Limnodrilus claparedianus Ratzel, 1868

Zhou, Tingting, Peng, Yu, Wang, Hongzhu, Erséus, Christer & Cui, Yongde, 2021, Molecular taxonomy and description of a new species of Limnodrilus (Naididae, Clitellata, Annelida) in China, Zootaxa 5082 (4), pp. 301-321 : 316-318

Limnodrilus claparedianus Ratzel, 1868

( Figures 7 , 8 )

Limnodrilus claparedianus Ratzel, 1868: 590 , fig. 24; Liu et al. 2017a.

Limnodrilus claparedeanus Ratzel. Bretscher 1896: 504 .

Limnodrilus claparèdeianus Ratzel. Michaelsen, 1900: 45 .

Limnodrilus claparedeianus Ratzel. Brinkhurst 1971: 468 , fig. 8.3; Liang 1987.

(Here only different spellings of the same species epitheton are considered. For synonymies and chresonymies see Brinkhurst 1971.)

New material from China. IHB SX20181128 a (CW0023), 1 mature specimen from Hanjiang River , Shanxi ; IHB JS20191116 a (CW0223), 1 immature specimen from Yixing , Jiangsu ; IHB HLJ20191001 a–e (CW0268, CW0270– 0271, CW0276–0277), 5 immature specimens from Heilongjiang .

Description of new material. Length of first 12 segments 2.0– 4.2 mm, width at clitellum 0.62–0.98 mm. Prostomium rounded ( Fig. 7A ). Clitellum inconspicuous.All chaetae bifid ( Figures 7B,C ; 8A,B ); upper tooth clearly or slightly longer than, but usually about as thick as lower. Anterior bundles with 4–7 chaetae, 85–110 µm long, 2.5 µm wide, and with nodulus 1/3 from distal end. Posterior segments with 1–2 chaetae per bundle. No modified spermathecal chaetae. Spermathecal pores paired ventrally in middle of X; male pores paired ventrally in middle of XI. Chloragogen cells from VI. No coelomocytes. Male genitalia paired. Vas deferens long, entering atrium apically. Atrium small, fusiform. Prostate gland large, connected to middle of atrium. Penis sheath ( Fig. 8C,D ) elongate, cylindrical, slender, terminal end bent with an angle. Sheath 835 µm long, 35 µm wide at its base, 20 µm wide at the top, 24 times longer than broad in the mature specimen. Spermatheca pear-shaped, with spermatozeugmata.

Distribution and habitat. A more or less cosmopolitan species, but here recorded and genetically confirmed from Provinces Shanxi, Jiangsu and Heilongjiang in China. Freshwater.

Remarks. In L. claparedianus , the upper tooth of the anterior chaetae is longer than the lower tooth, which is consistent with the description by Brinkhurst (1971). The shape of the apical penis sheath is triangular in L. claparedianus ( Ratzel 1868) . The same is true of our specimen. Different researchers have concluded that the length: width ratio of the penis sheath varies in this species. Bretscher (1896) found a ratio of 8–10. Brinkhurst (1965), however, noted that the ratio was 17–43. For Chinese specimens, the value was 20 in Nanjing and Nanchang ( Chen 1940). This may be due to regional genetic differences or the developmental stage of worms, but it may also be the result of different methods of measuring the sheath by various researchers. Moreover, as indicated above, it may be possible that some of the previous records of alleged L. claparedianus were based on misidentified specimens of L. paraclaparedianus or even some other, still undescribed, species. The following characteristics were not mentioned in the original description of L. claparedianus: First , the prostomium is conical with a pointed tip in L. paraclaparedianus , while the prostomium is rounded in our specimens of L. claparedianus . Second, the upper tooth of the anterior ventral chaetae is slightly longer and thinner than the lower in L. paraclaparedianus , but clearly longer than, and about as thick as or thicker than the lower in L. claparedianus (e.g., Kennedy 1969; Brinkhurst 1971). Third, there is a distinct constriction in the outer end of the penis sheath of the former ( Fig. 5C,D ; see also Liu et al. 2017a, fig. 3), while the sheath tapers off slowly in the latter ( Fig. 8C,D ).

As discussed in Remarks for L. paraclaparedianus above, and shown also by Liu et al. (2017a, Table 1 ), the penis sheaths of L. claparedianus and L. paraclaparedianus are similar, both in size and proportions; the most clearcut difference is the size of the upper teeth in chaetae of anterior segments (comp. Figs. 5A,B , 8A,B ).

Limnodrilus claparedianus has a worldwide distribution, but in China it does not appear to be as common as L. paraclaparedianus . We only collected the species in Shanxi, Jiangsu and Heilongjiang, Liu et al. (2017a) reported it from the Province Shanxi too ( Hanjiang River ) .

Figures

FIGURE 5. Limnodrilus paraclaparedianus n. sp., chitinous structures.A–D. Ventral chaetae in II, III, IV andV.E. Penis sheath.

FIGURE 7. Limnodrilus claparedianus Ratzel, 1868, SEM micrographs. A. Anterior body end, dorsal-lateral view. B, C. Tip of ventral chaetae, anterior segment.

FIGURE 8. Limnodrilus claparedianus Ratzel, 1868. A, B. Dorsal chaetae in III and IV, respectively. C, D. Penis sheaths. Scale bars: A, B 10μm; C, D 70μm.