Obelia Medusa: Second Generation

The elegant medusa jellyfish, illustrated in the photomicrograph below, is one of two forms that the hydrozoan Obelia takes during its two-generation life cycle. The free-swimming medusae reproduce sexually, producing eggs and sperm that fertilize to become ciliated, free-swimming larvae (planulae). The planulae remain pelagic for a period of time, eventually attaching to a surface and developing into polyps.