Laver spire shells Hydrobia ulvae, copyright G.-U. Tolkiehn.

Belongs within: Truncatelloidea.

The Hydrobiinae are a group of minute snails that are mostly found in brackish or marginal marine environments around the North Atlantic.

The Hydrobiinae: North Atlantic mud-snails
Published 1 January 2014

The fine-looking animal above (photographed by Roy Anderson) is Hydrobia acuta neglecta, a member of the subfamily Hydrobiinae of the family Hydrobiidae. Most members of the Hydrobiidae are freshwater snails but Hydrobia and genera closely related to it are found in brackish or marine environments. They are grazers on algae and detritus, and can be very abundant. The group is found in coastal, muddy regions on either side of the North Atlantic, extending on the European side through the Mediterranean and into the Black Sea. Hydrobiids as a whole are not well-studied animals, mostly for one ultimate reason: they’re really tiny. Most hydrobiids are only a few millimetres in length. And coupled with that small size is a strong conservatism in external appearance. Compare Hydrobia acuta neglecta above with another hydrobiine, Ecrobia ventrosa, also photographed by Roy Anderson:

The external shell of a hydrobiid supplies few details to distinguish and classify taxa, and dissecting out a snail that small to examine its soft parts is no cake-walk.

Monophyly of the saltwater hydrobiids is supported by molecular data (Wilke et al. 2013), and they form the core of the Hydrobiinae. Bouchet & Rocroi (2005) also listed the family-group taxa ‘Pyrgorientaliinae’ and ‘Pseudocaspiidae’ as synonyms of Hydrobiinae. These were both established for freshwater species: the Pyrgorientaliinae for two genera from Turkey, and Pseudocaspiidae for two genera from central Asia (Kabat & Hershler 1993). Whether these taxa are truly associated with the hydrobiines, I suspect, requires further investigation (it should also be noted that many other authors have used ‘Hydrobiinae’ to refer to more extensive groupings included taxa listed by Bouchet et al. as separate subfamilies).

Systematics of Hydrobiinae
    |--Pyrgorientalia Radoman 1973 [Pyrgorientaliinae]BR05
    |    `--*P. zilchi (Schütt 1964) [=Chilopyrgula zilchi]BR17
    |--Pseudocaspia Starobogatov 1972 [Pseudocaspiidae]BR05
    |    |--*P. issykkulensis (Clessin 1894) [=Caspia issykkulensis]BR17
    |    |--P. kainarensis Starobogatov 1972BV86
    |    |--P. ljovuschkini Starobogatov 1972BV86
    |    `--P. starostini Starobogatov 1972BV86
    `--Hydrobia Hartmann 1821BR05
         |--*H. acuta (Draparnaud 1805)KC60 (see below for synonymy)
         |--H. accrensis Connolly 1929V07
         |--H. ameghiniO05
         |--H. balatonicaB91
         |--H. chopardiana (de Loriol 1865) [=Bithinia chopardiana]B91
         |--H. compactaC64
         |--H. gondwanica Cox 1953TTE93
         |--H. parchappiO05
         |--H. stagnalisB91
         |--H. truncataDPS84
         |--H. ulvae (Pennant 1777)BM88 [incl. H. ulvae var. barleeiN79]
         |--H. ventrosa [incl. Paludestrina stagnalis]B68
         `--H. zhichengensisNG13

*Hydrobia acuta (Draparnaud 1805)KC60 [=Cyclostoma acutumKC60, Bulimus (Elisma) acutusG40, Helix acutaPB27, Paludestrina acutaPB27; incl. Bulimus articulatusG40, Helix bifasciataG40, Elisma fasciataG40, Bulimus fasciatusG40, Lymnaea fasciataG40, Turbo fasciatusG40, Bulimus variabilisG40]

*Type species of generic name indicated


[B91] Bandel, K. 1991. Gastropods from brackish and fresh water of the Jurassic–Cretaceous transition (a systematic reevaluation). Berliner Geowissenschaftliche Abhandlungen, Reihe A 134: 9–55.

[B68] Bernard, F. R. 1968. Sexual dimorphism in Polinices lewisi (Naticidae). Nautilus 82 (1): 1–3.

[BM88] Bieler, R., & P. M. Mikkelsen. 1988. Anatomy and reproductive biology of two western Atlantic species of Vitrinellidae, with a case of protandrous hermaphroditism in the Rissoacea. Nautilus 102 (1): 1–29.

[BV86] Bole, J., & F. Velkovrh. 1986. Mollusca from continental subterranean aquatic habitats. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 177–208. E. J. Brill/Dr W. Backhuys: Leiden.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[DPS84] Davis, G. M., & M. C. Pons da Silva. 1984. Potamolithus: morphology, convergence, and relationships among hydrobioid snails. Malacologia 25 (1): 73–108.

[G40] Gray, J. E. 1840. A Manual of the Land and Fresh-water Shells of the British Islands, with figures of each of the kinds. By William Turton, M.D. A new edition, thoroughly revised and much enlarged. Longman, Orme, Brown, Green, and Longmans: London.

Kabat, A. R., & R. Hershler. 1993. The prosobranch snail family Hydrobiidae (Gastropoda: Rissooidea): review of classification and supraspecific taxa. Smithsonian Contributions to Zoology 547: 1–94.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

[NG13] Ni, X., D. L. Gebo, M. Dagosto, J. Meng, P. Tafforeau, J. J. Flynn & K. C. Beard. 2013. The oldest known primate skeleton and early haplorhine evolution. Nature 498: 60-64.

[N79] Norman, A. M. 1879. The Mollusca of the fiords near Bergen, Norway. Journal of Conchology 2: 8–77.

[O05] Outes, F. F. 1905. Sobre un instrumento paleolítico de Luján (Provincia de Buenos Aires). Anales del Museo Nacional de Buenos Aires, serie 3, 6: 169–173.

[PB27] Pilsbry, H. A., & J. Bequaert. 1927. The aquatic mollusks of the Belgian Congo, with a geographical and ecological account of Congo malacology. Bulletin of the American Museum of Natural History 53 (2): 69–602, pls 10–77.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

[V07] Verdcourt, B. 2007. Miscellaneous notes on tropical African non-marine Mollusca. Annales Historico-Naturales Musei Nationalis Hungarici 99: 189–197.

Wilke, T., M. Haase, R. Hershler, H.-P. Liu, B. Misof & W. Ponder. 2013. Pushing short DNA fragments to the limit: phylogenetic relationships of ‘hydrobioid’ gastropods (Caenogastropoda: Rissooidea). Molecular Phylogenetics and Evolution 66 (3): 715–736.

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