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Abstract
We studied individual traits related to the sexual reproduction of Lychnorhiza lucerna and reviewed earlier studies of sexual maturation in scyphomedusae, focusing on non-brooding species. Lychnorhiza lucerna is a gonochoric species and sexual dimorphism was noted in the gonadal colour. There were no brooding structures or any other distinguishable features enabling macroscopic determination of sex. Gametogenesis resembled descriptions available for other rhizostomes and semaeostomes. Both processes are asynchronous, with gametes at all stages of development occurring together. Oocytes arose from the gastrodermis and maintained contact with it via trophocytes throughout vitellogenesis. Spermatogenesis occurred within spermatic follicles arising from nested primary spermatogonia. Population features of sexual reproduction were defined by characterizing and quantifying individuals at different stages of sexual maturity. In Scyphozoa, sexually mature medusae can be detected by (1) the presence of fully developed gametes in the gonads indicating incipient spawning, or (2) the presence of spent follicles as evidence of ongoing or recent spawning. Whereas the former allows more detailed study of sexual reproductive patterns of any species, the latter constitutes an option for non-brooders (as in L. lucerna) equivalent to the search of fertilized eggs or planulae for brooder species.
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark
Acknowledgements
We are indebted to fishermen from San Clemente del Tuyú and Mar de Ajó for their help in jellyfish collection. A.S. is grateful to Gustavo Macchi for providing support and facilities at the Histology Laboratory (INIDEP) and to Marta Estrada for her assistance in preparation of histological slides. We also thank Drs Kylie Pitt, Kevin Eckelbarger, Jack Costello, Naoki Iguchi and Dale Calder for providing useful information and comments improving the manuscript. This work was funded by INIDEP, CONICET PIP 5009, FONCyT PICT 1553, CNPq (490348/2006-8) and FAPESP (1999)/05374-7). This is INIDEP contribution No. 1609.
Notes
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark