CONICET | Buscador de Institutos y Recursos Humanos

In medusae with metagenetic life cycles timing and intensity of blooms are related to polyp reproduction. Scyphistomae multiply through different asexual modes (non-motile buds, free-swimming particles, stolons, cysts). Such modes can increase dispersion capabilities or provide means to withstand adverse conditions. In this sense, the utilization of one or more asexual modes may have ecological implications related to blooming potential. Temperature and food supply are known to influence polyp reproduction rates but results of environmental factors inducing and regulating specific modes are meager and controversial. We tested 10 scyphistomae species in 6 combinations of temperature and food supply over a 6-weeks experiment. Reproduction rates increased with food availability and warmer temperatures for all species and observed reproduction modes (lateral budding, swimming buds, stolons, podocysts). Aurelia sp. strains and Sanderia malayensis reached the highest densities (up to 401 polyps from a single specimen) through lateral budding (70-96%), stolons (12-30%) and free-swimming particles (<5%). Between 60 and 97% of the stolons were reabsorbed. Reabsorption percentage was higher under starvation and colder temperatures. Cassiopea sp., Cephea cephea and Mastigias papua achieved intermediate densities (up to 86 polyps) only through free-swimming buds. Temperature increases not only enhanced budding rate but also its settlement rate. Lychnorhiza lucerna, Rhizostoma pulmo and Rhopilema esculentum produced only podocysts even under starvation but podocyst production increased under feeding and warmer conditions. No excystment was observed. We concluded blooms might be defined phylogenetically by the specific asexual modes each species developed which, in turn, are regulated by environmental conditions.