Heterogen japonica (Martens, 1861)

Saito, Takumi & Kagawa, Osamu, 2020, New insights from museum specimens: a case of Viviparidae (Caenogastropoda: Mollusca) in Iwakawa's collection preserved in the National Museum of Nature and Science, Tokyo, Biodiversity Data Journal 8, pp. 52233-52233 : 52233

Heterogen japonica (Martens, 1861)

Paludina japonica von Martens 1861: 44. Type locality: Japan. (original description).

Vivipara sclateri Frauenfeld 1865: 531, pl. 22, unnumbered figs. Type locality: Japan. (original description); Pilsbry 1895: 158; Kobelt 1909: 102, pl. 16, figs. 3-6, 8 [part; pl. 16, fig. 9 and pl. 17, figs. 3 and 5 seemingly have the intermediate morphology between H. japonica and H. longispira , see discussion]; Annandale 1921: 46 [part].

Paludina ingallsiana - Kobelt 1879: 124, pl. 10, fig. 14 [part; pl. 10, figs. 15-16 and 18 seemingly have intermediate morphology between H. japonica and H. longispira , see discussion]; Iwakawa 1895: 412, pl. 19, figs. 8-9 [part]; Iwakawa 1897a: 86, pl. 5, fig. 7 [part] (Japanese viviparid catalogue); Iwakawa 1897b: 5.

Paludina oxytropis - Kobelt 1879: 123, pl. 11, fig. 6.

Paludina sclateri - Kobelt 1879: 121, pl. 11, fig. 3; Tanba et al. 1883: 368; Tanba et al. 1891: 216; Iwakawa 1895: 357, pl. 19, fig. 2; Kitahara 1895: 89.

Paludina oxytropis var. japonica - Iwakawa 1897a: 88, pl. 5, figs. 15 and 17 [Iwakawa noted that fig. 15 was an intermediate form between P. oxytropis oxytropis and P. o. japonica ]; Iwakawa 1897b: 9, pl. 2, fig. 13.

Paludina oxytropis var. sclateri - Iwakawa 1897a: 89, pl. 5, figs. 13-14 and 16 [Iwakawa noted that figs. 13 and 16 were an intermediate form between P. oxytropis oxytropis and P. o. sclateri ]; Iwakawa 1897b: 9, pl. 2, figs. 7-9 and 11.

Vivipara oxytropis - Pilsbry 1895: 158.

Viviparus japonicus - Pilsbry 1902: 117, pl. 9, fig. 1.

Viviparus japonicus var. iwakawa Pilsbry 1902: pl. 9, fig. 3. Type locality: Furukawa, Rikuzen [Furukawa City, Miyagi Pref., Japan]. (original description).

Viviparus sclateri - Pilsbry 1902: 118 [part]; Iwakawa 1919: 72 [part].

Vivipara japonica - Kobelt 1909: 99, pl. 15, figs. 1-4.

Vivipara japonica var. iwakawa - Kobelt 1909: 100, pl. 15, figs. 5-7.

Idiopoma (Idiopoma) japonica - Hannibal 1912: 194.

Viviparus japonicus iwakawa - Iwakawa 1919: 71-72.

Viviparus japonecus - Kanamaru 1920: 4, pl. 2, fig. 85. [sic].

Lecythoconcha japonica - Annandale 1921: 401.

Lecythoconcha sclateri - Annandale 1921: 401, fig.3; Annandale 1922: 133.

Viviparus (Idiopoma) japonicus - Hirase 1927: 1380, fig. 2653.

Viviparus (Idiopoma) japonicus iwakawa - Hirase 1927: 1381, fig. 2654.

Vivipara japonica var. iwakawae - Prashad 1928: 173, pl. 19, fig. 12. [sic].

Viviparus (Cipangopaludina) japonicus - Prashad 1928: 172.

Viviparus (Dactylochlamys) iwakawae - Prashad 1928: 173, pl. 19, fig. 12. [sic].

Viviparus (Viviparus) sclateri - Prashad 1928: 172, pl. 19, fig. 5 [part?].

Viviparus (Cipangopaludina) japonicus iwakawa - Kuroda 1929: 102.

Viviparus (Cipangopaludina) japonicus sclateri - Kuroda 1929: 102; Yagura 1932: 28.

Viviparus oxytropis - Taki 1933 in Horikoshi and Itabashi 1994: 20.

Viviparus iwakawai - Taki 1946: 202, fig. 8 [sic].

Cipangopaludina japonica - Hirase and Kuroda 1947c: 1161, fig. 3304; Kuroda 1947b: 3.

Cipangopaludina japonica iwakawa - Hirase and Kuroda 1947a: 1162, fig. 3305.

Cipangopaludina ( Ussuriensis ?) japonica - Habe 1990: 4.

Heterogen japonica - Hirano et al. 2019b: 5033, figs. 1, 4-5 and 8.

Materials

Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965303; catalogNumber: 2959J ex.NSMT-Mo 2959 ; occurrenceRemarks: NMST-Mo 2959 from Kasumigaura was presumed as one record of 2950, Viviparussclateri from Kasumigaura in Iwakawa’s catalogue (1919) (see data resources).; recordNumber: Probably 2950 in Iwakawa 1919; individualCount: 3; lifeStage: adults; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2959J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Ibaraki; locality: Lake Kasumigaura ; verbatimLocality: Kasumigaura (in Japanese) [Lake Kasumigaura]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965315; catalogNumber: 2960J ex.NSMT-Mo 2960 ; recordNumber: 2960 in Iwakawa 1919; individualCount: 1; lifeStage: adult; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2960J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Nagano; locality: Lake Suwa ; verbatimLocality: Suwako (in Japanese) [Lake Suwa]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965316; catalogNumber: 2961J ex.NSMT-Mo 2961 ; recordNumber: 2961 in Iwakawa 1919; individualCount: 27; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2961J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Nagano; locality: Lake Suwa ; verbatimLocality: Suwako (in Japanese) [Lake Suwa]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965304; catalogNumber: 2962J ex.NSMT-Mo 2962 ; recordNumber: 2962 in Iwakawa 1919; individualCount: 6; lifeStage: adult; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2962J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Nagano; locality: Lake Suwa ; verbatimLocality: Tenryu-gawa-no-suigen (in Japanese) [The water source of Tenryu River = Lake Suwa]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965307; catalogNumber: 2963J ex.NSMT-Mo 2963 ; recordNumber: 2963 in Iwakawa 1919; individualCount: 1; lifeStage: adult; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2963J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Aichi; locality: western part of Aichi Prefectue ; verbatimLocality: Owari (in Japanese) [Old name of western part of Aichi Prefectue]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965302; catalogNumber: 2964J ex.NSMT-Mo 2964 ; recordNumber: 2964 in Iwakawa 1919; individualCount: 1; lifeStage: adult; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2964J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: Lakw Biwa ; verbatimLocality: Biwa-ko (in Japanese) [Lake Biwa]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965311; catalogNumber: 2966J ex.NSMT-Mo 2966 ; recordNumber: 2966 in Iwakawa 1919; individualCount: 1; lifeStage: adult; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2966J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: Hikone, Hikone City ; verbatimLocality: Hikone (in Japanese) [Hikone, Hikone City]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965312; catalogNumber: 2967J ex.NSMT-Mo 2967 ; recordNumber: 2967 in Iwakawa 1919; individualCount: 7; lifeStage: adults; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2967J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: Maibara City, Irie ; verbatimLocality: Irie-mura (in Japanese) [Irie Village, old name of Irie, Maibara City]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965309; catalogNumber: 2968J ex.NSMT-Mo 2968 ; recordNumber: 2968 in Iwakawa 1919; individualCount: 15; lifeStage: 13 adults 2 young; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2968J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: Tsukuma Ragoon ; verbatimLocality: Tsukuma-uchiko (in Japanese) [Tsukuma Ragoon]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965310; catalogNumber: 2969J ex.NSMT-Mo 2969 ; recordNumber: 2969 in Iwakawa 1919; individualCount: 4; lifeStage: 3 adults 1 young; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2969J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: Ohtsu City, Zeze ; verbatimLocality: Zeze (in Japanese) [Zeze, Ohtsu City]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; identificationRemarks: Some specimens seemingly have the intermediate morphology between H.japonica and H.longispira (see taxon discussion section).; Event: year: before 1919; Record Level: language: japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: occurrenceDetails: https://www.gbif.org/occurrence/2864965317; catalogNumber: 2970J ex.NSMT-Mo 2970 ; recordNumber: 2970 in Iwakawa 1919; individualCount: 2; lifeStage: 2 juveniles; preparations: shell (dried); previousIdentifications: Viviparussclateri (Frauenfeld, 1865) in Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; occurrenceID: paper:SK2020:2970J; Taxon: scientificName: Heterogenjaponica (Martens, 1860); kingdom: Animalia; phylum: Mollusca; family: Viviparidae; vernacularName: Oh-tanishi (in Japanese name); Location: country: Japan; stateProvince: Shiga; locality: theSeta River ; verbatimLocality: Seta-gawa (in Japanese) [the Seta River]; Identification: identifiedBy: Takumi Saito; dateIdentified: 2020-02-03/04; identificationRemarks: Some specimens seemingly have the intermediate morphology between H.japonica and H.longispira (see taxon discussion section).; Event: year: before 1919; Record Level: language: Japanese; bibliographicCitation: Tomotaro Iwakakawa. 1919. Catalogue of Japanese Mollusca in the Natural history department, Tokyo Imperial Museum, the Tokyo Imperial Museum, Tokyo, Japan, p. 72.; institutionCode: NSMT; collectionCode: Mo; basisOfRecord: PreservedSpecimen

Diagnosis

Adult shell large and thick; shell shape subconical to pyramidal. Adult shell colour dark brown or brown or dark olive, often covered with many environmental attachments, such as alga; shell surface glossy, sometimes having weak hollows, growth lines and spiral striae. Suture moderately deep. Young shell small, relatively thin and fragile; shell shape pyramidal. Young shell colour yellowish-olive; shell surface quite glossy with no spiral ridges on the upper part of the spire.

Taxon discussion

Heterogen japonica can be distinguished from other Japanese Viviparidae by the following criteria which are based on the illustrations and information from literature (Suppl. material 1).

H. japonica can basically be distinguished from Cipangopaludina chinensis laeta by its subconical to pyramidal shell shape ( Kihira et al. 2009; Fig. 2 ). In addition, the spire is higher, the spire angle is narrower and the shell apex is more pointed than those of C. c. laeta . Furthermore, C. c. laeta often has a lipped aperture, but the aperture of H. japonica does not have a pronounced lip ( Masuda and Uchiyama 2004). Next, the differences with C. chinensis chinensis are not fully revealed, as the shell morphology of C. c. chinensis in Japan was not examined in depth. Nevertheless, based on the analysis and illustration of Hirano et al. (2019a), the only study that explicitly examined Japanese C. c. chinensis , the shell shape of C. c. chinensis is similar to that of C. c. laeta except for the pointed shell apex of C. c. chinensis. In any case, C. c. chinensis is distributed only around Kyushu Island, the south-western part of Japan ( Hirano et al. 2019a) and no specimens of this subspecies were included in our study.

Adult Sinotaia quadrata histrica is generally smaller than H. japonica . There is a high morphological diversity in the shell shape of S. q. histrica ( Kihira et al. 2009); however, the body whorl and the spire whorl are more rounded and arched than that of H. japonica . In addition, the shell apex of S. q. histrica is more rounded and the aperture is relatively smaller than those of specimens of H. japonica having the similar shell shape, as the spire is dense. Moreover, the shell colour of S. q. histrica seems to be brighter than that in H. japonica and often has a yellowish colour.

H. japonica differs in shell shape from H. longispira ( Hirano et al. 2019b). Quantitatively, H. japonica has a lower spire and a broader spiral angle than H. longispira ( Kihira et al. 2009). In addition, H. longispira has a strong basal angulation even on the adult shell ( Okada and Kurasawa 1950). Furthermore, the body whorl and the spire whorl of H. longispira are linear (like vertical) in lateral view and the upper periphery of the whorls turns sharply to nearly horizontal. Accordingly, the suture is quite deep and whorls have a strong shoulder just below the suture. This feature is extremely pronounced in juveniles and young shells and this morphological difference is diagnostic between two species ( Okada and Kurasawa 1950, Hirano et al. 2019b). In addition, a difference that rarely appears in the shell shape is the distinct spiral ridges on the upper whorl of adult H. longspira ( Hirano et al. 2019b). The early whorl of adult H. japonica does not have such spiral ridges. Moreover, Heterogen sp. has weak spiral ridges on the upper whorls and so this is a distinguishing feature from Heterogen sp., which is not distinguished by the shell shape ( Hirano et al. 2019b). The spiral ridges of H. longispira are also pronounced on the body whorl of the adult shell. Furthermore, some H. japonica usually has greenish shells without reddish colour (e.g. Fig. 2 h), whereas the shell colour of most H. longispira contains reddish colour and accordingly are often brown or dark brown in colour.

Besides, H. japonica has one morphotype, ver. iwakawa , which had been described and synonymised. This morphotype has a pyramidal shell shape, a broad spire angle and a strong basal angulation (e.g. Fig. 2 d). Typical specimens of Viviparus japonicus var. iwakawa ( Pilsbry 1902) is very easy to distinguish from any other Japanese Viviparidae ; however, the morphology is continuous with H. japonica ( Okada and Kurasawa 1950).

Notes

Heterogen japonica was identified in all 11 studied lots (Figs 2 , 3 ). Some specimens (Fig. 2 b-c, h and l) have the high spire and the narrow spire angle and the shell shapes of these specimens are relatively similar to H. longispira . However, specimens assigned to H. japonica lack a lot of the distinctive features of H. longispira . Lots Mo2969 and Mo2970 contained specimens with an intermediate morphology between H. japonica and H. longispira (e.g. Fig. 3 c and g-h). Therefore, in this study, we treated only specimens that were clearly distinguished from H. longispira (e.g. Fig. 3 a-b and l) as H. japonica .

Based on the previous taxonomy ( Habe 1973), synonymy included species-group name, iwakawa (and its mandatory changes in spelling and incorrectsubsequentspellings) in addition to species-group name, japonica (and its mandatory changes in spelling and incorrectsubsequentspellings). Furthermore, since Paludina oxytropis in Kobelt (1879) and Vivipara oxytropis in Pilsbry (1895) were later synonymised by the authors themselves ( Kobelt 1909, Pilsbry 1902), these were also listed in synonymy. As to the species-group names Paludina ingallsiana and sclateri , we refer to the discussion.

Figures

Figure 2. Representative shells of Heterogen japonica (Martens, 1861) from Japan, deposited in the collection of the National Museum of Nature and Science, Tokyo, which were treated as Viviparus sclateri (Frauenfeld, 1865) in Iwakawa (1919). a: 2959 J from Lake Kasumigaura, Ibaraki Pref. b-g: specimens from Lake Suwa, Nagano Pref. (b: 2960 J, c-e: 2961 J, f-g: 2962 J). h: 2963 J from the western part of Aichi Pref. i: 2964 J from Lake Biwa, Shiga Pref. j: 2966 J from Hikone City, Shiga Pref. k: 2967 J from Maibara City, Shiga Pref. l-m: 2968 J from Tsukuma Lagoon, Shiga Pref. (l: adult, m: young).

Figure 3. Shells of Heterogen japonica (Martens, 1861), H. longispira (Smith, 1886), and the intermediate morphology between the two species stored at the National Museum of Nature and Science, Tokyo, which were treated as Viviparus sclateri (Frauenfeld, 1865) in Iwakawa's catalogue (1919). a-b: H. japonica in 2969 J from Otsu City, Shiga Pref. c-d: non-typical H. longispira in 2969 L from Otsu City, Shiga Pref. e: typical H. longispira in 2969 L from Otsu City, Shiga Pref. f: subadult H. japonica in 2969 J from Otsu City, Shiga Pref. g-j: non-typical and intermediate H. longispira in 2970 L from the Seta River, Shiga Pref. K: typical H. longispira in 2970 L from the Seta River, Shiga Pref. l: a juvenile shell of H. japonica in 2970 J from the Seta River, Shiga Pref. m: a typical juvenile shell of H. longispira in 2970 L from the Seta River, Shiga Pref.