A New Nonparasitic Species of the Holarctic Lamprey Genus Lethenteron Creaser and Hubbs, 1922, (Petromyzonidae) from Northwestern North America with Notes on Other Species of the Same Genus

Abstract

A new nonparasitic lamprey, Lethenteron alaskense from Alaska and Northwest Territories is described and illustrated. The holotype (No. NMC 76-614) is deposited in the National Museum of Natural Sciences, Ottawa, Canada. The study was based on 67 metamorphosed specimens. The species, by its permanently non-functional intestinal tract and weak dentition, smaller disc and much smaller size (maximum 188 mm), is easily separable from the parasitic Lenthenteron japonicum (maximum length 625 mm) found in the same areas. It is distinguishable from nonparasitic L. lamottenii, found in eastern and southern North America, by 1) a generally weaker dentition but possessing more anterials and supplementary marginals; 2) typically with five velar tentacles as opposed to seven in L. lamottenii; 3) differences in pigmentation pattern of the second dorsal fin and a lack of dark pigmentation on the gular region; 4) smaller size in comparison to 299 mm maximum length in L. lamottenii; and 5) distinct areas of geographical distribution separated from each other by 2400 km. All three, L. alaskense, L. lamottenii, and L. japonicum have usually 66 to 72 trunk myomeres. L. alaskense, by its higher number of myomeres is separable from two other nonparasitic species: L. reissneri from Asia with less than 64 myomeres and L. meridionale from eastern tributaries of the Gulf of Mexico with 50 to 58 myomeres.