to the atrial ampulla is described as ental ( nahe seinem entalen Ende einmündet). The figures that Hrabě included in his description (1938: figs.7, 8) from the Řicka R. are from transversally sectioned individuals, where we were not able to determine the position of the vasa deferentia junction. However, this character was clearly seen in both sagittal sections and whole-mounts from the Říčka River collection examined by the authors .

On the other hand, the Trichodrilus population from Cave Býčí Skála is identified here as T. stygodytes sp. nov., conspecific with the population from Bizkaia, Spain (see above), which shares the structure of the reproductive system. In order to facilitate future DNA-based studies, the holotype of this species was selected from the Spanish population and not from the slide collection of the National Museum of Prague.

In the original description of T. moravicus , there is another population from the Glatzer Schneeberg (near Králický, Czech Republic), a subterranean river in Cave Quarglöcher (Hr 1027), that was not examined here. With the lectotype designation, these specimens are no longer syntypes of T. moravicus .

As Hrabě (1960) pointed out, T. moravicus is morphologically close to T. tenuis in several characteristics: very small worms, atrium ampulla round to oval, with narrow musculature, the posterior vas deferens passes into segment XI and joins subapically to the atrial ampulla. This species can be separated from T. tenuis by the size and shape of atrium [described by Hrabě (1960) as “slightly different”]. The atrium is petiolate in T. moravicus , i.e. with the cylindrical duct well-separated from the ampulla, while in T. tenuis , the duct gradually narrows and it appears as if contained within the ectal part of the ampulla, or protrudes forming a conspicuous penis. Total length of the atrium in T. moravicus is about half the body diameter, while in T. tenuis it is usually about one third.

Habitat and distribution. Trichodrilus moravicus has been reported so far in headwaters of karst rivers, interstitial waters and the profundal zone of a lake in Czech Republic, Slovakia and Poland ( Fig. 6 ). Kasprzak (1979: 73–74, fig.14) described a small population of T. moravicus in Poland, with very thick atrial musculature and few tiny prostatic cells, which does not match the original description of T. moravicus . The presence of T. moravicus in several European countries should be confirmed in light of the new taxonomic data.

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Figures

FIGURE 6. Distribution map of Trichodrilus tenuis (in red) and T. moravicus (in green) (from Timm & Abarenkov), and Iberian T. tenuis from the present study (in black). Karst areas of Spain (Oliveira et al. 2009) in the upper left square, marked in black.

FIGURE 8. T. moravicus Hrabě, 1937 and T. stygodytes sp. nov. A–C, T. moravicus, Říčka River type collection: A, atrium in transverse histological section, paralectotype (Hr1015-2 #17). B, atrium and posterior vas deferens junction in longitudinal section, lectotype (Hr1007-2(IV)#11). C, spermatheca in transverse sections (Hr1015-2 #17). D–H, T. stygodytes sp. nov., Býčí Skála collection: D–G, atrium. H, spermatheca.All scales 50 µm.