Jawless lampreys still clamp on with a toothed suction disc
Lampreys are jawless fishes of order Petromyzontiformes—roughly thirty-eight living species—famed for funnel mouths lined with keratin teeth. Genetic data link them to hagfish as cyclostomes. Stem fossils appear by the latest Devonian (~360 Ma); modern-looking forms arise in the Jurassic (~163 Ma).
Three families divide the map: southern Geotriidae and Mordaciidae, northern Petromyzontidae. Most of life is the blindish ammocoete larva buried in silt, filter-feeding for up to eight years (Arctic lamprey maybe one to two) before a months-long metamorphosis without eating. Only eighteen species become carnivorous adults that rasp fish—or rarely marine mammals—for blood or flesh; nine of those migrate from sea to spawn, nine stay freshwater. Non-feeders live off larval stores. Sea lampreys reach about 1.2 m; adults lack paired fins, show one top nostril and seven gill pores per side.
After metamorphosis the ancestral lifestyle was blood-and-fluid feeding: oral discs clamp, then three horny tongue plates scrape to fluids, with anticoagulants from buccal glands. Some lineages shifted to flesh, even invading organs. Ammocoetes need rich suspended organics (≥4 mg/L). Distribution hugs temperate coasts and fresh waters; heat-sensitive larvae keep them from tropics. Dams block spawning runs, yet canals helped sea lampreys invade the Great Lakes. Thames cleanups have returned sightings to London.
Often miscalled “lamprey eels,” they swim with striking efficiency by creating low-pressure zones that pull the body forward. Many show countershading; Geotria australis wears blue stripes that fade near spawning. Petromyzontids carry vertebrate-high chromosome counts (164–174). Their variable lymphocyte receptors offer a convergent adaptive immune system studied for evolutionary clues.
The etymology may be Latin lampetra, “stone licker”—fitting fish that still brace on rocks while climbing upstream to nest.
Source: Lamprey
