List of Ranatra Species (Heteroptera: Nepomorpha) from the tributaries of the Xingu River in the Brazilian Amazon.

Abstract

Areas of endemism are geographic units characterized by unique biological diversity and evolutionary histories, enabling the formulation of hypotheses about the processes shaping regional ecosystems. Aquatic insects are essential components of freshwater environments, and the genus Ranatra Fabricius, 1790 is commonly found in slow-flowing streams rich in leaf litter and submerged roots. Known as "water scorpions", 35 species have been reported across Brazil to date. Despite growing research efforts, substantial gaps remain regarding the diversity of these insects, particularly in terms of species identity (Linnean shortfall) and distribution (Wallacean shortfall). In this study, we present a species list of Ranatra Fabricius, 1790 from streams of the Xingu Basin, Pará State, a region located within the Tapajós and Xingu Areas of Endemism in the Brazilian Amazon. We sampled 165 individuals belonging to 13 species, including three new distributional records for the state of Pará, R. brasiliensis De Carlo, 1946, R. doesburgi De Carlo, 1963, and R. rabida White, 1879. Our findings emphasize the importance of expanding research and monitoring efforts in freshwater systems, particularly in highly diverse regions increasingly threatened by anthropogenic pressures and climate change, such as those of the Amazon biome.