A second nonparasitic species of Entosphenus Gill, 1862 (Petromyzonidae) from Klamath River System, California

A new nonparasitic lamprey, Entosphenus folletti from the Klamath River system, California, is described and illustrated. The holotype (No. NMC 75-1549) is deposited in the National Museum of Natural Sciences, Ottawa, Canada. The species, by its non-functional intestinal tract, is easily separable from the two parasitic species: E. tridentatus and E. minimus. It differs from the nonparasitic E. lethophagus, of the same river system, by having (1) a larger disc: 6.6–7.8% of total length (4.1–6.1% in E. lethophagus), (2) a stronger dentition and a higher number of inner lateral cusps: 2-3-3-2 against 2-2-2-2, (3) a median velar tentacle that is well developed and the same size as the lateral, while in E. lethophagus it is greatly reduced in size in comparison with lateral tentacles, and (4) a darker body coloration and heavily pigmented second dorsal fin. In ammocoetes of E. folletti the bulb of the tongue precursor has a dark pigmentation that is absent in E. lethophagus. The description is based on a study of six transformed individuals and 25 ammocoetes.