The red swamp crayfish Procambarus clarkii is a decapod considered among the most invasive species in freshwater systems . Native to south-c entral USA and north-east Mexico, the species was introduced in Costa Rica for farming purposes in the '60s. Many studies on the impact of P. clarkii on the ecosystem and its feeding habits have been conducted , especially in Europe and North America, revealing its negative effects on the local invertebrate communities and the consequent reduction of endemic species. The red swamp crayfish has been found to be an opportunistic, omnivorous feeder that ingests high amounts of macrophytes, algae, invertebrates, and detritus, thus altering ecological characteristics of the ecosystem as well as its heterogeneity. Despite representing a threat to the natural biodiversity, very limited information is currently available on the effect of P. clarkii in Costa Rican freshwater ecosystems.
The purpose of our study was to analyze the diet of P. clarkii in order to estimate its impact on the local biodiversity. Gut content analyse s were conducted with individuals collected at five different sites in the central valley of Costa Rica. A total of 187 stomachs were analyzed and the contents were classified into 16 food categories. The most frequent food items were fine vegetal detritus, fibrous plant material, remains of crustaceans and, interestingly, plastic residuals which were found in 5% of the stomachs analyzed and represented up to 30% of the total gut content in some individuals . Since studies on the uptake of microplastics by decapod crustaceans in freshwater systems are still limited, a special focus was put on this food category. Procambarus clarkii most likely ingested plastic particles from sediments when feeding and burrowing, and may act as a vector for harmful contaminants , as the species constitutes a prey of seve ral vertebrate species of fish and mammals, as well as being a food source for humans.