Eels are elongated fish, ranging in length from 5 centimetres (2.0 in) in the one-jawed eel (Monognathus ahlstromi) to 4 metres (13 ft) in the slender giant moray.[2] Adults range in weight from 30 grams to well over 25 kilograms. They possess no pelvic fins, and many species also lack pectoral fins. The dorsal and anal fins are fused with the caudal or tail fin, forming a single ribbon running along much of the length of the animal.[1]Most eels live in the shallow waters of the ocean and burrow into sand, mud, among rocks, or in cracks found in coral reefs. A majority of eel species are nocturnal, and thus are rarely seen. Sometimes, they are seen living together in holes, or "eel pits". Some species of eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 metres (13,000 ft). Only members of the Anguillidae family regularly inhabit fresh water, but they too return to the sea to breed.[3]
Eels begin life as flat and transparent larvae, or leptocephali. Eel larvae drift in the surface waters of the sea feeding on marine snow, small particles that float in the water. Eel larvae then metamorphose into glass eels and then become elvers before finally seeking out their juvenile and adult habitats.[2]
This classification follows FishBase in dividing the eels into fifteen families. Additional families that are included in other classifications (notably ITIS and Systema Naturae 2000) are noted below the family with which they are synomized in the Fish Base system.
The origin of the fresh water species has been problematic. Genomic studies indicate that they are a monophyleticgroup which originated among the deep-sea eels.[4]
Freshwater eels (unagi) and marine eels (conger eel,anago) are commonly used in Japanese cuisine; foods such as Unadon and Unajuu are popular but expensive. Eels are also very popular in Chinese cuisine, and are prepared in many different ways. Hong Kong eel prices have often reached 1000 HKD per kilogram, and once exceeded 5000 HKD per kilogram. Eel is also popular inKorean cuisine and is seen as a source of stamina for men.[citation needed] The European eel and other freshwater eels are eaten in Europe, the United States, and other places. A traditional east London food is jellied eels, although their demand has significantly declined since World War II. The Basque delicacy angulas consists ofdeep-fried elver (young eels); elver eels usually reach prices of up to 1000 euro per kilogram.[5] New Zealand longfin eelis a traditional Māori food in New Zealand. In Italian cuisineeels from the Comacchio area (a swampy zone along theAdriatic coast) are specially prized along with freshwater eels of Bolsena Lake. In northern Germany, The Netherlands, the Czech republic, Poland, Denmark andSweden, smoked eel is considered a delicacy.
Fishermen consumed elvers as a cheap dish, but environmental changes have reduced eel populations. They are now considered a delicacy and are priced at up to £700 per kg in the United Kingdom.[citation needed]
Eel blood is toxic to humans[6] and other mammals[7][8][9], but both cooking and the digestive process destroy the toxic protein. The toxin derived from eel blood serum was used by Charles Richet in his Nobel winning research which discovered anaphylaxis (by injecting it into dogs and observing the effect).
Eelskin leather is highly prized. It is very smooth and exceptionally strong. However, it does not come from eels. It comes from the Pacific Hagfish, a jawless fish which is also known as the slime eel.[10][11]
The English name eel descends from Old English ǽl,Common Germanic *ǣlaz. Also from the common Germanic are German Aal, Middle Dutch ael, Old High German âl, Old Norse áll. Katz (1998) identifies a number ofIndo-European cognates, among them the second part of the Latin name of the eels, anguilla, which is attested in its simplex form illa in a glossary only, and likewise the Greek word for "eel", egkhelys, the second part being attested inHesychius as elyes.[13] The first compound member,anguis "snake", is cognate to other Indo-European words for "snake", cf. Old Irish escung "eel", Old High German unc"snake", Lithuanian angìs, Greek ophis, okhis, Vedic Sanskrit áhi, Avestan aži, Armenian auj, iž, Old Church Slavonic *ǫžь, all from Proto-Indo-European*oguhis, ēguhis. The word also appears in Old English igil "hedgehog" (named as the "snake eater"), and perhaps in the egi- of Old High German egidehsa "wall lizard". The name of Bellerophon(Βελλεροφόντης, attested in a variant Ἐλλεροφόντης in Eustathius of Thessalonica) according to this theory is also related, translating to "the slayer of the serpent" (ahihán), the ελλερο- being an adjective for a lost ελλυ- "snake", directly comparable to Hittite ellu-essar- "snake pit". This myth likely came to Greece via Anatolia, and in the Hittite version, the dragon is called Illuyanka, the illuy- part being cognate to the illa word, and the -anka part being cognate to the angu word for "snake". As designations for "snake" (and similar shaped animals) are often liable to taboo in many Indo-European and non-Indo-European languages, no unambiguous Proto-Indo-European form for the eel word can thus be reconstructed, it could have been *ēl(l)-u-, *ēl(l)-o- or similar.
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