6. Radix (Radix) plicatula (Benson in Cantor, 1842) Figs 3J-L; 4E; 5D.

Limnaea plicatula Cantor 1842: 487.

Limnaea swinhoei H. Adams 1866: 319, pl. 33, fig. 13.

Limnaeus plicatulus - Martens 1867: 221.

Limnaea yunnanensis Nevill 1877: 26, 27.

Limnaeus chefouensis Clessin 1878-1886: 391, Taf. 55, fig. 6.

Limnaeus heudi Clessin 1878-1886: 394, Taf. 55, fig. 10.

? Limnaea annamitica Wattebled 1886: 57, pl. IV, fig. 4.

Limnaea (Gulnaria) pettiti Jones and Preston 1904: 142, fig. 3.

Limnaea (Gulnaria) whartoni Jones and Preston 1904: 142, fig. 1.

Limnaea (Gulnaria) lumleyi Jones and Preston 1910: 11, textfig.

Limnaea (Gulnaria) schwilpi Jones and Preston 1910: 10, textfig.

Limnaea (Gulnaria) sinensis Jones and Preston 1910: 11, textfig.

Radix plicatulus - Yen 1939: 65, Taf. 5, fig. 40.

Radix swihhoei - Yen 1939: 66, Taf. 5, fig. 43.

Radix plicatula - Aksenova et al. 2018a: 4

TL.

China, Chusan Island.

Types.

Probable syntypes are kept in NHMUK (see Taxonomic remark below).

The actual range of R. plicatula is not ascertained yet. In our molecular analysis, we studied samples of this species from Beijing, southern and western China that may indicate it is distributed throughout the country. The presence of R. plicatula in adjacent states (Laos, Vietnam) is also very probable, although, as far as we can judge, it is absent from India (Subba Rao 1989). The records of R. auricularia swinhoei (Adams) from Thailand (Brandt 1974) may refer to this species, but a special study is needed to check it.

The shell of R. plicatula is rather oblong, with relatively high spire and moderately inflated body whorl (see Fig. 3J-L). The copulative apparatus is typical for this genus (see Fig. 5D). In all individuals dissected in this study, the penis sheath was slightly longer than the praeputium (see Table 1), thus ICA <1.0.

Taxonomic remark.

Radix plicatula is almost indistinguishable from R. euphratica by its shell habitus (compare Fig. 2F and 2L) and the copulatory organ structure, but molecular analyses have revealed that the two species are distinct and their ranges are almost non-overlapping (Aksenova et al. 2018a). We found the shells of this species, collected in the type locality, in NHMUK (accession No. 42.9.30.50.51.487). These possibly once belonged to Benson’s collection and may be considered the probable syntypes (see Fig. 3F). Their morphology is very similar to that in R. plicatula snails examined genetically by us. Having studied the type series of some nominal species of Radix described from China and South-East Asia (kept in NHMUK, NMNH and ZMB), we ascertained they are junior synonyms of R. plicatula (see Vinarski 2016a and synonymy above).