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{{Short description|Order of jawless fish}}{{Other uses}}{{Use dmy dates|date=December 2015}}{{Automatic taxobox

Late Devonian

ref={{FishBase order

year=2009|month=January}}}}| image = Jõesilmud2.jpg| image_upright = 1.1| image_caption = A European river lamprey (Lampetra fluviatilis)| taxon = Petromyzontiformes

Leo S. Berg>Berg, 1940HTTP://WWW.FOSSILWORKS.ORG/CGI-BIN/BRIDGE.PL?A=TAXONINFO&TAXON_NO=34112 >TITLE=FOSSILWORKS: PETROMYZONTIDA, fossilworks.org, | subdivision_ranks = Subgroups| subdivision = {{extinct}}Caeruleum {{extinct}}Hardistiella {{extinct}}Mayomyzon {{extinct}}Mesomyzon {{extinct}}Pipiscius {{extinct}}Priscomyzon {{extinct}}Yanliaomyzon Geotriidae Mordaciidae Petromyzontidae| synonyms = Hyperoartia Müller 1844| type_species = Petromyzon marinus

Carl Linnaeus>Linnaeus, 1758}}(File:Petromyzon marinus.jpg|upright=1.2|thumb|Sea lamprey, Petromyzon marinus)File:Boca de lamprea.1 - Aquarium Finisterrae.JPG|thumb|Mouth of a sea lamprey, Petromyzon marinusPetromyzon marinusFile:Lamprey Anatomy (50693755972).jpg|thumb|318x318px|Median section of Lamprey demonstrating internal anatomy]](File:Lamprey Larva x sect pharynx labelled.png|thumb|Microscopic cross section through the pharynx of a larva from an unknown lamprey species)Lampreys {{IPAc-en|'|l|ae|m|p|r|e:|z}} (sometimes inaccurately called lamprey eels) are a group of jawless fish comprising the order Petromyzontiformes {{IPAc-en|,|p|E|t|r|ou|m|I|'|z|Q|n|t|áµ»|f|É”r|m|iː|z}}. The adult lamprey is 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.WEB, lamprey, Oxford University Press, 12 February 2014,weblink Lamprey is sometimes seen for the plural form.WEB,weblink Sea Lamprey: The Ancient Fish, Connecticut River Conservancy, 10 July 2016, 23 August 2020, There are about 38 known extant species of lampreysJOURNAL, Docker, Margaret F, Bill Beamish's Contributions to Lamprey Research and Recent Advances in the Field., Guelph Ichthyology Reviews, 2006, 7,weblink 12 June 2014, dead,weblink" title="web.archive.org/web/20140827081335weblink">weblink 27 August 2014, dmy-all, and around seven known extinct species.JOURNAL, Huang, Weijia, 2023-09-01, A new species of fossil lamprey (Petromyzontida: Petromyzontiformes) from Hebei, China, Historical Biology, en, 1–13, 10.1080/08912963.2023.2252443, 0891-2963, They are classified in three families: two small families in the Southern Hemisphere (Geotriidae, Mordaciidae) and one large family in the Northern Hemisphere; (Petromyzontidae).Genetic evidence suggests that lampreys are more closely related to hagfish, the only other living group of jawless fish, than they are to jawed vertebrates, forming the superclass Cyclostomi. The oldest fossils of stem-group lampreys are from the latest Devonian, around 360 million years ago, with modern looking forms only appearing during the Jurassic, around 163 million years ago, with the modern families likely splitting from each sometime between the Middle Jurassic and the end of the Cretaceous.Modern lampreys spend the majority of their life in the juvenile "ammocoete" stage, where they burrow into the sediment and filter feed.JOURNAL, Mallatt, Jon, 2023-02-02, Vertebrate origins are informed by larval lampreys (ammocoetes): a response to Miyashita et al. , 2021,weblink Zoological Journal of the Linnean Society, en, 197, 2, 287–321, 10.1093/zoolinnean/zlac086, 0024-4082, free, Adult carnivorous lampreys are the most well-known species, and feed by boring into the flesh of other fish (or in rare cases marine mammals) to consume flesh and/or blood;{{Citation |last1=Renaud |first1=Claude B. |title=Post-metamorphic Feeding in Lampreys |date=2019 |url=|work=Lampreys: Biology, Conservation and Control |pages=247–285 |editor-last=Docker |editor-first=Margaret F. |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-024-1684-8_3 |isbn=978-94-024-1682-4 |last2=Cochran |first2=Philip A.}} but only 18 species of lampreys engage in this predatory lifestyleJOURNAL, 2002-11-01, Trophic strategies, animal diversity and body size, Trends in Ecology & Evolution, en, 17, 11, 507–513, 10.1016/S0169-5347(02)02615-0, 0169-5347, Lafferty, Kevin D, Kuris, Armand M, JOURNAL, Gill, Howard S., Renaud, Claude B., Chapleau, François, Mayden, Richard L., Potter, Ian C., Douglas, M. E., Phylogeny of Living Parasitic Lampreys (Petromyzontiformes) Based on Morphological Data, Copeia, 2003, 4, 687–703, 10.1643/IA02-085.1, 2003, 85969032, (with Caspiomyzon suggested to feed on carrion rather than live prey). 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.{{Citation |last1=Potter |first1=Ian C. |title=The Taxonomy, Phylogeny, and Distribution of Lampreys |date=2014-11-25 |url=https://www.springer.com/cda/content/document/cda_downloaddocument/9789401793056-c1.pdf?SGWID=0-0-45-1486832-p176846628 |work=Lampreys: Biology, Conservation and Control |pages=35–73 |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-017-9306-3_2 |isbn=978-94-017-9305-6 |access-date=2018-10-21 |last2=Gill |first2=Howard S. |last3=Renaud |first3=Claude B. |last4=Haoucher |first4=Dalal |archive-date=3 August 2018 |archive-url=https://web.archive.org/web/20180803014120weblink |url-status=dead }} Adults of the non-carnivorous species do not feed; they live on reserves acquired as ammocoetes. 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,JOURNAL, Silva, S., Araújo, M. J., Bao, M., Mucientes, G., Cobo, F., 2014, The haematophagous feeding stage of anadromous populations of sea lamprey Petromyzon marinus: low host selectivity and wide range of habitats, Hydrobiologia, 734, 1, 187–199, 10.1007/s10750-014-1879-4, 10261/98126, 17796757, 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.JOURNAL, Almeida, Pedro R., Arakawa, Hiroaki, Aronsuu, Kimmo, Baker, Cindy, Blair, Stevie-Rae, Beaulaton, Laurent, Belo, Ana F., Kitson, Jane, Kucheryavyy, Aleksandr, Kynard, Boyd, Lucas, Martyn C., Moser, Mary, Potaka, Ben, Romakkaniemi, Atso, Staponkus, Robertas, 2021-12-01, Lamprey fisheries: History, trends and management, Journal of Great Lakes Research, Supplement on Sea Lamprey International Symposium III (SLIS III), en, 47, S159–S185, 10.1016/j.jglr.2021.06.006, 2021JGLR...47S.159A, 0380-1330, 10174/31871, 237752229, 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.WEB, Parishes: Petersham,weblink British History Online, 26 July 2023, The reduction of pollution in the Thames and River Wear has led to recent sightings in London and Chester-le-Street.NEWS,weblink Prehistoric bloodsucker in Thames, 1 July 2009, BBC News, 27 September 2012, NEWS,weblink Giant blood sucker found in River Wear, The Northern Echo, 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 control programs to control lampreys are undergoing modifications due to concerns of drinking water quality in some areas.WEB, Lehman, Don, Chemical concerns may halt Lake Champlain treatments,weblink poststar.com, 15 August 2016, The Post Star, Biology (File:Lamprey anatomy.png|400px|thumb|Basic external anatomy of a lamprey) Anatomy Adults superficially resemble eels in that they have scaleless, elongated bodies, with the largest species, the sea lamprey having a maximum body length of around {{Convert|1.2|m|ft}}. Lacking paired fins,JOURNAL, Tulenko, Frank J., McCauley, David W., MacKenzie, Ethan L., Mazan, Sylvie, Kuratani, Shigeru, Sugahara, Fumiaki, Kusakabe, Rie, Burke, Ann C., 2013-07-16, Body wall development in lamprey and a new perspective on the origin of vertebrate paired fins, Proceedings of the National Academy of Sciences, en, 110, 29, 11899–11904, 10.1073/pnas.1304210110, free, 0027-8424, 3718130, 23818600, adult lampreys have one nostril atop the headJOURNAL, Aurangzeb, Zeenat, Daghfous, Gheylen, Innes, Liessell, Dubuc, Réjean, Zielinski, Barbara, December 2021, Current understanding of lamprey chemosensory systems, Journal of Great Lakes Research, en, 47, S650–S659, 10.1016/j.jglr.2021.04.020, free, 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.JOURNAL, XU, Yang, ZHU, Si-Wei, LI, Qing-Wei, 2016-09-18, Lamprey: a model for vertebrate evolutionary research, Zoological Research, 37, 5, 263–269, 10.13918/j.issn.2095-8137.2016.5.263, 2095-8137, 5071338, 27686784, Lampreys have been described as the only living vertebrates to have four eyes,NEWS, 2018-04-05, Three-eyed lizards are not uncommon. Four-eyed ones are a novelty, The Economist,weblink 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).BOOK, Nieuwenhuys, R, The central nervous system of vertebrates, Springer, 1998, 978-3-540-56013-5, Berlin New York, 454, The eyes of juvenile lampreys are poorly developed eyespot-like structures that are covered in non-transparent skin, while the eyes of adult lampreys are well developed.JOURNAL, Suzuki, Daichi G., Grillner, Sten, August 2018, The stepwise development of the lamprey visual system and its evolutionary implications, Biological Reviews, en, 93, 3, 1461–1477, 10.1111/brv.12403, 29488315, 1464-7931, 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.BOOK, V. Kardong, Kenneth, Vertebrates: Comparative Anatomy, Function, Evolution., McGraw Hill, 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.JOURNAL, Potter, Ian C., Gill, Howard S., 2003, Adaptive Radiation of Lampreys, Journal of Great Lakes Research, 29, 95–112, 2003JGLR...29...95P, 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.JOURNAL, Khidir, K. Teresa, 2003, Oral fimbriae and papillae in parasitic lampreys (Petromyzontiformes), Environmental Biology of Fishes, 66, 3, 271–278, 10.1023/A:1023961910547, 10254661, The teeth on their oral disc are primarily used to help the animal attach itself to its prey.BOOK, Rohde, Klaus,weblink Marine Parasitology, 2005-09-13, Csiro, 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.BOOK, Ehrlich, Hermann,weblink Biological Materials of Marine Origin: Vertebrates, 2014-12-01, Springer, 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 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.BOOK, Warren, Melvin L. Jr.,weblink Freshwater Fishes of North America: Volume 1: Petromyzontidae to Catostomidae, Burr, Brooks M., 2014-07-10, JHU Press, 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.JOURNAL, Renaud, C. B., Gill, H. S., Potter, I. C., 2009, Relationships between the diets and characteristics of the dentition, buccal glands and velar tentacles of the adults of the parasitic species of lamprey,weblink Journal of Zoology, 278, 3, 231–242, 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.NEWS, What we know about lampreys – the arctic bloodsuckers that swarm Alaska rivers by the millions,weblink 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.JOURNAL, Yokoyama, Hiromasa, Yoshimura, Miho, Suzuki, Daichi G., Higashiyama, Hiroki, Wada, Hiroshi, January 2021, Development of the lamprey velum and implications for the evolution of the vertebrate jaw, Developmental Dynamics, en, 250, 1, 88–98, 10.1002/dvdy.243, 1058-8388, free, 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)WEB, Haaramo, Mikko, 11 March 2008, Mikko's Phylogeny Archive,weblink 26 January 2009, but DNA evidence suggests that they are in fact the sister taxon of lampreys.JOURNAL, Heimberg, A. M., Cowper-Sal-Lari, R., Sémon, M., Donoghue, P. C., Peterson, K. J., 2010, MicroRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate, Proceedings of the National Academy of Sciences of the United States of America, 107, 45, 19379–83, 10.1073/pnas.1010350107, 2984222, 20959416, 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.JOURNAL, Mano, Hiroaki, Fukada, Yoshitaka, 2007, A Median Third Eye: Pineal Gland Retraces Evolution of Vertebrate Photoreceptive Organs†, Photochemistry and Photobiology, en, 83, 1, 11–18, 10.1562/2006-02-24-IR-813, 16771606, 1751-1097, 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.JOURNAL, Barany, A., Shaughnessy, C. A., Fuentes, J., Mancera, J. M., McCormick, S. D., 2020-02-01, Osmoregulatory role of the intestine in the sea lamprey (Petromyzon marinus), American Journal of Physiology. Regulatory, Integrative and Comparative Physiology, 318, 2, R410–R417, 10.1152/ajpregu.00033.2019, 1522-1490, 31747320, free, (File:Lamprey skeleton lateral view.jpg|alt=Lamprey skeleton|thumb|The cartilaginous skeleton of a lamprey washed up on a beach in North Carolina.)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.NEWS,weblink In swimming, jellyfish and lampreys really pull their weight, 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,WEB, 2017-07-06, A Leap in Lampreys: Unlovely Fish Make Welcome Comback,weblink 2021-03-27, Friends of the Eel River, en-US, but provide it with limited climbing ability so that it can travel upstream and up ramps or rocks to breed.JOURNAL, Reinhardt, Ulrich, November 2008, Lamprey climbing behavior,weblink Canadian Journal of Zoology, 86, 10.1139/Z08-112, 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|alt=Lamprey camouflage|thumb|The lamprey's light-colored underside and darker back allow it to blend in when viewed from above or below, an example of countershadingcountershadingMany lampreys exhibit countershading, a form of camouflage.JOURNAL, Gabbott, Sarah E., Donoghue, Philip C. J., Sansom, Robert S., Vinther, Jakob, Dolocan, Andrei, Purnell, Mark A., 2016-08-17, Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye, Proceedings of the Royal Society B: Biological Sciences, en, 283, 1836, 20161151, 10.1098/rspb.2016.1151, 0962-8452, 5013770, 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.JOURNAL, Todd, P. R., Wilson, R. D., 1983-03-01, Epidermal pigmentation and liver coloration in the southern hemisphere lamprey, Geotria austral is Gray, New Zealand Journal of Marine and Freshwater Research, 17, 1, 21–26, 10.1080/00288330.1983.9515983, 0028-8330, free, 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. Genetics and immunology 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).JOURNAL, Nagawa, Fumikiyo, Kishishita, Natsuko, Shimizu, Kazumichi, Hirose, Satoshi, Miyoshi, Masato, Nezu, Junnya, Nishimura, Toshinobu, Nishizumi, Hirofumi, Takahashi, Yoshimasa, Hashimoto, Shu-ichi, Takeuchi, Masaki, Miyajima, Atsushi, 9, 2007, Antigen-receptor genes of the agnathan lamprey are assembled by a process involving copy choice, Nature Immunology, 8, 2, 206–13, 10.1038/ni1419, 17187071, 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.JOURNAL, Pancer, Z., Amemiya, C. T., Ehrhardt, G. T. R. A., Ceitlin, J., Gartland, G., Cooper, M. D., 2004, Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey,weblink Nature, 430, 6996, 174–180, 2004Natur.430..174P, 10.1038/nature02740, 15241406, 876413, free, 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.JOURNAL, Macey, D. J., Cake, M. H., Potter, I. C., 1988, Exceptional iron concentrations in larval lampreys (Geotria australis) and the activities of superoxide radical detoxifying enzymes, Biochemical Journal, 252, 1, 167–172, 10.1042/bj2520167, 1149120, 3421899, Lifecycle (File:Lamprey larva labelled.png|thumb|{{center|Larva of an unknown lamprey species}})The adults spawn in nests of sand, gravel and pebbles in clear streams. After hatching from the eggs, young larvae—called ammocoetesWEB,weblink Ammocoete Definition & Meaning, Dictionary.com, 2022-08-06, WEB,weblink 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.THESIS, Evans, Thomas M., Assessing Food and Nutritional Resources of Native and Invasive Lamprey Larvae Using Natural Abundance Isotopes, Ohio State University,weblink 2012, The eyes of the larvae are underdeveloped, but are capable of discriminating changes in illuminance.BOOK,weblink 204, Jawless Fishes of the World: Volume 2, 978-1-4438-9240-7, Orlov, Alexei, Beamish, Richard, 2016-04-26, Cambridge Scholars, Ammocoetes can grow from {{convert|3|–|4|in|cm|0|abbr=off}} to about {{convert|8|in|cm}}.BOOK,weblink The Chordates, 978-0-521-23658-4, McNeill Alexander, R., 1981-08-06, CUP Archive, BOOK, September 2008, Ecology of the New Zealand Lamprey (Geotria australis) - A literature review, Securing Blue Duck in the Central North Island: Technical Report,weblink 978-0-478-14542-7, 1179-1659, Many species change color during a diurnal cycle, becoming dark at day and pale at night.JOURNAL, July 1935, The Photoreceptors of Lampreys: II. The Functions of the Pineal Complex,weblink Journal of Experimental Biology, 12, 3, 254–270, Young, J. Z., 10.1242/jeb.12.3.254, free, The skin also has photoreceptors, light sensitive cells, most of them concentrated in the tail, which helps them to stay buried.BOOK,weblink 229, Animal Diversity, 978-94-011-6035-3, Kershaw, Diana R., 2012-12-06, Springer, Lampreys may spend up to eight years as ammocoetes,BOOK,weblink 109, Lampreys: Biology, Conservation and Control, 978-94-017-9306-3, Docker, Margaret F., 2014-11-24, 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.BOOK,weblink Lampreys: Biology, Conservation and Control, 978-94-017-9306-3, Docker, Margaret F., 2014-11-24, Springer, While metamorphosing, they do not eat.JOURNAL, Silva, S., Servia, M. J., Vieira-Lanero, R., Cobo, F., 2013, Downstream migration and hematophagous feeding of newly metamorphosed sea lampreys (Petromyzon marinus Linnaeus, 1758), Hydrobiologia, 700, 277–286, 10.1007/s10750-012-1237-3, 16752713, File:Oeufs002b,57.png|72px|left|{{center|A hagfish egg, illustration by Adolphe MillotAdolphe MillotThe 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 (