Brachyuran Zoeae Obtain UV-radiation Protection from Diatom Prey

FENUCCI JORGE L; MARCOVAL MARIA ALEJANDRA; PAN JERONIMO

Providence, Rhode Island, USA

Congreso; Estuarine Research Federation 2007. USA.; 2007

Cyrtograpsus angulatus (Brachyura: Grapsidae), an itertidal crab from brackish waters of the SW Atlantic, releases zoeae into the open coast that later reinvade estuarine environments as megalopae. To study the photoprotective mechanisms during early planktonic stages, stage I Cyrtograpsus zoeae were reared from ovigerous females and fed the diatom Chaetoceros gracilis from semi-continuous cultures in exponential phase. Phytoplankton was grown under two radiation regimes: (a) visible light (PAR, 400-700 nm) and (b) visible light and ultraviolet radiation (UVR+PAR, 280-700 nm). Upon hatching, 500 zoeae were placed into 5-litre aerated tanks (n=3) and provided a daily diet of 100,000 diatoms/ml from the two radiation treatments. After 6 days, no differences between treatments were observed in survival (~80 %), ingestion rates (1500 cells/min), and growth (fitted to an exponential curve; R2= 0.99). Thereafter, the surviving zoeae (stage IV) were placed under moderate UVR stress for 24 h. Survival was ~70% and ~30% for zoeae previously fed diatoms from UVR+PAR and PAR treatments, respectively. Moreover, pigments extracted from zoeae fed UVR+PAR diatoms presented an absorbance peak in the UVA range (334-337 nm). Phytoplanktophagous larval stages (zoeae I-IV) of Cyrtograpsus angulatus bioaccumulate UVR-absorbing compounds through their diet, as a protecting mechanism from UVR-induced stress.