First record of the Neotropical cladoceran Diaphanosoma fluviatile in the Great Lakes basin.

The ctenopod Diaphanosoma fluviatile has been reported primarily from the Neotropical region and occasionally from the southern United States. D. fluviatile was collected in the Great Lakes basin (the Maumee River, Western Lake Erie, and Lake Michigan) in 2015 and 2018, far north from its previously known distribution. The occurrence of this southern species in the Maumee River and Great Lakes may be the result of an anthropogenic introduction, although a natural range expansion cannot be excluded. This report documents the northernmost record of D. fluviatile in the Nearctic region, extending the known distribution of the species to 42°N, which is a notable increase of 11 degrees latitude. Our detection of D. fluviatile is the first record of this southern species from the Laurentian Great Lakes drainage.