A new criterion to identify sexual maturity in a non-brooding scyphomedusa

SCHIARITI, A.; CHRISTIANSEN, E.

Mar del Plata

Simposio; Third International Jellyfish Blooms Symposium; 2010

Jellyfish play an important role in marine ecosystems and have received particular attention in recent years in the context of their hypothetical biomass increases. However, knowledge about their life histories and population dynamics is still lacking. When ecological aspects of sexual reproduction are considered, an essential goal is to determine when and where reproduction occurs. To accomplish that, it is crucial to recognize when a medusa has reached sexual maturity. Here, we review how sexual maturity is defined for scyphomedusae and discuss the particular case of non-brooders. In case of brooders ripe medusae are recognized by the presence of sperm-filled appendages, embryos or planulae. Conversely, in non-brooders the search of such spawning indicators requires microscopic examination of gonads. As methodologies used in earlier studies could not be applied to Lychnorhiza lucerna at population scale, we studied gametogenesis and gonadal maturation of L. lucerna, and propose a new criterion for the identification of sexual maturity for this species. Gonadal maturation in L. lucerna seems to be a quick process with "spawning prints" hard to find and identify. Therefore, we suggest that the presence of gametes at their maximum stage of development can be used as an indicator of sexual maturity, showing that the spawning is imminent, ongoing or that the medusa has already spawned. This approach was successfully used to study the life history of L. lucerna; nonetheless further investigation is necessary to evaluate the utility of this criterion to determine sexual maturity in other medusae species.