Temporal range: Late Devonian–Holocene 
|A lamprey attached to a fish|
Lampreys (sometimes also called lamprey eels) are an order of jawless fish, whose adults are characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is derived from lampetra, which translated from Latin means "stone licker" (lambere "to lick" + petra "stone").
While lampreys are well known for those species which bore into the flesh of other fish to suck their blood, most species of lamprey are not parasitic and never feed on other fish. The lampreys are a very ancient lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute.
Adults physically resemble eels, in that they have no scales, and can range anywhere from 13 to 100 centimetres (5 to 40 inches) long. Lacking paired fins, adult lampreys have large eyes, one nostril on the top of the head, and seven gill pores on each side of the head. The unique morphological characteristics of lampreys, such as their cartilaginous skeleton, suggest they are the sister taxon (see cladistics) of all living jawed vertebrates (gnathostomes), and are usually considered the most basal group of the Vertebrata. Parasitic lampreys feed on prey as adults by attaching their mouthparts to the target animal's body, then using their teeth to cut through surface tissues until they reach blood and body fluid. Although attacks on humans do occur, they will generally not attack humans unless starved. Non-parasitic lampreys, which are usually freshwater species, do not feed as adults; they live off reserves acquired as ammocoetes, which they obtain through filter feeding.
Lampreys provide valuable insight into the evolution of the adaptive immune system, as they possess a convergently evolved adaptive immunity with cells that function like the T cells and B cells seen in higher vertebrates. Lamprey leukocytes express surface variable lymphocyte receptors (VLRs) generated from somatic recombination of leucine-rich repeats gene segments in a recombination activating gene-independent manner. Northern Lampreys (family Petromyzontidae) have the highest number of chromosomes (164-174) among vertebrates.
Pouched Lamprey (Geotria australis) larvae also have a very high tolerance for free iron in the body, and have well-developed biochemical systems for detoxification of the large quantities of these metal ions.
The lamprey has been extensively studied because its relatively simple brain is thought in many respects to reflect the brain structure of early vertebrate ancestors. Beginning in the 1970s, Sten Grillner and his colleagues at the Karolinska Institute in Stockholm have used the lamprey as a model system to work out the fundamental principles of motor control in vertebrates, starting in the spinal cord and working toward the brain. In a series of studies, they found neural circuits within the spinal cord are capable of generating the rhythmic motor patterns that underlie swimming, these circuits are controlled by specific locomotor areas in the brainstem and midbrain, and these areas, in turn, are controlled by higher brain structures, including the basal ganglia and tectum. In a study of the lamprey tectum published in 2007, they found electrical stimulation could elicit eye movements, lateral bending movements, or swimming activity, and the type, amplitude, and direction of movement varied as a function of the location within the tectum that was stimulated. These findings were interpreted as consistent with the idea that the tectum generates goal-directed locomotion in the lamprey as it does in other species.
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.
Lampreys live mostly in coastal and fresh waters, although some species (e.g. Geotria australis, Petromyzon marinus, Entosphenus tridentatus) travel significant distances in the open ocean, as evidenced by their lack of reproductive isolation between populations. Some species are found in land-locked lakes. They are found in most temperate regions except those in Africa. Their larvae (ammocoetes) have a low tolerance for high water temperatures, which may explain why they are not distributed in the tropics.
Lamprey distribution may be adversely affected by over-fishing and pollution. In Britain, at the time of the conquest, Lampreys were found as far upstream in the River Thames as Petersham. Reduction of pollution in the Thames and River Wear has led to recent sightings in London and Chester-le-Street.
Distribution may also be adversely affected by dams and other construction projects disrupting migration routes, obstructing access to spawning grounds. Conversely, the construction of artificial channels has exposed new habitats for colonisation notably in North America where Sea lampreys have become a significant introduced pest in the Great Lakes.
Life cycle 
Adult lampreys spawn in rivers and then die. The young larvae, also called "ammocoetes", spend several years in the rivers, where they live burrowed in fine sediment, filter feeding on detritus and microorganisms. Then, ammocoetes undergo a metamorphosis that lasts several months. Some species do not feed after metamorphosis, while others migrate to the sea or lakes, where they feed on different species of fish and even on marine mammals. Individuals who migrate to the sea can also start feeding in the river before the downstream migration. After one or two years at sea or lakes,
Taxonomy and systematics 
Taxonomists place lampreys and hagfish in the subphylum Vertebrata of the phylum Chordata, which also includes the invertebrate subphyla Tunicata (sea-squirts) and the fish-like Cephalochordata (lancelets or Amphioxus). Recent molecular and morphological phylogenetic studies place lampreys and hagfish in the superclass Agnatha or Agnathostomata (both meaning without jaws). The other vertebrate superclass is Gnathostomata (jawed mouths) and includes the classes Chondrichthyes (sharks), Osteichthyes (bony fishes), Amphibia, Reptilia, Aves (birds), and Mammalia.
Some researchers have classified lampreys as the sole surviving representatives of the Linnean class Cephalaspidomorphi. Cephalaspidomorpha is sometimes given as a subclass of the Cephalaspidomorphi. Fossil evidence now suggests lampreys and cephalaspids acquired their shared characters by convergent evolution. As such, many newer works, such as the fourth edition of Fishes of the World, classify lampreys in a separate group called Hyperoartia or Petromyzontida, but whether this is actually a clade is disputed. Namely, it has been proposed that the non-lamprey "Hyperoartia" are in fact closer to the jawed vertebrates.
The debate about their systematics notwithstanding, lampreys constitute a single order Petromyzontiformes. Sometimes still seen is the alternative spelling "Petromyzoniformes", based on the argument that the type genus is Petromyzon and not "Petromyzonta" or similar. Throughout most of the 20th century, both names were used pretty much indiscriminately, even by the same author in subsequent publications. In the mid-1970s, the ICZN was called upon to fix one name or the other, and after much debate had to resolve the issue by voting. Thus, in 1980 the spelling with a "t" won out, and in 1981 it became official that all higher-level taxa based on Petromyzon have to start with "Petromyzont-".
The following taxonomy is based upon the treatment by FishBase as of April 2012. Within the order, there are 10 living genera in three families. Two of the latter are monotypic at genus level today, and in one of them a single living species is recognized (though it may be a cryptic species complex):
- Family Geotriidae – Pouched Lamprey
- Genus Geotria
- Family Mordaciidae – southern topeyed lampreys
- Genus Mordacia
- Family Petromyzontidae – northern lampreys
Fossil record 
Lamprey fossils are rare because cartilage does not fossilize as readily as bone. The first fossil lampreys were originally found in Early Carboniferous limestones, marine sediments laid down more than 300 million years ago in North America: Mayomyzon pieckoensis and Hardistiella montanensis, from the Mississippian Mazon Creek lagerstätte and the Bear Gulch Limestone sequence.
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, laid down around some 120 million years ago. The new species, morphologically similar to Carboniferous and modern forms, was given the name Mesomyzon mengae ("Meng Qingwen's Mesozoic 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. Unlike the North American fossils, its habitat was almost certainly freshwater.
Months later, in the 27 October issue of Nature, a fossil lamprey even older than the Mazon Creek genera, 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.
As food 
Lampreys have long been used as food for humans. They were highly appreciated by ancient Romans. 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."
Especially in southwestern Europe (Portugal, Spain, and France), larger lampreys are still a highly prized delicacy. Petromyzon marinus, the sea lamprey, is the most sought species in Portugal and one of only two that can legally bear the commercial name "lamprey" (lampreia): the other one being Lampetra fluviatilis, the European river lamprey, both according to Portaria (Government regulation no. 587/2006, from 22 June). Overfishing has reduced their number in those parts. Lampreys are also consumed in Sweden, Finland, Russia, New Zealand, the Baltic countries, Japan and South Korea.
The mucus and serum of several Lamprey species including the Caspian lamprey (Caspiomyzon wagneri), River Lampreys (Lampetra fluviatilis and L. planeri) and Sea lamprey (Petromyzon marinus), are known to be toxic, and require thorough cleaning before cooking and consumption.
As pests 
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. Lampreys are now found 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 do not eradicate the lampreys from the lakes, but merely keep them in check. New programs are being developed, including the use of chemically sterilized male lampreys in a method akin to the sterile insect technique. Research currently under way on the use of pheromones and how they may be used to disrupt the life cycle has met with some success. 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 high populations of sea lampreys that warrant 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.
Lampreys are called "nine-eyed eels" (i.e., per side) from a counting of their seven external gill slits on a side with one eye and the nostril. A German word for lamprey is Neunauge, which means "nine-eye".
In literature 
- ...one of his slaves had broken a crystal cup. Vedius ordered him to be seized and then put to death, but in an unusual way. He ordered him to be thrown to the huge lampreys which he had in his fish pond. Who would not think he did this for display? Yet it was out of cruelty. The boy slipped from the captor’s hands and fled to Augustus' feet asking nothing else other than a different way to die – he did not want to be eaten. Augustus 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
- So, when Domitius said to Crassus the orator, Did not you weep for the death of the lamprey you kept in your fish pond? – Did not you, said Crassus to him again, bury three wives without ever shedding a tear? – Plutarch, On the Intelligence of Animals, 976a
- And in my mind I compare myself from time to time with the orator Crassus, of whom it is reported that he grew so excessively enamoured of a tame lamprey – a dumb, apathetic, red-eyed fish in his ornamental pond – that it became the talk of the town; and when one day in the Senate Domitius reproached him for having shed tears over the death of this fish, attempting thereby to make him appear a fool, Crassus answered, "Thus have I done over the death of my fish as you have over the death of neither your first nor your second wife."
- "I know not how oft this Crassus with his lamprey enters my mind as a mirrored image of my Self, reflected across the abyss of centuries."
"Lampreys have been seen before attacking a human in the great lakes. The lamprey let go a few seconds later after realizing its mistake. The man (who chose to be not named) was taken to the hospital with various injuries." – From Jules Verne's novel Twenty Thousand Leagues Under the Sea.
- Froese, Rainer, and Daniel Pauly, eds. (2009). "Petromyzontiformes" in FishBase. January 2009 version.
- Hardisty, M. W.; Potter, I. C. (1971). In Hardisty, M. W.; Potter, I. C. The Biology of Lampreys (1 ed.). Academic Press. ISBN 9780123248015.
- "CANADA: A Surfeit of Lampreys". Time. 9 May 1955. Retrieved 7 June 2008.
- Liem, Karel F.; William E. Bemis, Warren F. Walker, Jr., Lance Grande (2001). Functional Anatomy of the Vertebrates. The United States of America: Thomson: Brooks/Cole. p. 50. ISBN 0-03-022369-5.
- Haaramo, Mikko (11 March 2008). "Mikko's Phylogeny Archive". Retrieved 26 January 2009.
- Alaska Department of Fish and Game (2004). "Lampreys". Retrieved 8 July 2012.
- Pancer, Z.; Amemiya, C. T.; Ehrhardt, G. T. R. A.; Ceitlin, J.; Larry Gartland, G.; Cooper, M. D. (2004). "Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey". Nature 430 (6996): 174–180. doi:10.1038/nature02740. PMID 15241406.
- Nagawa, Fumikiyo; Kishishita, Natsuko; Shimizu, Kazumichi; Hirose, Satoshi; Miyoshi, Masato; Nezu, Junnya; Nishimura, Toshinobu; Nishizumi, Hirofumi et al. (2007). "Antigen-receptor genes of the agnathan lamprey are assembled by a process involving copy choice". Nature immunology 8 (2): 206–13. doi:10.1038/ni1419. PMID 17187071. Unknown parameter
- Froese, Rainer, and Daniel Pauly, eds. (2011). "Petromyzontidae" in FishBase. February 2011 version.
- Macey, D. J.; Cake, M. H.; Potter, I. C. (1988). "Exceptional iron concentrations in larval lampreys (Geotria australis) and the activities of superoxide radical detoxifying enzymes". Biochemical Journal 252 (1): 167–172. PMC 1149120. PMID 3421899.
- Grillner, S. (2003). "The motor infrastructure: From ion channels to neuronal networks". Nature Reviews Neuroscience 4 (7): 573–586. doi:10.1038/nrn1137. PMID 12838332.
- Saitoh, K.; Menard, A.; Grillner, S. (2007). "Tectal Control of Locomotion, Steering, and Eye Movements in Lamprey". Journal of Neurophysiology 97 (4): 3093–3108. doi:10.1152/jn.00639.2006. PMID 17303814.
- Brodin, L.; Shupliakov, O. (2006). "Giant reticulospinal synapse in lamprey: Molecular links between active and periactive zones". Cell and Tissue Research 326 (2): 301–310. doi:10.1007/s00441-006-0216-2. PMID 16786368.
- Petersham in the Domesday Book
- "Prehistoric bloodsucker in Thames". BBC News. 1 July 2009. Retrieved 27 September 2012.
- "Giant blood sucker found in River Wear". The Northern Echo. 25 June 2009.
- Evans, Thomas M. (2012). Assessing Food and Nutritional Resources of Native and Invasive Lamprey Larvae Using Natural Abundance Isotopes. Thesis. Ohio State University.
- Silva, S., Servia, M. J., Vieira-Lanero, R. & Cobo, F. (2013). Downstream migration and hematophagous feeding of newly metamorphosed sea lampreys (Petromyzon marinus Linnaeus, 1758). Hydrobiologia 700: 277–286. Doi: 10.1007/s10750-012-1237-3
- Beamish, F. W. H. (1980). Biology of the North American anadromous sea lamprey, Petromyzon marinus. Canadian Journal of Fisheries and Aquatic Sciences 37:1924−1943. doi: 10.1139/f80-233.
- Nichols, O. C. & U. T. Tscherter, 2011. Feeding of sea lampreys Petromyzon marinus on minke whales Balaenoptera acutorostrata in the St Lawrence Estuary. Journal of Fish Biology 78: 338–343.
- Silva, S., Servia, M. J., Vieira-Lanero, R., Nachón, D. J. & Cobo, F. (2013). Haematophagous feeding of newly metamorphosed European sea lampreys Petromyzon marinus on strictly freshwater species. Journal of Fish Biology. doi:10.1111/jfb.12100.
- Silva, S., Servia, M. J., Vieira-Lanero, R., Barca, S. & Cobo, F. (2013). Life cycle of the sea lamprey Petromyzon marinus: duration of and growth in the marine life stage. Aquatic Biology 18: 59–62. doi: 10.3354/ab00488.
- Halliday R. G. (1991) Marine distribution of the sea lamprey (Petromyzon marinus) in the northwest Atlantic. Canadian Journal of Fisheries and Aquatic Sciences 48:832−842.
- Bergstedt R. A., Swink W. D. (1995). Seasonal growth and duration of the parasitic life stage of landlocked sea lampreys (Petromyzon marinus). Canadian Journal of Fisheries and Aquatic Sciences 52: 1257−1264.
- Nelson, J. S. (2006). Fishes of the World (4th ed.). New York: John Wiley and Sons, Inc. pp. 601 pp. ISBN 0-471-25031-7.
- Forey, Peter; Janvier, Philippe (2000). "Agnathans and the origin of jawed vertebrates". In Gee, Henry. Shaking the tree: readings from Nature in the history of life. USA: University of Chicago Press; Nature/Macmillan Magazines. pp. 251–266. ISBN 978-0-226-28497-2
- Janvier, P. (2008). "Early Jawless Vertebrates and Cyclostome Origins". Zoological Science 25 (10): 1045–1056. doi:10.2108/zsj.25.1045. PMID 19267641.
- Froese, Rainer, and Daniel Pauly, eds. (2012). "Petromyzontiformes" in FishBase. April 2012 version.
- Chang, M. M.; Zhang, J.; Miao, D. (2006). "A lamprey from the Cretaceous Jehol biota of China". Nature 441 (7096): 972–974. doi:10.1038/nature04730. PMID 16791193.
- "Discovery of the Oldest Fossil Lamprey in the World". University of the Witwatersrand. 26 October 2006. Retrieved 8 June 2008.[dead link]
- "Scientists find lamprey a 'living fossil'". University of Chicago Medicine. 26 October 2006.
- Gess, R. W.; Coates, M. I.; Rubidge, B. S. (2006). "A lamprey from the Devonian period of South Africa". Nature 443 (7114): 981–984. doi:10.1038/nature05150. PMID 17066033.
- Green, Judith A. (March 2006). Henry I King of England and Duke of Normandy. Queen's University Belfast. ISBN 9780521591317.
- "Gloucester lamprey pie is fit for the Queen". BBC News. 20 April 2012.
- Froese, Rainer and Pauly, Daniel, eds. (2012). "Lampetra fluviatilis" in FishBase. September 2012 version. (citing Bristow, Pamela (30 April 1992). The Illustrated Encyclopedia of Fishes. London: Chancellor Press. ISBN 9781851521364.).
- Deshpande, S. S. (29 Aug 2002). Handbook of Food Toxicology. CRC Press. p. 695. ISBN 978-0824707606.
- Sorensen, P. W.; Fine, J. M.; Dvornikovs, V.; Jeffrey, C. S.; Shao, F.; Wang, J.; Vrieze, L. A.; Anderson, K. R. et al. (2005). "Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey". Nature Chemical Biology 1 (6): 324–328. doi:10.1038/nchembio739. PMID 16408070.
- Black, Richard (20 January 2009). "Sex smell lures 'vampire' to doom". BBC News.
- Seneca the Younger. L. ANNAEI SENECAE AD NOVATVM DE IRA LIBER III [On Anger] (in Latin) III. Thelatinlibrary.com.
- Plutarch. The Morals V. William W. Goodwin. Online Library of Liberty. Translated by William Watson Goodwin.
- von Hofmannsthal, Hugo (1902). "The Letter of Lord Chandos".
Further reading 
- Renaud, C.B. (2011) Lampreys of the world. An annotated and illustrated catalogue of lamprey species known to date FAO Species Catalogue for Fishery Purposes. No. 5. Rome. ISBN 978-92-5-106928-8.
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