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Everything about Petromyzontidae totally explained

A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. While lampreys are well known for those species which bore into the flesh of other fish to suck their blood, these species make up the minority. In zoology, lampreys are often not considered to be true fish because of their vastly different morphology and physiology.

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 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 why they're not found in the tropics.
   Outwardly resembling eels, in that they've no scales, an adult lamprey can range anywhere from 13 to 100 centimetres (5 to 40 inches) long. Lampreys have no paired fins, large eyes, one nostril on the top of the head, and seven gills on each side. The unique morphological characteristics of lampreys, such as their cartilaginous skeleton, mean that they're the sister taxon (see cladistics) of all living jawed vertebrates (gnathostomes) and are not classified within the Vertebrata itself. This is disputed by some, who place lampreys within Vertebrata. Hagfish, which superficially resemble lampreys, are the sister taxon of the lampreys and gnathostomes (a clade termed the Craniata).
Studies reported in Nature suggest that lampreys have 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 biochemical defenses to detoxify this metal.

Life cycle

Lampreys begin life as burrowing freshwater larvae (ammocoetes). At this stage, they're toothless, have rudimentary eyes, and feed on microorganisms. This larval stage can last five to seven years and so was originally thought to be an independent organism. They transform into adults in a metamorphosis which is at least as radical as that seen in amphibians. It involves a radical rearrangement of internal organs, development of eyes and transformation from a mud-dwelling filter feeder into an efficient swimming parasite/predator that typically moves to the sea. The adult feeds by attaching its mouth to a fish, secreting an anticoagulant to the host, and feeding on the blood and tissues of the host. In most species this phase lasts about 18 months.
   Some lampreys are landlocked and remain in fresh water, and some of these stop feeding when they leave the larval stage. The landlocked species are usually rather small. To reproduce, lampreys return to fresh water, build a nest, spawn (that is, females lay eggs, males excrete semen), then invariably die. In Geotria australis, the time from ceasing to feed at sea to spawning can be up to 18 months.

Fossils

Lamprey fossils are rare because cartilage doesn't fossilize as readily as bone. Until 2006, the oldest known fossil lampreys were from Early Carboniferous limestones, laid down in marine sediments in North America: Mayomyzon pieckoensis and Hardistiella montanensis.
   In the 22 June 2006 issue of Nature, Mee-mann Chang and colleagues reported on a fossil lamprey from the same Early Cretaceous lagerstätten that have yielded feathered dinosaurs, in the Yixian Formation of Inner Mongolia. The new species, morphologically similar to Carboniferous and modern forms, was given the name Mesomyzon mengae ("Middle lamprey"). The exceedingly well-preserved fossil showed a well-developed sucking oral disk, a relatively long branchial apparatus showing branchial basket, seven gill pouches, gill arches and even the impressions of gill filaments, and about 80 myomeres of its musculature.
   Months later, in the 27 October issue of Nature, an even older fossil lamprey, dated 360 million years ago, was reported from Witteberg Group rocks near Grahamstown, in the Eastern Cape of South Africa. This species, dubbed Priscomyzon riniensis still strongly resembled modern lampreys despite its Devonian age.(External Link)

Taxonomy

The taxonomy presented here's that given by Fisher, 1994. This work classifies lampreys as the sole living members of the class Cephalaspidomorphi. The lampreys entail the single order Petromyzontiformes and family Petromyzontidae.
   Within this family, there are 40 recorded species in nine genera and three subfamilies:
Some taxonomists place lampreys and hagfish in the phylum Chordata under the super-class Agnathostomata (without jaws). The other super-class of the phylum is Gnathostomata (jaw-having) and includes the classes Chondrichthyes, Osteichthyes, Amphibia, Reptila, Aves, and Mammalia.

Relation to humans

Uses

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 "a surfeit of lampreys" . On 4th March 1953 the Queen was made a coronation pie using lampreys by the Royal Air Force.
   Especially in southwestern Europe (Portugal, Spain, France), larger lampreys are still a highly prized delicacy. Overfishing has reduced their number in those parts. Lampreys are also consumed in Sweden, Finland, the Baltic countries, and South Korea.
   In Britain, lampreys are commonly used as bait, normally as dead bait. Pike, perch and chub all can be caught on lampreys. Lampreys can be bought frozen from most bait and tackle shops.
   Lampreys are used as a model organism in biomedical research where their large reticulospinal axons are used to investigate synaptic transmission . The axons of lamprey are particularly large and allow for microinjection of substances for experimental manipulation.

As pests

On the other hand, sea lampreys have become a major plague in the North American Great Lakes after artificial canals allowed their entry during the early 20th century. They are considered an invasive species, have no natural enemies in the lakes and prey on many species of commercial value, such as lake trout. Since the majority of North American consumers, unlike Europeans, refuse to accept lampreys as food, the Great Lakes fishery has been adversely affected by their invasion. Lampreys are now fought mostly in the streams that feed the lakes, with special barriers to prevent the upstream movement of adults, or by the application of toxicants called lampricides, which are harmless to most other aquatic species. However those programs are complicated and expensive, and don't eradicate the lampreys from the lakes but merely keep them in check. New programs are being developed including the use of chemically sterilized male lamprey in a method akin to the sterile insect technique. Research is currently under way on the use of pheromones and how they may be used to disrupt the life cycle (Sorensen, et al., 2005). Control of sea lampreys in the Great Lakes is conducted by the U.S. Fish and Wildlife Service and the Canadian Department of Fisheries and Oceans. The work is coordinated by the Great Lakes Fishery Commission. Lake Champlain, bordered by New York State, Vermont, and Quebec, and New York's Finger Lakes are also home to populations of sea lampreys whose high populations have also warranted control. Lake Champlain's lamprey control program is managed by the New York State Department of Environmental Conservation, the Vermont Department of Fish and Wildlife, and the U.S. Fish and Wildlife Service. New York's Finger Lakes sea lamprey control program is managed solely by the New York State Department of Environmental Conservation.

In literature

Vedius Pollio was punished by Augustus for attempting to feed a clumsy slave to the lampreys in his fishpond. » ...one of his slaves had broken a crystal cup. Vedius ordered him to be seized and to be put to death in an unusual way. He ordered him to be thrown to the huge lampreys which he'd in his fish pond. Who wouldn't think he did this for display? Yet it was out of cruelty. The boy slipped from the captor’s hands and fled to Caesar’s feet asking nothing else other than a different way to die—he didn't want to be eaten. Caesar was moved by the novelty of the cruelty and ordered him to be released, all the crystal cups to be broken before his eyes, and the fish pond to be filled in... – Seneca, On Anger, III, 40 (External Link)

Christopher Warner, a character in Philip Larkin's early novel Jill is said to have attended a fictional minor public school called Lamprey College.
   Lamprey pies are an appreciated dish often referred in George R.R. Martin's popular fantasy series A Song of Ice and Fire.

Further Information

Get more info on 'Petromyzontidae'.


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