The relatively small area of upper Klamath Basin, Oregon, has a diverse lamprey fauna with five named species: two nonparasitic forms (Lampetra lethophaga and Lampetra folletti), and three parasitic forms (Lampetra similis, a nonanadromous form of Lampetra tridentata, and a species thought to be extinct). The dwarfed, parasitic Miller Lake Lamprey, Lampetra minima, was exterminated by chemical treatment of Miller Lake in 1958 (Bond and Kan, 1973).

In 1992, an adult lamprey collected in the Williamson River (R) above Klamath Marsh (OS 13887) was identified as L. minima, and, in 1996, unidentified lamprey were collected in Miller Creek (Cr), the outflow stream of Miller Lake. Subsequent surveys in the summers of 1997–1999 reconfirmed the species extermination in Miller Lake but led to the discovery of several populations of L. minima within and outside the Miller Lake subbasin. The purpose of this report is to document the existence of these populations, redescribe L. minima, and compare it with other Lampetra in upper Klamath Basin.

Materials and Methods

All morphological data were collected from postmetamorphic adults, originally preserved in 10% formalin and transferred to 50% isopropyl alcohol. Postpreservation shrinkage in TL was described by the equation: Preserved Length = (Live Length × 1.01) − 7.18; (r² = 97.4%, n = 23). Metamorphosing individuals were recognized in part by their relatively small, flexible teeth lacking wear, incomplete oral disc formation and short prebranchial distance which lengthens relative to the branchial length during metamorphosis. These individuals were excluded from the morphological analysis. Recent collections preserved in 95% ethanol were also excluded because of postpreservation morphological differences with formalin-fixed specimens. The ethanol-preserved collections were used for mitochondrial DNA sequencing and also included for distributional purposes. During field surveys between 4 June and 25 August 1998, additional data on size, sex, stage, and condition were collected from 189 L. minima found dead in streams. Over 80% of these specimens were postspawning adults, although ammocoetes and metamorphosing specimens were also collected. All were in a state of decay that precluded their use in morphological analyses. Institutional abbreviations are as listed in Leviton et al. (1985).

Material of L. minima include 16 historical specimens (including the holotype and two paratypes), collected in Miller Lake between 1949 and 1952, and 42 recent specimens collected between 1992 and 1999 in Miller Cr, Williamson R, Jack Cr, Long Cr, and Sycan R. Other species examined were L. lethophaga (25 specimens from upstream of Klamath Falls), L. similis (19 specimens, four upstream and 15 downstream of Klamath Falls), and nonanadromous L. tridentata (14 specimens, 12 upstream and two downstream of Klamath Falls).

Lampetra folletti is thought to be restricted to the Lost River subbasin, the lower Klamath R, and the Goose Lake subbasin of the Sacramento drainage (Vladykov and Kott, 1976). Hubbs (1971) described normal and neotenic forms of L. lethophaga and other local variability that he felt did not “warrant specific or subspecific distinction.” Vladykov and Kott (1976) appear to attribute species differences to some of this variability based on six metamorphosed specimens from two subbasins of the Klamath drainage and one subbasin of the Sacramento drainage. However, Hubbs et al. (1979), referring in part to L. folletti, noted that “the validity of localized forms is in need of critical appraisal.” Such an appraisal is beyond the scope of this paper. Furthermore, the distribution of nominal L. folletti does not overlap that of L. minima. Thus, we do not include material of L. folletti in our analysis.

Measurements followed Vladykov and Follett (1965) with the following additions. First dorsal fin height was maximum height, as Vladykov and Follett describe for second dorsal fin height. Three body depth measures were taken: at the posterior edge of the seventh gill pore, at the first dorsal fin origin, and at the second dorsal fin origin. Myomere counts follow Vladykov and Follett (1965), with trunk myomeres determined as described by Hubbs and Trautman (1937). Tooth counts and terminology follow Vladykov and Follett (1965, 1967).

Mitochondrial DNA was extracted from fin or tail clippings preserved in 70% or 95% ethanol. Carcasses of some individuals were cataloged. Tissues were digested for six hours at 37 C with proteinase K, and the suspensions were cleaned with phenol chloroform (1:1) and the DNA precipitated with NaOAc and isopropanol. The 5′-end of the cytochrome b gene was amplified using the polymerase chain reaction (PCR) with primers located in the tRNA-Glu and cytochrome b genes: GLUDG-L (5′-TGACTTGAARAAC-CAYCGT TG-3′) and CB2-H (5′-CCCTCAGAATGATATTTGTCCTCA-3′), respectively (Palumbi, 1996). Each 25 µl reaction was run in a PTC-200 thermocycler (MJ Research, Watertown, MA) as described by Docker et al. (1999). PCR products were sequenced using OpenGene Automated DNA Sequencing System and Thermo Sequenase Cycle Sequencing Core Kit (Visible Genetics Inc., Toronto, Ontario). Sequencing was performed from the 3′-end (Docker et al., 1999), following the manufacturer's instructions, and comparisons were made on 384 bp at the 5′-end of cytochrome b.

Results

Lampetra minima Bond and Kan 1973 Miller Lake Lamprey

Description

A small, predatory Lampetra with mature adult length of 72–126 mm TL and transformed immature lengths up to 145 mm TL (both formalin-fixed maxima). Among Klamath Basin lampreys, L. minima has a relatively large eye and moderate disc. Eye length averages 2.6% of TL (range 2.1–3.3%) and 39% of disc length (range 29–48%), whereas disc length averages 67% of branchial length (range 54–85%; Table 1). Trunk myomeres average 63, with a range of 60–66. Adult dentition is well developed and variable. Body coloration varies from slate in immature individuals to dusky brown or purple in mature specimens; dorsal fins are pale, with mottled gray pigmentation on the posterior and basal portion of the second dorsal fin.

Table 1. Total Length (mm) and Selected Body Proportions as Percent of TL for Klamath Basin Lampetra. Upper figure = mean/standard deviation; lower figure = total range; L = length; n = sample size

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During maturation, metamorphosed individuals appear to shrink. Immature specimens averaged 117 mm TL (n = 23), whereas mature specimens averaged 104 mm TL (n = 35), a statistically significant difference in means (t = 3.32, P = 0.002) that suggests approximately 10–15 mm as the magnitude of postmetamorphic shrinkage. Maturation is also associated with increases in body depth (Fig. 1), first and second dorsal fin height, and acquisition of secondary sexual characters (pseudo-anal fin in females and anal papilla in males). Immature metamorphosed adults have low, well-separated dorsal fins, relatively slim bodies, and well-developed teeth. Mature metamorphosed adults have deeper bodies and higher dorsal fins, often with frilled edges, and little or no gap between dorsal fins (Fig. 2). During maturation, disc length was isometric with TL. As a percent of TL, disc length remained constant with a slope less than 0.001 when regressed on any of the three body depth measures (P > 0.38). The ratio of first dorsal fin height to disc length served as a proxy for maturation state and was less than 0.36 for sexually immature specimens and greater than 0.36 for all but one sexually mature adult with well-developed secondary sexual characteristics (Fig. 3). Trunk and tail length of immature specimens of both sexes were similar, but these measurements were sexually dimorphic among mature specimens (females with longer trunks and shorter tails; Fig. 4).

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Males accounted for 61% of 23 immature specimens and 77% of 35 mature specimens measured, resulting in an overall sex ratio similar to the 73% male bias in Bond and Kan's (1973) measured series. In contrast, males accounted for only 11% of 158 dead specimens collected in summer 1998 (n = 189, 31 unsexable). There was no significant difference in mean TL between sexes of L. minima used for our morphological studies (t = −1.51, P = 0.14), although males, on average, were significantly larger than females (t = −5.17, P < 0.0001) in our collections of dead specimens. Bond and Kan (1973) also reported a greater average size in males (86 mm) than females (80 mm).

Life history

Lampetra minima was described as a dwarfed parasitic lamprey that fed voraciously on trout and tui chubs (Bond and Kan, 1973; Kan and Bond, 1981), the ultimate example of a lamprey feeding on small hosts (Cochran and Jenkins, 1994). Extant L. minima in Miller Cr, Jack Cr, Sycan R, and Williamson R are also predatory. One specimen from Miller Cr was collected while attached to a brook trout, Salvelinus fontinalis (OS 16885). At lower elevations in the Sycan R, many dead Speckled Dace (Rhinichthys osculus klamathensis) were collected with single or multiple lamprey wounds (e.g., OS 15866, five specimens 48–55 mm SL), and at higher elevations dead brook trout were collected with lamprey wounds (three measured 30 July 1997, 85–140 mm FL). A speckled dace with a single lamprey wound (OS 17530, 72 mm SL) was also collected in Jack Cr, although the attached lamprey escaped capture. Finally, a Williamson R specimen, raised in a lab from an ammocoete, attacked a small Rainbow Trout, Oncorhynchus mykiss, after metamorphosis. Although no observations of scavenging were made, we often found prey fish with multiple wound marks, perhaps indicating a scavenging form of feeding reported by Kan and Bond (1981).

Spawning was observed by DFM and S. Peets on 10 June 1997 (1030–1045 h), in the Sycan R upstream of the ZX Ranch bridge (water temperature 12 C). The small nest was a pitlike clearing about 10 cm wide and 3 cm deep made on a substrate of gravel/cobble in a sand matrix. The nest was located in water about 30 cm deep and about 3 m from shore. Five spawning lamprey (four female, one male) were seen with a sixth specimen nearby (OS 15866; this is one of the few collections of live specimens in which females dominate). Some individuals were observed moving small gravel. About six spawning events were observed during which a female would attach to a rock embedded in substrate at the upstream margin of the pit. The larger male would bite the head and attach to the female who would arch her back, inserting her tail in sand. The larger male would partly coil around the smaller female, and both would quiver. Egg release could not be seen, and the nest was not sampled or disturbed.

Cytochrome b

Eleven haplotypes (GenBank Accession Numbers AF257120–AF257134) were found in the Klamath drainage including a lower river type identical to all eight anadromous L. tridentata examined from coastal Oregon and British Columbia by Docker et al. (1999). All resident Lampetra in the Klamath Basin differed from the andromous haplotype by a shared, third position transition (C→T) at position 234, and all adult L. minima (n = 16) shared an additional third position transition at position 177 (C→T). The three L. minima haplotypes were also found in other Klamath Basin species, but those species more frequently had haplotypes lacking the transition at position 177. The most common haplotype in Klamath Basin only had the 234 transition, and all other Klamath Basin haplotypes differed either by one or two transitions. The two-transition haplotypes appeared to be restricted to the Sprague R subbasin and were found in 11 L. minima and one L. tridentata.

Two adult specimens, one from Jack Cr and another from Watson Cr, appeared intermediate in morphology between L. lethophaga and L. minima (though ethanol preservation confounds identification) and were identified as L. sp. Only the Watson Cr specimen possessed the transition at position 177. Because other Jack Cr specimens clearly represent L. minima (see Material Examined), these fish may indicate sympatry or hybridization between L. lethophaga and L. minima in Jack Cr and Watson Cr or that the transition at position 177 is not found in all L. minima. The adult specimen, as well as one ammocoete, collected from Jack Cr had the common Klamath Basin 234-transition haplotype.

Dentition

The four upper Klamath lamprey species share a common dentition pattern with three supraoral lamina cusps, five infraoral lamina cusps, and four inner laterals, with a 2-3-3-2 cusp arrangement, on either side of the disc. As Hubbs (1971) noted, L. lethophaga is particularly variable in inner lateral cusp counts. Our data indicate similarity between L. lethophaga and L. minima in variability of some tooth counts. Counts of supraoral lamina and inner laterals are much more variable in these species than in L. similis and nonanadromous L. tridentata. Lampetra minima tend to have the highest bicuspid posterial counts, but these counts were also highly variable. In fact, variability in dentition in our sample of Klamath Basin Lampetra was large enough that counts overlapped extensively among all species and were not useful in differentiating L. minima from other taxa. We attribute much of the variability to state of maturation: immature specimens had well-developed, easily counted cusps, and mature fish often had worn or degraded dentition and appeared to have lost cusps after maturation. Lingual lamina cusps, reported as 17–23 by Vladykov and Kott (1976), could not be determined in most L. minima.

Geographic variation

Extant populations of L. minima occur in Miller Cr, Jack Cr, Williamson R above Klamath Marsh, and the Sycan drainage at and above Sycan Marsh (Fig. 5) at an average elevation of 1731 m (1402–2134 m, n = 27). Mean eye diameter as a percentage of TL in L. minima from these sites was significantly smaller than that observed in Miller Lake specimens (t = 4.68, P < 0.0001). Disc length as a percent of TL, on average, was also significantly larger in Miller Lake (t = 4.77, P < 0.0001), but both the relatively larger eye and disc are a reflection of allometry associated with the smaller TL in most Miller Lake specimens (Table 1). Extinct Miller Lake L. minima differ from Miller Cr, Jack Cr, Williamson R, and Sycan drainage specimens in having, on average, significantly fewer anterials (mean = 6.6, range 3–10 vs mean = 10.3, range 0–16; t = −6.03, P < 0.0001). Bond and Kan (1973) considered posterials in L. minima to be diagnostic and reported that bicuspid posterials usually numbered 2–6 in their specimens. We found similar results in specimens from Miller Lake, Miller Cr, Jack Cr, and Williamson R, which showed a range of 0–8 bicuspid posterials. Specimens from the upper Sycan drainage, however, exhibited much greater variability, with bicuspid posterial counts ranging from 1–16. Coloration was similar in Miller Cr, Williamson R, and Sycan R specimens, except that the ventral surface of the body tended to be darker in those from Miller Cr. Coloration of Miller Lake specimens is badly faded because of time in preservative.

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Comparison with other upper Klamath Basin Lampetra

Bond and Kan (1973) considered the small size, low number of trunk myomeres, higher number of posterials, larger eye, longer prebranchial length, and pale color to distinguish L. minima from L. lethophaga. We found more broadly overlapping size ranges for metamorphosed adults of the two species (Table 1), although differences in mean TL between L. minima and L. lethophaga were significant (t = −7.92, P < 0.0001), confirming the general small size of L. minima. As Hubbs (1971) noted, the lack of feeding by adult L. lethophaga results in postmetamorphic shrinkage. Consequently, mature L. lethophaga specimens may fall within the TL range of L. minima. We obtained trunk myomere counts similar to those reported by Bond and Kan (1973; 60–66 in L. minima, n = 57; 63–71 in L. lethophaga, n = 25) but find great overlap. The average width of myomeres is smaller in L. minima (0.75 mm, range 0.54–1.00 mm) than in L. lethophaga (0.96 mm, range 0.79–1.22 mm), and this feature is often noticeable (Fig. 6). We find the total range in number of posterials in L. minima (12–19) to more broadly overlap with L. lethophaga (6–18). Bailey (1980) previously discounted the taxonomic importance of posterials in Lampetra. The eye (mean 2.6% TL, range 2.1–3.3%) in L. minima appears larger than in L. lethophaga (mean 1.8% TL, range 1.4–2.3%), but the absolute dimension of eyes is constant over the size range of these species (2.0–3.3 mm). A regression of eye diameter on TL for these two species has a slope of 0 and is not significant (P = 0.44); thus the difference in relative eye size primarily reflects differences in total body length. Average prebranchial length was significantly longer (t = 6.53, P < 0.0001) in L. minima (12.2–17% TL) than in L. lethophaga (10.4–13.7% TL), especially among similar size, mature specimens. Vladykov and Kott (1976) report a difference in velar tentacles of 5–7 in L. minima (n is unreported) and 7–11 in L. lethophaga (n = 5). We find a range of 5–9 in L. minima (n = 21) and 5–12 in L. lethophaga (n = 14).

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Despite overlap between L. minima and L. lethophaga for all measurements and counts previously considered diagnostic, these species can be consistently distinguished by comparing a combination of morphological characters. Eye diameter as a percent of TL versus prebranchial length as a percent of branchial length effectively separates immature and mature specimens of both species (Fig. 7). These features also reflect differences in overall appearance of the head region (Fig. 2) that may be useful in the field. Coloration also differs between L. minima and L. lethophaga, although the specimens that we observed do not confirm the diagnosis given in the original species description. In their diagnosis, Bond and Kan (1973) characterize L. minima as having a “paler and simpler” coloration than L. lethophaga. Their description was based on L. minima specimens that had spent over 15 years in preservative, whereas most of the specimens we examined for pigmentation had been preserved for less than one year. We find that body coloration in L. minima is simpler than in L. lethophaga but tends to be darker overall in both immature and mature specimens. This is particularly true of the dorsal fins and ventral portion of the body in immature L. lethophaga specimens, which are quite pale, with only a small amount of gray mottling. Body coloration of mature L. lethophaga specimens differs from mature L. minima by having a brown overall hue and a ventral area with lighter pigmentation.

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Differentiation of L. minima from L. similis and nonanadromous L. tridentata is more obvious. The average TL of metamorphosed L. minima is significantly smaller than L. similis (t = −10.87, P < 0.0001) or nonanadromous L. tridentata (t = −14.42, P < 0.0001), although there is some overlap in size range with L. similis (Table 1). Disc length of L. minima is significantly smaller (t = −15.09, P < 0.0001) than that of L. similis and the disc length-branchial length relationship of L. minima/L. lethophaga differs from L. similis/L. tridentata (Fig. 8). Myomere counts of L. minima (60–66, mean 63, n = 57) are similar to both nonanadromous L. tridentata (63–66: mean 64, n = 14) and L. similis (60–65: mean 63, n = 19).

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Discussion

Bond and Kan (1973) described L. minima from 45 specimens, 35 of which were designated as the type series. The holotype was collected from a spawning redd on 20 August 1950 and 34 paratypes (OS 2875, 72–97 mm TL), were collected on one day (17 July 1952). The largest specimen examined by Bond and Kan (1973) was a 129 mm TL male (OS 2873), collected 13 September 1949. Some differences we report between populations may reflect developmental variation and related sampling bias associated with capture date. For example, dentition variation was greater in mature fish regardless of location. Other differences reflect size or may reflect population differences. For example, relative eye and disc sizes mostly reflect mean differences in body length as noted above.

Body length of mature lamprey represents an important reproductive isolating mechanism. Beamish and Neville (1992) found spawners differing in size by 25% or more were unsuccessful, and Malmqvist (1986) reported maximum success in L. planeri when male to female size ratio was 1.05:1.14. Collectively, sizes of all L. minima center around a size of 100 mm with the size range of all sexually mature adults (72–126) close to Beamish and Neville's expected size difference. However, life-history variability and body size changes before and during spawning can confound patterns. Kan and Bond (1981) speculated that L. minima could either feed or not feed (“a starvation diet”) before spawning and that feeders shrink about 13% in length from feeding to spawning stage. Malmqvist (1986) reported loss of body mass during spawning, ranging from 23–34% in males and 38–42% in females in other species. Thus, although average TL decreases during maturation in L. minima, the amount of shrinkage may differ considerably between individuals, depending on how much they feed. Size-related differences between species might be similarly confounded. As noted before, shrinkage also occurs in L. lethophaga adults (Hubbs 1971), and this could bring mature specimens into the size range of L. minima.

Kan and Bond (1981) proposed rapid speciation of L. minima from a L. tridentata-type ancestor, based on a hypothesis of isolation caused by the Mt. Mazama eruption about 6600 years ago. The ash from that eruption buried the mouth of Miller Cr causing it to go subsurface near Beaver Marsh, Oregon, and separating it from the Williamson drainage. Jack Cr was similarly isolated from the Williamson drainage by the Mazama eruption. The upper Sycan population is also apparently disjunct from the Williamson population (Fig. 5). The distribution of L. minima would be consistent with historical drainage of the upper Sycan R north of Taylor Butte into the Williamson R rather than SSE into the lower Sycan, but we know of no evidence to support such conjecture. The alternate dispersal route would be down the Sycan and Sprague rivers and up the Williamson R, although no intermediate populations are known to exist along this path. The current geographic range in high-elevation headwater streams of the Williamson drainage suggests that speciation occurred prior to isolation of the Miller Lake subbasin. Both Miller Lake and Miller Cr populations were presumably isolated from the Williamson drainage at the same time (approximately 6600 YBP) and maintained at least downstream gene flow. Nevertheless, they show slight morphological differences, with the modern Miller Cr population more similar to other stream populations in the Williamson and Sycan Rivers. The observed differences between Miller Lake and other populations may be a result of sampling differences in sex composition, maturation state, and preservation; or they may reflect ecological differences between the deep, oligotrophic habitat of Miller Lake, and the lotic habitats occupied by modern populations.

Each Klamath Basin Lampetra species contained at least two cytochrome b haplotypes. The three haplotypes of L. minima (Table 2) differ from one another by one or two base-pair transitions at positions 303 and 309. At these two positions, the Miller Cr haplotype resembles nonanadromous L. tridentata and similis. The two coexisting L. minima haplotypes in the Sycan R are more different from each other (two transitions) than either is from the Miller Cr haplotype (one transition). Because the latter differs by only one transition from nonanadromous L. tridentata and because that haplotype is also found in L. similis, there is no compelling reason to attribute this diversity to speciation or population events. Similarly the position 177 transition is found in all L. minima but not exclusively (Table 2). The only unique patterns are geographic rather than taxonomic: the position 234 transition in all nonanadromous Klamath Basin Lampetra; and the positions 303 and 309 transitions (haplotypes 10 and 11) only in the Sprague drainage. These data are consistent with observations by Docker et al. (1999) that members of paired species show great similarity or are genetically indistinguishable at this gene.

Table 2. Polymorphic Loci for 384 bp at 5′-End of the Cytochrome b Gene in 49 Adult and 45 Larval Lampetra from the Klamath Basin (Oregon Unless Stated Otherwise). Each haplotype (type) is numbered; n denotes sample size for adults (Adt) and larvae (Lrv); “*” = anadromous Lampetra tridentata. All other L. tridentata are nonanadromous from Upper Klamath Basin. Boldface shows transitions mentioned in text. Larval identifications based on drainage except those labeled “?” which were collected in areas where two or more species may co-occur

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Beamish (1985) suggested that nonparasitic species could evolve from a parasitic freshwater ancestor rather than directly from an anadromous parasitic species. The alternate possibility, a parasitic species evolving atavistically from a nonparasitic ancestor, is not often considered. Because L. minima and L. lethophaga are more similar and have contiguous, and possibly sympatric, distributions (Fig. 5), the simplest working assumption is that they are sister species and that L. minima was not derived from a L. tridentata-like ancestor as Bond and Kan (1973) suggested. The possibility that both species might have nonfeeding individuals leads to the parsimony argument favoring a nonparasitic ancestor. Such a scenario would require isolation of a nonparasitic ancestor, subsequent isolation of a high-elevation (1402–2134 m), proto-Williamson-upper Sycan species (L. minima) from a low-elevation (1280–1859 m) proto-Sprague R species (L. lethophaga), and atavistic reversal to parasitism (or facultative parasitism) in L. minima. Finally, stream capture of the upper Sycan by the Sprague R and stream truncations by Mazama ash would create the current disjunct patterns.

The distribution of L. minima, currently centered on the Williamson R drainage, appears to be unique. Native species that might have been prey and had similar distributions to L. minima are Bull Trout (Salvelinus confluentus), Redband Trout (Oncorhynchus mykiss ssp.), speckled dace, and Tui Chub. Bull trout, redband trout, and speckled dace are known from the upper Sycan but not from the Miller Lake subdrainage, whereas tui chub are known from both. Tui chub were also extirpated from Miller Lake but few were saved in museums, whereas those from the Sycan have never been critically examined. It would be worthwhile to examine other species to determine whether the L. minima distribution pattern is, in fact, unique.

The distribution of L. lethophaga was originally described to include the upper Sacramento drainage (Pit R and Goose Lake), and reports of parasitic lamprey in Goose Lake suggest reasons to compare those fish with L. minima. However, a survey of cytochrome b sequences from Goose Lake lampreys suggests significant differences from upper Klamath lampreys (M. F. Docker, unpubl. data). Thus, the distribution of L. minima and L. lethophaga outside the upper Klamath Basin is not at all clear.

Material Examined

Catalog numbers with asterisks indicate ethanol-preserved samples not used for morphological study. Lampetra minima, Miller Lake (Lk) subbasin: USNM 353919 (formerly, OS 3180), holotype, Miller Lk, (1950, n = 1), OS 2875, paratypes, Miller Lk, (1952, n = 2), OS 2873, Miller Lk, (1949, n = 1), OS 2876, Miller Lk, (1953, n = 3), OS 2879, Miller Lk, (1952, n = 4), OS 2881, Miller Lk, (1952, n = 4), OS 16666, Evening Cr, (1950, n = 1), OS 16885, Miller Cr, (1998, n = 1), OS 16844, Miller Cr, (1998, n = 6), OS 16880*, Miller Cr, (1998, n = 2), OS 16881*, Miller Cr, (1998, n = 2), OS 16886*, Miller Cr, (1998, n = 1), OS 16906, Miller Cr, (1998, n = 1), OS 16907, Miller Cr, (1998, n = 3), OS 16902*, Miller Cr, (1998, n = 1), OS 17153, Miller Cr, (1998, n = 3), OS 17154, Miller Cr, (1998, n = 1); Jack Cr subbasin: OS 17527, Jack Cr, (1999, n = 1), OS 17528, Jack Cr, (1999, n = 2); Williamson R subbasin: OS 13887, Williamson R above Klamath Marsh, (1992, n = 1); Sycan R subbasin: OS 15884, Sycan R, (1997, n = 3), OS 15883, Sycan R, (1997, n = 5), OS 15866, Sycan R, (1997, n = 2), OS 15869, Sycan R, (1997, n = 2), OS 15882*, Sycan R, (1997, n = 2), OS 16843, Sycan R, (1998, n = 5), OS 16884*, Sycan R, (1998, n = 2), OS 16883*, Sycan R, (1998, n = 2), OS 16882*, Sycan R, (1998, n = 2), OS 16904, Sycan R, (1998, n = 1), OS 16905, Sycan R, (1998, n = 1), OS 17155, Sycan R, (1998, n = 1), OS 17156, Long Cr, (1998, n = 3), OS 16797*, Long Cr, (1998, n = 2). Lampetra lethophaga, Agency Lk, subbasin: OS 15761, Fort Cr, (1997, n = 1), OS 2857, Crooked Cr, (1970, n = 1), OS 2856, Crooked Cr, (1970, n = 4), OS 20, Crooked Cr, (1951 n = 4), OS 4933, Crooked Cr, (1977, n = 1), OS 4091, Crooked Cr, (1970, n = 2), OS 17150*, Crooked Cr, (1998, n = 2); Williamson R subbasin: OS 16790, Big Springs Cr, (1993, n = 1), OS 16791, Big Springs Cr, (1993, n = 2), OS 16792, Big Springs Cr, (1993, n = 4), OS 4934, Williamson R, (1973, n = 2); Sprague R subbasin: OS 16798, Whitworth Cr, (1998, n = 1), OS 16891*, Whitworth Cr, (1998, n = 1), OS 16795*, S. Fork Sprague R, (1998, n = 1), OS 16890*, S. Fork Sprague R, (1998, n = 2), OS 4084, Meryl Cr, (1965, n = 1), OS 4932, unnamed Cr, (1974, n = 1). Lampetra similis, Agency Lk, subbasin: OS 4090, Sevenmile Cr, (1970, n = 1); Upper Klamath Lake: OS 2902, (1965, n = 1); Williamson R: OS 16793 (1992, n = 2); Klamath R: OS 13717, Spencer Cr, (1992, n = 5), OS 16887*, Spencer Cr, (1998, n = 4), OS 16779*, Link R, (1998, n = 1), OS 16780*, Link R, (1998, n = 1), OS 16781*, Link R, (1998, n = 1), OS 16908, Clear Cr, (1997, n = 2), OS 16909, Seiad Cr, (1997, n = 3), OS 16910, Beaver Cr, (1997, n = 4), OS 16911, Beaver Cr, (1997, n = 1). Lampetra tridentata, Agency Lk,: OS 16785 (1992, n = 1), OS 16786 (1992, n = 1), OS 16788 (1992, n = 2), OS 16789 (1992, n = 1), OS 16787, Thomason Cr, (1992, n = 1); Sprague R subbasin: OS 2872 (1970, n = 5), OS 4925, (1974, n = 1); Klamath R: OS 16782*, Link R, (1997, n = 1), OS 16783*, Link R, (1997, n = 2), OS 16784, J.C. Boyle Res. (1998, n = 2). Lampetra sp., Jack Cr subbasin: OS 16889*, Jack Cr, (1998, n = 1); Sycan R subbasin: OS 16796*, Watson Cr, (1998, n = 1).