Factors Influencing the Sensitivity of Gammarus aequicauda Population from Mar Piccolo in Taranto (Southern, Italy)

Laboratory experiments were performed on the amphipod Gammarus aequicauda in order to evaluate the relationship between the seasonal sensitivity to a reference toxicant and seasonal lipid content, temperature and algal biomass. The organisms were collected in a clean site in the Mar Piccolo of Taranto (Ionian sea) from March 2003 to February 2004. The total lipid content of G. aequicauda varied from 5.5% in spring to a maximum of 19% in autumn, then decreased until reaching 9.8% of dry weight in winter. Triacyglycerols (TG) were the most abundant lipid class in G. aequicauda, except in spring, when there was a higher percentage of phospholipids (PL). Sterol levels were lower. The sensitivity of G. aequicauda during different seasons was significantly affected by total lipids (r ¼ 0.97; po0.01), but no relationship was found with algal biomass (r ¼ 0.21; p40.05) and temperature (r ¼ 0.29; p40.05). The highest LC50 values appeared with an increase of total lipids. This study will be used to improve the interpretation of ecotoxicological test results with G. aequicauda.