Macrobrachium amazonicum (Decapoda, Palaemonidae): geographic distribution, new occurrences and biogeographic insights

The shrimp Macrobrachium amazonicum (Heller, 1862) is a widely distributed native species in South America. This study presents an updated geographic distribution of the species through a systematic review of primary and secondary data, as well as reports of new native and non-native occurrences. The distribution extends approximately 4976 km, from the Maracaibo hydrographic ecoregion (Venezuela) to Lower Paraná (Argentina), between the latitudes 10°40’37”N and 27°20’31”S, and about 5226 km, from the Tuira River (Panama) to the Northeastern Atlantic hydrographic region (Rio Grande do Norte, Brazil), between the longitudes 79°31’30”W and 35°12’7”W. Covering much of South America and 2 hydrographic ecoregions in Panama, geographic expansion was detected with new continental and coastal records, both in native and non-native areas. New occurrences were recorded in the hydrographic ecoregions of Gurupi (Maranhão, Brazil); Lower Piranhas-Açu (Rio Grande do Norte, Brazil); Middle São Francisco (Bahia, Brazil); Upper Tocantins (Goiás, Brazil); Middle Paraguay (Mato Grosso do Sul, Brazil); Tarauacá (Amazonas, Brazil); Maracaibo, Trinidad, and Orinoco (Venezuela); Magdalena-Sinu (Colombia); Chagres (Panama); and the High Andes of the Amazon (Bolivia). The new record in Maracaibo extended the species’ range by 361 km to the north, and in Chagres, Panama, in Central America, by 51 km to the west. M. amazonicum exhibited the neotropical distribution which was already known for the species. Evidence of anthropogenic introduction in Brazilian reservoirs is supported by the absence of records in connection sites with the Orinoco and Amazon basins, which are geologically separated from the La Plata basin. The wide distribution of the species highlights its high adaptability to various environments.