Yamasaki Yasuhiro

To ensure the stable supply of the euglenophyte Eutreptiella eupharyngea in the seed production of bivalves during the winter, we evaluated the growth potential of E. eupharyngea under low water temperatures through laboratory and outdoor experiments. In laboratory experiments, no significant difference was found in the maximum yield of E. eupharyngea between water temperatures of 10 and 20℃, whereas the maximum yield of the diatom Chaetoceros neogracile known as a common diet alga for the seed production of bivalves significantly decreased at 10℃ compared with 20℃. In an outdoor experiment on a 150-L scale at a salinity of 25, furthermore, E. eupharyngea grew well in mid-winter, and reached the maximum cell density of 3.7 × 10^5 cells mL^–1. During the outdoor experiment, water temperatures ranged from 0.5 to 23.7℃, with a mean of 10.7℃. Although the water temperature in the mass-culture tank fluctuated significantly with the weather and day or night, E. eupharyngea maintained more than 2.2×10^5 cells mL^-1 for 12 days. Therefore, E. eupharyngea may contribute to the stable supply of the feed throughout seed production of bivalves in late fall and spring.