Cotylorhiza tuberculata (Cnidaria: Scyphozoa) ‐ Life History of a Stationary Population

Abstract. The life history of a stationary population of Cotylorhiza tuberculata (Maori, 1778) was studied on the Ionian island of Lefkada, Greece, in 1980 and 1981. Occurrence, growth, maturation, and aging of medusae indicated an annual life cycle of this rhizostomous jellyfish. Ephyrae are liberated during strobilation peaks in spring and summer; exceptionally high growth rates lead to medusa diameters of up to 40 cm after six months. Due to symbiotic zooxanthellae the medusae are potentially autotrophic; P: R values ranged from 0.36 to 1.17. The gonochoristic medusae mature during summer; a sexual dimorphism is evident by brood‐carrying filaments in females. The life span of the medusae is about half a year, while scyphistomae are potentially perennial. The observed annual metagenetic cycle is interpreted as a life history adaptation to a highly seasonal environment.SummaryIn the Ionian Sea the metagenetic cycle of a stationary bay population of Cotylorhiza tuberculata is annual. Strobilation occurs during spring and summer. Rapid growth leads to medusa diameters of up to 40 cm within 6 months. The medusae are potentially autotrophic due to their zooxanthellae. The gonochoristic medusae exhibit sexual dimorphism, and spermatozoa are released as spermatozeugmata. Fertilization is internal, with embryogenesis taking place inside the female moutharm canals. The life span of the medusae is limited by deterioration of somatic tissue to about half a year; no medusae of the bay population survive winter. The planula is the only stage within the metagenetic cycle without zooxanthellae, and infection with algal symbionts occurs in scyphistomae. In the laboratory, the potentially perennial scyphistomae preferentially colonize the underside of hard substrates and reproduce by lateral budding; strobilation is monodiscous.