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

Torres

Workshop; GLEON 10 Workshop; 2010

Mycosporine-Like aminoacids (MAAs) are common photoprotective compounds ocurring in certain groups of freshwater and marine organisms. These compounds act as sunscreen or antioxidants and thus provide protection against harmful ultraviolet radiacion (UVR). MAAs can be synthesized by a wide variaty of organisms including bacteria, fungi and algae and their sysnthesis and bioaccumulation is inducible by UVR and visible light. Animals appear to acquire MAAs from their diet and/or from symbiotic organisms. The sysnthesis of MAAs involves the shikimic acid pathway, which as far as we know, has not been found in metazoans. The bioccumulation of MAAs in three species of calanoid copepods endemic to patagonia (Boeckella antiqa, B. gracilis and B. brevicaudata) correlares with UVR exposure, supporting their role as photoprotective compounds and revealing a common mechanism in Boeckella spp towithstand 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 col-adapted especies of Boeckella as well. Peaks of MAAs bioaccumulation in Boeckella spp were recorded netween 12ºC 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 theses compounds such as endosimbiotic bacteria. bath culture experiments testing the effect of bateria suppression on MAAs accumulation showed a decrease in the bioaccumulation of these compounds cultures treated with the basteriostatic Chloramphenicol. This results points our that prokaryotic biota likely contributes to the bioaccumulation of MAAs in boeckella spp. Further more, experimental analyses testing for 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.