Taxonomic Status and Distribution of the Lamprey Ichthyomyzon cf. gagei

Abstract

A nonparasitic lamprey of uncertain taxonomic status, Ichthyomyzon cf. gagei, occurs in streams of the upper Mississippi River basin. We analyzed morphological data to determine if this lamprey was a new species or a highly disjunct representative of I. gagei, which otherwise is limited to the southern United States. In univariate comparisons, I. cf. gagei had significantly more bicuspid teeth, longer relative branchial, eye and tail lengths and a shorter relative snout length than I. gagei. Males of I. gagei had a relatively longer genital papilla than those of I. cf. gagei. Multivariate comparisons indicated differences in shape, with L cf. gagei having relatively large eyes and a short snout and disk. However, for all morphological comparisons, overlap between the two forms was extensive. We conclude that morphological analyses alone cannot resolve the taxonomic status of I. cf. gagei. Ichthy- omyzon cf. gagei is more widespread and abundant than previously thought, and is locally common in the upper St. Croix watershed of Wisconsin and Minnesota, and the upper Black and Wisconsin river watersheds of Wisconsin.