HETERODORUS BREVIDENTATUS (Thorne, 1939) Andrássy, 2009

(Fig. 8)

Females (n = 6). L = 1.48-1.85 mm; a = 28-34; b = 5.2-6.0; c = 32-36; c’ = 1.7-1.8; V = 49-52%.

Body moderately slender, mostly C-shaped upon fixation. Cuticle thin and apparently smooth. Lip region separated by a depression, 11-13 µm wide; lips amalgamated. Body at posterior end of oesophagus 3.3-4.0 times as wide as head. Odontostyle small and thin, 12-13 µm, about as long as labial width; odontophore simple. Oesophagus 285-310 µm long, expanded at 62-64%. Dorsal nucleus located at 70-74% of oesophagus length or at 12- 14% of entire length of body. AS1 = 21-25%, AS2 = 28- 33%. Posterior pair of nuclei unusually large and located far from posterior margin of cylindrus: PS1 = 48-54%, PS2 = 48-56%. Glandularium 84-94 µm long.

Pre-rectum as long as 2.3-3.3 anal body diameters, rectum as long as or slightly longer than the latter diameter. Vulva transverse with heavily sclerotized inner lips, vagina 32-34 µm long, occupying more than half body diameter. Female genital tract well developed and long, Gonads 4.8-6.4 times as long as mid-body width, or occupying 15-18% of total length of body. Tail conoid, ventrally curved, 45-52 µm long, only 3% of total length of body.

On the basis of the original specimens of Thorne (1939) and the freshly collected Spanish and Romanian specimens, good re-descriptions are due to Guerrero and Peña-Santiago (2007), Guerrero et al. (2007), and Ciobanu et al. (2009). According to them, H. brevidentatus is closely related to H. morgensis (Loof, 1989) Andrássy, 2009, but differs from the latter by the more anteriorly located dorsal oesophageal nucleus (67-72 vs. 80-82%), and the strongly sclerotized vulval lips. The Albanian specimens fit the descriptions of the Spanish/Romanian authors, except for the smooth cuticle (vs. faintly striated), the shape of the vulval sclerotization and the very long gonads. In the length of the body they are closer to the American specimens (1.45-1.70 mm), but in the length of the odontostyle to the European ones (1.15-1.30 µm, while 1.45-1.70 µm in American specimens).

Distribution. Heterodorus brevidentatus, a rather rare representative of the genus, has hitherto been recorded from Europe (Hungary, Romania, Italy, Spain) and North America (United States). The present specimens were found in mosses at locality No. 16b.