The antennules of crayfish, like in other decapod crustaceans, have been reported as olfactory organs involved in food searching, mating and agonistic behaviour (Fedotov, 2009). The range of stimulatory compounds may vary among species, but typically includes amino acids, nucleotides and their derivatives, amines, bile acids and, in some cases, carbohydrates. The red swamp crayfish Procambarus clarkii (Girard, 1852) (Crustacea: Decapoda), a worldwide invasive species, has biramous antennules with a lateral flagellum bearing aesthetasc chemoreceptors with a role in intraspecific communication (Horner et al., 2008) and a medial flagellum, the sensory processing of which is still unclear. In the present study we evaluate the stimulatory effectiveness, on the antennular chemoreceptors of adult P. clarkii, of a few amino acids and carbohydrates to which the pereopod (walking leg) chemoreceptors were previously reported to be responsive, and taurocholic acid, which instead does not stimulate pereopods (Corotto and O’Brien, 2002; Corotto et al., 2007). To this end, the firing patterns in the nerves emerging from both the lateral and medial flagellum were recorded under chemical perfusion, by way of extracellular suction electrodes (A-M System differential amplifier). Results show that, among the tested compounds, maltose and taurocholic acid stimulate chemoreceptor cells from both the lateral and medial flagellum of antennules in adult crayfish, with the latter stimulus being effective in males as well as in females. Even though at present a functional significance of the antennular sensitivity to maltose and taurocholic acid cannot be assigned, the antennular vs. pereopod activity is discussed in the light of possible overlapping/complementary roles of the two sensory organs in providing the animal with the ability to locate key odours and eventually for the development of strategies for population control programmes. Poster