Detection of lamprey in Southernmost South America by environmental DNA (eDNA) and molecular evidence for a new species

Lampreys are jawless fishes belonging to the order Petromyzontiformes. Geotria australis is the sole representative lamprey species of the Geotriidae family and is widely distributed around South America, Australia, New Zealand, and sub-Antarctic Islands. In South America, the presence and distribution of G. australis are well characterized in Western Patagonia, in rivers flowing into the Pacific Ocean. In contrast, there is scarce information about the presence of this species in Eastern Patagonia, in rivers flowing into the Atlantic Ocean. Here, we provide the first report on the distribution of lamprey at the extreme south of Patagonia and suggest the occurrence of a new lamprey species. We developed an environmental DNA (eDNA) method to detect G. australis from water samples and obtained positive results in five basins flowing into the Atlantic Ocean and one river basin flowing into the Beagle Channel. Lampreys were captured from two eDNA-positive basins and used for genetic analysis. An 875 bp-sequence of the cytochrome b mitochondrial gene was obtained, and a phylogenetic analysis was carried out with this sequence and those available in GenBank, revealing Argentinean lamprey reported here, as a sister species of G. australis from Chile, Australia, and New Zealand. Also, the genetic distance values between lamprey reported here and G. australis were consistent with the genetic distances between species of different genera. Our results suggest that the Argentinean lamprey corresponds to a new specific taxon that could represent a new monotypic genus in Geotriidae.