Life cycle of the jellyfish Lychnorhiza lucerna Haeckel, 1880 (Scyphozoa, Rhizostomeae).

SCHIARITI, A.; KAWAHARA, M.; UYE, S-I; MIANZAN H. W

Gold Coast, Australia.

Simposio; 2nd International Jellyfish Blooms Symposium; 2007

Griffith University

Lychnorhiza lucerna is the most abundant rhizostome in southern Southwestern Atlantic being considered the possibility of the development of a jellyfish fishery of this species. The life cycle of L. lucerna was studied based on laboratory experiments. Mature specimens were collected from the beach in Samborombón Bay (Argentina). L. lucerna displayed the typical metagenetic life cycle reported for all rhizostomes with the alternation of medusoid and polypoid generations. The fertilized egg develops into a small and motile planula. After several hours the planula attaches into hard substrates and metamorphose into a sessile four-tentacled scyphistoma. Scyphistomae growth and develop reaching up to 22 tentacles and attaining around 1500 µm height. They reproduce asexually only by the formation of podocysts from where newly polyps eventually emerge. Scyphistoma become strobila and undergoes polydisk strobilation from where three ephyrae are released. Strobila returns to normal scyphistoma and is capable of repeated strobilation. Ephyrae develop into metephyrae and then into medusae, completing the life cycle. We present a description of L. lucerna ephyrae which can be used to distinguish between Rhizostome species with described ephyrae presented in the South Atlantic Ocean. We hypothesizes that L. lucerna would be able of reproducing asexually and sexually all along its range of distribution in Argentina being limited by availability of suitable substrates. The knowledge of its life cycle was the first step in the study of L. lucerna population dynamics and was essential to investigate which factors are responsible of the interannual fluctuations of jellyfish abundance.