Bioaccumulation and potencial origin of photoprotective compounds (Mycosporine like amino-acids) in freshwater copepods from Patagonia.

4. GARCÍA, P. E.; M. C. DIEGUÉZ. ; FERRARO, M. A.; ZAGARESE, H. E. Y PÉREZ, A. P.

TORRES, BRASIL

Workshop; GLEON 10; 2010

GLEON

García, P. E.1; Diéguez, M. C.1; Ferraro, M. A.2; Zagarese, H. E2 and Pérez, A. P.1 Bioaccumulation and potential origin of photoprotective compounds (Mycosporine-like Amino Acids) in freshwater copepods from Patagonia 1Laboratorio de Fotobiología. UNC. IMIBIOMA. Bariloche (Argentina). 2Laboratorio de ecología y fotobiología acuática. IIB-INTECH. Chascomus (Argentina). Abstract Mycosporine-like amino acids (MAAs) are common photoprotective compounds occurring in certain groups of freshwater and marine organisms. These compounds act as sunscreen or antioxidants and thus provide protection against harmful ultraviolet radiation (UVR). MAAs can be synthesized by a wide variety of organisms including bacteria, fungi and algae and their synthesis and bioaccumulation is inducible by UVR and visible light. Animals appear to acquire MAAs from their diet and/or from symbiotic organisms. The synthesis of MAAs involves the shikimic acid pathway, which as far as we know, has not been found in metazoans. The bioaccumulation of MAAs in three species of calanoid copepods endemic to Patagonia (Boeckella antiqua, B. gracilis and B. breviucaudata) correlates with UVR exposure, supporting their role as photoprotective compounds and revealing a common mechanism in Boeckella spp to withstand the high levels of UV experienced in their natural environments. Concomitantly, temperature appears as a factor regulating the process of bioaccumulation of MAAs and the survivorship of cold-adapted species of Boeckella as well. Peaks of MAAs bioaccumulation in Boeckella spp. were recorded between 12 ºC and 16ºC. Experiments performed with B. antiqua fed with algae devoid of MAAs resulted in higher levels of MAAs implying that the process may rely in an alternative source of these compounds such as endosimbiotic bacteria.  Batch culture experiments testing the effect of bacteria suppression on MAAs accumulation showed a decrease in the bioaccumulation of these compounds cultures treated with the basteriostatic Chloramphenicol. This result points out that prokaryotic biota likely contributes to the bioaccumulation of MAAs in Boeckella spp. Furthermore, experimental analyses testing for the incidence of actual MAAs concentration on the uptake rate of MAAs in B. antiqua indicated that individuals bearing high levels of MAAs do not accumulate or even loss these compounds.