Photorepair mechanisms and protective compounds in two zooplanktonic species, Daphnia menucoensis (Cladocera) and Metacyclops sp. (Copepoda), from freshwater bodies of Patagonia, Argentina

R. J. GONCALVES; V. E. VILLAFAÑE; E. W. HELBLING

Québec (Canada)

Congreso; 30th Annual Meeting of the American Society for Photobiology; 2002

Specimens of Daphnia menucoensis, Cladocera (from Laguna Cacique Chiquichano, 43ºS) and Metacyclops sp., Copepoda (from Laguna Parque de la Ciudad, 43ºS) were used in experiments designed to evaluate the effectiveness of a) photorepair mechanisms, and b) UV-absorbing compounds to cope with detrimental effects of UV-B (280-320 nm). In both species UV-B caused a significant dose-dependent mortality, with Metacyclops sp. being more resistant than D. menucoensis, having a maximum mortality of 30% and 100%, respectively after receiving a dose of 150 KJ m-2. A significant decrease of mortality (i.e., higher survival) were observed in both species when exposed also to PAR (60 W m-2), suggesting an active photorepair. Although this mechanism was more evident in D. menucoensis, the effectiveness ofphotorepair (i.e., increased survival divided by total death) was about the same for both species. Biological weighting functions (BWFs) also suggested the higher resistance to UV-B wavelengths of copepods as compared to cladocerans. This higher resistance seems to be related to the presence of mycosporine like aminoacids -MAAs- (i.e., shinorine and porphyra-334), and carotenoids, which would add an adaptive advantage to Metacyclops sp. This work was supported by Fundación Antorchas (project 13887-83) and Fundación Playa Unión.