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

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

Hiroshima, Japón

Congreso; The Plankton Society of Japan & The Japanese Association of Benthology. Joint Meeting in 2006.; 2006

The Plankton Society of Japan, The Japanese Association of Benthology

It is widely argued that jellyfish are increasing their biomass in the last 20 years, possibly as a consequence of global heating, over fishing and eutrophication. Their large swarms often greatly affect the marine environment and several human activities as well, but they do not always constitute a problem. Medusae are the basis of commercial fisheries in several parts of the world. Although jellyfish fishery is an ancient activity, more studies are needed on jellyfish population dynamics to develop adequate management strategies. In this sense, knowledge of life cycles is essential. The scyphozoan Lychnorhiza lucerna is the most abundant rhizostome species in Argentina and the possibilities of development of jellyfish fishery are currently challenged in this country. We succeed in obtaining fertilized eggs of this species by artificial fertilization and followed the development up to metephyrae in the laboratory for the first time. Specimens of L. lucerna were collected from the beach in March 2006 in San Clemente del Tuyú, Argentina. The absence of fertilized eggs or planulae within female body suggests that fertilization occurs in the water although more studies are necessary to be sure. Planulae settled on styrene and glass slides, shells, and the air-water interface. Settlement on natural substrata, as well as on artificial ones, indicates that larvae have non-specific settlement preferences, or that in the absence of their preferred settlement site they will settle on a variety of surfaces. Larvae metamorphosed into four-tentacled polyps around 24 h after settlement. Fully developed scyphistomae were found 20-25 d later and bore from 18 to 22 filiform tentacles. Podocyst formation was the only observed method of asexual reproduction. Polidisk strobilation with the formation of 3 ephyrae was completed in about 8 d. L. lucerna strobilated under constant temperature, salinity, food and light conditions. None of the examined stages of L. lucerna contained algal symbionts. Well-fed polyps strobilated repeatedly over 3 months. Newly liberated ephyrae possessed typically 8 pair of lappets and 8 rhopalia. They reached a metephyrae stage in 10-15 d.