Effect of temperature and cypermethrin on the sentinel species Mytilus galloprovincialis measured through a suite of biomarkers in gills

Abstract

Currently one of the biggest problems facing the salmon industry worldwide is high proliferation and spread of sea lice, copepod ectoparasites that reaches high population densities in intensive farms. This problem generates great economic losses to the industry by reducing the health of the fish and indirectly by high treatment costs. In Chile the main insecticides used to lower the parasite loads through direct bathe with skirts at sea are pyrethroids (cypermethrin and deltamethrin). These insecticides are applied at high concentrations. Periodic treatments have generated parasite resistance causing treatments to become increasingly ineffective. This has resulted, in turn, in increased volumes of pyrethroids directly discharged to the marine environment. Few studies on environmental toxicological effects on non-target marine species have been performed. This laboratory study evaluated the sub-acute exposure to realistic cypermethrin concentrations in the sentinel mussel Mytilus galloprovincialis at different temperatures and two exposure times using a factorial design. Two general biomarkers of oxidative stress Catalase (CAT) and Glutathione S-transferase (GST) and two specific biomarkers Acetilcholinesterase (AChE) and Carboxylesterase (CbE) were determined in mussel gills. A synergistic effect between cypermethrin and its vehicle (acetone) at 96 hours was found in cypermethrin treatments with an increase activity in CAT and GST, becoming this effect significant at a different temperature for each biomarker. The effect of cypermethrin as active ingredient was detected in mussels acclimated to 22 ºC as an increase of CbE activity in cypermethrin treatments. It was found a strong effect of acetone, used as solvent, inhibiting AChE activity and CbE activity. Temperature acclimation by itself was also found to have a significant effect on enzymatic activities (all of them measured at 20 ºC), mainly by inhibiting the CAT activity, increasing AChE activity and producing a bell effect on GST activity (17-22-27 °C).