Redescription of the Presumed-Extinct Miller Lake Lamprey, Lampetra minima
Lampetra minima, believed eradicated in 1958 and extinct, survives in upper tributaries of the historical Williamson drainage in Klamath and Lake Counties, Oregon. The species, the smallest known parasitic lamprey, was believed to be endemic to Miller Lake. Its current disjunct distribution includes Miller Creek, Jack Creek, and upper sections of the Williamson and Sycan Rivers. We compare new specimens with the type series and other Klamath Basin lampreys and redescribe L. minima. It appears most similar to Lampetra lethophaga but is smaller (72–145 mm vs 115–170 mm TL), has a larger disc length (5.0–8.6% vs 4.2–6.4% TL), larger prebranchial length (11.0–17.0% vs 8.8–13.7% TL), and larger eye (2.1–3.3% vs 1.4–2.3% TL). Klamath Basin Lampetra differ from anadromous Lampetra tridentata in a single transition in cytochrome b, and L. minima have an additional, but not unique, transition. Our data do not support the suggestion that L. minima recently evolved from a L. tridentata–like ancestor; rather we suggest a more ancient separation and a sister relationship with L. lethophaga.Abstract

Relationship between body depth and TL on maturation state in Lampetra minima

(A) Mature Lampetra minima (OS 15866, 96 mm TL); (B) mature Lampetra lethophaga (OS 16791, 123 mm TL)

Relationship between first dorsal fin height as a percent of disc length and TL (mm) on maturation state in Lampetra minima

Relationship between trunk length and tail length as percents of TL on sex and maturation state in Lampetra minima

Upper Klamath Basin, showing locations of Lampetra minima and Lampetra lethophaga collections

Immature transformed specimens of four Upper Klamath Basin Lampetra species. (A) Lampetra minima (OS 16885, 121 mm TL); (B) Lampetra lethophaga (OS 4091, 169 mm TL); (C) Lampetra similis (OS 13717, 154 mm TL); (D) Lampetra tridentata (OS 10468, 142 mm TL)

Relationship between eye diameter relative to TL and prebranchial length relative to branchial length for Lampetra minima and Lampetra lethophaga. (A) immature specimens; (B) mature specimens

Relationship between disc length and branchial length for Upper Klamath Basin Lampetra