Sundadontina mabilli ( Rochebrune, 1882 )

Sundadontina mabilli ( Rochebrune, 1882) View in CoL

Type and type locality. Syntype MNHN-IM-2000-1740; “Shigloni Breithon, Cochinchine (M. Pierre), M.P.” ( Rochebrune 1882). Other spellings of this toponym are as follows: “Spigloni-Briton”, “Spiglumi- Britton”, “Spiglumi-Breiton” (see Fischer 1891). At first glance, this locality could be decoded as follows: Saigon – Bến Thành, Cochinchine [= Bến Thành Market, 10.7725°N, 106.6980°E, Ho Chi Minh City, Southern Vietnam]. If our assumption is correct, the mussel sample was bought in the central market of Saigon (now Ho Chi Minh City). Historically, this market was situated on the shore of the Saigon River next to the Citadel of Saigon. “ MP ” means M[uséum] [de] P[Paris]; “Harmand, Mekong” [= Lower Mekong, 10.44°N, 105.58°E, Southern Vietnam]. This writing is marked on the syntype label and inside of both valves ( Figure 3 View Figure 3 ). Thus, type locality includes two sites, one of which corresponds to the original description (market in Saigon), and the other complies with the label (Lower Mekong).

Images of the syntype are available on the online database of the Muséum national ďHistoire naturelle, Paris ( MNHN; https://science.mnhn.fr/institution/mnhn/collection/im/item/2000- 1740?listIndex=2&listCount=6) .

Material examined. SOUTHERN VIETNAM: unnamed stream, 11.4105° N, 107.4166° E, tributary of Dong Nai River , 04.xi.2023, 8 specimens ( RMBH biv 1647, including biv 1647/1, biv 1647/2 and biv 1647/3 sequenced), D. M. Palatov leg. GoogleMaps ;

La Ngà River, 11.1413° N, 107.4289° E, Dong Nai River basin, 25.xi.2014, 8 specimens ( FEB RAS № 2797657 (shells); Genetic data: RMBH biv 1814, including biv 1814/2 and biv 1814/3 sequenced), L. A. Prozorova and N. X. Quang leg. GoogleMaps ;

artificial channel at the Bay Nui Mountains, 10.4534° N, 105.0362° E, An Giang Province, Tri Ton District, Mekong Delta , 24.xi.2012, 1 specimen ( FEB RAS No. 2797657, No. 7519 LAP, only empty shell), L. A. Prozorova and N. X. Quang leg. GoogleMaps

Diagnosis. The shell is elliptic, elongated, solid, moderately inflated; anterior margin is prognathous, rounded, the ventral margin is curved, the dorsal margin is slightly elevated, and the posterior slope has two hardly visible radial folds, stretching from the umbo to the posterior margin. The umbo is rather small, moderately projected, eroded. Periostracum is dark brown, sometimes with a copper color tint in the posterior margin, growth lines are clearly visible; the nacre is shining and area around the umbo has golden color. The pseudocardinal tooth on the right valve is massive, somewhat triangular and convex, shifted with the dorsal edge towards the umbo; the pseudocardinal tooth in the left valve is usually smaller, knob-like and concave. Lateral teeth are reduced. The anterior adductor muscle scars are ovalshaped, rather deep, connected or closely banded with the anterior retractor and protractor muscle scars. The posterior adductor muscle scars are more rounded and usually less developed. The pallial line is contiguous, becoming more visible with age.

Habitat and ecology. This species inhabits mountain watercourses with different type of substrate. As for the newly collected samples, some specimens inhabited a small mountain stream with cobble substrate ( Figure 5A, B View Figure 5 ); the others were found in a stream with clay substrate and an artificial channel (only dry shell, Figure 5C, D View Figure 5 ).

Distribution. Dong Nai River basin and Mekong Delta in Southern Vietnam.

Comments. Rochebrune (1882) studied the Indochinese collection of the Muséum national ďHistoire naturelle, Paris, from Cochinchine and Cambodia. The type locality of S. mabilli in the original description record ( Rochebrune 1882) was defined as Cochinchine, which should correspond to the southern region of Vietnam.

Discussion

A number of questions arose regarding the exact type locality of Sundadontina mabilli . Rochebrune (1882) separated Cochinchine and Cambodia in his work, as did the French botanist Jean Baptiste Louis Pierre ( Pierre 1880 -1907), who was mentioned as a collector. The original description of S. mabilli states Cochinchine ( Rochebrune 1882) as the type locality, that is, more likely, points on Southern Vietnam. However, the available museum syntype also has an original label “Harmand, Mekong” ( Figure 3 View Figure 3 ). In the subsequent works, some malacologists such as Morlet (1889) and Fischer (1891) also added Tonle Sap Lake, Cambodia (“Lac Tonle Sap”) as a habitat. Among the synonyms of Bineurus mouhotii (Lea, 1863) , Brandt (1974) listed “ Pseudodon mabillei Rochebrune ” and mentioned site “Mekong pres Sombor-Sombor” [Mekong River at Sambour, Cambodia], which, more likely, was confused with the type locality of Bineurus anodontinum ( Rochebrune, 1882) ( Konopleva et al. 2021) . Our suggestion is to compromise and recognize both localities. The proposed localities cover Southern Vietnam (former Cochinchine) and the watercourses in the range of this territory, including the Lower Mekong Basin. Site “Shigloni Breithon” remains the unknown locality, so it was reasonable to assume, that specimen could get to Pierre and later into Rochebrune’s collection from the central market of Saigon (Ho Chi Minh). Pierre himself worked and directed the Saigon Zoo and Botanical Gardens for a long time ( Oustalet 1880 -1881, p.64; Pierre 1880 -1907) and had an opportunity to get some biological material from Southern Vietnam and surrounding areas.

Based on morphological, phylogenetic, and distribution data, we confirmed the validity of Sundadontina mabilli , a nominal species from Southern Vietnam. The range of this species apparently covers Dong Nai River basin and Mekong Delta with preferable habitats in small mountain watercourses. Living specimens of S. mabilli were found only in the Dong Nai River basin. However, a single dry shell, morphologically identical to this species, was also collected from the Mekong Delta. This is not surprising, because several ichthyological studies confirmed a similarity of fish fauna of the Dong Nai River and the Lower Mekong due to the past connections during the Quaternary ( Freyhof et al. 2000; Huy et al. 2022).

Sundadontina mabilli View in CoL is apparently a habitat specialist, as are the majority of species in the genus Sundadontina View in CoL (see Bolotov et al. 2023), which prefers lotic ecosystems in mountain and submountain areas in a restricted territory. The fact, that only one dry shell without living specimens was collected in the anthropogenic habitat of the Mekong Delta, confirmed the negative effect of artificial channels, dam pond constructions and other anthropogenic impacts ( Zieritz et al. 2018). Specific environmental conditions suitable for Sundadontina mabilli View in CoL propose further studies and monitoring efforts for this species.

Acknowledgements

We appreciate Dr. Arthur E. Bogan and Dr. Ekgachai Jeratthitikul for their valuable comments and suggestions which help to improve the previous versions of this work. This study was supported by the Ministry of Science and Higher Education of the Russian Federation (project No. FUUW-2025-0022). Field surveys were supported as well by the Ministry of Science and Higher Education of the Russian Federation (theme No. 124012400285–7). We greatly thank curators Virginie Heros and Germinal Rouhan from the Muséum national d'Histoire naturelle (Paris, France) for their kind help with the searching and giving information concerning Sundadontina mabilli . We also appreciate Priscillia Gaël Bourguignon ( MNHN) for the high resolution images of the syntype with label .

References

Bolotov, I. N., Kondakov, A. V., Vikhrev, I. V., Aksenova, O. V., Bespalaya, Y. V., Gofarov, M. Y., Kolosova, Y. S., Konopleva, E. S., Spitsyn, V. M., Tanmuangpak, K. & Tumpeesuwan, S. (2017 a) Ancient river inference explains exceptional Oriental freshwater mussel radiations. Scientific Reports, 7, 2135. https://doi.org/10.1038/s41598-017-02312-z

Bolotov, I. N., Konopleva, E. S., Vikhrev, I. V., Gofarov, M. Y., Lopes-Lima, M., Bogan, A. E., Zau Lunn, Nyein Chan, Than Win, Aksenova, O. V., Tomilova, A. A., Tanmuangpak, K., Tumpeesuwan, S. & Kondakov, A. V. (2020) New freshwater mussel taxa discoveries clarify biogeographic division of Southeast Asia. Scientific Reports, 10, 6616.

https://doi.org/10.1038/s41598-020-63612-5

Bolotov, I. N., Vikhrev, I.V., Kondakov, A.V., Konopleva, E.S., Gofarov, M.Y., Aksenova, O.V. & Tumpeesuwan, S. (2017 b) New taxa of freshwater mussels (Unionidae) from a species-rich but overlooked evolutionary hotspot in Southeast Asia. Scientific Reports, 7, 11573.

https://doi.org/10.1038/s41598-017-11957-9

Bolotov, I.N., Konopleva, E.S., Vikhrev, I.V., Gofarov, M.Y., Kondakov, A.V., Lyubas, A.A., Soboleva, A.A., Nyein Chan, Zau Lunn, Than Win & Inkhavilay, K. (2023) Integrative taxonomic reappraisal and evolutionary biogeography of the most diverse freshwater mussel clade from Southeast Asia (Pseudodontini). Water, 15, 3117.

https://doi.org/10.3390/w15173117

Brandt, R.A.M. (1974) The non-marine aquatic mollusca of Thailand. Archiv für Molluskenkunde, 105, 1–423.

Do, T.V., Tuan, L.Q. & Bogan, A.E. (2018) Freshwater mussels (Bivalvia: Unionida) of Vietnam: Diversity, distribution, and conservation status. Freshwater Mollusk Biology and Conservation, 21, 1–18. https://doi.org/10.31931/fmbc.v21i1.2018.1-18.

Fischer, P. (1891) Catalogue et distribution géographique des mollusques terrestres, fluviatiles & marins d'une partie de l'Indo-Chine. Imprimerie Dejussieu Pére et Fils, Autun, 193 pp.

Freyhof, J., Serov D. V. & Nguyen T. N. (2000) A preliminary checklist of the freshwater fishes of the River Dong Nai, South Vietnam. Bonner Zoologische Beitraege, 49 (1- 4), 93–99.

Haas, F. (1920) Die Neumayrschen Najaden aus der Ausbeute des Grafen Széchenyi. Senckenbergiana, 2, 146–151.

Haas, F. (1969) Superfamilia Unionacea. Das Tierreich, 88, 1–663.

He, J. & Zhuang, Z. (2013) The Freshwater Bivalves of China. Conchbooks, Harxheim, 198 pp.

Hoang, D.T., Chernomor, O., von Haeseler, A., Minh, B.Q. & Vinh, L.S. (2017) UFBoot2: Improving the ultrafast bootstrap approximation. Molecular Biology and Evolution, 35, 518–522.

https://doi.org/10.1093/molbev/msx281

Huy, H., Pham, H. & Tran, N. (2022) Phylogenetic relationship of indigenous freshwater fishes in the Sai Gon - Dong Nai river and adjacent drainage basins. Science & Technology Development Journal: Natural Sciences, 6 (1), 1915–1932.

https://doi.org/https://doi.org/10.32508/stdjns.v6i1.1120

Jeratthitikul, E., Paphatmethin, S., Sutcharit, C., Ngor, P. B., Inkhavilay, K. & Prasankok, P. (2022) Phylogeny and biogeography of Indochinese freshwater mussels in the genus Pilsbryoconcha Simpson, 1900 (Bivalvia: Unionidae) with descriptions of four new species. Scientific Reports, 12, 20458. https://doi.org/10.1038/s41598-022-24844-9

Jeratthitikul, E., Sutcharit, C. & Prasankok P. (2024) Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin. Zoosystematics and Evolution, 100 (4), 1333–1345.

https://doi.org/10.3897/zse.100.130929

Jeratthitikul, E., Sutcharit, C. & Prasankok, P. (2025) An integrative approach to a revision of the freshwater mussel genus Songkhlanaia (Bivalvia, Unionidae), with the description of a new species. ZooKeys, 1224, 187–209. https://doi.org/10.3897/zookeys.1224.140549

Jeratthitikul, E., Sutcharit, C., Ngor, P. B. & Prasankok, P. (2021) Molecular phylogeny reveals a new genus of freshwater mussels from the Mekong River Basin (Bivalvia: Unionidae). European Journal of Taxonomy, 775, 119‒142. https://doi.org/10.5852/ejt.2021.775.1553

Jeratthitikul, E. & Sutcharit, C. (2023) Multi-locus Phylogeny Reveals a New Freshwater Mussel in the Genus Bineurus Simpson, 1900 (Unionidae: Pseudodontini) from Thailand. Tropical Natural History, 7, 173–180.

Kalyaanamoorthy, S., Minh, B.Q., Wong, T.K.F., von Haeseler, A. & Jermiin, L.S. (2017) ModelFinder: Fast model selection for accurate phylogenetic estimates. Nature Methods, 14, 587–589.

https://doi.org/10.1038/nmeth.4285

Konopleva, E. S., Bolotov, I. N., Pfeiffer, J. M., Vikhrev, I. V., Kondakov, A. V., Gofarov, M. Y., Tomilova, A. A., Tanmuangpak, K. & Tumpeesuwan, S. (2021) New freshwater mussels from two Southeast Asian genera Bineurus and Thaiconcha (Pseudodontini, Gonideinae, Unionidae). Scientific Reports, 11, 8244. https://doi.org/10.1038/s41598-021-87633-w

Konopleva, E. S., Lheknim, V., Sriwoon, R., Kondakov, A. V., Tomilova, A. A., Gofarov, M. Y., Vikhrev, I. V. & Bolotov, I. N. (2022) Diversity and phylogenetics of freshwater mussels (Unionidae) from Southern Thailand with the description of one new genus and five new species-group taxa. Diversity, 15 (1), 10. https://doi.org/10.3390/d15010010

Morlet, L. (1889) Catalogue des Coquilles recueillies, par M. Pavie, dans le Cambodge et le Royaume de Siam, et description d’espèce nouvelles. Journal de Conchyliologie, 37, 121–199.

Oustalet, M.E. (1880 -1881) Notes d'Ornithologie. Observations sur les Barbus de la Cochinchine, du Cambodge, du Laos et du royaume de Siam. Bulletin de la Société Philomathique de Paris, 7 (1), 63–71.

Pierre, L. (1880 –1907) Flore forestière de la Cochinchine. O. Doin, Paris.

Rochebrune, A.-T. (1882) Documents sur la faune malacologique de la Cochinchine et du Cambodge. Bulletin de la Société Philomathique de Paris, 7 (6), 35–74.

Tamura, K., Stecher, G. & Kumar, S. (2021) MEGA11: Molecular Evolutionary Genetics Analysis Version 11. Molecular Biology and Evolution, 38, 3022–3027.

https://doi.org/10.1093/molbev/msab120

Trifinopoulos, J., Nguyen, L.T., von Haeseler, A. & Minh, B.Q. (2016) W-IQ-TREE: a fast online phylogenetic tool for maximum likelihood analysis. Nucleic Acids Research, 44 (W 1), W232– W235. https://doi.org/10.1093/nar/gkw256

Zieritz, A., Bogan, A. E., Froufe, E., Klishko, O., Kondo, T., Kovitvadhi, U., Kovitvadhi, S., Lee, J. H., Lopes-Lima, M., Pfeiffer, J. M., Sousa, R., Van Do, T., Vikhrev, I., & Zanatta, D. T. (2018)

Diversity, biogeography and conservation of freshwater mussels ( Bivalvia: Unionida ) in East and Southeast Asia. Hydrobiologia, 810, 29–44. https://doi.org/10.1007/s10750-017-3104-8