Pesticide resistance and differences in cholinesterase activities in the invasive freshwater bivalve Anodonta woodiana (Lea, 1834) (Bivalvia: Unionacea) and in the indigenous species of the genus Anodonta sp. (Linneaus, 1758).

Organophosphate insecticides (OP) used in agricultural pest control and contaminating inland waters may cause serious neurotoxic effects in non-target species such as aquatic invertebrates. Two freshwater bivalves, Anodonta woodiana (Lea, 1834), a non-indigenous species, and Anodonta sp. (Linnaeus, 1758), a indigenous species of Italian waters were investigated for their in vitro sensitivity to OP insecticides by measuring cholinesterase activities (ChEs) in digestive gland, foot, gonads, adductor muscle and gill tissues.The invasive species (A. woodiana) showed significantly greater ChE vs ASCh activity than the endemic species and this activity was more widely distributed in tissues involved in movement (adductor muscle and foot), respiration, feeding (gills) and reproduction (gonads). Moreover, only A. woodiana showed detectable ChE activity in gill tissue. No substrate specificity was observed in any tissue of either species