Fish hosts, glochidia features and life cycle of the endemic freshwater pearl mussel Margaritifera dahurica from the Amur Basin

Abstract

Margaritiferidae is a small freshwater bivalve family with 16 species. In spite of a small number of taxa and long-term history of research, several gaps in our knowledge on the freshwater pearl mussels still exist. Here we present the discovery of host fishes for Margaritifera dahurica , i.e. Lower Amur grayling, sharp-snouted lenok, and blunt-snouted lenok. The host fishes were studied in rivers of the Ussuri Basin. The identification of glochidia and fish hosts was confirmed by DNA analysis. The life cycle of M . dahurica and its glochidia are described for the first time. The SEM study of glochidia revealed that the rounded, unhooked Margaritifera dahurica larvae are similar to those of the other Margaritiferidae. Margaritifera dahurica is a tachytictic breeder, the larvae of which attach to fish gills during the Late August – September and finish the metamorphosis in June. Ancestral host reconstruction and a review of the salmonid - pearl mussel coevolution suggest that the ancestral host of the Margaritiferidae was a non-salmonid fish, while that of the genus Margaritifera most likely was an early salmonid species or their stem lineage. The overfishing of lenoks and graylings appears to be the most significant threat for this rare mussel species.

Comparative diversity in glochidia of Australasian freshwater mussels

“…Glochidia from C. novaehollandiae, H. australis and E. aucklandica were exceptional in their smaller size compared to those of the other species included in this study. Cucumerunio novaehollandae has perhaps one of the smallest recorded glochidia globally, rivalled only by a few margaritiferid species, Margaritifera dahurica (Middendorff, 1850), Margaritifera falcata (Gould, 1851), M. margaritifera and Cumberlandia monodonta (Say, 1829) (see Harms, 1909;Howard, 1915;Murphy, 1942;Bauer, 1994;Nezlin et al, 1994;Pekkarinen and Valovirta, 1996;Baird, 2000;Ieshko et al, 2014;Vikhrev et al, 2019), all of which are similarly miniscule in shell length (<60 μm). It has been proposed that such small glochidia (<65 μm in size) may be an adaptation to enhance suspension in the water column (Barnhart et al, 2008).…”

Fresh- and Brackish-Water Cold-Tolerant Species of Southern Europe: Migrants from the Paratethys That Colonized the Arctic

“…Judging by paleontological and genetic data, the genus Margaritifera originated in the Pacific Ocean basin, where most members of this genus (four species) still live [87]. Margaritifera dahurica (Middendorff, 1850), inhabiting the Amur basin and adjacent aquatic systems, is the closest to M. margaritifera according to molecular genetic data [87]; the main hosts of the glochidia of M. dahurica are lenoks (Brachymystax) [88].…”

“…Thus, numerous data indicate that freshwater pearl mussels lived in water bodies of the Paratethys basin for a long time together with their salmonid hosts belonging to the Salmo-Brachymystax-Hucho clade. A number of forms of Margaritifera arose here, apparently including the ancestors of the modern M. dahurica and M. margaritifera, which parasitize precisely salmonids belonging to this group of fish [83,88].…”