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6 June 2007 |
Mussel of the Month
The June 2007 Mussel of the Month is Nodularia douglasiae. As we currently treat it, Nodularia is a genus of four species occurring from the Russian Far East south into Indochina.
ZMB 55619. Hatanggyon am Naemingang [Korea].
(type of Nodularia douglasiae var. sinuolata von Martens, 1905)
The taxonomy of Nodularia douglasiae is representative of an on-going disagreement that has clouded the literature on Palearctic freshwater mussels for the last thirty years. For example, according to Fritz Haas (1969), Nodularia douglasiae is a single widespread species with seven subspecies distributed from the Amur Basin and the Russian Far East, to Japan, Korea, China and Taiwan. However, recent treatments by Russian followers of the "Comparatory" Method treat the Russian populations as no fewer than ten distinct species (e.g. Starobogatov et al., 2004).
The Comparatory Method, as it is applied in the modern malacological literature, is a typological species concept, in contrast to other species concepts that treat species as evolutionary lineages. Unfortunately, this dichotomy in philosophy and methodology provides two extreme views: there are either 45 Biological Palearctic species of freshwater mussels or 156 Comparatory species. We estimate that the true value will be found to be somewhere between those two values (although probably much closer to 45 than 156).
Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida
Superfamily UNIONOIDEA Rafinesque, 1820
Family UNIONIDAE s.s.
Subfamily UNIONINAE s.s.
Tribe UNIONINI s.s.
Genus Nodularia Conrad, 1853
Species Nodularia douglasiae (Griffith & Pidgeon, 1834)
For more information about Nodularia, the Comparatory method and the classification of Palearctic freshwater mussels, check out:
- Haas, F. 1969. Superfamilia Unionacea. Das Tierreich (Berlin) 88: 663 pp.
- Starobogatov, Ya.I., L.A. Prozorova, V.V. Bogatov & E.M. Sayenko. 2004. Bivalvia. Key to the Freshwater Invertebrates of Russia and Adjacent Lands, vol. 6 (molluscs, polychaetes, nemerteans). pp. 11-251.
- Kantor, Yu.I. & A.V. Sysoev. 2005. Catalogue of Molluscs of Russia and Adjacent Countries. KMK Scientific Press Ltd., Moscow, Russia. 627 pp.
- Graf, D.L. In press. Palearctic freshwater mussel (Mollusca: Bivalvia: Unionoida) diversity and the Comparatory Method as a species concept. Proceedings of the Academy of Natural Sciences.
- Palearctic Freshwater Mussels, a special project on the MUSSEL Project Web Site (this site).
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