Sea Lamprey

Lamprey
Missing image Sea_Lamprey_mouth.jpg The mouth of a Sea Lamprey, showing teeth and tongue
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Cephalaspidomorphi Order: Petromyzontiformes Family: Petromyzontidae
Subfamilies
Geotriinae Mordaciinae Petromyzontinae

A lamprey is a jawless fish with a toothed, funnel-like sucking mouth, with which most species bore into the flesh of other fishes to suck their blood. In zoology, lampreys are not considered to be true fish because of their vastly different morphology and physiology.

Contents

1 Physical description 2 Taxonomy 3 Relation to humans 4 References

Physical description

Lampreys live mostly in coastal and fresh waters, 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 of a specimen in the Southern Ocean between Australia and Antarctica. 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. In most species this phase lasts about 18 months. Whether lampreys are predators or parasites is a blurred question.

Not all lampreys can be found in the sea. Some lampreys are landlocked and remain in fresh water, and some of these stop feeding altogether as soon as they have left the larval stage. The landlocked species are usually rather small.

To reproduce, lampreys return to fresh water (if they left it), build a nest, then spawn, that is, lay their eggs or excrete their semen, and then invariably 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.

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 (G?, 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.

Relation to humans

Lampreys have long been used as food for humans. During the Middle Ages, they were widely eaten by the upper classes throughout Europe, especially during fasting periods, since their taste is much meatier than that of most true fish. King Henry I of England is said to have died from eating spoiled lampreys.

Especially in Southwestern Europe (Portugal, Spain, France) they are still a highly prized delicacy and fetch up to $25 a pound. Overfishing has reduced their number in those parts.

On the other hand, lampreys have become a major plague in the North American Great Lakes after artificial canals allowed their entry during the early 20th century. They have no natural enemies in the lakes and prey on many species of commercial value, such as trouts. Since North American consumers, unlike Europeans, refuse to accept lampreys as food fish, the Great Lakes fishery has been very adversely affected by their invasion. They are now fought mostly in the streams which feed the lakes, with special barriers and special poisons called lampricides, which are harmless to other species (as lampreys are not true fish). However those programs are complicated and expensive, and they do not eradicate the lampreys from the lakes but merely keep them in check.

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)
• Lampreys as food, including recipes (http://www.sciencenews.org/pages/sn_arch/8_10_96/food.htm)

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