Korniushin (2000: 45) diagnosed Sphaerinova as follows: "Shells small (length up to 9 mm, usually 7 to 8 mm) compared with that in nominate subgenus[i.e. Musculium in his classification]; beaks usually slightly shifted posteriorly, not protruding, prodissoconch sometimes separated by growth break line but never forming bean-shaped cap. Ligament externally visible, elevated in largest specimens. Siphons short, especially their fused part; dorsal retractor muscles of inhalant siphon markedly reduced and scars merged with those of posterior adductors. Outer demibranch 0.3 to 0.4 height of inner demibranch (depending on stage of development)."
Both Sphaerium and Musculium have small shells (length up to 9 mm, usually 7-8 mm) with their beaks usually slightly shifted posteriorly, not protruding, prodissoconch sometimes separated by growth break line but never forming a bean-shaped cap. The ligament is externally visible, and elevated in the largest specimens. Siphons are short, especially their fused part, and the dorsal retractor muscles of the inhalant siphon are markedly reduced, and their scars merged with those of the posterior adductors. The kidney has a broad to narrow and elongate dorsal lobe. The outer demibranch is 30-40% the height of the inner demibranch (depending on stage of development) (based on Korniushin, 2000).
According to Korniushin (2002) the autapomorphies of Sphaerium are (1) interlamellar septae in inner demibranch are developed on all gill filaments and (2) and there is similtaneous development of several broods (asynchronous brooding) and the released juveniles have an outer demibranch present. In Musculium a cap is present on the umbo and the inner cardinal tooth on the left valve is straight. Sphaerinova differs from Sphaerium in having weak upper retractors of the branchial siphon.
Diagnosis of Sphaerium given by Bespalyala et al. (2024): Shell large-sized (shell length in adults varies between 6 and 25 mm), rounded to ovate in shape, typically thick walled.
The beaks rounded and slightly prominent or narrow, pore density varies among species. Cardinal and lateral teeth well developed. Nephridia moderately elongated. Two siphons (exhalant and inhalant) are present. The outer and inner demibranch relatively well developed.Sphaerium (Sphaerinova) Iredale, 1924
Infraclass Heteroconchia
Cohort Heterodonta
Megaorder Neoheterodontei
Order Sphaeriida
Superfamily Sphaerioidea
Family Sphaeriidae
Subfamily Sphaeriinae
Genus Sphaerium Scopoli, 1777
Type species: Tellina cornea Linnaeus, 1758. Europe.
Subgenus Sphaerinova Iredale, 1943
Type species: Sphaerium macgillivrayi E. A. Smith, 1882 (= Sphaerium tasmanicum Tenison Woods, 1876)
Original reference: Iredale, T. (1943). A basic list of the fresh water Mollusca of Australia. Australian Zoologist 10: 188-230.
The two subgenera of Sphaerium that are recognised here follows Bespalyala et al. (2024), although this author had doubts about the status of Musculium.
Inhabit almost all types of freshwater habitats including springs, rivers, lakes, ponds, billabongs, waterholes, small creeks, drains and peat bogs. Brood young in multiple brood pouches. Suspension and deposit feeder. Live in sediment and in weeds.
Australia, and taxa from New Zealand, India and Japan.
Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.
Bespalaya, Y. V., Vinarski, M. V., Aksenova, O. V., Babushkin, E. S., Gofarov, M.Y., Kondakov, A. V., Konopleva, E. S., Kropotin, A. V., Mabrouki, Y., Ovchankova, N. B., Palatov, D. M., Sokolova, S. E., Shevchenko, O. V. T., Abdelkhaleq, F. T., Soboleva, A. A., Zubrii, N. A. & Bolotov, I. N. (2024). Phylogeny, taxonomy, and biogeography of the Sphaeriinae (Bivalvia: Sphaeriidae). Zoological Journal of the Linnean Society 201: 305-338.
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Iredale, T. (1943). A basic list of the fresh water Mollusca of Australia. Australian Zoologist 10: 188-230.
Lee, T. (2019). Sphaeriidae Deshayes, 1855 (1820). Pp. 197-201 in C. Lydeard & Cummings, K. S. Freshwater Mollusks of the World: a Distribution Atlas. Baltimore, John Hopkins University Press.
Korniushin, A. V. (2000). Review of the family Sphaeriidae (Mollusca: Bivalvia) of Australia, with the description of four new species. Records of the Australian Museum 52: 41-102.
Korniushin, A. V. & Glaubrecht, M. (2002). Morphological characters analysis, the intergroup phylogenetic relationships and possible outgroups of the family Sphaeriidae (Mollusca, Bivalvia). Vestbuj zoologii 36(4): 3-22.
Kuiper, J. G. J. (1983). The Sphaeriidae of Australia. Basteria 47: 3-52.
Lamprell, K. & Healy, J. (1998). Bivalves of Australia, volume 2. Leiden, Backhuys Publishers.
Lee, T. & Ó Foighil, D. (2003). Phylogenetic structure of the Sphaeriinae, a global clade of freshwater bivalve molluscs, inferred from nuclear (ITS-1) and mitochondrial (16S) ribosomal gene sequences. Zoological Journal of the Linnean Society 137: 245-260.
Smith, B. J. & Kershaw, R. C. (1979). Field guide to the non-marine Molluscs of South-eastern Australia. Canberra, A.N.U. Press.
Smith, B. J. & Kershaw, R. C. (1981). Tasmanian Land and Freshwater Molluscs. Hobart, University of Tasmania.
