This paper presents new records that considerably expand the geographical range of the invasive shrimp Palaemon macrodactylus in Argentina to include new estuarine areas on the Argentine south Atlantic coast: Bahía Samborombón, and the Bahía Blanca and Río Negro estuaries. The latter 2 locations are the southernmost reports for this species. The epibiotic barnacle Balanus amphitrite and a microphallid metacercaria Odhneria sp. are reported for the first time in P. macrodactylus. The prevalence of white spot syndrome virus (WSSV) was 10% in the Bahía Blanca estuary. Our results strongly suggest that WSSV is spreading in crustacean populations in the Argentine Sea and that P. macrodactylus plays a role in the ecology of parasite infections in this environment.Centro de Estudios Parasitológicos y de Vectores