Effect of Salinity on the Development and Dormancy of Cladonema digitatum

Some hydrozoan species are known for their high adaptability and dormancy ability, e.g., Cladonema species, which are also promising model organisms. Since salinity affects the development and distribution of hydrozoan species, it is important to get further understanding of salinity tolerance and dormancy ability of Cladonema species. Cladonema digitatum is a cryptic species and is discovered only in artificial environments. In this study, multiple experiments have been conducted to determine how salinity affects the development of C. digitatum polyps and medusae, to describe the dormancy and recovery of the C. digitatum polyps, and to find the possible prevention and disposal protocol for the occurrence of Cladonema in artificial environments. As results, salinity range of 35–40 ppt was optimal for C. digitatum polyps, while C. digitatum medusae lived best in 30–35 ppt; C. digitatum would form menonts at 15, 50–60 ppt, revive and change their survival strategies after salinity upturned to 35 ppt, which could enhance their tolerance and adaptability. Cladonema digitatum medusae also showed different death rates when faced with sharp hypersaline and hyposaline stress. In summary, this research provided ecological information about salinity range and dormancy ability of C. digitatum , which not only facilitated tracing the wild habitats of the C. digitatum , but also provided the theoretical basic of elimination and prevention of Cladonema species intrusion and breeding conservation in the laboratory.