Distribution and status of Smicridea McLachlan, 1871 (Trichoptera: Hydropsychidae) in the Rio Doce Basin, Southeastern Brazil a decade after the tailings dam disaster

The greatest diversity of the genus Smicridea (Trichoptera: Hydropsychidae) is found in the Neotropical region, where 72 species have been recorded from Brazil—43 belonging to the subgenus S. (Rhyacophylax) and 29 to S. (Smicridea). Despite this richness, gaps remain in the knowledge of their geographical distribution, particularly in regions impacted by human activities. The Doce River Basin, which contains the second-largest river in Southeastern Brazil, has experienced extensive environmental degradation due to intense mineral exploitation. This situation was further exacerbated by the 2015 collapse of a tailings dam, the largest socio-environmental disaster in Brazil's history, which directly affected the local aquatic fauna. To expand and integrate knowledge of the Smicridea fauna of the Doce River Basin, this study reports 12 species occurring in the region, including six new state records: three for Espírito Santo (S. (Rhyacophylax) appendiculata Flint, 1972, S. (Rhyacophylax) scalprum Vilarino, Dias & Calor, 2019, and S. (Rhyacophylax) vilela Flint, 1978) and three for Minas Gerais (S. (Rhyacophylax) atrobasis Flint, 1983, S. (Rhyacophylax) palmar Sganga, 2005, and S. (Rhyacophylax) vilela). Additionally, a new species, Smicridea (Rhyacophylax) exu sp. n., is described and illustrated based on males collected from the Rio Doce and its tributaries in Minas Gerais. It can be distinguished by a combination of genital characters, particularly the tergum X, which has a rounded apex with a strong, narrow apicomesal lobe bearing approximately six to eight short, stout spines on the mesal region. The phallic apparatus is also diagnostic, featuring a long subapicolateral spine directed posterad and one to four medium-sized dorsal spines directed posterad.