The effect of water temperature on the early-life development, growth and survival of the freshwater mussel Hyriopsis bialata

The effect of water temperature on early-life development, growth and survival of the freshwater mussel, Hyriopsis bialata, was studied under controlled conditions. Gravid female mussels carrying gastrula embryos or early glochidia larvae were reared at 4 temperatures (25, 28, 31 and 34 °C) until they released mature glochidia; glochidia were then allowed to develop into juveniles. The highest survival rate of glochidia released from mussels carrying gastrula embryos was at 25 °C (91.4%), while survival for glochidia released from mussels carrying early glochidia larvae ranged from 83.2–91.3%. Average larval development time for gravid females carrying gastrula embryos or early glochidia larvae was between 5.0 and 9.2 days and 2.6–3.6 days, respectively. The survival of glochidia cultured to early juveniles in artificial medium was high in gravid mussels with gastrula embryos originally reared at 25 °C (93.9%) or 28 °C (93.6%), but was markedly decreased when originally reared at 31 °C (49.6%), while survival rates of those in gravid mussels with early glochidia larvae originally reared at 25, 28 or 31 °C were 92.3, 90.2 and 87.7%, respectively. The average transformation period from glochidia to early juvenile was 8–11 days, regardless of the temperature. Juveniles were reared for 1 month, and survival and length were measured. For glochidia released from gravid females with gastrula embryos, survival (85.7%) and length (0.49 ± 0.05 mm) were highest when originally reared at 25 °C, and both measures were significantly decreased at 28 and 31 °C. For glochidia released from gravid females carrying early glochidia larvae, survival (82.2%) and length (0.45 ± 0.06 mm) were highest when originally reared at 28 °C and lower when reared at 25 or 31 °C. Our results indicate that the optimal water temperature for culturing gravid female mussels carrying gastrula embryos or early glochidia larvae was 25 and 28 °C, respectively. These temperatures allowed high juvenile survival and growth.