Morphological Diagnosis of Entosphenus and Lampetra Ammocoetes (Petromyzontidae) in Washington, Oregon, and California
Damon Goodman, Andrew P. Kinziger, Stewart B. Reid, and Margaret F. Docker
Abstract.—The objective of this study was to assess the utility of new and previously published morphological characters for identifying lamprey ammocoetes to genus (Entosphenus and Lampetra) in coastal rivers of California, Oregon, and Washington. We surveyed four morphological characters on 382 ammocoetes (60.0–169.0 mm total length) from 15 localities and compared these against genus assignments using genetic methods. Pigmentation of the caudal fin was dark in Entosphenus versus peppered or absent in Lampetra and allowed for 95.6% proper genus diagnosis when compared to identification by genetic methods. Pigmentation of the caudal ridge faded from dark to light (anteriorly to posteriorly) in Entosphenus, in contrast to a uniformly dark caudal ridge in Lampetra, and allowed for 98.7% proper genus diagnosis. Ventral pigmentation and myomere number differed between the two genera but did not allow for diagnosis by themselves. When applied together, the three pigment characters provided 99.7% agreement with genetic identification. We conclude that the morphological characters, alone and in combination, provide valid genus assignments of lamprey ammocoetes within the study area and size range evaluated.