Lamprey

Physical description

Lampreys live mostly in coastal and freshwaters, although at least one species, Geotria australis probably travels significant distances in the open ocean, as is evidenced by the lack of reproductive isolation between Australian and New Zealand populations, and the capture a specimen in the Southern Ocean between Australia and Antartica. They are found in most temperate regions except Africa. Their larvae have a low tolerance for high water temperatures, which is probably the reason that they are not found in the tropics. Outwardly resembling eels in that they have no scales, an adult lamprey can range anywhere from 5 to 40 inches (13 to 100 centimetres) long. Lampreys have one or two dorsal fins, large eyes, one nostril on the top of their head, and seven gills on each side. A lamprey has cartilage instead of bones and is on the borderline between vertebrates and invertebrates.

Lampreys begin life as burrowing, freshwater larvae (ammocoetes). At this stage, they are toothless, have rudimentary eyes, and feed on microorganisms. This larval stage can last five to seven years, and hence, was originally thought to be an independent organism. After these five to seven years, they transform into adults in a metamorphosis which is at least as radical as that seen in amphibians, and which involves a radical rearangement of internal organs, development of eyes and transformation from a mud-dwelling filter feeder into an efficient swimming predator, which typically moves into the sea to begin a predatory/parasitic life, attaching to a fish by their mouths and feeding on the blood and tissues of the host. Whether lampreys are predators or parasites is a blurred question.

To reproduce, lampreys return to freshwater, build a nest, then spawn, that is, lay their eggs, and die. In Geotria australis, the time between ceasing to feed at sea and spawning can be up to 18 months long - surely one of the most remarkable endurance events in the animal kingdom. Not all lampreys can be found in the sea. Some lampreys are landlocked and remain in freshwater, and some of these stop feeding altogether as soon as they have left the larval stage.

Lampreys have long been used as food for humans.

Recent studies reported in Nature suggest that lampreys have evolved a unique type of immune system with parts that are unrelated to the antibodies found in mammals.

They also have a very high tolerance to iron overload, and have evolved biochemical defenses to detoxify this metal.

Taxonomy

The taxonomy presented here is that given by Fisher, 1994. The lampreys comprise an entire class Cephalaspidomorphi, containing a single order Petromyzontiformes and family Petromyzontidae.

Within this family, there are 40 recorded species in 9 genera and 3 subfamilies:

• Subfamily Geotriianae
  • Genus Geotria
    • Geotria australis (Gray,1851)
• Subfamily Mordaciinae
  • Genus Mordacia
    • Mordacia lapicida (Gray, 1851)
    • Mordacia mordax (Richardson, 1846)
    • Mordacia praecox (Potter, 1968)
• Subfamily Petromyzontinae
  • Genus Caspiomyzon
    • Caspiomyzon wagneri (Kessler, 1870)
  • Genus Eudontomyzon
    • Eudontomyzon danfordi (Regan, 1911)
    • Eudontomyzon hellenicus (Vladykov, Renaud, Kott and Economidis, 1982)
    • Eudontomyzon mariae (Berg, 1931)
    • Eudontomyzon morii (Berg, 1931)
    • Eudontomyzon stankokaramani (Karaman, 1974)
    • Eudontomyzon vladykovi (Oliva and Zanandrea, 1959)
  • Genus Ichthyomyzon
    • Ichthyomyzon bdellium (Jordan, 1885) - Ohio Lamprey
    • Ichthyomyzon castaneus Girard, 1858 - Chestnut Lamprey
    • Ichthyomyzon fossor (Reighard and Cummins, 1916) - Northern Brook Lamprey
    • Ichthyomyzon gagei (Hubbs and Trautman, 1937) - Southern Brook Lamprey
    • Ichthyomyzon greeleyi (Hubbs and Trautman, 1937) - Mountain Brook Lamprey
    • Ichthyomyzon unicuspis (Hubbs and Trautman, 1937) - Silver Lamprey
  • Genus Lampetra
    • Lampetra aepyptera (Abbott, 1860) - Least Brook lamprey
    • Lampetra alaskensis (Vladykov and Kott, 1978)
    • Lampetra appendix (DeKay, 1842) - American Brook Lamprey
    • Lampetra ayresii (Günther, 1870)
    • Lampetra fluviatilis (Linnaeus, 1758)
    • Lampetra hubbsi (Vladykov and Kott, 1976) - Kern Brook lamprey
    • Lampetra lamottei (Lesueur, 1827)
    • Lampetra lanceolata (Kux and Steiner, 1972)
    • Lampetra lethophaga (Hubbs, 1971) - Pit-Klamath Brook Lamprey
    • Lampetra macrostoma (Beamish, 1982) - Vancouver Lamprey
    • Lampetra minima (Bond and Kan, 1973) - Miller Lake Lamprey
    • Lampetra planeri (Bloch, 1784)
    • Lampetra richardsoni (Vladykov and Follett, 1965) - Western Brook Lamprey
    • Lampetra similis (Vladykov and Kott, 1979) - Klamath Lamprey
    • Lampetra tridentata (Richardson, 1836) - Pacific Lamprey
  • Genus Lethenteron
    • Lethenteron camtschaticum (Tilesius, 1811)
    • Lethenteron japonicum (Martens, 1868)
    • Lethenteron kessleri (Anikin, 1905)
    • Lethenteron matsubarai (Vladykov and Kott, 1978)
    • Lethenteron reissneri (Dybowski, 1869)
    • Lethenteron zanandreai (Vladykov, 1955)
  • Genus Petromyzon
    • Petromyzon marinus (Linnaeus, 1758) - Sea Lamprey
  • Genus Tetrapleurodon
    • Tetrapleurodon geminis (Alvarez, 1964)
    • Tetrapleurodon spadiceus (Bean, 1887)

Notes:

• Cephalaspidomorpha is sometimes given as a subclass of the Cephalaspidomorphi.
• Petromyzoniformes and Petromyzonidae are sometimes used as alternative spellings for Petromyzontiformes and Petromyzontidae respectively.

References

• Study on the lamprey immune system (http://www.nature.com/news/2004/040705/full/040705-2.html)
• ITIS report on the lampreys (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=159697)
• Fisher (1994). Fishes of the World, Third Edition. John Wiley and Sons. ISBN 0471547131.

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