Simple Genetic Assay Distinguishes Lamprey Genera <i>Entosphenus</i> and <i>Lampetra</i>: Comparison with Existing Genetic and Morphological Identification Methods

Abstract

Abstract Several species of lamprey belonging to the genera Entosphenus and Lampetra, including the widely distributed Pacific Lamprey E. tridentatus and Western Brook Lamprey L. richardsoni, co-occur along the West Coast of North America. These genera can be difficult to distinguish morphologically during their first few years of larval life in freshwater, thus hampering research and conservation efforts. However, existing genetic identification methods are time consuming or expensive. Here, we describe a simpler genetic assay using the Pacific Lamprey microsatellite locus Etr-1; the assay was found to be 100% reliable in distinguishing Entosphenus from Lampetra, even in genetically divergent Lampetra populations. Using a sample of 244 larvae (18–136 mm TL) from the Columbia River basin, we tested the accuracy with which previously described differences in caudal fin pigmentation can distinguish these genera. Attempts at morphological identification were abandoned for 50-mm and smaller larvae because differences in caudal fin pigmentation were very difficult to discern. However, morphological identification was correct for 81.8% of 51–70-mm larvae and 100% of 71-mm and larger larvae, which roughly corresponds with the results of previous studies. In agreement with previous work using mitochondrial DNA, our assay also supported placement of the Kern Brook Lamprey L. hubbsi (formerly E. hubbsi) into the genus Lampetra. Received November 23, 2015; accepted March 9, 2016 Published online July 7, 2016