Annual reproductive cycle of mussle, Mytilus coruscus (Gould, 1861) on the east coast of Ulleungdo Island in the East Sea of Korea

Abstract

Gametogenesis of the mussle Mytilus coruscus (Gould, 1861) on the east coast of Ulleungdo Island, Korea was investigated monthly (May 2013 to May 2014). Gametogenesis in females and males in September when the water temperature reached 23.7°C. Ripe gametes were observed from December 2013 to May 2014 in both sexes. First spawning males and females were observed in March (10.2°C) and April (12.6°C) as the lowest surface water temperature during the sampling periods. Partially spawned mussles were evident from March to July and April to July in male and female, respectively, when the water temperature increasing period ranged 10.2-23.2°C. Most mussles collected in April and May exhibited partially empty follicles with large eggs, suggesting that these two months are the major spawning periods. From June to September, most of the mussles were in spent and resting stages. In contrast, all male and female mussles were in resting stage exhibiting no gametes in the follicles in August. Our data suggested that M. coruscus is a winter spawner, and their annual gametogenesis is closely associated with the seasonal variation in the surface water temperature. Resting phase of the male and female mussles from June to October and such prolonged period of resting could be, in part, explainable by poor food condition in the study site. The present study first provided fundamental information on life history of M. coruscus, which°C. Ripe gametes were observed from December 2013 to May 2014 in both sexes. First spawning males and females were observed in March (10.2°C) and April (12.6°C) as the lowest surface water temperature during the sampling periods. Partially spawned mussles were evident from March to July and April to July in male and female, respectively, when the water temperature increasing period ranged 10.2-23.2°C. Most mussles collected in April and May exhibited partially empty follicles with large eggs, suggesting that these two months are the major spawning periods. From June to September, most of the mussles were in spent and resting stages. In contrast, all male and female mussles were in resting stage exhibiting no gametes in the follicles in August. Our data suggested that M. coruscus is a winter spawner, and their annual gametogenesis is closely associated with the seasonal variation in the surface water temperature. Resting phase of the male and female mussles from June to October and such prolonged period of resting could be, in part, explainable by poor food condition in the study site. The present study first provided fundamental information on life history of M. coruscus, which