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Survival duration of six unionid mussel species under experimental emersion

Nakano, Mitsunori
Hydrobiologia 2018 v.809 no.1 pp. 111-120
Nodularia, aquatic organisms, drought, lotic systems, mussels
Drought often causes emersion, which can seriously damage aquatic organisms in inland aquatic ecosystems. To identify mussel characteristics associated with emersion tolerance, I investigated relationships between survival duration and mussel characteristics under an experimental emersion treatment. The survival durations of six lotic unionid mussel species (Nodularia douglasiae biwae, Pronodularia japanensis, Obovalis omiensis, Lanceolaria grayii, Inversidens brandtii, and Sinanodonta japonica) during emersion in an incubator at 25°C were determined. Shell length, body mass, moisture loss per day, shell thickness, and overall shell shape (shell length/shell height) were measured, and the relationships between these characteristics and survival duration were estimated using Cox’s regression analyses both by species (single-species analysis) and overall, excluding I. brandtii (multispecies analysis). The mussels survived 0.5–8.5 days, and survival duration differed among species. Single-species analyses indicated that in P. japanensis and L. grayii, longer shells and greater mass increased survival. O. omiensis survived longer as moisture loss from their soft bodies occurred more slowly. Multispecies analyses indicated shorter survival by mussels that had relatively heavy body mass, rapid moisture loss, and thin shells. Species with such characteristics are expected to be the most sensitive to emersion and may require conservation.