Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin , which may mean "stone licker" ( "to lick" + "stone"), though the etymology is uncertain. ''Lamprey'' is sometimes seen for the plural form. There are about 38 known extant species of lampreys and five known extinct species. Parasitic carnivorous species are the most well-known, and feed by boring into the flesh of other fish to suck their blood; but only 18 species of lampreys engage in this

micropredator Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

y lifestyle. Of the 18 carnivorous species, nine migrate from saltwater to freshwater to breed (some of them also have freshwater populations), and nine live exclusively in freshwater. All non-carnivorous forms are freshwater species. Adults of the non-carnivorous species do not feed; they live on reserves acquired as ammocoetes ( larvae), which they obtain through filter feeding.

Distribution

Lampreys live mostly in coastal and fresh waters and are found in most temperate regions. Some species (e.g. '' Geotria australis'', '' Petromyzon marinus'', and '' Entosphenus tridentatus'') travel significant distances in the open ocean, as evidenced by their lack of

reproductive isolation The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring ...

between populations. Other species are found in land-locked lakes. 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 overfishing and pollution. In Britain, at the time of the Conquest, lampreys were found as far upstream in the River Thames as Petersham . The reduction of pollution in the Thames and

River Wear The River Wear (, ) in North East England rises in the Pennines and flows eastwards, mostly through County Durham to the North Sea in the City of Sunderland. At long, it is one of the region's longest rivers, wends in a steep valley through th ...

has led to recent sightings in London and Chester-le-Street. Distribution of lampreys may also be adversely affected by dams and other construction projects due to disruption of migration routes and obstruction of 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. Active control programs to control lampreys are undergoing modifications due to concerns of drinking water quality in some areas.

Biology

Anatomy

Adults superficially resemble eels in that they have scaleless, elongated bodies, and can range from in length. Lacking paired fins, adult lampreys have large eyes, one nostril atop the head, and seven gill pores on each side of the head. The brain of the lamprey is divided into the telencephalon,

diencephalon The diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the 'tweenbrain in ol ...

, midbrain,

cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...

, and medulla. The heart of the lamprey is anterior to the intestines. It contains the sinus, one atrium, and one ventricle protected by the pericardial cartilages. The

pineal gland The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep, sleep patterns in both circadian rhythm, circ ...

, a photosensitive organ regulating

melatonin Melatonin is a natural product found in plants and animals. It is primarily known in animals as a hormone released by the pineal gland in the brain at night, and has long been associated with control of the sleep–wake cycle. In vertebrates ...

production by capturing light signals through the

photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiatio ...

converting them into intercellular signals of the lamprey is located in the midline of its body, for lamprey, the pineal eye is accompanied by the parapineal organ. The buccal cavity, anterior to the

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

s, is responsible for attaching the animal, through suction, to either a stone or its prey. This then allows the tongue to make contact with the stone to rasp

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, or tear at the flesh of their prey to yield blood. The pharynx is subdivided; the ventral part forming a respiratory tube that is isolated from the mouth by a valve called the velum. This is an adaptation to how the adults feed, by preventing the prey's body fluids from escaping through the gills or interfering with gas exchange, which takes place by pumping water in and out of the gill pouches instead of taking it in through the mouth. One of the key physical components to the lamprey are the intestines, which are located ventral to the

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consis ...

. Intestines aid in osmoregulation by intaking water from its environment and desalinating the water they intake to an iso-osmotic state with respect to blood, and are also responsible for digestion. Near the gills are the eyes, which are poorly developed and buried under skin in the larvae. The eyes consummate their development during metamorphosis, and are covered by a thin and transparent layer of skin that becomes opaque in preservatives.

Morphology

The unique morphological characteristics of lampreys, such as their cartilaginous

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

, suggest they are the sister taxon (see cladistics) of all living jawed vertebrates ( gnathostomes). They are usually considered the most basal group of the Vertebrata. Instead of true vertebrae, they have a series of cartilaginous structures called arcualia arranged above the notochord. Hagfish, which resemble lampreys, have traditionally been considered the sister taxon of the true vertebrates (lampreys and gnathostomes) but DNA evidence suggests that they are in fact the sister taxon of lampreys. Studies have shown that lampreys are among the most energy-efficient swimmers. Their swimming movements generate low-pressure zones around the body, which pull rather than push their bodies through the water. Research on sea lampreys has revealed that sexually mature males use a specialized heat-producing tissue in the form of a ridge of fat cells near the anterior dorsal fin to stimulate females. After having attracted a female with pheromones, the heat detected by the female through body contact will encourage spawning. Due to certain peculiarities in their adaptive immune system, the study of lampreys provides valuable insight into the evolution of vertebrate adaptive immunity. Generated from a somatic recombination of

leucine-rich repeat A leucine-rich repeat (LRR) is a protein structural motif that forms an α/β horseshoe fold. It is composed of repeating 20–30 amino acid stretches that are unusually rich in the hydrophobic amino acid leucine. These tandem repeats common ...

gene segments, lamprey leukocytes express surface

variable lymphocyte receptors Variable lymphocyte receptors (VLRs) belong to the Leucine-rich repeat (LRR) family and mediate adaptive immune responses in the jawless vertebrates, lampreys and hagfish. See also * Adaptive immunity in jawless fish Agnatha, Jawless vertebrates, ...

(VLRs). This convergently evolved characteristic allows them to have lymphocytes that work as the T cells and

B cell B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or ...

s present in higher vertebrates immune system. Northern lampreys (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 their bodies, and have well-developed biochemical systems for detoxification of the large quantities of these metal ions. Lampreys are the only extant vertebrate to have four eyes. Most lampreys have two additional parietal eyes: a pineal and parapineal one (the exception is members of '' Mordacia'').

Adaptations

Different species of lamprey have many shared physical characteristics. The same anatomical structure can serve different functions in the lamprey depending on whether or not it is

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

. For example, non-carnivorous species use their teeth to scrape algae from rocks for food, rather than drilling into the flesh of hosts. The mouth and suction capabilities of the lamprey not only allow it to cling to a fish as a parasite, but provide it with limited climbing ability so that it can travel upstream and up ramps or rocks to breed. This ability has been studied in an attempt to better understand how lampreys battle the current and move forward despite only being able to hold onto the rock at a single point. Some scientists are also hoping to design ramps that will optimize the lamprey's climbing ability, as lampreys are valued as food in the Northwest United States and need to travel upstream to reproduce. The last common ancestor of lampreys appears to have been specialized to feed on the blood and body fluids of other fish after metamorphosis. They attach their mouthparts to the target animal's body, then use three horny plates (laminae) on the tip of their piston-like tongue, one transversely and two longitudinally placed, to scrape through surface tissues until they reach body fluids. The teeth on their oral disc are primarily used to help the animal attach itself to its prey. Made of keratin and other proteins, lamprey teeth have a hollow core to give room for replacement teeth growing under the old ones. Some of the original blood-feeding forms have evolved into species that feed on both blood and flesh, and some who have become specialized to eat flesh and may even invade the internal organs of the host. Tissue feeders can also involve the teeth on the oral disc in the excision of tissue. As a result, the flesh-feeders have smaller buccal glands as they do not require the production of anticoagulant continuously and mechanisms for preventing solid material entering the branchial pouches, which could otherwise potentially clog the gills. A study of the stomach content of some lampreys has shown the remains of intestines, fins and vertebrae from their prey. Although attacks on humans do occur, they will generally not attack humans unless starved. Carnivorous forms have given rise to the non-carnivorous species that feed on algae, and "giant" individuals amongst the otherwise small American brook lamprey have occasionally been observed, leading to the hypothesis that sometimes individual members of non-carnivorous forms return to the carnivorous lifestyle of their ancestors. Another important lamprey adaptation is its countershading, a form of camouflage. Similarly to many other aquatic species, most lampreys have a dark-colored back, which enables them to blend in with the ground below when seen from above by a predator. Their light-colored undersides allow them to blend in with the bright air and water above them if a predator sees them from below. Lamprey coloration can also vary according to the region and specific environment in which the species is found. Some species can be distinguished by their unique markings – for example, ''Geotria australis'' individuals display two bluish stripes running the length of its body as an adult. These markings can also sometimes be used to determine what stage of the life cycle the lamprey is in; ''G. australis'' individuals lose these stripes when they approach the reproductive phase and begin to travel upstream. Another example is '' Petromyzon marinus'', which shifts to more of an orange color as it reaches the reproductive stage in its life cycle.

Lifecycle

The adults spawn in nests of sand, gravel and pebbles in clear streams. After hatching from the eggs, young larvae—called ammocoetes—will drift downstream with the current till they reach soft and fine sediment in silt beds, where they will burrow in silt, mud and detritus, taking up an existence as

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

s, collecting detritus, algae, and microorganisms. The eyes of the larvae are underdeveloped, but are capable of discriminating changes in illuminance. Ammocoetes can grow from to about . Many species change color during a diurnal cycle, becoming dark at day and pale at night. The skin also has photoreceptors, light sensitive cells, most of them concentrated in the tail, which helps them to stay buried. Lampreys may spend up to eight years as ammocoetes, while species such as the

Arctic lamprey The Arctic lamprey (''Lethenteron camtschaticum''), also known as the Japanese river lamprey or Japanese lampern (''Petromyzon japonicus'' Martens 1868, ''Lampetra fluviatilis japonica'' (Martens 1868), '' Lampetra japonica'' (Martens 1868), '' L ...

may only spend one to two years as larvae, prior to undergoing a metamorphosis which generally lasts 3–4 months, but can vary between species. While metamorphosing, they do not eat. The rate of water moving across the ammocoetes' feeding apparatus is the lowest recorded in any suspension feeding animal, and they therefore require water rich in nutrients to fulfill their nutritional needs. While the majority of (invertebrate) suspension feeders thrive in waters containing under 1 mg suspended organic solids per litre (<1 mg/L), ammocoetes demand minimum 4 mg/L, with concentrations in their habitats having been measured up to 40 mg/L. During metamorphosis the lamprey loses both the gallbladder and the

biliary tract The biliary tract, (biliary tree or biliary system) refers to the liver, gallbladder and bile ducts, and how they work together to make, store and secrete bile. Bile consists of water, electrolytes, bile acids, cholesterol, phospholipids and co ...

, and the endostyle turns into a thyroid gland. Some species, including those that are not carnivorous and do not feed even following metamorphosis, live in freshwater for their entire lifecycle, spawning and dying shortly after metamorphosing. In contrast, many species are

anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...

and migrate to the sea, beginning to prey on other animals while still swimming downstream after their metamorphosis provides them with eyes, teeth, and a sucking mouth. Those that are anadromous are carnivorous, feeding on fishes or marine mammals. Anadromous lampreys spend up to four years in the sea before migrating back to freshwater, where they spawn. Adults create nests (called redds) by moving rocks, and females release thousands of eggs, sometimes up to 100,000. The male, intertwined with the female, fertilizes the eggs simultaneously. Being semelparous, both adults die after the eggs are fertilized.

Classification

Taxonomists place lampreys and hagfish in the subphylum Vertebrata of the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Chordata A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fiv ...

, 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 Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species. Among recent animals, cyclostomes ...

(both meaning without jaws). The other vertebrate superclass is Gnathostomata (jawed mouths) and includes the classes Chondrichthyes (sharks),

Osteichthyes Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilage ...

(bony fishes), Amphibia, Reptilia,

Aves Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

, 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 ''Fishes of the World'' by the American ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the ...

'', classify lampreys in a separate group called Hyperoartia or Petromyzontida, but whether this is actually a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

is disputed. Namely, it has been proposed that the non-lamprey "Hyperoartia" are in fact closer to the

jawed vertebrates Gnathostomata (; from Greek: (') "jaw" + (') "mouth") are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living ...

. The debate about their systematics notwithstanding, lampreys constitute a single

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 indiscriminately, even by the same author in subsequent publications. In the mid-1970s, the

ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...

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 with phylogeny compiled by Mikko Haaramo. Within the order 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): *''Geotria australis'' Gray 1851 ( Pouched lamprey) *''Mordacia lapicida'' (Gray 1851) (

Chilean lamprey ''Mordacia lapicida'', also known as the Chilean lamprey, is a species of southern topeyed lamprey endemic to southern Chile, where it can be found in riverine and marine habitats. This species is anadromous. This parasitic Parasitism ...

) *''Mordacia mordax'' (Richardson 1846) (

Australian lamprey ''Mordacia mordax'', known as the short-headed lamprey, Australian lamprey or Murray lamprey, is a species of Mordacia that lives in south-eastern Australia and Tasmania. Mordaciidae is made up of three species: ''M. praedox'', ''M. mordax'', and ...

) *''Mordacia praecox'' Potter 1968 (Non-parasitic/

Australian brook lamprey ''Mordacia praecox'', the Australian brook lamprey or nonparasitic lamprey, is a freshwater species of southern topeyed lamprey that occurs in south-eastern Australia. It has a thin eel-like body around 12 to 15 cm long, with two low dorsal ...

) *''Petromyzon marinus'' Linnaeus 1758 ( Sea lamprey) *''Ichthyomyzon bdellium'' (Jordan 1885) (

Ohio lamprey The Ohio lamprey (''Ichthyomyzon bdellium'') is a lamprey found in the Ohio River drainage basin in the United States and is a parasitic species of lampreys. They are considered to be an endangered/rare species in some states, due to siltation, ...

) *''Ichthyomyzon castaneus'' Girard 1858 (

Chestnut lamprey The chestnut lamprey (''Ichthyomyzon castaneus'') is a species of lamprey. Description The chestnut lamprey has a maximum length of around , in Canada, with dark grey to olive skin color, blue-black after spawning, and with five to eight bicusp ...

) *''Ichthyomyzon fossor'' Reighard & Cummins 1916 (

Northern brook lamprey The northern brook lamprey (''Ichthyomyzon fossor'') is a freshwater fish in the family Petromyzontidae. It is closely related to the silver lamprey (''I. unicuspis'') and may represent an ecotype of a single species with ''I. unicuspis''. Desc ...

) *''Ichthyomyzon gagei'' Hubbs & Trautman 1937 (

Southern brook lamprey The southern brook lamprey (''Ichthyomyzon gagei'') is a lamprey found in the Southern United States including Arkansas, Louisiana, Mississippi, Alabama, and Georgia. It is a jawless fish with a sucking mouth on one end of it (like a leech). It ...

) *''Ichthyomyzon greeleyi'' Hubbs & Trautman 1937 (

Mountain brook lamprey The mountain brook lamprey or Allegheny brook lamprey (''Ichthyomyzon greeleyi'') is a lamprey found in parts of the Mississippi river basin, New York, Pennsylvania, Ohio, and in the Cumberland River and Tennessee River The Tennessee Riv ...

) *''Ichthyomyzon unicuspis'' Hubbs & Trautman 1937 (

Silver lamprey The silver lamprey (''Ichthyomyzon unicuspis'') is a lamprey commonly found in the Northern and Central United States, as well as a large part of southern Canada. Its binomial name means "sucking fish" in Greek and "one-pointed" in Latin. The si ...

) *''Caspiomyzon wagneri'' (Kessler 1870) Berg 1906 (

Caspian lamprey The Caspian lamprey, ''Caspiomyzon wagneri'', is a species of lamprey native to the Caspian Sea, and a member of the Petromyzontidae family. '' Eudontomyzon hellenicus'' and '' E. graecus'' (if separate from ''E. hellenicus'') also possibly belon ...

) *''Caspiomyzon graecus'' (Renaud & Economidis 2010) (

Ionian brook lamprey Ionic or Ionian may refer to: Arts and entertainment * Ionic meter, a poetic metre in ancient Greek and Latin poetry * Ionian mode, a musical mode or a diatonic scale Places and peoples * Ionian, of or from Ionia, an ancient region in western A ...

) *''Caspiomyzon hellenicus'' (Vladykov et al. 1982) (

Greek lamprey The Greek lamprey (''Caspiomyzon hellenicus'') (also known as the Greek brook lamprey) is a species of Agnatha, jawless fish in the Northern lampreys, Petromyzontidae family. It is Endemism, endemic to Greece. Its natural habitats are rivers and f ...

) *''Tetrapleurodon geminis'' Álvarez 1964 (

Mexican brook lamprey Mexican may refer to: Mexico and its culture *Being related to, from, or connected to the country of Mexico, in North America ** People *** Mexicans, inhabitants of the country Mexico and their descendants *** Mexica, ancient indigenous peopl ...

) *''Tetrapleurodon spadiceus'' (Bean 1887) (

Mexican lamprey ''Tetrapleurodon'' is a genus of lampreys that are endemic to the Lerma– Chapala basin in west–central Mexico. Both species are threatened. Species There are two recognized species in this genus according to FishBase. They are sometimes inc ...

) *''Entosphenus folletti'' Vladykov & Kott 1976 (

Northern California brook lamprey Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United States * Northern Province, Sri Lanka * Northern Range, a ra ...

) *''Entosphenus lethophagus'' (Hubbs 1971) ( Pit-Klamath brook lamprey) *''Entosphenus macrostomus'' (Beamish 1982) ( Lake lamprey) *''Entosphenus minimus'' (Bond & Kan 1973) (

Miller Lake lamprey The Miller Lake lamprey (''Entosphenus minimus'') is a species of lamprey in the Petromyzontidae family endemic to the United States. Its natural habitat is the Miller Lake drainage in the state of Oregon. This species is of special interest bec ...

) *''Entosphenus similis'' Vladykov & Kott 1979 (

Klamath river lamprey Klamath may refer to: Ethnic groups *Klamath people, a Native American people of California and Oregon **Klamath Tribes, a federally recognized group of tribes in Oregon *Klamath language, spoken by the Klamath people Places in the United States * ...

) *''Entosphenus tridentatus'' (Richardson 1836) (

Pacific lamprey The Pacific lamprey (''Entosphenus tridentatus'') is an anadromous parasitic lamprey from the Pacific Coast of North America and Asia. It is a member of the Petromyzontidae family. The Pacific lamprey is also known as the three-tooth lamprey and ...

) *''Lethenteron alaskense'' Vladykov & Kott 1978 (

Alaskan brook lamprey Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

) *''Lethenteron appendix'' (DeKay 1842) ( American brook lamprey) *''Lethenteron camtschaticum'' (Tilesius 1811) (

) *''Lethenteron kessleri'' (Anikin 1905) (

Siberian brook lamprey Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

) *''Lethenteron ninae'' Naseka, Tuniyev & Renaud 2009 (

Western Transcaucasian lamprey Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...

) *''Lethenteron reissneri'' (Dybowski 1869) (

Far Eastern brook lamprey ''Lethenteron reissneri'', the Far Eastern brook lamprey, is a species of non-parasitic lamprey. It is found in lakes and rivers in China, Japan, Korea, Mongolia, and the Russian Far East. It may be identical to the Siberian brook lamprey, ''Let ...

) *''Lethenteron zanandreai'' (Vladykov 1955) (

Lombardy lamprey ''Lethenteron zanandreai'', the Lombardy lamprey, is a species of lamprey in the Petromyzontidae family. It is found in Croatia, Italy, and Slovenia. Its natural habitats are rivers and freshwater springs. It is threatened by habitat loss ...

) *''Eudontomyzon stankokaramani'' (Karaman 1974) (

Drin brook lamprey ''Eudontomyzon stankokaramani'', the Drin brook lamprey, is a non-predatory, freshwater resident species of lamprey found in the Drin river system of Albania and Kosovo and the basins of Lakes Ohrid Ohrid ( mk, Охрид ) is a city in Nort ...

) *''Eudontomyzon morii'' (Berg 1931) (

Korean lamprey Korean may refer to: People and culture * Koreans, ethnic group originating in the Korean Peninsula * Korean cuisine * Korean culture * Korean language ** Korean alphabet, known as Hangul or Chosŏn'gŭl **Korean dialects and the Jeju languag ...

) *''Eudontomyzon danfordi'' Regan 1911 (

Carpathian brook lamprey ''Eudontomyzon danfordi'', the Carpathian brook lamprey or Danube lamprey, is a species of lamprey in the family Petromyzontidae. It is found in Austria, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Hungary, Moldova, Romania, Serbi ...

) *''Eudontomyzon mariae'' (Berg 1931) (

Ukrainian brook lamprey The Ukrainian brook lamprey (''Eudontomyzon mariae'') is a species of lamprey in the Petromyzontidae family. It is found in brackish and freshwater areas in Austria, Belarus, Bulgaria, the Czech Republic, Georgia, Hungary, Moldova, North Macedoni ...

) *''Eudontomyzon vladykovi'' (Oliva & Zanandrea 1959) (

Vladykov's lamprey ''Eudontomyzon vladykovi'', or Vladykov's lamprey, is a species of lamprey in the family Petromyzontidae. It is found in Austria, Germany, The Czech Republic, Bulgaria, Romania, Serbia, and Montenegro ) , image_map = Europe-Mo ...

) *''Lampetra aepyptera'' (Abbott 1860) ( Least brook lamprey) *''Lampetra alavariensis'' Mateus et al. 2013 (

Portuguese lamprey Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portu ...

) *''Lampetra auremensis'' Mateus et al. 2013 ( Qurem lamprey) *''Lampetra ayresi'' (Günther 1870) (

Western river lamprey ''Lampetra ayresii'' is a species of lamprey in the family Petromyzontidae. It is also called the river lamprey or western river lamprey. It is found in the eastern Pacific, specifically from Tee Harbor, Juneau in Alaska to the Sacramento River, ...

) *''Lampetra fluviatilis'' (Linnaeus 1758) ( European river lamprey) *''Lampetra hubbsi'' (Vladykov & Kott 1976) (

Kern brook lamprey The Kern brook lamprey (''Lampetra hubbsi'') is a species of lamprey in the Petromyzontidae family endemic to the United States. It is found on the east side of San Joaquin Valley, in lower Merced, Kaweah, Kings, and San Joaquin rivers in Califo ...

) *''Lampetra lanceolata'' Kux & Steiner 1972 (

Turkish brook lamprey Turkish may refer to: *a Turkic language spoken by the Turks * of or about Turkey ** Turkish language *** Turkish alphabet ** Turkish people, a Turkic ethnic group and nation *** Turkish citizen, a citizen of Turkey *** Turkish communities and mi ...

) *''Lampetra lusitanica'' Mateus et al. 2013 (

lusitanic lamprey Lusitanic is a term used to refer to people who share the linguistic and cultural traditions of the Portuguese-speaking nations, territories, and populations, including Portugal, Brazil, Madeira, Macau, Timor-Leste, Azores, Angola, Mozambique, Ca ...

) *''Lampetra pacifica'' Vladykov 1973 (

Pacific brook lamprey The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

) *''Lampetra planeri'' (Bloch 1784) ( European brook lamprey) *''Lampetra richardsoni'' Vladykov & Follett 1965 (

Western brook lamprey The Western brook lamprey (''Lampetra richardsoni'') is a small (<18 cm), widely distributed, non-parasitic species of

jawless fish ...

) *''Entosphenus macrostomus'' Dr. Dick Beamish 1980 (

Cowichan lake lamprey Cowichan may refer either to: *the Cowichan Tribes First Nation located in and around Duncan, British Columbia *the Cowichan Valley, a region on Vancouver Island centred on Duncan, British Columbia, which contains: ** Cowichan Valley Regional Dist ...

)

Lamprey and chordate synapomorphies

Synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

are certain characteristics that are shared over evolutionary history. Organisms possessing a

dorsal hollow nerve cord The dorsal nerve cord is a unique feature to chordates, and it is mainly found in the Vertebrata chordate subphylum. The dorsal nerve cord is only one embryonic feature unique to all chordates, among the other four chordate features-- a notochord, ...

, pharyngeal slits, pituitary gland/ endostyle, and a post anal tail during the process of their development are considered to be Chordates. Lampreys contain these characteristics that define them as chordates. Lamprey anatomy is very different based on what stage of development they are in. The

is derived from the

mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical E ...

and is one of the defining characteristics of a chordate. The notochord provides signaling and mechanical cues to help the organism when swimming. The

dorsal nerve cord The dorsal nerve cord is a unique feature to chordates, and it is mainly found in the Vertebrata chordate subphylum. The dorsal nerve cord is only one embryonic feature unique to all chordates, among the other four chordate features-- a notochord, ...

is another characteristic of lampreys that defines them as chordates. During development this part of the ectoderm rolls creating a hollow tube. This is often why it is referred to as the dorsal "hollow" nerve cord. The third Chordate feature, which are the pharyngeal slits, are openings found between the pharynx or throat. Pharyngeal slits are filter feeding organs that help the movement of water through the mouth and out of these slits when feeing. During the lamprey's larval stage they rely on filter feeding as a mechanism for obtaining their food. Once lampreys reach their adult phase they become parasitic on other fish, and these gill slits become very important in aiding in the respiration of the organism. The final Chordate synapomorphy is the post anal tail which is a muscular tail that extends behind the anus. Oftentimes adult amphioxus and lamprey larvae are compared by anatomists due to their similarities. Similarities between adult amphioxus and lamprey larvae include a pharynx with pharyngeal slits, a notochord, a dorsal hollow nerve cord and a series of somites that extend anterior to the otic vesicle.

Fossil record

Lamprey fossils are rare because

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

fossilizes less readily than bone. The first fossil lampreys were originally found in Early

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

limestones, marine sediments in North America: '' Mayomyzon pieckoensis'' and ''

Hardistiella montanensis ''Hardistiella montanensis'' is a fossil fish and extinct species of lamprey found, dating from the Carboniferous period, at the Bear Gulch Limestone site in the U.S. state of Montana Montana () is a state in the Mountain West divisi ...

'', from the

Mississippian Mississippian may refer to: * Mississippian (geology), a subperiod of the Carboniferous period in the geologic timescale, roughly 360 to 325 million years ago *Mississippian culture, a culture of Native American mound-builders from 900 to 1500 AD ...

Mazon Creek The Mazon Creek fossil beds are a conservation ' found near Morris, in Grundy County, Illinois. The fossils are preserved in ironstone concretions, formed approximately in the mid-Pennsylvanian epoch of the Carboniferous period. These concre ...

'' lagerstätte'' and the Bear Gulch Limestone sequence. None of the fossil lampreys found to date have been longer than , and all the Paleozoic forms have been found in marine deposits. In the 22 June 2006 issue of '' Nature'', Mee-mann Chang and colleagues reported on a fossil lamprey from the Yixian Formation of Inner Mongolia. The new species, morphologically similar to Carboniferous and other forms, was given the name ''

Mesomyzon mengae ''Mesomyzon mengae'' is an extinct lamprey from freshwater strata of the Early Cretaceous-aged Yixian Formation, in China. So far, ''M. mengae'' is the only lamprey known from post-Paleozoic fossils. The animal's exquisitely preserved fossils s ...

'' ("

Meng Qingwen Meng may refer to: * Meng (surname) (孟), a Chinese surname * Master of Engineering (MEng or M.Eng.), an academic or professional master's degree in the field of engineering * , "M with hook", letter used in the International Phonetic Alphabet * ...

's Mesozoic lamprey"). The exceedingly well-preserved fossil showed a well-developed sucking oral disk, a relatively long branchial apparatus showing a 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 fresh water. Months later, a fossil lamprey even older than the Mazon Creek genera was reported from

Witteberg Group The Witteberg or Witteberge is a South African mountain range just off the south-west corner of Lesotho. The range, which rises to 2408 metres, stretches for about 60 km from Lundin's Neck in the east to Lady Grey in the west. The range ...

rocks near Grahamstown, in the

Eastern Cape The Eastern Cape is one of the provinces of South Africa. Its capital is Bhisho, but its two largest cities are East London and Gqeberha. The second largest province in the country (at 168,966 km2) after Northern Cape, it was formed in ...

of South Africa. Dating back 360 Million years, this species, ''

Priscomyzon riniensis ''Priscomyzon riniensis'' is an extinct lamprey that lived some 360 million years ago during the Famennian ( Late Devonian) in a marine or estuarine environment in South Africa. This small agnathan is anatomically similar to the Mazon Creek l ...

'', is very similar to lampreys found today. 310 to 360 million years old fossils of P. riniensis hatchlings indicate that the ammocoete larva is a more recent evolutionary trait among the lampreys. The hatchlings, measuring 15mm in length, still had their yolk sac, but were found in marine sediments and already had large eyes and a toothed suction disk.

Use in research

Olfactory-locomotor circuitry in lampreys 1

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 followed on from extensive work on the lamprey started by Carl Rovainen in the 1960s that 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 by Rovainen and his student James Buchanan, the cells that formed the neural circuits within the spinal cord capable of generating the rhythmic motor patterns that underlie swimming were examined. Note that there are still missing details in the network scheme despite claims by Grillner that the network is characterised (Parker 2006, 2010). Spinal cord circuits are controlled by specific locomotor areas in the brainstem and midbrain, and these areas are in turn 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. Lampreys are used as a

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

in biomedical research, where their large reticulospinal axons are used to investigate

synaptic transmission Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron), ...

. The axons of lamprey are particularly large and allow for microinjection of substances for experimental manipulation. They are also capable of full functional recovery after complete spinal cord transection. Another trait is the ability to delete several genes from their

somatic cell A somatic cell (from Ancient Greek σῶμα ''sôma'', meaning "body"), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compo ...

lineages, about 20% of their DNA, which are vital during development of the embryo, but which in humans can cause problems such as cancer later in life, after they have served their purpose. How the genes destined for deletion are targeted is not yet known.

In human culture

As food

Lampreys have long been used as food for humans. They were highly appreciated by the ancient Romans. During the Middle Ages they were widely eaten by the upper classes throughout Europe, especially during

Lent Lent ( la, Quadragesima, 'Fortieth') is a solemn religious observance in the liturgical calendar commemorating the 40 days Jesus spent fasting in the desert and enduring temptation by Satan, according to the Gospels of Matthew, Mark and Luke ...

, when eating meat was prohibited, due to their meaty taste and texture. King

Henry I of England Henry I (c. 1068 – 1 December 1135), also known as Henry Beauclerc, was King of England from 1100 to his death in 1135. He was the fourth son of William the Conqueror and was educated in Latin and the liberal arts. On William's death in ...

is claimed to have been so fond of lampreys that he often ate them late into life and poor health against the advice of his physician concerning their richness, and is said to have died from eating "a

surfeit Surfeit is a human gene cluster that consists of a group of very tightly linked genes on chromosome 9 that do not share sequence similarity. Genes in this cluster are numbered 1 through 6: SURF1, SURF2, SURF3, SURF4, SURF5, and SURF6 Surfeit ...

of lampreys". Whether or not his lamprey indulgence actually caused his death is unclear. The pie made for the coronation of

Elizabeth II of the United Kingdom Elizabeth II (Elizabeth Alexandra Mary; 21 April 1926 – 8 September 2022) was Queen of the United Kingdom and other Commonwealth realms from 6 February 1952 until her death in 2022. She was queen regnant of 32 sovereign states during h ...

on 4 March 1953 was a lamprey pie. However, after many decades, the city of Gloucester had to use Great Lakes lampreys for her Diamond Jubilee in 2012 because few lampreys could be found in the River Severn. In southwestern Europe ( Portugal, Spain, and France), Finland and in

Latvia Latvia ( or ; lv, Latvija ; ltg, Latveja; liv, Leţmō), officially the Republic of Latvia ( lv, Latvijas Republika, links=no, ltg, Latvejas Republika, links=no, liv, Leţmō Vabāmō, links=no), is a country in the Baltic region of ...

(where lamprey is routinely sold in supermarkets), lampreys are a highly prized delicacy. In Finland (county of Nakkila), and Latvia (

Carnikava Municipality Carnikava Municipality ( lv, Carnikavas novads) is a former municipality in Vidzeme, Latvia. The municipality was formed in 2006 by reorganization of Carnikava Parish of the Riga District, with the administrative centre being Carnikava. The popul ...

), the river lamprey is the local symbol, found on their coats of arms. In 2015 the lamprey from Carnikava was included in the

Protected designation of origin The protected designation of origin (PDO) is a type of geographical indication of the European Union and the United Kingdom aimed at preserving the designations of origin of food-related products. The designation was created in 1992 and its main ...

list by the European Commission. Sea lamprey is the most sought-after 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). "Arroz de lampreia" or lamprey rice is one of the most important dishes in

Portuguese cuisine The oldest known book on Portuguese cuisine, entitled ''Livro de Cozinha da Infanta D. Maria de Portugal'', from the 16th century, describes many popular dishes of meat, fish, poultry and others. ''Culinária Portuguesa'', by António-Maria De O ...

Lampreys are also consumed in

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

, Russia,

Lithuania Lithuania (; lt, Lietuva ), officially the Republic of Lithuania ( lt, Lietuvos Respublika, links=no ), is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea. Lithuania ...

, Estonia,

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, and South Korea. In Finland, they are commonly eaten grilled or smoked, but also pickled, or in vinegar. The mucus and

serum Serum may refer to: *Serum (blood), plasma from which the clotting proteins have been removed **Antiserum, blood serum with specific antibodies for passive immunity * Serous fluid, any clear bodily fluid * Truth serum, a drug that is likely to mak ...

of several lamprey species, including the

(''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. In Britain, lampreys are commonly used as bait, normally as dead bait. Northern pike, perch, and

chub Chub is a common fish name. It pertains to any one of a number of ray-finned fish in several families and genera. In the UK, the term ''chub'' usually refers to the species ''Squalius cephalus''. In addition, see sea chub. In family Cyprinidae ...

all can be caught on lampreys. Frozen lampreys can be bought from most bait and

tackle Tackle may refer to: * In football: ** Tackle (football move), a play in various forms of football ** Tackle (gridiron football position), a position in American football and Canadian football ** Dump tackle, a forceful move in rugby of picking ...

shops.

As pests

Sea lampreys have become a major

pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious disease, an illness resulting from an infection ** ...

in the North American Great Lakes. It is generally believed that they gained access to the lakes via canals during the early 20th century, but this theory is controversial. They are considered an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

, 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, and controlled 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, these 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. Finally, pheromones critical to lamprey migratory behaviour have been isolated, their chemical structures determined, and their impact on lamprey behaviour studied, in the laboratory and in the wild, and active efforts are underway to chemically source and to address regulatory considerations that might allow this strategy to proceed. 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 Fisheries and Oceans Canada (DFO; french: Pêches et Océans Canada, MPO), is a department of the Government of Canada that is responsible for developing and implementing policies and programs in support of Canada's economic, ecological and sci ...

, and is coordinated by the Great Lakes Fishery Commission. Lake Champlain, bordered by

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

, 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 New York State Department of Environmental Conservation (informally referred to as NYSDEC, DEC, EnCon or NYSENCON) is a department of New York state government. The department guides and regulates the conservation, improvement, and protection ...

, 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 folklore

In folklore, lampreys are called "nine-eyed eels". The name is derived from the seven external gill slits that, along with one nostril and one eye, line each side of a lamprey's head section. Likewise, the German word for lamprey is ''Neunauge'', which means "nine-eye", and in Japanese they are called ''yatsume-unagi'' (八つ目鰻, "eight-eyed eels"), which excludes the nostril from the count. In British folklore, the monster known as the Lambton Worm may have been based on a lamprey, since it is described as an eel-like creature with nine eyes.

In literature

Vedius Pollio Publius Vedius Pollio (died 15 BC) was a Roman of equestrian rank, and a friend of the Roman emperor Augustus, who appointed him to a position of authority in the province of Asia. In later life, he became infamous for his luxurious tastes and crue ...

kept a pool of lampreys into which

slaves Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...

who incurred his displeasure would be thrown as food. On one occasion, Vedius was punished by Augustus for attempting to do so in his presence: This incident was incorporated into the plot of the 2003 novel ''Pompeii'' by Robert Harris in the incident of Ampliatus feeding a slave to his lampreys. Lucius Licinius Crassus was mocked by Gnaeus Domitius Ahenobarbus (cos. 54 BC) for weeping over the death of his pet lamprey: This story is also found in Aelian (Various Histories VII, 4) and Macrobius (Saturnalia III.15.3). It is included by Hugo von Hofmannsthal in the Chandos Letter: In George R. R. Martin's novel series, ''

A Song of Ice and Fire ''A Song of Ice and Fire'' is a series of epic fantasy novels by the American novelist and screenwriter George R. R. Martin. He began the first volume of the series, ''A Game of Thrones'', in 1991, and it was published in 1996. Martin, who init ...

'', Lord Wyman Manderly is mockingly called "Lord Lamprey" by his enemies in reference to his rumored affinity to lamprey pie and his striking obesity. Kurt Vonnegut, in his late short story " The Big Space Fuck", posits a future America so heavily polluted – "Everything had turned to shit and beer cans", in his words – that the Great Lakes have been infested with a species of massive, man-eating ambulatory lampreys.

In television

In season 3, episode 5 of “The Borgias”, whilst out on a hunting trip, Cesare Borgia’s mercenary, Micheletto, kills the King of Naples by pushing him into a pool filled with lampreys that King Firante had built during his reign of Naples.

References

External links

* * *
Long-accepted theory of vertebrate origin upended by fossilized lamprey larvae
* A Tree of Life diagram showing the relation of Lampreys to other organisms. {{Authority control . Hematophages Parasitic vertebrates Devonian fish Extant Late Devonian first appearances Fish described in 1940