Ichthyomyzon unicuspis
    Silver Lamprey

 Silver Lamprey

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Name:
  • Ichthyomyzon, from the Greek, "fish to suck", a reference to its feeding habits.
  • unicuspis, from the Latin, "one point", a reference to the presence of a single cusp on each tooth.
  • Common name from its silvery color
  • Other common names include: Bloodsucker, Blue Lamprey, Hitch-hiker, Lamper, Lamprey Eel

Taxonomy:
  • Kingdom Animalia
    • Phylum Chordata, animals with a spinal chord
    • Subphylum Vertebrata, animals with a backbone
      • Superclass Agnatha
      • Class Cephalaspidomorphi
      • Subclass Cephalaspidomorpha
        • Order Petromyzontiformes
          • Family Petromyzontidae, lampreys
            • Genus Ichthyomyzon, lampreys

Description:
  • A slender, primitive, eel-like fish
  • Length to 12"
  • Coloration
    • upper body silvery or bluish
    • fades to light beneath
  • Body
    • 49-52 clearly defined segments between last gill slit and anus.
    • dorsal fin continuous, not divided into two separate fins
    • cartilaginous skeleton (boneless)
  • Head
    • mouth a jaw-less, sucking disc; wider than the body when expanded.
    • teeth in circular row around the mouth; nearly all unicuspid (single pointed).
    • gill pores seven in number, in a straight line immediately behind the eye
    • single nostril between the eyes.

Identification:
  • Easily distinguished from other Northwoods fishes by its eel-like shape and sucking mouthparts.
  • Distinguished from the other native lamprey by its silvery color, continuous dorsal fin, and unicuspid teeth.

Distribution:
  • Generally distributed along the Great Lakes and in the large tributaries of the Mississippi and Ohio Rivers from Minnesota to Nebraska, Tennessee, and West Virginia.
  • Isolated records from the Hudson Bay drainage and from the Mississippi River in the State of Mississippi.

Habitat:

  • Parasitic adults live in larger streams and lakes where they find their fish hosts.
  • Larval ammocoetes require sand and dark mud, relatively free of clay silt.

Food:
  • Adults parasitic upon other fishes, attaching to host with suction-cup mouth. Sharp teeth cut through skin and scales and the blood is extracted.
  • Remains attached to host over a long period of time unless brushed off by the distressed fish. Fishes almost colorless from the loss of blood have been observed with several lampreys attached, but they seldom kill the host since that would deprive them of their food source.
  • Adults attack a variety of fish including trout, Whitefish (Coregonus clupeaformis), Smelt (Osmerus mordax), Pike (Esox lucius), White Sucker (Catostomus commersoni), Brown Bullhead (Ictalurus nebulosus), Rock Bass (Ambloplites rupestris), Walleye (Stizostedion vitreum), and even the armored Lake Sturgeon (Acipenser fulvescens).
  • Ammocoetes (larval young) feed on drifting plankton and detritus.

History:
  • The earliest known lampreys, Mayomyzon, are from the Pennsylvanian Period, about 300 million years ago. They are thought to be related to an extinct group of jawless fishes, the ostracoderms, which flourished earlier.
  • Populations of native lamprey are generally in decline throughout their range.

Uses:
  • Parasitic feeding habits limit their appeal to anglers.
  • May have some value as forage for predatory game fish.

Reproduction:
  • Spawns in May and June when the water temperature reaches 50º F. Adults ascend small tributary streams to spawn among rocks in sand and gravel bottom riffles.
  • Nests are built in shallow gravelly riffles. The adults constantly work on the nests with short interruptions for spawning. The female attaches to a rock and the male attaches to her head, wrapping his tail around hers to bring the genital openings close together. The pair vibrates as the eggs and sperm are released; then they separate and return to nest building.
  • The adults die when spawning is completed.
  • Eggs are approximately 1mm in diameter; the average female produces 10,800 eggs. Larvae (known as ammocetes) resemble their parents except that they are blind and the mouth hooded, toothless, and provided with a fine-mesh tissue sieve.
  • After hatching, the ammocoetes drift downstream to quiet waters where they live in small burrows in the bottom ooze for 4-7 years. At this stage they are not parasitic, feeding largely on algae and microscopic animals.
  • Ammocetes metamorphose in the fall when they are about 3" long. They remain in the streams over winter, then move downstream to rivers and lakes in search of hosts.
  • After one, or possibly two, years as parasites, the adults return upstream to spawn and die.

Comments:
  • The native lamprey species of the genus Ichthyomyzon should not be confused with the exotic and destructive Sea Lamprey (Petromyzon marinus), which wreaked havoc on native game fish in the Great Lakes before vigorous control measures brought it to check. The native lamprey have evolved with, and live in balance with, their host populations.
  • Listed as a species of special concern in Ontario, Nebraska, Vermont

Links:
  • Lampreys, a general article from the Tree of Life

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Last updated on 13 November 1999