Total oxidant scavenging capacity of Antarctic, Arctic, and Mediterranean scallops

The Total Oxyradical Scavenging Capacity (TOSC) assay was used in three spe cies of scallops for quantifying their ability to neutralise peroxyl (ROO.) and hydroxyl ((OH)-O-.) radicals and peroxynitrite (HOONO). Adamussium col becki and Chlamys islandicus represent key organisms for monitoring Antarct ic and Arctic regions while Pecten jacobaeus was chosen for comparison with a related temperate species. TOSC values for ROO. were significantly highe r in A. colbecki, indicating that this species is the most efficient ROO. s cavenger. Mediterranean scallops had the lowest TOSC for ROO., Adamussium, colbecki also exhibited the highest scavenging capacity for (OH)-O-. with v alues more than two-fold greater than for C. islandicus and P. jacobaeus. T OSC values for HOONO were lower for all scallops as compared to those for R OO. or (OH)-O-.; for microsomes they were not significantly differ ent amon g the species for any reactive oxygen species studied, and the percentage c ontribution to the specific TOSC for the various oxidants of microsomes of all scallops accounted for 1-3% of the total TOSC of the post-mitochondrial fraction. The specific TOSC of scallop microsomes for (OH)-O-. was similar to 10 times lower than that for ROO. or HOONO. The higher basal capability of the. Antarctic scallop to neutralise different reactive oxygen species is discussed in terms of a possible adaptation to this extreme environment, and TOSC is validated as a quantifiable measure of susceptibility to oxida tive stress in marine organisms. In a second part of this study, the season al fluctuations of susceptibility to oxidative stress were analysed in the Antarctic scallop Adamussium colbecki by the TOSC Assay. A marked increase in the capability to neutralise peroxyl radicals and hydroxyl radicals was demonstrated at the end of December, while resistance towards peroxynitrite did not show significant variations during the Antarctic summer. The incre ased resistance to these specific oxyradicals a as almost contemporary with the period of highest feeding activity and the development of gonadic tiss ues. Sensitivity to hydroxyl radicals and peroxyl radicals toxicity was als o influenced by W-B and UV-A wavelengths, as indicated by the lower TOSC va lues in scallops exposed under laboratory conditions. Toxicity of UV radiat ion seems partly mediated by formation of reactive oxygen species caused by the direct exposure of mantle edges and/or the photochemical production of hydrogen peroxide in sea water.