Alaskan brook lamprey

The Alaskan Brook Lamprey is a freshwater fish belonging to the family Petromyzontidae, the lampreys, which are among the most primitive vertebrates alive today. Known scientifically as <em>Lethenteron alaskense</em>, this species typically attains a maximum recorded length of approximately 18.8 cm. Lampreys are jawless fishes belonging to the class Petromyzontida, a lineage that diverged from jawed vertebrates over 400 million years ago. Unlike parasitic lamprey species, the Alaskan Brook Lamprey is a non-parasitic species, meaning adults do not feed. After metamorphosing from filter-feeding larvae called ammocoetes, adults live only long enough to reproduce before dying. The ammocoete stage may last several years, during which larvae burrow into soft sediments of cold, clear streams and rivers, filter-feeding on fine organic particles and algae. <em>Lethenteron alaskense</em> is native to freshwater streams of Alaska, where it occupies clear, cold headwater and mid-elevation stream habitats. Its non-parasitic life history means it has no economic impact on fish populations, unlike its sea lamprey relative. Details of habitat and range for this species remain limited in the ichthyological literature beyond its known Alaskan freshwater distribution. Population ecology and specific habitat requirements are subjects of ongoing research in subarctic ichthyology.