Eels are elongated fish, ranging in length from 5 cm (2 in) in the one-jawed eel (Monognathus ahlstromi) to 4 m (13 ft) in theslender giant moray.[8] Adults range in weight from 30 g (1 oz) to well over 25 kg (55 lb). They possess nopelvic fins, and many species also lackpectoral fins. Thedorsal andanal fins are fused with thecaudal fin, forming a single ribbon running along much of the length of the animal.[1] Eels swim by generating waves that travel the length of their bodies. They can swim backward by reversing the direction of the wave.[9]
Most eels live in the shallow waters of theocean and burrow into sand, mud, or amongst rocks. Most eel species arenocturnal, and thus are rarely seen. Sometimes, they are seen living together in holes or "eel pits". Some eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 m (13,000 ft). Only members of theAnguilla regularly inhabit fresh water, but they, too, return to the sea to breed.[10]
The heaviest true eel is theEuropean conger. The maximum size of this species has been reported as reaching a length of 3 m (10 ft) and a weight of 110 kg (240 lb).[11] Other eels are longer, but do not weigh as much, such as theslender giant moray, which reaches 4 m (13 ft).[12]
Eels begin life as flat and transparentlarvae, calledleptocephali. Eel larvae drift in the sea's surface waters, feeding onmarine snow, small particles that float in the water. Eel larvae then metamorphose into glass eels and become elvers before finally seeking out their juvenile and adult habitats.[8] Some individuals of anguillid elvers remains in brackish and marine areas close to coastlines,[13] but most of them enter freshwater where they travel upstream and are forced to climb up obstructions, such asweirs, dam walls, and natural waterfalls.
Eel eggs hatch firstly into theleptocephalus larval stage.
Larval eels becomeglass eels as they transition from the ocean to fresh water.
As freshwater elvers, eels work their way upstream.
Mature silver stage eels migrate back to the ocean to mate.
Gertrude Elizabeth Blood found that the eel fisheries atBallisodare were greatly improved by the hanging of loosely plaited grass ladders over barriers, enabling elvers to ascend more easily.[14]
Several sets of classifications of eels exist; some, such asFishBase which divide eels into 20 families, whereas other classification systems such asITIS andSystema Naturae 2000 include additional eel families, which are noted below.
Genomic studies indicate that there is amonophyletic group that originated among the deep-sea eels.[15]
Taxonomy
The earliest fossil eels are known from the LateCretaceous (Cenomanian) ofLebanon. These early eels retain primitive traits such aspelvic fins and thus do not appear to be closely related to any extant taxa. Body fossils of modern eels do not appear until theEocene, althoughotoliths assignable to extant eel families and even some genera have been recovered from theCampanian andMaastrichtian, indicating some level of diversification among the extant groups prior to theCretaceous-Paleogene extinction, which is also supported by phylogenetic divergence estimates. One of these otolith taxa, the mud-dwellingPythonichthys arkansasensis, appears to have thrived in the aftermath of the K-Pg extinction, based on its abundance.[16][17][18]
Elvers, often fried, were once a cheap dish in theUnited Kingdom. During the 1990s, their numbers collapsed across Europe.[41] They became a delicacy, and the UK's most expensive species.[42]
The English name "eel" descends fromOld Englishǣl,Common Germanic*ēlaz. Also from the common Germanic areWest Frisianiel,Dutchaal,GermanAal, andIcelandicáll. Katz (1998) identifies a number ofIndo-European cognates, among them the second part of the Latin word for eels,anguilla, attested in its simplex formilla (in a glossary only), and the Greek word for "eel",ἔγχελυςenkhelys (the second part of which is attested inHesychius aselyes).[49][50][51] The first compound member,anguis ("snake"), is cognate to other Indo-European words for "snake" (compare Old Irishescung "eel", Old High Germanunc "snake", Lithuanianangìs, Greekophis, okhis,Vedic Sanskritáhi,Avestanaži, Armenianauj, iž,Old Church Slavonic*ǫžь, all from Proto-Indo-European*h₁ogʷʰis). The word also appears in the Old English word for "hedgehog", which isigil (meaning "snake eater"), and perhaps in theegi- of Old High Germanegidehsa "wall lizard".[52][53]
According to this theory, the nameBellerophon (Βελλεροφόντης, attested in a variant Ἐλλεροφόντης inEustathius of Thessalonica) is also related, translating to "the slayer of the serpent" (ahihán). In this theory, the ελλερο- is an adjective form of an older word, ελλυ, meaning "snake", which is directly comparable to Hittiteellu-essar- "snake pit". This myth likely came to Greece via Anatolia. In the Hittite version of the myth, the dragon is calledIlluyanka: theilluy- part is cognate to the wordilla, and the-anka part is cognate toangu, a word for "snake". Since the words for "snake" (and similarly shaped animals) are often subject to taboo in many Indo-European (and non-Indo-European) languages, no unambiguous Proto-Indo-European form of the word for eel can be reconstructed. It may have been*ēl(l)-u-,*ēl(l)-o-, or something similar.
Timeline of genera
Timeline
In culture
The large lake ofAlmere, which existed in the early MedievalNetherlands, got its name from the eels which lived in its water (the Dutch word for eel isaal orael, so: "ael mere" = "eel lake"). The name is preserved in the new city ofAlmere inFlevoland, given in 1984 in memory of this body of water on whose site the town is located.
The daylight passage in the spring ofelvers upstream along theThames was at one time called "eel fare". The word 'elver' is thought to be a corruption of "eel fare".[14]
A famous attraction on theFrench Polynesian island ofHuahine (part of theSociety Islands) is the bridge across a stream hosting three- to six-foot-long eels, deemed sacred by local culture.
Eel fishing inNazi-eraDanzig plays an important role inGünter Grass' novelThe Tin Drum. The cruelty of humans to eels is used as a metaphor for Nazi atrocities, and the sight of eels being killed by a fisherman triggers the madness of the protagonist's mother.
Sinister implications of eels fishing are also referenced inJo Nesbø'sCockroaches, the second book of theHarry Hole detective series. The book's background includes a Norwegian village where eels in the nearby sea are rumored to feed on the corpses of drowned humans, making the eating of these eels verge on cannibalism.
The 2019 bookThe Gospel of the Eels by Patrick Svensson commented on the 'eel question' (origins of the order) and its cultural history.
^Thomas J. Near; Christine E. Thacker (2024). "Phylogenetic Classification of Living and Fossil Ray-Finned Fishes (Actinopterygii)".Bulletin of the Peabody Museum of Natural History.65 (1):3–302.doi:10.3374/014.065.0101.
^Pl. 661 inGarsault, F. A. P. de 1764. Les figures des plantes et animaux d'usage en medecine, décrits dans la Matiere Medicale de Mr. Geoffroy medecin, dessinés d'après nature par Mr. de Gasault, gravés par Mrs. Defehrt, Prevost, Duflos, Martinet &c. Niquet scrip. [5]. - pp. [1-4], index [1-20], Pl. 644–729. Paris.
^Acou, Anthony, et al. "Assessment of the Quality of European Silver Eels and Tentative Approach to Trace the Origin of Contaminants – A European Overview." The science of the total environment. 743 (2020): n. pag. Web.
^Katz, J. (1998). "How to be a Dragon in Indo-European: Hittite illuyankas and its Linguistic and Cultural Congeners in Latin, Greek, and Germanic". In Jasanoff; Melchert; Oliver (eds.).Mír Curad. Studies in Honor of Calvert Watkins. Innsbruck. pp. 317–334.ISBN3-85124-667-5.{{cite book}}: CS1 maint: location missing publisher (link)
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