This study sought to evaluate the sensitivity of two epibenthic amphipods (Hyalenigraand Hyaleyoungi) to reference substances inorder toevaluate their potential as test-organisms in ecotoxicological studies. First, theoptimal ranges of salinity, temperature, and pH were estimated for both species. Then, toxicity tests with different reference toxicants were conducted. The selected contaminants were cadmium chloride (CdCl2), sodium dodecyl sulfate detergent (C12H25NaO4S), ammonium chloride (NH4Cl2), potassium dichromate (K2Cr2O7), and zinc sulfate (ZnSO4).The mortalities were recorded and the effectiveconcentrations to 50% organisms (LC5096h)were estimated. Sensitivities of both species were similar to those reported in studies on other amphipods, which is evidence of the potential of these species to serve as test organisms in ecotoxicological studies
