lamprey

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,{{cite journal |last1=Silva |first1=S. |last2=Araújo |first2=M. J. |last3=Bao |first3=M. |last4=Mucientes |first4=G. |last5=Cobo |first5=F. |year=2014 |title=The haematophagous feeding stage of anadromous populations of sea lamprey Petromyzon marinus: low host selectivity and wide range of habitats |journal=Hydrobiologia |volume=734 |issue=1 |pages=187–199 |doi=10.1007/s10750-014-1879-4 |hdl=10261/98126 |s2cid=17796757 |hdl-access=free}} as evidenced by their lack of reproductive isolation 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 river habitat loss, overfishing, and pollution.{{Cite journal |last1=Almeida |first1=Pedro R. |last2=Arakawa |first2=Hiroaki |last3=Aronsuu |first3=Kimmo |last4=Baker |first4=Cindy |last5=Blair |first5=Stevie-Rae |last6=Beaulaton |first6=Laurent |last7=Belo |first7=Ana F. |last8=Kitson |first8=Jane |last9=Kucheryavyy |first9=Aleksandr |last10=Kynard |first10=Boyd |last11=Lucas |first11=Martyn C. |last12=Moser |first12=Mary |last13=Potaka |first13=Ben |last14=Romakkaniemi |first14=Atso |last15=Staponkus |first15=Robertas |date=2021-12-01 |title=Lamprey fisheries: History, trends and management |url= |journal=Journal of Great Lakes Research |series=Supplement on Sea Lamprey International Symposium III (SLIS III) |language=en |volume=47 |pages=S159–S185 |doi=10.1016/j.jglr.2021.06.006 |bibcode=2021JGLR...47S.159A |issn=0380-1330|hdl=10174/31871 |s2cid=237752229 |hdl-access=free }} In Britain, at the time of the 11th-century Norman Conquest of England, lampreys were found as far upstream in the River Thames as Petersham.{{cite web |title=Parishes: Petersham |url=https://www.british-history.ac.uk/vch/surrey/vol3/pp525-532 |website=British History Online |access-date=26 July 2023}} The reduction of pollution in the Thames and River Wear has led to recent sightings in London and Chester-le-Street.{{cite news |url=http://news.bbc.co.uk/1/hi/england/london/8127483.stm |title=Prehistoric bloodsucker in Thames |date=1 July 2009 |work=BBC News |access-date=27 September 2012}}{{cite news |url=http://www.thenorthernecho.co.uk/news/4459745.Giant_blood_sucker_found_in_North_East_river/ |title=Giant blood sucker found in River Wear |newspaper=The Northern Echo |date=25 June 2009}}

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 programs to control lampreys are undergoing modifications due to concerns of drinking-water quality in some areas.{{cite web |last1=Lehman |first1=Don |title=Chemical concerns may halt Lake Champlain treatments |url=http://poststar.com/news/local/chemical-concerns-may-halt-lake-champlain-treatments/article_4d174308-103c-53a2-9570-e0305c4f6e0f.html |website=poststar.com |date=15 August 2016 |publisher=The Post Star}}

File:Lamprey anatomy.png

Adults superficially resemble eels in that they have scaleless, elongated bodies, with the largest species, the sea lamprey having a maximum body length around {{Convert|1.2|m|ft|abbr=on}}. Lacking paired fins,{{Cite journal |last1=Tulenko |first1=Frank J. |last2=McCauley |first2=David W. |last3=MacKenzie |first3=Ethan L. |last4=Mazan |first4=Sylvie |last5=Kuratani |first5=Shigeru |last6=Sugahara |first6=Fumiaki |last7=Kusakabe |first7=Rie |last8=Burke |first8=Ann C. |date=2013-07-16 |title=Body wall development in lamprey and a new perspective on the origin of vertebrate paired fins |journal=Proceedings of the National Academy of Sciences |language=en |volume=110 |issue=29 |pages=11899–11904 |doi=10.1073/pnas.1304210110 |doi-access=free |issn=0027-8424 |pmc=3718130 |pmid=23818600|bibcode=2013PNAS..11011899T }} adult lampreys have one nostril atop the head{{Cite journal |last1=Aurangzeb |first1=Zeenat |last2=Daghfous |first2=Gheylen |last3=Innes |first3=Liessell |last4=Dubuc |first4=Réjean |last5=Zielinski |first5=Barbara |date=December 2021 |title=Current understanding of lamprey chemosensory systems |journal=Journal of Great Lakes Research |language=en |volume=47 |pages=S650–S659 |doi=10.1016/j.jglr.2021.04.020|doi-access=free |bibcode=2021JGLR...47S.650A }} and seven gill pores on each side of the head.

The brain of the lamprey is divided into the telencephalon, diencephalon, midbrain, cerebellum, and medulla.{{Cite journal |last1=XU |first1=Yang |last2=ZHU |first2=Si-Wei |last3=LI |first3=Qing-Wei |date=2016-09-18 |title=Lamprey: a model for vertebrate evolutionary research |journal=Zoological Research |volume=37 |issue=5 |pages=263–269 |doi=10.13918/j.issn.2095-8137.2016.5.263 |issn=2095-8137 |pmc=5071338 |pmid=27686784}}

Lampreys have been described as the only living vertebrates to have four eyes,{{Cite news |date=2018-04-05 |title=Three-eyed lizards are not uncommon. Four-eyed ones are a novelty |newspaper=The Economist |url=https://www.economist.com/news/science-and-technology/21739951-they-had-languished-museum-drawer-1870s-three-eyed-lizards-are-not |access-date=2018-04-10}} having a single pair of regular eyes, as well as two parietal eyes, a pineal and parapineal one (the exception is members of Mordacia).{{cite book |last=Nieuwenhuys |first=R |title=The central nervous system of vertebrates |publisher=Springer |year=1998 |isbn=978-3-540-56013-5 |location=Berlin New York |page=454}} The eyes of juvenile lampreys are poorly developed eyespot-like structures that are covered in translucent skin, while the eyes of adult lampreys are well developed.{{Cite journal |last1=Suzuki |first1=Daichi G. |last2=Grillner |first2=Sten |date=August 2018 |title=The stepwise development of the lamprey visual system and its evolutionary implications |url=|journal=Biological Reviews |language=en |volume=93 |issue=3 |pages=1461–1477 |doi=10.1111/brv.12403 |pmid=29488315 |issn=1464-7931}} Accommodation is done by flattening the cornea, which pushes the lens towards the retina.{{Cite book |last=Khanna |first=D. R. |url=https://books.google.com/books?id=E0Oy1i-8vfsC&q=lampreys%2520flattening%2520cornea%2520lens&pg=PA153 |title=Biology Of Fishes |date=2004 |publisher=Discovery Publishing House |isbn=978-81-7141-908-1 |language=en}} The eye of family Mordaciidae possess just a single type of photoreceptor (rod-like), the family Petromyzontidae possess two photoreceptor types (a cone-like and a rod-like), and the family Geotriidae possesses five types of photoreceptors.{{Cite journal |last1=Collin |first1=H. Barry |last2=Ratcliffe |first2=Julian |last3=Collin |first3=Shaun P. |date=2021 |title=The Functional Anatomy of the Cornea and Anterior Chamber in Lampreys: Insights From the Pouched Lamprey, Geotria australis (Geotriidae, Agnatha) |journal=Frontiers in Neuroanatomy |volume=15 |pages=786729 |doi=10.3389/fnana.2021.786729 |doi-access=free |pmc=8733561 |pmid=35002638}}

The buccal cavity, anterior to the gonads, 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, or tear at the flesh of their prey to yield blood.{{Cite book |last=V. Kardong |first=Kenneth |title=Vertebrates: Comparative Anatomy, Function, Evolution. |publisher=McGraw Hill |page=88}}

The last common ancestor of lampreys appears to have been specialized to feed on the blood and body fluids of other fish after metamorphosis.{{cite journal |last1=Potter |first1=Ian C. |last2=Gill |first2=Howard S. |year=2003 |title=Adaptive Radiation of Lampreys |journal=Journal of Great Lakes Research |volume=29 |pages=95–112 |bibcode=2003JGLR...29...95P |doi=10.1016/S0380-1330(03)70480-8}} 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.{{cite journal |last1=Khidir |first1=K. Teresa |year=2003 |title=Oral fimbriae and papillae in parasitic lampreys (Petromyzontiformes) |journal=Environmental Biology of Fishes |volume=66 |issue=3 |pages=271–278 |doi=10.1023/A:1023961910547 |bibcode=2003EnvBF..66..271T |s2cid=10254661}} The teeth on their oral disc are primarily used to help the animal attach itself to its prey.{{Cite book |last1=Rohde |first1=Klaus |url=https://books.google.com/books?id=ktTOf3l66QQC&pg=PT228 |title=Marine Parasitology |date=2005-09-13 |publisher=Csiro |isbn=978-0-643-09927-2}} Made of keratin and other proteins, lamprey teeth have a hollow core to give room for replacement teeth growing under the old ones.{{Cite book |last1=Ehrlich |first1=Hermann |url=https://books.google.com/books?id=QNSlBQAAQBAJ&q=lampreys+hollow+core+replacement+teeth&pg=PA7 |title=Biological Materials of Marine Origin: Vertebrates |date=2014-12-01 |publisher=Springer |isbn=978-94-007-5730-1}} Some of the original blood-feeding forms have evolved into species that feed on both blood and flesh, and some 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.{{Cite book |last1=Warren |first1=Melvin L. Jr. |url=https://books.google.com/books?id=iUrcAwAAQBAJ&pg=PA121 |title=Freshwater Fishes of North America: Volume 1: Petromyzontidae to Catostomidae |last2=Burr |first2=Brooks M. |date=2014-07-10 |publisher=JHU Press |isbn=978-1-4214-1201-6}} 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.{{Cite journal |last1=Renaud |first1=C. B. |last2=Gill |first2=H. S. |last3=Potter |first3=I. C. |year=2009 |title=Relationships between the diets and characteristics of the dentition, buccal glands and velar tentacles of the adults of the parasitic species of lamprey |url=https://www.researchgate.net/publication/227745051 |journal=Journal of Zoology |volume=278 |issue=3 |pages=231–242 |doi=10.1111/j.1469-7998.2009.00571.x}} A study of the stomach content of some lampreys has shown the remains of intestines, fins and vertebrae from their prey.{{cite news |title=What we know about lampreys – the arctic bloodsuckers that swarm Alaska rivers by the millions |url=https://www.adn.com/alaska-news/science/2016/07/07/what-we-know-about-lampreys-the-arctic-bloodsuckers-that-swarm-alaska-rivers-by-the-millions/}}

Close to the jaws of juvenile lampreys, a muscular flap-like structure called the velum is present, which serves to generate a water current towards the mouth opening, which enables feeding and respiration.{{Cite journal |last1=Yokoyama |first1=Hiromasa |last2=Yoshimura |first2=Miho |last3=Suzuki |first3=Daichi G. |last4=Higashiyama |first4=Hiroki |last5=Wada |first5=Hiroshi |date=January 2021 |title=Development of the lamprey velum and implications for the evolution of the vertebrate jaw |journal=Developmental Dynamics |language=en |volume=250 |issue=1 |pages=88–98 |doi=10.1002/dvdy.243 |issn=1058-8388|doi-access=free |pmid=32865292 }}

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). 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){{cite web |last=Haaramo |first=Mikko |date=11 March 2008 |title=Mikko's Phylogeny Archive |url=http://www.helsinki.fi/~mhaaramo/metazoa/deuterostoma/chordata/vertebrata.html#Chondrichthyes |access-date=26 January 2009}} but DNA evidence suggests that they are in fact the sister taxon of lampreys.{{Cite journal |last1=Heimberg |first1=A. M. |last2=Cowper-Sal-Lari |first2=R. |last3=Sémon |first3=M. |last4=Donoghue |first4=P. C. |last5=Peterson |first5=K. J. |year=2010 |title=MicroRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=107 |issue=45 |pages=19379–83 |doi=10.1073/pnas.1010350107 |pmc=2984222 |pmid=20959416 |doi-access=free}}

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, a photosensitive organ regulating melatonin production by capturing light signals through the photoreceptor cell 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.{{Cite journal |last1=Mano |first1=Hiroaki |last2=Fukada |first2=Yoshitaka |date=2007 |title=A Median Third Eye: Pineal Gland Retraces Evolution of Vertebrate Photoreceptive Organs† |journal=Photochemistry and Photobiology |language=en |volume=83 |issue=1 |pages=11–18 |doi=10.1562/2006-02-24-IR-813 |pmid=16771606 |issn=1751-1097 |doi-access=free}}

One of the key physical components to the lamprey are the intestines, which are located ventral to the notochord. 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.{{Cite journal |last1=Barany |first1=A. |last2=Shaughnessy |first2=C. A. |last3=Fuentes |first3=J. |last4=Mancera |first4=J. M. |last5=McCormick |first5=S. D. |date=2020-02-01 |title=Osmoregulatory role of the intestine in the sea lamprey (Petromyzon marinus) |journal=American Journal of Physiology. Regulatory, Integrative and Comparative Physiology |volume=318 |issue=2 |pages=R410–R417 |doi=10.1152/ajpregu.00033.2019 |issn=1522-1490 |pmid=31747320 |doi-access=free}}File:Lamprey skeleton lateral view.jpgStudies 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.{{cite news |url=https://www.latimes.com/science/sciencenow/la-sci-sn-jellyfish-lamprey-swimming-pressure-bioinspired-20151103-story.html |title=In swimming, jellyfish and lampreys really pull their weight |work=Los Angeles Times}}

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. The mouth and suction capabilities of the lamprey not only allow it to cling to a fish as a parasite,{{cite web |date=2017-07-06 |title=A Leap in Lampreys: Unlovely Fish Make Welcome Comback |url=https://eelriver.org/2017/07/06/a-leap-in-lampreys-unlovely-fish-make-welcome-comback/ |access-date=2021-03-27 |website=Friends of the Eel River |language=en-US}} but provide it with limited climbing ability so that it can travel upstream and up ramps or rocks to breed.{{Cite journal |last=Reinhardt |first=Ulrich |date=November 2008 |title=Lamprey climbing behavior |url=https://www.researchgate.net/publication/233600184 |journal=Canadian Journal of Zoology |volume=86 |doi=10.1139/Z08-112 |via=ResearchGate}} 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.

File:スナヤツメ（南方種）.jpg]]

Many lampreys exhibit countershading, a form of camouflage.{{Cite journal |last1=Gabbott |first1=Sarah E. |last2=Donoghue |first2=Philip C. J. |last3=Sansom |first3=Robert S. |last4=Vinther |first4=Jakob |last5=Dolocan |first5=Andrei |last6=Purnell |first6=Mark A. |date=2016-08-17 |title=Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=283 |issue=1836 |pages=20161151 |doi=10.1098/rspb.2016.1151 |issn=0962-8452 |pmc=5013770 |pmid=27488650}} 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.{{Cite journal |last1=Todd |first1=P. R. |last2=Wilson |first2=R. D. |date=1983-03-01 |title=Epidermal pigmentation and liver coloration in the southern hemisphere lamprey, Geotria austral is Gray |journal=New Zealand Journal of Marine and Freshwater Research |volume=17 |issue=1 |pages=21–26 |doi=10.1080/00288330.1983.9515983 |issn=0028-8330 |doi-access=free|bibcode=1983NZJMF..17...21T }} 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.

Northern lampreys (Petromyzontidae) have the highest number of chromosomes (164–174) among vertebrates.{{FishBase family|family=Petromyzontidae|month=February|year=2017}} 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 gene segments, lamprey leukocytes express surface variable lymphocyte receptors (VLRs).{{cite journal |last1=Nagawa |first1=Fumikiyo |last2=Kishishita |first2=Natsuko |last3=Shimizu |first3=Kazumichi |last4=Hirose |first4=Satoshi |last5=Miyoshi |first5=Masato |last6=Nezu |first6=Junnya |last7=Nishimura |first7=Toshinobu |last8=Nishizumi |first8=Hirofumi |last9=Takahashi |first9=Yoshimasa |last10=Hashimoto |first10=Shu-ichi |last11=Takeuchi |first11=Masaki |last12=Miyajima |first12=Atsushi |display-authors=9 |year=2007 |title=Antigen-receptor genes of the agnathan lamprey are assembled by a process involving copy choice |journal=Nature Immunology |volume=8 |issue=2 |pages=206–13 |doi=10.1038/ni1419 |pmid=17187071 |s2cid=23222989}} This convergently evolved characteristic allows them to have lymphocytes that work as the T cells and B cells present in higher vertebrates immune system.{{Cite journal |last1=Pancer |first1=Z. |last2=Amemiya |first2=C. T. |last3=Ehrhardt |first3=G. T. R. A. |last4=Ceitlin |first4=J. |last5=Gartland |first5=G. |last6=Cooper |first6=M. D. |year=2004 |title=Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey |url=https://deepblue.lib.umich.edu/bitstream/2027.42/62870/1/nature02740.pdf |journal=Nature |volume=430 |issue=6996 |pages=174–180 |bibcode=2004Natur.430..174P |doi=10.1038/nature02740 |pmid=15241406 |s2cid=876413 |hdl-access=free |hdl=2027.42/62870}} 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.{{cite journal |last1=Macey |first1=D. J. |last2=Cake |first2=M. H. |last3=Potter |first3=I. C. |year=1988 |title=Exceptional iron concentrations in larval lampreys (Geotria australis) and the activities of superoxide radical detoxifying enzymes |journal=Biochemical Journal |volume=252 |issue=1 |pages=167–172 |doi=10.1042/bj2520167 |pmc=1149120 |pmid=3421899}}

File:Lamprey larva labelled.png

The adults spawn in nests of sand, gravel and pebbles in clear streams. After hatching from the eggs, young larvae—called ammocoetes{{cite web|url=https://www.dictionary.com/browse/ammocoete |title=Ammocoete Definition & Meaning |publisher=Dictionary.com |date= |accessdate=2022-08-06}}{{cite web | url=https://www.britannica.com/animal/chordate/Internal-features | title=Chordate – Internal features | Britannica }}—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 feeders, collecting detritus, algae, and microorganisms.{{Cite thesis |last=Evans |first=Thomas M. |title=Assessing Food and Nutritional Resources of Native and Invasive Lamprey Larvae Using Natural Abundance Isotopes |publisher=Ohio State University |url=http://rave.ohiolink.edu/etdc/view?acc_num=osu1343410278 |year=2012}} The eyes of the larvae are underdeveloped, but are capable of discriminating changes in illuminance.{{Cite book |url=https://books.google.com/books?id=yTT5DAAAQBAJ&pg=PA204 |page=204 |title=Jawless Fishes of the World: Volume 2 |isbn=978-1-4438-9240-7 |last1=Orlov |first1=Alexei |last2=Beamish |first2=Richard |date=2016-04-26|publisher=Cambridge Scholars }} Ammocoetes can grow from {{convert|3|–|4|in|cm|0|abbr=off}} to about {{convert|8|in|cm}}.{{Cite book|url=https://books.google.com/books?id=Vqs8AAAAIAAJ&pg=PA41 |title=The Chordates |isbn=978-0-521-23658-4 |last1=McNeill Alexander |first1=R. |date=1981-08-06|publisher=CUP Archive }}{{Cite book |last=Jamesk |first=Alex |date=September 2008 |title=Ecology of the New Zealand Lamprey (Geotria australis): A Literature Review |url=https://www.doc.govt.nz/documents/conservation/land-and-freshwater/Freshwater/ecology-of-nz-lamprey.pdf |series=Te Tai Hauauru - Whanganui Conservancy Fauna Series 2008/1 |location=Wanganui, New Zealand |publisher=Department of Conservatiion, Wanganui Conservancy |isbn=978-0-478-14542-7 |issn=1179-1659}} Many species change color during a diurnal cycle, becoming dark at day and pale at night.{{Cite journal |date=July 1935 |title=The Photoreceptors of Lampreys: II. The Functions of the Pineal Complex |url=http://jeb.biologists.org/content/12/3/254 |journal=Journal of Experimental Biology |volume=12 |issue=3 |pages=254–270 |last1=Young |first1=J. Z. |doi=10.1242/jeb.12.3.254 |doi-access=free}} The skin also has photoreceptors, light sensitive cells, most of them concentrated in the tail, which helps them to stay buried.{{Cite book |url=https://books.google.com/books?id=uiv4CAAAQBAJ&pg=PA299 |page=229 |title=Animal Diversity |isbn=978-94-011-6035-3 |last1=Kershaw |first1=Diana R. |date=2012-12-06|publisher=Springer }} Lampreys may spend up to eight years as ammocoetes,{{Cite book |url=https://books.google.com/books?id=ugGXBQAAQBAJ&pg=PA109 |page=109 |title=Lampreys: Biology, Conservation and Control |isbn=978-94-017-9306-3 |last1=Docker |first1=Margaret F. |date=2014-11-24|publisher=Springer }} while species such as the Arctic lamprey may only spend one to two years as larvae,{{Citation |title=Lampreys |url=https://www.adfg.alaska.gov/static/education/wns/lampreys.pdf |publisher=Alaska Department of Fish and Game}} prior to undergoing a metamorphosis which generally lasts 3–4 months, but can vary between species.{{Cite book |url=https://books.google.com/books?id=ugGXBQAAQBAJ&pg=PA118 |title=Lampreys: Biology, Conservation and Control |isbn=978-94-017-9306-3 |last1=Docker |first1=Margaret F. |date=2014-11-24|publisher=Springer }} While metamorphosing, they do not eat.{{cite journal |last1=Silva |first1=S. |last2=Servia |first2=M. J. |last3=Vieira-Lanero |first3=R. |last4=Cobo |first4=F. |year=2013 |title=Downstream migration and hematophagous feeding of newly metamorphosed sea lampreys (Petromyzon marinus Linnaeus, 1758) |journal=Hydrobiologia |volume=700 |pages=277–286 |doi=10.1007/s10750-012-1237-3 |s2cid=16752713}}

File:Oeufs002b,57.png from Nouveau Larousse Illustré (1897-1904)}}|alt=A lamprey egg, illustration by Adolphe Millot from Nouveau Larousse Illustré (1897–1904)]]

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.{{Cite journal |year=1984 |title=Feeding ecology of the earliest vertebrates |url=https://dokumen.tips/documents/feeding-ecology-of-the-earliest-vertebrates.html |journal=Zoological Journal of the Linnean Society |volume=82 |issue=3 |pages=261–272 |first=Jon |last=Mallatt |doi=10.1111/j.1096-3642.1984.tb00643.x}}

During metamorphosis the lamprey loses both the gallbladder and the biliary tract,{{Cite book |url=https://books.google.com/books?id=ugGXBQAAQBAJ&q=larval+lampreys+biliary+tree+bile+intestine+metamorphosis&pg=PA19 |title=Lampreys: Biology, Conservation and Control |isbn=978-94-017-9306-3 |last1=Docker |first1=Margaret F. |date=2014-11-24|publisher=Springer }} and the endostyle turns into a thyroid gland.{{cite journal |pmid=15592682 |doi=10.1007/s00427-004-0450-0 |volume=215 |issue=1 |title=Anatomical and molecular reinvestigation of lamprey endostyle development provides new insight into thyroid gland evolution |year=2005 |journal=Dev Genes Evol |pages=32–40 |last1=Kluge |first1=B |last2=Renault |first2=N |last3=Rohr |first3=KB |s2cid=21813092}}

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.{{cite web |url=http://www.adfg.alaska.gov/static/education/wns/lampreys.pdf |title=Lampreys |website=Alaska Department of Fish and Game |year=2004 |access-date=8 July 2012}} In contrast, many species are anadromous 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.{{cite journal |last1=Silva |first1=S. |last2=Servia |first2=M. J. |last3=Vieira-Lanero |first3=R. |last4=Nachón |first4=D. J. |last5=Cobo |first5=F. |year=2013 |title=Haematophagous feeding of newly metamorphosed European sea lampreys Petromyzon marinus on strictly freshwater species |journal=Journal of Fish Biology |volume=82 |issue=5 |pages=1739–1745 |doi=10.1111/jfb.12100 |pmid=23639169|bibcode=2013JFBio..82.1739S }} Those that are anadromous are carnivorous, feeding on fishes or marine mammals.{{cite journal |last1=Beamish |first1=F. W. H. |year=1980 |title=Biology of the North American anadromous sea lamprey, Petromyzon marinus |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=37 |issue=11 |pages=1924–1943 |doi=10.1139/f80-233}}{{cite journal |last1=Nichols |first1=O. C. |last2=Tscherter |first2=U. T. |year=2011 |title=Feeding of sea lampreys Petromyzon marinus on minke whales Balaenoptera acutorostrata in the St Lawrence Estuary |journal=Journal of Fish Biology |volume=78 |issue=1 |pages=338–343 |doi=10.1111/j.1095-8649.2010.02842.x |pmid=21235565}}

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.{{cite journal |last1=Beamish |first1=F W H |last2=Medland |first2=T E |title=Age Determination for Lampreys |journal=Transactions of the American Fisheries Society |date=1988 |volume=117 |issue=1 |pages=63–71 |doi=10.1577/1548-8659(1988)117<0063:ADFL>2.3.CO;2|bibcode=1988TrAFS.117...63B }}

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.{{Cite news |last=Poppick |first=Laura |date=2015-11-02 |title=Only the hot sea lamprey guys get sex – thermally, that is |work=NBC News |url=https://www.nbcnews.com/science/science-news/only-hot-sea-lamprey-guys-get-sex-thermally-f6C10506147}}

File:Petromyzontiformes phylogeny.png

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 infraphylum Agnatha or Agnathostomata (both meaning without jaws). The other vertebrate infraphylum is Gnathostomata (jawed mouths) and includes the classes Chondrichthyes (sharks), Osteichthyes (bony fishes), Amphibia, Reptilia, Aves, and Mammalia.

Some researchers have classified lampreys as the sole surviving representatives of the Linnean class Cephalaspidomorphi.{{cite book |author=Nelson, J. S. |year=2006 |title=Fishes of the World |publisher=John Wiley and Sons, Inc |location=New York |edition=4th |pages=601 pp |isbn=978-0-471-25031-9}} Cephalaspidomorpha is sometimes given as a subclass of the Cephalaspidomorphi. Fossil evidence now suggests lampreys and cephalaspids acquired their shared characters by convergent evolution.{{Cite book |year=2000 |contribution=Agnathans and the origin of jawed vertebrates |title=Shaking the tree: readings from Nature in the history of life |editor-last=Gee |editor-first=Henry |editor-link=Henry Gee |pages=251–266 |place=USA |publisher=University of Chicago Press; Nature/Macmillan Magazines |isbn=978-0-226-28497-2 |last1=Forey |first1=Peter |last2=Janvier |first2=Philippe}}{{Cite journal |last1=Janvier |first1=P. |title=Early Jawless Vertebrates and Cyclostome Origins |doi=10.2108/zsj.25.1045 |journal=Zoological Science |volume=25 |issue=10 |pages=1045–1056 |year=2008 |pmid=19267641 |s2cid=5983614|doi-access=free }} The 5th edition of Fishes of the World classifies lampreys within the Class Petromyzontida,{{cite book |author1=Nelson, J.S. |author1-link=Joseph S. Nelson |author2=Grande, T.C. |author3=Wilson, M.V.H. |year=2016 |title=Fishes of the World |edition=5th |publisher=John Wiley & Sons |place=Hoboken, NJ |pages=518–526 |isbn=978-1-118-34233-6 |lccn=2015037522 |oclc=951899884 |ol=25909650M |doi=10.1002/9781119174844}} a taxon called Petromyzonti in Eschmeyer's Catalog of Fishes.{{cite web |url=https://www.calacademy.org/scientists/catalog-of-fishes-classification/ |title=Eschmeyer's Catalog of Fishes Classification |access-date=18 October 2024 |work=Eschmeyer's Catalog of Fishes |publisher=California Academy of Sciences}}

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 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-".

Phylogeny based on Brownstein & Near, 2023.

{{clade| style=font-size:100%;line-height:80%

|label1= Petromyzontiformes

|1={{clade

|1={{clade

|label1=Geotriidae

|1=Geotria Gray 1851 (pouched lampreys)

|label2=Mordaciidae

|2=Mordacia Gray 1853 (southern topeyed lampreys)

}}

|label2=Petromyzontidae

|2={{clade

|1={{clade

|label1=Petromyzontinae

|1={{clade

|1=Caspiomyzon Berg 1906

|2={{clade

|1=Petromyzon Linnaeus 1758 (Sea lamprey)

|2=Ichthyomyzon Girard 1858

}}

}}

|label2=Lampetrinae

|2={{clade

|label1=Entosphenini

|1={{clade

|1=Entosphenus Gill 1863

|2=Tetrapleurodon Creaser & Hubbs 1922 (Mexican lampreys)

}}

|label2=Lampetrini

|2={{clade

|1=Western American "Lampetra"

|2={{clade

|1=Lethenteron Creaser & Hubbs 1922

|2={{clade

|1=Eudontomyzon Regan 1911

|2=Lampetra sensu stricto Bonnaterre 1788 (Eastern American and European Lampetra)

}}

}}

}}

}}

}}

}}

}}

}}

{{Hidden begin|title=List of species, from FishBase in 2023.{{FishBase family |family=Petromyzontidae|year=2017|month=February|id=1}}{{Cite journal |title=Petromyzontidae |url=http://deeplyfish.com/wp-content/uploads/2017/03/Family-Petromyzontidae-PDF.pdf |access-date=18 May 2017 |website=Deeplyfish- fishes of the world |archive-date=12 September 2017 |archive-url=https://web.archive.org/web/20170912191707/http://deeplyfish.com/wp-content/uploads/2017/03/Family-Petromyzontidae-PDF.pdf |url-status=dead }} Click "show" to expand.|titlestyle=background:#e6e6e6;width:60%;}}

• Geotria australis Gray 1851 (Pouched lamprey)
• Geotria macrostoma (Burmeister 1868) (Argentinian lamprey)
• Mordacia lapicida (Gray 1851) (Chilean lamprey)
• Mordacia mordax (Richardson 1846) (Australian lamprey)
• Mordacia praecox Potter 1968 (Non-parasitic/Australian brook lamprey)
• Petromyzon marinus Linnaeus 1758 (Sea lamprey)
• Ichthyomyzon bdellium (Jordan 1885) (Ohio lamprey)
• Ichthyomyzon castaneus Girard 1858 (Chestnut lamprey)
• Ichthyomyzon fossor Reighard & Cummins 1916 (Northern brook lamprey)
• Ichthyomyzon gagei Hubbs & Trautman 1937 (Southern brook lamprey)
• Ichthyomyzon greeleyi Hubbs & Trautman 1937 (Mountain brook lamprey)
• Ichthyomyzon unicuspis Hubbs & Trautman 1937 (Silver lamprey)
• Caspiomyzon wagneri (Kessler 1870) Berg 1906 (Caspian lamprey)
• Caspiomyzon graecus (Renaud & Economidis 2010) (Ionian brook lamprey)
• Caspiomyzon hellenicus (Vladykov et al. 1982) (Greek lamprey)
• Tetrapleurodon geminis Álvarez 1964 (Mexican brook lamprey)
• Tetrapleurodon spadiceus (Bean 1887) (Mexican lamprey)
• Entosphenus folletti Vladykov & Kott 1976 (Northern California brook lamprey)
• Entosphenus lethophagus (Hubbs 1971) (Pit-Klamath brook lamprey)
• Entosphenus macrostomus (Beamish 1982) (Lake lamprey)
• Entosphenus minimus (Bond & Kan 1973) (Miller Lake lamprey)
• Entosphenus similis Vladykov & Kott 1979 (Klamath river lamprey)
• Entosphenus tridentatus (Richardson 1836) (Pacific lamprey)
• Lethenteron alaskense Vladykov & Kott 1978 (Alaskan brook lamprey)
• Lethenteron appendix (DeKay 1842) (American brook lamprey)
• Lethenteron camtschaticum (Tilesius 1811) (Arctic lamprey)
• Lethenteron kessleri (Anikin 1905) (Siberian brook lamprey)
• Lethenteron ninae Naseka, Tuniyev & Renaud 2009 (Western Transcaucasian lamprey)
• Lethenteron reissneri (Dybowski 1869) (Far Eastern brook lamprey)
• Lethenteron zanandreai (Vladykov 1955) (Lombardy lamprey)
• Eudontomyzon stankokaramani (Karaman 1974) (Drin brook lamprey)
• Eudontomyzon morii (Berg 1931) (Korean lamprey)
• Eudontomyzon danfordi Regan 1911 (Carpathian brook lamprey)
• Eudontomyzon mariae (Berg 1931) (Ukrainian brook lamprey)
• Eudontomyzon vladykovi (Oliva & Zanandrea 1959) (Vladykov's lamprey)
• Lampetra aepyptera (Abbott 1860) (Least brook lamprey)
• Lampetra alavariensis Mateus et al. 2013 (Portuguese lamprey)
• Lampetra auremensis Mateus et al. 2013 (Qurem lamprey)
• Lampetra ayresi (Günther 1870) (Western river lamprey)
• Lampetra fluviatilis (Linnaeus 1758) (European river lamprey)
• Lampetra hubbsi (Vladykov & Kott 1976) (Kern brook lamprey)
• Lampetra lanceolata Kux & Steiner 1972 (Turkish brook lamprey)
• Lampetra lusitanica Mateus et al. 2013 (lusitanic lamprey)
• Lampetra pacifica Vladykov 1973 (Pacific brook lamprey)
• Lampetra planeri (Bloch 1784) (European brook lamprey)
• Lampetra richardsoni Vladykov & Follett 1965 (Western brook lamprey)
• Entosphenus macrostomus Dr. Dick Beamish 1980 (Cowichan lake lamprey)

{{Hidden end}}

Recent studies differ regarding the timing of the last common ancestor of all living lampreys, with some suggesting a Middle Jurassic date, around 175 million years ago,{{Cite journal |last1=Brownstein |first1=Chase Doran |last2=Near |first2=Thomas J. |date=2023-01-23 |title=Phylogenetics and the Cenozoic radiation of lampreys |journal=Current Biology |language=en |volume=33 |issue=2 |pages=397–404.e3 |doi=10.1016/j.cub.2022.12.018 |pmid=36586410 |s2cid=255278945 |issn=0960-9822|doi-access=free |bibcode=2023CBio...33E.397B }} while other studies have suggested a younger split, dating to the Late Cretaceous.{{Cite journal |last1=Wu |first1=Feixiang |last2=Janvier |first2=Philippe |last3=Zhang |first3=Chi |date=2023-10-31 |title=The rise of predation in Jurassic lampreys |journal=Nature Communications |language=en |volume=14 |issue=1 |page=6652 |doi=10.1038/s41467-023-42251-0 |issn=2041-1723 |pmc=10618186 |pmid=37907522|bibcode=2023NatCo..14.6652W }} The older date study posited that the Northern and Southern Hemisphere lampreys diverged as part of the breakup of Pangea, while the Late Cretaceous study suggested that modern lampreys emerged in the Southern Hemisphere. It is thought that most modern lamprey diversity emerged during the Cenozoic, particularly within the last 10–20 million years.

File:Ammocoetes-l reissneri-01.jpg|Ammocoetes larva of Lethenteron reissneri

File:Lampreys.jpg|Several species of European lampreys

File:Geotria australis.jpg|Pouched lamprey

File:Yanliaomyzon.png from the Middle Jurassic of China]]

The oldest fossil lamprey, Priscomyzon, is known from the latest Devonian of South Africa around 360 million years ago, with other stem-group lampreys, like Pipiscius, Mayomyzon and Hardistiella known from the Carboniferous of North America. These Paleozoic stem-lampreys are small relative to modern lampreys, and while they had well developed oral discs with a small number of radially arranged teeth, they lacked the specialised, heavily toothed discs with plate-like laminae present in modern lampreys, and it is possible that they fed by scraping algae off of animals, rather than feeding by predation/parasitism. They also lacked the modern three stage life cycle including ammocoetes found in modern lampreys, with the juvenile stages of these species closely resembling adults.{{Cite journal |last1=Miyashita |first1=Tetsuto |last2=Gess |first2=Robert W. |last3=Tietjen |first3=Kristen |last4=Coates |first4=Michael I. |date=2021-03-18 |title=Non-ammocoete larvae of Palaeozoic stem lampreys |url=https://www.nature.com/articles/s41586-021-03305-9 |journal=Nature |language=en |volume=591 |issue=7850 |pages=408–412 |doi=10.1038/s41586-021-03305-9 |pmid=33692547 |bibcode=2021Natur.591..408M |issn=0028-0836}} Myxineidus from the Carboniferous of France, often considered to be a hagfish, has been found to be a lamprey in some studies.{{Cite journal |last1=Germain |first1=Damien |last2=Sanchez |first2=Sophie |last3=Janvier |first3=Philippe |last4=Tafforeau |first4=Paul |date=2014 |title=The presumed hagfish Myxineidus gononorum from the Upper Carboniferous of Montceau-les-Mines (Saône-et-Loire, France): New data obtained by means of Propagation Phase Contrast X-ray Synchrotron Microtomography |url=|journal=Annales de Paléontologie |volume=100 |issue=2 |pages=131–135 |doi=10.1016/j.annpal.2013.12.003 |bibcode=2014AnPal.100..131G |issn=0753-3969}} The earliest lamprey with the specialised toothed oral disc typical of modern lampreys is Yanliaomyzon from the Middle Jurassic of China around 163 million years old, which is thought to have had a predatory lifestyle like modern lampreys, and probably had a three stage life cycle including ammocoetes. Mesomyzon from the Early Cretaceous of China, which displays the three stage life cycle with ammocoetes, was found in one study to be more closely related to the family Petromyzonidae than to other living lampreys, though other studies have found it to be outside the group containing all living lampreys.

File:Lamprey Anatomy.png

Synapomorphies are certain characteristics that are shared over evolutionary history. Organisms possessing a notochord, dorsal hollow nerve cord, 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.{{Cite journal |last1=Green |first1=Stephen A. |last2=Bronner |first2=Marianne E. |date=January 2014 |title=The lamprey: A jawless vertebrate model system for examining origin of the neural crest and other vertebrate traits |url=|journal=Differentiation |volume=87 |issue=1–2 |pages=44–51 |doi=10.1016/j.diff.2014.02.001 |pmid=24560767 |issn=0301-4681 |pmc=3995830}} The notochord is derived from the mesoderm 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 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.{{cite web |title=Morphology of the Chordata |url=https://ucmp.berkeley.edu/chordata/chordatamm.html |access-date=2021-05-11 |website=ucmp.berkeley.edu}} Pharyngeal slits are filter feeding organs that help the movement of water through the mouth and out of these slits when feeding. During the lamprey's larval stage they feed by filter feeding.{{cite web |title=Natural history |url=https://www.biologicaldiversity.org/species/fish/Pacific_lamprey/natural_history.html |access-date=2021-05-11 |website=www.biologicaldiversity.org}} 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 muscular and 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.{{Cite journal |last1=Diogo |first1=Rui |last2=Ziermann |first2=Janine M. |date=2015 |title=Development, metamorphosis, morphology, and diversity: The evolution of chordate muscles and the origin of vertebrates |journal=Developmental Dynamics |language=en |volume=244 |issue=9 |pages=1046–1057 |doi=10.1002/dvdy.24245 |pmid=26095777 |issn=1097-0177 |doi-access=free}}{{Retracted|doi=10.1002/dvdy.24236|pmid=25476723|http://retractionwatch.com/2015/08/25/sea-squirt-draft-published-by-mistake/ Retraction Watch|intentional=yes}}

File:Olfactory-locomotor circuitry in lampreys 1.png of a sea lamprey{{cite journal |last1=Derjean |first1=D |last2=Moussaddy |first2=A |last3=Atallah |first3=E |last4=St-Pierre |first4=M |last5=Auclair |first5=F |last6=Chang |first6=S |last7=Dubuc |first7=R |year=2010 |title=A novel neural substrate for the transformation of olfactory inputs into motor output |journal=PLOS Biology |volume=8 |issue=12 |page=e1000567 |doi=10.1371/journal.pbio.1000567 |pmid=21203583 |pmc=3006349 |doi-access=free }}]]

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.{{Cite journal |last1=Grillner |first1=S. |title=The motor infrastructure: From ion channels to neuronal networks |doi=10.1038/nrn1137 |journal=Nature Reviews Neuroscience |volume=4 |issue=7 |pages=573–586 |year=2003 |pmid=12838332 |s2cid=4303607}}

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{{cite journal |last1=Parker |first1=D |year=2006 |title=Complexities and uncertainties of neuronal network function |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=361 |issue=1465 |pages=81–99 |doi=10.1098/rstb.2005.1779 |pmid=16553310 |pmc=1626546}}{{cite journal |last1=Parker |first1=D |year=2010 |title=Neuronal network analyses: premises, promises and uncertainties |journal=Phil Trans R Soc Lond B |volume=365 |issue=1551 |pages=2315–2328 |doi=10.1098/rstb.2010.0043 |pmid=20603354 |pmc=2894952}}). 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,{{Cite journal |last1=Saitoh |first1=K. |last2=Ménard |first2=A. |last3=Grillner |first3=S. |doi=10.1152/jn.00639.2006 |title=Tectal Control of Locomotion, Steering, and Eye Movements in Lamprey |journal=Journal of Neurophysiology |volume=97 |issue=4 |pages=3093–3108 |year=2007 |pmid=17303814}} 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 in biomedical research, where their large reticulospinal axons are used to investigate synaptic transmission.{{Cite journal |last1=Brodin |first1=L. |last2=Shupliakov |first2=O. |doi=10.1007/s00441-006-0216-2 |title=Giant reticulospinal synapse in lamprey: Molecular links between active and periactive zones |journal=Cell and Tissue Research |volume=326 |issue=2 |pages=301–310 |year=2006 |pmid=16786368 |s2cid=24204394}} 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 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.{{cite web |url=https://arstechnica.com/science/2018/01/odd-vertebrate-gets-rid-of-hundreds-of-genes-early-in-development/ |title=Odd vertebrate gets rid of hundreds of genes early in development |last=Gitig |first=Diana |date=2018-01-28}}{{Cite journal |doi=10.1038/s41588-017-0036-1 |pmid=29358652 |pmc=5805609 |title=The sea lamprey germline genome provides insights into programmed genome rearrangement and vertebrate evolution |journal=Nature Genetics |volume=50 |issue=2 |pages=270–277 |year=2018 |last1=Smith |first1=Jeramiah J. |last2=Timoshevskaya |first2=Nataliya |last3=Ye |first3=Chengxi |last4=Holt |first4=Carson |last5=Keinath |first5=Melissa C. |last6=Parker |first6=Hugo J. |last7=Cook |first7=Malcolm E. |last8=Hess |first8=Jon E. |last9=Narum |first9=Shawn R.| last10=Lamanna| first10=Francesco |last11=Kaessmann |first11=Henrik |last12=Timoshevskiy |first12=Vladimir A. |last13=Waterbury |first13=Courtney K. M. |last14=Saraceno |first14=Cody |last15=Wiedemann |first15=Leanne M. |last16=Robb |first16=Sofia M. C. |last17=Baker |first17=Carl |last18=Eichler |first18=Evan E. |last19=Hockman |first19=Dorit| last20=Sauka-Spengler| first20=Tatjana |last21=Yandell |first21=Mark |last22=Krumlauf |first22=Robb |last23=Elgar |first23=Greg |last24=Amemiya |first24=Chris T.}}

Although attacks on humans have been documented,{{cite magazine |date=9 May 1955 |title=CANADA: A Surfeit of Lampreys |url=http://www.time.com/time/magazine/article/0,9171,861450,00.html |url-status=dead |magazine=Time |archive-url=https://web.archive.org/web/20081215055314/http://www.time.com/time/magazine/article/0,9171,861450,00.html |archive-date=15 December 2008 |access-date=7 June 2008}} they will generally not attack humans unless starved.{{cite book |last=Liem |first=Karel F. |title=Functional Anatomy of the Vertebrates |author2=William E. Bemis |author3=Warren F. Walker Jr. |author4=Lance Grande |publisher=Thomson: Brooks/Cole |year=2001 |isbn=978-0-03-022369-3 |location=The United States of America |page=50}}

People have long eaten lampreys.{{Cite book |title=Jawless Fishes of the World: Volume 2 |last1=Araujo |first1=Mario |last2=Silva |first2=Sergio |last3=Stratoudakis |first3=Yorgos |last4=Gonçalves |first4=Marta |last5=López |first5=Rodrigo |last6=Carneiro |first6=Miguel |last7=Martins |first7=Rogélia |last8=Cobo |first8=Fernando |last9=Antunes |first9=Carlos |date=2016-03-01 |isbn=978-1-4438-8719-9 |editor-last=Orlov |editor-first=Alexei |pages=115–148 |chapter=Sea Lamprey Fisheries in the Iberian Peninsula |publisher=Cambridge Scholars |editor2-last=Beamish |editor2-first=Richard |chapter-url=https://www.researchgate.net/publication/297716168}} 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, when eating meat was prohibited, due to their meaty taste and texture. King Henry I of England 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 of lampreys". Whether or not his lamprey indulgence actually caused his death is unclear,{{Cite book |url=https://books.google.com/books?isbn=0521591317 |isbn=978-0-521-59131-7 |page=1 |title=Henry I: King of England and Duke of Normandy |last1=Green |first1=Judith A. |date=2006-03-02|publisher=Cambridge University Press }} but the phrase persists in British culture.

A lamprey pie was made for the coronation of Elizabeth II in 1953. Sixty years later, the city of Gloucester had to use fish from North America for her Diamond Jubilee, because few lampreys could be found in the River Severn.{{cite news |last=Smith |first=Lewis |title=Older than the dinosaurs: Lamprey fish return to UK rivers after 200 years |url=https://www.theguardian.com/environment/2015/sep/04/older-than-the-dinosaurs-lamprey-fish-return-to-uk-rivers-after-200-years |access-date=16 February 2022 |work=The Guardian}}{{cite news |url=https://www.bbc.co.uk/news/uk-england-gloucestershire-17791695 |title=Gloucester lamprey pie is fit for the Queen |work=BBC News |date=20 April 2012}}

In southwestern Europe (Portugal, Spain, and France), Finland and in Latvia (where lamprey is routinely sold in supermarkets), lampreys are a highly prized delicacy. In Finland (county of Nakkila),{{Cn|date=August 2024}} and Latvia (Carnikava Municipality), 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 list by the European Commission.{{Cite news |url=http://www.baltic-course.com/eng/good_for_business/?doc=102773 |title=Lamprey eel from Latvian Carnikava included on EU's Protected Designations of Origin list |date=23 February 2015 |publisher=The Baltic Course |access-date=8 November 2015}}

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" (lamprey rice) and "Lampreia à Bordalesa" (Bordeaux style lamprey) are some of the most important dishes in Portuguese cuisine.

Lampreys are also consumed in Sweden, Russia, Lithuania, Estonia, Japan, and South Korea.{{citation needed|date=December 2017}} In Finland, they are commonly eaten grilled or smoked, but also pickled, or in vinegar.{{cite web |url=http://www.dlc.fi/~marianna/gourmet/lamprey.htm |title=Lamprey |website=Nordic Recipe Archive |access-date=2017-12-01 |archive-date=13 March 2016 |archive-url=https://web.archive.org/web/20160313111207/http://www.dlc.fi/~marianna/gourmet/lamprey.htm |url-status=dead }}

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.{{FishBase |genus=Lampetra |species=fluviatilis |month=September |year=2012}} (citing {{cite book |first1=Pamela |last1=Bristow |title=The Illustrated Encyclopedia of Fishes |publisher=Chancellor Press |location=London |date=30 April 1992 |isbn=978-1-85152-136-4}}).{{cite book |url=https://books.google.com/books?id=Mk-IdNTTJB0C&pg=PA695 |first=S. S. |last=Deshpande |date=29 August 2002 |title=Handbook of Food Toxicology |page=695 |publisher=CRC Press |isbn=978-0-8247-0760-6}}

In Britain, lampreys are commonly used as bait, normally as dead bait. Northern pike, perch, and chub all can be caught on lampreys. Frozen lampreys can be bought from most bait and tackle shops.

Indigenous American tribes of the Pacific Northwest have traditionally fished the Pacific lamprey (Entosphenus tridentatus).{{cite news |author1=Patricia Leigh Brown |date=April 15, 2015 |title=Hooking a Slippery Prize Where the Klamath River Meets the Pacific |url=https://www.nytimes.com/2015/04/13/us/hooking-an-eel-where-the-klamath-river-meets-the-pacific.html |access-date=April 15, 2015 |work=The New York Times}}{{Cite web |last=Nelson |first=Jon |date=2017-05-09 |title=The Historical Significance of the Lamprey |url=https://highdesertmuseum.org/historical-significance-lamprey/ |access-date=2023-10-25 |publisher=High Desert Museum |language=en}}

File:Portuguese Lamprey rice.jpg|Portuguese lamprey rice

File:Spit-roasted lamprey.jpg|Yatsume kabayaki in Japan

File:Nakkila.vaakuna.svg|The European river lamprey in the coat of arms of Nakkila, Finland. Lampreys are a traditional delicacy in locality.[https://nakkila.fi/en/home/ Home – Nakkila]

File:Sea Lamprey fish.jpg.]]

Sea lampreys have become a major pest in the North American Great Lakes. It is generally believed that they gained access to the lakes via canals during the early 20th century,{{cite book |editor1-last=Gunn |editor1-first=J.M. |editor2-last=Steedman |editor2-first=R.J. |editor3-last=Ryder |editor3-first=R.A. |title=Boreal Shield Watersheds Lake Trout Ecosystems in a. |date=2003 |publisher=CRC Press |location=London |isbn=978-0-203-49508-7 |page=40 |url=https://books.google.com/books?id=Zy6vWdxggW4C&pg=PA40 |access-date=8 November 2015}}{{cite book |last1=Alexander |first1=Jeff |title=Pandora's locks the opening of the Great Lakes-St. Lawrence Seaway |date=2009 |publisher=Michigan State University Press |location=East Lansing, Mich. |isbn=978-1-60917-197-1 |url=https://books.google.com/books?id=T1WQpFTUfe0C&pg=PT50 |access-date=8 November 2015}} but this theory is controversial.

{{

cite book

| last1=Williams

| first1=Ted

| title=Something's Fishy: an Angler's Look at Our Distressed Gamefish and Their Waters – And How We Can Preserve Both.

| date=2007

| publisher=Skyhorse Publishing, Inc.

| location=New York

| isbn=978-1-62873-197-2

| page=[https://archive.org/details/somethingsfishya00will/page/358 358]

| url=https://archive.org/details/somethingsfishya00will

| url-access=registration

| access-date=2022-06-06

}}

They are considered an invasive species, have no natural predators 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.{{cite book |editor1-last=O'Sullivan |editor1-first=P.E. |editor2-last=Reynolds |editor2-first=C.S. |title=The Lakes Handbook, Volume 2. |date=2007 |publisher=John Wiley & Sons |location=Oxford |isbn=978-1-4051-4110-9 |page=81 |url=https://books.google.com/books?id=bibY60NWOlEC&pg=PA81 |access-date=8 November 2015}}

New programs are being developed, including the use of chemically sterilized male lampreys in a method akin to the sterile insect technique.{{cite journal |last1=Siefkes |first1=Michael J |last2=Bergstedt |first2=Roger A |last3=Twohey |first3=Michael B |last4=Li |first4=Weiming |title=Chemosterilization of male sea lampreys (Petromyzon marinus) does not affect sex pheromone release |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=60 |issue=1 |year=2003 |pages=23–31 |issn=0706-652X |doi=10.1139/f02-169}} 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.Peter W. Sorensen, 2015, "Applications of pheromones in invasive fish control and fishery conservation (Ch. 12)," in Fish Pheromones and Related Cues (P.W. Sorensen & B.D. Wisenden, Eds.), pp. 255–268, {{ISBN|978-0813823867}}, Hoboken, NJ, USA:Wiley-Blackwell, see [http://www.wiley.com/WileyCDA/WileyTitle/productCd-0813823862.html] and [https://books.google.com/books?id=aZ_ingEACAAJ], accessed 1 July 2015.{{Cite journal |doi=10.1111/j.1095-8649.2007.01681.x |title=A critical review of the discovery and application of a migratory pheromone in an invasive fish, the sea lamprey Petromyzon marinus L |journal=Journal of Fish Biology |volume=71 |pages=100–114 |year=2007 |last1=Sorensen |first1=P. W. |last2=Hoye |first2=T. R.|bibcode=2007JFBio..71S.100S }}Mary L. Moser, Pedro R. Almeida, Paul S. Kemp & P.W. Sorensen, 2014, "Lamprey spawning migration (Ch. 5, §5.6.1, Pheromones)," in Lampreys: Biology, Conservation and Control, Vol. 1 (Margaret F. Docker, Ed., Vol. 37, Fish & Fisheries Series), Berlin, BE, DEU:Springer, {{ISBN|9401793069}}, see [https://books.google.com/books?id=ugGXBQAAQBAJ], accessed 1 July 2015.

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, and is coordinated by the Great Lakes Fishery Commission.{{cite web |url=http://www.glfc.org/factsheets/FACT%205_all.pdf |title=Sea Lamprey Control in the Great Lakes A remarkable success! |publisher=Great Lakes Fishery Commission |archive-url=https://web.archive.org/web/20150427192447/http://www.glfc.org/factsheets/FACT%205_all.pdf |archive-date=27 April 2015}} Lake Champlain, bordered by New York, 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.{{cite web |url=http://www.dec.ny.gov/animals/6998.html |title=Sea Lamprey Lake Champlain Sea Lamprey Control |date=July 2009 |website=New York State Department of Environmental Conservation}} New York's Finger Lakes sea lamprey control program is managed solely by the New York State Department of Environmental Conservation.

In folklore,{{which |date=April 2024}} lampreys are called "nine-eyed eels". The name derives from misconstruing the seven gill pores behind each eye as additional eyes, and doing the same with the nostril on the top of the head (even though there is only one of those, not one per side).{{citation needed |date=April 2024}} Likewise, in the German language, the word for lamprey is Neunauge, which means "nine-eye".[http://woerterbuchnetz.de/DWB/?lemma=Neunauge Entry in Grimm's German Dictionary, online edition at Trier University] 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.{{citation needed|date=December 2018}}

In Japanese, lamprey are called yatsume-unagi (八つ目鰻, "eight-eyed eels"), thus excluding the nostril from the count.{{citation needed |date=April 2024}}

File:Tacuinum Sanitatis-fishing lamprey.jpg, 15th century]]

Vedius Pollio kept a pool of lampreys into which slaves who incurred his displeasure would be thrown as food.Dio [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cassius_Dio/54*.html#23.2 52.23.2]; Pliny the Elder, Natural History [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+9.39 9.39]; Seneca the Younger, On Clemency 1.18.2. On one occasion, Vedius was punished by Augustus for attempting to do so in his presence:

{{Blockquote|... 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's 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{{cite book |author=Seneca the Younger |author-link=Seneca the Younger |title=L. ANNAEI SENECAE AD NOVATVM DE IRA LIBER III |trans-title=On Anger |volume=III |language=la |url=http://www.thelatinlibrary.com/sen/sen.ira3.shtml |publisher=Thelatinlibrary.com}}}}

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:

{{Blockquote|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{{cite book |author=Plutarch |author-link=Plutarch |title=The Morals |url=https://archive.org/details/plutarchsessaysm05plutiala |volume=V |publisher=Little, Brown and Company |translator=William Watson Goodwin |translator-link=William Watson Goodwin |others=Ralph Waldo Emerson |year=1909 }}}}

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:

{{Blockquote|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.|Philip, Lord Chandos, (fictional) younger son of the Earl of Bath, in a letter to Francis Bacon{{cite web |first=Hugo |last=von Hofmannsthal |author-link=Hugo von Hofmannsthal |url=http://depts.washington.edu/vienna/documents/Hofmannsthal/Hofmannsthal_Chandos.htm |title=The Letter of Lord Chandos |year=1902}}}}

In George R. R. Martin's novel series, A Song of Ice and Fire, Lord Wyman Manderly is mockingly called "Lord Lamprey" by his enemies in reference to his rumored affinity to lamprey pie and his striking obesity.{{cite book |last1=Martin |first1=George R. R. |title=A Clash of Kings |url=https://archive.org/details/clashofkingsason00geor_0 |url-access=registration |date=16 November 1998 |publisher=Voyager Books |isbn=978-0-00-224585-2 |edition=1st}}

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.{{cite web |url=http://www.pierretristam.com/Bobst/07/wf041307.htm |title=Kurt Vonnegut: 'The Big Space Fuck' |website=www.pierretristam.com |access-date=2017-03-22}}

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 Ferrante had built during his reign of Naples.{{cite web|url=https://www.denofgeek.com/tv/the-borgias-season-3-episode-5-the-wolf-and-the-lamb/?amp |title= The Borgias season 3 episode 5: The Wolf and the Lamb |website=www.denofgeek.com |date= 16 May 2013 |access-date=2022-04-07}}

{{reflist}}

• 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}}.

• {{cite journal |last1=Dittman |first1=Andrew |year=2005 |title=News and Views: Chemical cues for sea lamprey migration |journal=Nature Chemical Biology |volume=1 |issue=6 |pages=316–317 |doi=10.1038/nchembio1105-316 |pmid=16408065 |s2cid=42664483 |type=Submitted manuscript |url=https://zenodo.org/record/1233357}}, see [http://www.nature.com/nchembio/journal/v1/n6/full/nchembio1105-316.html Chemical cues for sea lamprey migration], accessed 1 July 2015. [Lay summary of Sorensen, et al. (2005)]
• {{cite journal |last1=Johnson |first1=Nicholas S. |last2=Yun |first2=Sang-Seon |last3=Thompson |first3=Henry T. |last4=Brant |first4=Cory O. |last5=Li |first5=Weiming |year=2009 |title=A synthesized pheromone induces upstream movement in female sea lamprey and summons them into traps |journal=Proceedings of the National Academy of Sciences |volume=106 |issue=4 |pages=1021–1026 |doi=10.1073/pnas.0808530106 |pmc=2633527 |pmid=19164592|doi-access=free }} [Primary source example.]
• Black, Richard (2009), [http://news.bbc.co.uk/1/hi/sci/tech/7838850.stm "Sex smell lures 'vampire' to doom"], BBC News, 20 January 2009, accessed 1 July 2015. [Lay summary of Johnson, et al. (2009); Subtitle: "A synthetic 'chemical sex smell' could help rid North America's Great Lakes of a devastating pest, scientists say."]
• {{cite journal |last1=Sorensen |first1=Peter W. |last2=Fine |first2=Jared M. |last3=Dvornikovs |first3=Vadims |last4=Jeffrey |first4=Christopher S. |last5=Shao |first5=Feng |last6=Wang |first6=Jizhou |last7=Vrieze |first7=Lance A. |last8=Anderson |first8=Kari R. |last9=Hoye |first9=Thomas R. |year=2005 |title=Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey |journal=Nature Chemical Biology |volume=1 |issue=6 |pages=324–328 |doi=10.1038/nchembio739 |pmid=16408070 |s2cid=43298112}}, see [http://www.nature.com/nchembio/journal/v1/n6/abs/nchembio739.html Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey], accessed 1 July 2015. Primary source example.

{{Wikispecies|Petromyzontiformes}}

{{Wikibooks|Dichotomous Key|Petromyzonidae}}

{{Commons category|Petromyzontiformes}}

• {{cite web |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=159697 |title=ITIS report on the lampreys |publisher=ITIS |access-date=27 September 2012}}
• {{cite web |url=http://www.fisheriesireland.ie/Search.html?ordering=&searchphrase=all&searchword=lamprey |title=Lamprey |publisher=Inland Fisheries Ireland |access-date=27 September 2012 |archive-date=25 April 2021 |archive-url=https://web.archive.org/web/20210425125027/https://www.fisheriesireland.ie/Search.html?ordering=&searchphrase=all&searchword=lamprey |url-status=dead }}
• [http://www.nature.ca/en/about-us/museum-news/news/press-releases/long-accepted-theory-vertebrate-origin-upended-fossilized-l Long-accepted theory of vertebrate origin upended by fossilized lamprey larvae] ({{Webarchive|url=https://web.archive.org/web/20210310231658/http://www.nature.ca/en/about-us/museum-news/news/press-releases/long-accepted-theory-vertebrate-origin-upended-fossilized-l |date=10 March 2021 }})
• {{cite web |url=http://www.tellapallet.com/tree_of_life.htm |title=The Tree of Life |access-date=27 September 2012 |archive-date=26 January 2016 |archive-url=https://web.archive.org/web/20160126130722/http://www.tellapallet.com/tree_of_life.htm |url-status=dead }} A Tree of Life diagram showing the relation of Lampreys to other organisms.

{{Petromyzontiformes|state=collapsed}}

{{Taxonbar|from1=Q261485|from2=Q188549|from3=Q22109932|from4=Q21286786}}

{{Authority control}}

Category:Devonian fish

Category:Extant Late Devonian first appearances

Category:Fish described in 1940

Category:Hematophages

Category:Parasitic vertebrates