Gastrotricha Metschnikoff, 1865 is a small phylum of acoelomatic animals common in both marine and freshwater environments. To date, close to 800 species are known from all over the world. The order Macrodasyida Remane, 1925 [Rao & Clausen, 1970] is almost exclusively marine except for the rare genera Marinellina Ruttner-Kolisko, 1955 and Redudasys Kisielewski, 1987. In this study, we present morphological and molecular data for a potentially new species of Redudasys from the Edwards Aquifer, Texas, USA. It is the first record of the genus from the Northern hemisphere. It has only previously been reported from Brazil. The Texan specimen, designated as Redudasys sp., has a single pair of anterior adhesive tubes and is considerably shorter than the specimens reported from Brazil. Molecular data from the 18S rRNA and COI mtDNA genes support a close relationship of Redudasys sp. to Redudasys fornerise Kisielewski, 1987. Barcodes are provided for both Redudasys sp. and R. fornerise. The limited material obtained does not justify the description of a new species, but the record is certainly important from a biogeographical standpoint. The colonization and invasion of marine species into freshwater habitats, in particular those of the Edwards Aquifer, is discussed. Although certain marine gastrotrichs appear to have an astonishing ability to adapt to changes in salinity Redudasys is likely to be a marine relic.
Redudasyidae, biogeography, artesian outflow, Edwards Aquifer, Texas, new record.