• Animal Systematics, Evolution and Diversity
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• v.13 no.3
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• pp.233-246
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• 1997

A genetic analysis using starch gel electrophoresis was performed to clarify the degrees of genetic differentiation and the phylogenetic relationships among four species of the genus Corbicula (Bivalvia, Corbiculidae). The average genetic similarity coefficients among the populations of each species on C. fluminea, C. leana and C. colorata were very closed (Rogers' S$\geq$0.970), whereas the other C. japonica was separated into two genetic groups (S=0.873) with distinct allelic difference at the Gpl locus. Thuefore additional taxonomic studies are needed on this species. On the other hand, these four species were well distinguished from each other genetically with distinct allelic differences at 4 to 9 loci. The genetic similarity coefficients (S) between C. leana and C. colorata, C. fluminea and C. leana, and C. fluminea and C. colorata were 0.737, 0.689, and 0.594, respectively. In particular, the average genetic similarity coefficients between these three species (inhabiting in freshwater) and the other C. japonica (inhabiting in brackishwater) were notably lower (S=0.370).

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.319-331
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• 2004

This study was conducted to evaluate the ecological impact of freshwater bivalve (Corbiculidae) on plankton communities in experimental enclosure systems (2 m ${\times}$ 2 m ${\times}$ 2 m). During the acclamation period of one month, cyanobacteria, including Microcystis viridis and Microcystis aeruginosa, dominated in both control and treatment enclosures with no noticeable density difference. After the addition of 100 mussels, dominant species of phytoplankton shifted from Microcystis to Scenedesmus in concert with slight decrease in the cell density and the increase of N/P ratio. However, cell density in the control quickly increased, accompanied with changes of dominant species to Oscillatoria spp. With the introduction of additional 500 musseles in the treatment enclosure, dominant phytoplankton species in both enclosures were replaced with Selenastrum spp. and Cryptomonas sp. In the initial stage, the total zooplankton abundance in the control was higher than that of treatment, but it was reversed after the addition 100 mussels. After mussel density increased up to 600 indivisuals, zooplankton density in the treatment decreased with dominance of small taxa, such as rotifers and nauplius. However, abundance and carbon biomass of large zooplankton, such as Bosmina longirostris and Diacyclops thomasi were maintained in a high level compared with those of control. During the study period, Chl. a concentration in mussel treatment and control increased with DIP and $NH_3-N$, respectively. Due to the increase of $NH_3-N$, especially after the introduction of additional 500 mussels, nitrogen limitation did not occur in the treatment enclosure in contrast with strong nutrient limitation occurred in the control. These results indicate that filter-feeding Corbicula could exert important impact on nutrient recycling and plankton community structure in a freshwater ecosystem, through direct feeding and competition for the same food resource as zooplankton on one hand, and through alteration of nutrient availability on the other.