抄録
The freshwater jellyfish Craspedacusta sowerbii is a small cnidarian belonging to the class Hydrozoa, inhabiting ponds and dam reservoirs. Like other hydrozoans, this species exhibits both an asexual polyp stage and a sexual free-swimming medusa stage. During the asexual stage, minuscule motile "frustules" develop into polyps, leading to enhanced clonal propagation. In contrast, the sexual stage involves the release of eggs and sperm by males and females, resulting in the formation of fertilized eggs. Craspedacusta sowerbii exhibits sporadic appearances and is rarely observed continuously in the same location over consecutive years. Even during mass occurrences, it is often the case that only one sex (either male or female) is present within the same site, leaving much of its ecology still shrouded in mystery. In September 2024, our team discovered C. sowerbii for the first time at Yanase Dam in Shikokuchuo City, Ehime Prefecture, Japan. Through sexual identification and molecular phylogenetic analysis, we identified that these individuals comprised at least two distinct male and female populations.
https://ror.org/03t78wx29 
