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| Semisulcospira davisi Sawada & Nakano, 2021 |
The type series of Semisulcospira multigranosa Boettger, 1886 was found in the Malacological Collection at the Senckenberg Naturmuseum for the first time ca. 135 years after its original description. The syntypes consisted of 38 specimens that can be classified into four species. The examination of adult shell morphology of these original materials revealed that the current taxonomic account of S. multigranosa should be amended. Therefore, we designate a lectotype for S. multigranosa, and thus describe S. multigranosa auct. as Semisulcospira davisi sp. nov. Semisulcospira davisi can be discriminated from the other congeners by the characteristics of adult and embryonic shells, and radulae morphology. The present study resolves one of the fundamental taxonomic problems remaining in Semisulcospira snails.
Key words: Freshwater snail, Lake Biwa, Syntypes, Viviparous, Radula morphology.
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| Shells of Semisulcospira davisi sp. nov. A–G, Holotype, KUZ Z3680. H–J, Specimen from Kitafunaki, KUZ Z3686. K–M, Specimen from Yokoehama, KUZ Z3687.N–P, Specimen from Okishima, KUZ Z3688. Q–S, Specimen from Yoshikawa, KUZ Z3690. A–C, H, K, N, Q, Adult shell. D, I, L, O, R, Operculum. E–G, J, M, P, S, Embryonic shell. Scale bars: 10 mm (A–D, H–I, K–L, N–O, Q–R), 2 mm (E–G, J, M, P, S). All specimens were treated with 12% sodium hypochlorite. |
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| Living specimen of Semisulcospira davisi sp. nov. collected from Kitafunaki. Scale bar = 10 mm. |
Semisulcospira davisi sp. nov.
[New Japanese name: Sazanami-kawanina]
Diagnosis: Viviparous semisulcospirid. Adult shell elongated [SH 29.5 ± 3.2 (mean ± SD); SW 9.7 ± 1.2]; 2.1 ± 0.5 BCN; 22.8 ± 2.6 curved ribs with distinct or indistinct nodes; 8.8 ± 1.0 SCN; 16.4 ± 2.2 degrees SA; 1.5 ± 0.1 ASR; 2.1 ± 0.2 WER. Embryonic shell large (SHE 4.3 ± 1.1), with ribs on surface; color in black background or beige background with brown bands.
Etymology: The specific name is dedicated to Dr. George M. Davis, who greatly contributed to the systematics of Japanese Semisulcospira.
Distribution and ecology: The new species was found from four sites of Lake Biwa in addition to its type locality: Kitafunaki, Yokoehama, Okishima, and Yoshikawa (Fig. 1). Except at Yoshikawa, the new species inhabits sandy and muddy bottom at depths of 5–7 m. At Yoshikawa, the new species was collected from muddy bottom at the depth of 10–15 m. Semisulcospira davisi was found with several other congeners: S. reticulata Kajiyama and Habe, 1961, S. decipiens and S. h. yamaguchi at Tsukide, Kitafunaki and Yokoehama; S. decipiens at Okishima; and S. reticulata at Yoshikawa.
Naoto Sawada and Takafumi Nakano. 2021. Revisiting A 135-Year-Old Taxonomic Account of the Freshwater Snail Semisulcospira multigranosa: Designating Its Lectotype and Describing A New Species of the Genus (Mollusca: Gastropoda: Semisulcospiridae). Zoological Studies. 60:7. DOI: 10.6620/ZS.2021.60-07
