American Brook Lamprey
  • Side View of an adult American brook lamprey.
  • Side view of an adult American brook lamprey.
  • Side view of an adult American brook lamprey.
  • Top view: Cylindrical body, typically 130-165 mm, max. 202 mm.
  • Bottom view: Cylindrical body, typically 130-165 mm, max. 202 mm.
  • Head-on view.
  • Close-up of flank: 64-75 trunk myomeres, lateral pores unpigmented.
  • Close-up of head.
  • Close-up of mouth and snout: Teeth are moderately developed.
  • Close-up of tail region.
  • Close-up dorsal fin: The dorsal fin has two separate rounded lobes.
  • Myomere count starts from last branchial pore and ends at anus (see arrows). The dorsal fins are separate.
  • 64-75 trunk myomeres. Count of myomeres starts past last branchial pore.
  • The dorsal fin consists of two clearly separate lobes.
  • Note bicuspid circumoral teeth and widely separated supraoral teeth.
  • Note bicuspid circumoral teeth and widely separated supraoral teeth.
  • Close-up of ammocoete (larval stage) mouth.
  • Close-up of ammocoete (larval stage) head.
  • Whole body of ammocoete (larval stage).
  • Close-up of ammocoete (larval stage) tail.
  • Comparison of adult and juvenile.
  • Genital papilla near anus identifies this as a an adult male.
  • Image of a juvenile, a transformer (interemediate stage when an ammocoetes transforms into an adult), and an adult.
DescriptionSimilar Species
Lampreys (Petromyzontidae)
Mouth and Snout: Sucking disk in adults, flexible hood in juveniles, no jaw. Teeth moderately developed in adults; none in juveniles. No barbels. Distinctive teeth. The circumoral teeth usually consist of three pairs of bicuspid teeth on each side. Gill openings consist of seven circular holes. Body Pattern: Solid color. Brownish to light gray or silver (adults only) on dorsal surface and flanks, grading to light gray/brown, olive or off-white ventrally. Lateral pores are unpigmented. No scales. Body Shape: Elongate, cylindrical, flexible body. Typical adult size is 130-165 mm, with a maximum of 202 mm. A very few records are of abnormally large adults (>250 mm) from the Great Lakes. Ammocoetes may reach longer lengths than adults, with shortening (up to 10%) occuring in transformation to adulthood.
Rounded tail. Dorsal fin with no spines. No anal, pectoral, pelvic, or adipose fins. The dorsal fin is divided into two lobes--the posterior is continuous with the caudal fin and the anterior is separate.
Distinguishing Characteristics
Distinguishing Characteristics: Eel-like body and sucking disk identify the lamprey family. First and second dorsal fins are separate. Lateral pores unpigmented. Adults only: maximum disk diameter less than maximum body diameter; supraorbital lamina teeth cusps widely separated, inner circumoral teeth bicuspid. Maximum length 202 mm. 64-75 trunk myomeres. Distinctive Features: Sucking disk or hood, no jaw. Flexible, snake-like body. See also similar species information.
Breeding Adults
Lampreys spend most of their lives as ammocoetes. They transform to the adult form in the fall, cease feeding, breed in the spring, and die. The adult form is the breeding form.
Ammocoete form. Distinguished from adults based on head and mouth characteristics. Ammocoetes lack eyes, have a hood-like covering of the mouth without a papillary fringe, and have soft sieve-like tissue in the mouth. Ammocoetes are grayish brown (not as silvery as adults), often with reddish pink around gills. Adults have large eyes.
None known from Wisconsin.
Compare Similar Species
1st and 2ndt Dorsal Fins
Lamprey, American BrookSeparated
Lamprey, ChestnutConnected
Lamprey, Northern BrookConnected
Lamprey, SeaSeparated
Lamprey, SilverConnected
Lamprey, Southern BrookConnected
Trunk Myomeres
Lamprey, American Brook64-75
Lamprey, Chestnut51-56
Lamprey, Northern Brook46-56
Lamprey, Sea63-73
Lamprey, Silver46-53
Lamprey, Southern Brook49-57
Lateral Pores
Lamprey, American BrookUnpigmented
Lamprey, ChestnutPigmented
Lamprey, Northern BrookUnpigmented
Lamprey, SeaUnpigmented
Lamprey, SilverUnpigmented (pigmented in large adults)
Lamprey, Southern BrookPigmented
Maximum Disk Diameter Relative to Maximum Body Diameter in Adults
Lamprey, American BrookLess
Lamprey, ChestnutGreater
Lamprey, Northern BrookLess
Lamprey, SeaGreater
Lamprey, SilverGreater
Lamprey, Southern BrookLess
Supraoral Lamina Teeth
Lamprey, American BrookWidely separated
Lamprey, ChestnutClose together
Lamprey, Northern BrookClose together
Lamprey, SeaClose together
Lamprey, SilverClose together
Lamprey, Southern BrookClose together
Inner Circumoral Teeth
Lamprey, American BrookBicuspid
Lamprey, ChestnutBicuspid
Lamprey, Northern BrookUnicupsid
Lamprey, SeaBicuspid
Lamprey, SilverUnicuspid (rarely 1 bicuspid)
Lamprey, Southern BrookBicuspid
Maximum Total Lenth (mm) in WI
Lamprey, American Brook202
Lamprey, Chestnut271
Lamprey, Northern Brook171
Lamprey, Sea760
Lamprey, Silver385
Lamprey, Southern Brook~170
Similarity Index
Lamprey, American BrookN/A
Lamprey, ChestnutVery similar as ammocoetes, moderately similar as adult
Lamprey, Northern BrookModerately similar
Lamprey, SeaVery similar as ammocoetes, moderately as adult
Lamprey, SilverVery similar as ammocoetes, moderately as adult
Lamprey, Southern BrookModerately similar