ClassACTINOPTERYGII Ray-finned fishes
FamiliesANGUILLIDAE(1)Freshwater Eels CHLOPSIDAE(2)False morays COLOCONGRIDAE(1)Short-tail congers CONGRIDAE(20)Conger eels CYEMATIDAE(1) DERICHTHYIDAE(2)Longneck eels EURYPHARYNGIDAE(1)Deepsea gulpers MORINGUIDAE(2)Spaghetti eels MURAENESOCIDAE(2)Pike eels MURAENIDAE(10)Moray eels NEMICHTHYIDAE(3)Snipe eels NETTASTOMATIDAE(4)Duckbill eels OPHICHTHIDAE(24)Snake eels ... SACCOPHARYNGIDAE(1) SERRIVOMERIDAE(1)Sawtooth eels SYNAPHOBRANCHIDAE(5)Cutthroat eels
The Order Anguilliformes, or true eels, contains 20 families and about 820 species, and includes some very bizarre groups.
Species are usually long and slender, with long-based dorsal and anal fins that are continuous with the caudal fin (if present) in all but one species. All species lack pelvic fins, and some groups lack pectoral fins. Scales are usually absent, or if present, are embedded in skin.
True eels range in size from about 5 cm to 4 metres in length, and all species pass through a pelagic, ribbon- or leaf-like larval stage called a leptocephalus larva.
Most species are nocturnal and live in shallow waters, burrowing into sandy or muddy bottoms, or hiding in crevices, caves and holes on coral and rocky reefs. Many species live at the bottom of the deep-sea, and a number of bizarre families inhabit the mesopelagic twilight zone or are bathypelagic.
Only members of the family Anguillidae regularly inhabit freshwater, and undertake long migrations to breed offshore in the deep water.
Most true eels are predators and belong to one of three families: Congridae (Conger eels), Muraenidae (Moray Eels) and Ophichthidae (snake eels and worm eels).
Some species are excellent food fish and form the basis of very important commercial fisheries.
In August 2011, a new family, the Protoanguillidae, comprising a single genus and species, Protanguilla palau, with a separate caudal fin and many other primitive characters was described. Morphological and molecular data suggest that this species is the most primitive living member of the Anguilliformes (Johnson et al. 2011).
The fossil record dates back to the Cretaceous about 100 million years ago.
Böhlke, E.B. (ed.) 1989. Fishes of the Western North Atlantic. Volume One: Orders Anguilliformes and Saccopharyngiformes. Volume Two: Leptocephali. Yale University : The Sears Foundation for Marine Research Part 9, 1055 pp.
Chow, S., Kurogi, H., Mochioka, N., Kaji, S., Okazaki, M. & Tsukamoto, K. 2009. Discovery of mature freshwater eels in the open ocean. Fish. Sci. 75, 257–259.
Forey, P.L., Littlewood, D.T.J., Ritchie, P. & Meyer, A. 1996. Interrelationships of elopomorph fishes. pp. 175-192 In Stiassny, M.L.J., Parenti, L.R. & Johnson, G.D. (eds). Interrelationships of Fishes. San Diego : Academic Press 496 pp.
Forey, P.L., Yi, L., Patterson, C. & Davies, C.E. 2003. Fossil fishes from the Cenomanian (Upper Cretaceous) of Namoura, Lebanon. J. Syst. Palaeontol. 1: 227–330.
Hoese, D.F., D.J. Bray, J.R. Paxton & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds.) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia, Part 1: xxiv-670.
Inoue, J.G., M. Miya, M.J. Miller, T. Sado, R. Hanel, K. Hatooka, J. Aoyama, Y. Minegishi, M. Nishida & K. Tsukamoto. 2010. Deep-ocean origin of the freshwater eels. Biology Letters 6(3): 363–366.
Inoue, J. G., Miya, M., Tsukamoto, K. & Nishida, M. 2004. Mitogenomic evidence for the monophyly of elopomorph fishes (Teleostei) and the evolutionary origin of the leptocephalus larva. Mol. Phylogenet. Evol. 32, 274–286.
Johnson, D.G., Ida, H., Sakaue, J., Sado, T., Asahida, T. & Miya, M. 2011. A 'living fossil' eel (Anguilliformes: Protoanguillidae, fam. nov.) from an undersea cave in Palau. Proceedings of the Royal Society B [Date published published online 17 August 2011]
McCosker, J.F. 1998. Anguilliformes, pp. 86–90. In Paxton, J.R. & Eschmeyer, W.N. (eds) Encyclopedia of Fishes. San Diego: Academic Press.
Mehta, R.S., A.B. Ward, M.E. Alfaro, P.C. Wainwright. 2010. Body Elongation in Eels. Integrative and Comparative Biology 50: 1091-1105.
Miller, M.J., Aoyama, J., Mochioka, N., Otake, T., Castle, P.H.J., Minagawa, G., Inagaki, T. & Tsukamoto, K. 2006. Geographic variation in the assemblages of leptocephali in the western South Pacific. Deep-Sea Res. I 53, 776–794.
Miller, M.J. & Tsukamoto, K. 2004. An introduction to leptocephali: biology and identification. Tokyo, Japan: Ocean Research Institute, The University of Tokyo.
Nelson, J.S. 2006. Fishes of the World. New Jersey : John Wiley & Sons, 601 p.
Prosek, J. 2010. Eels. New York: Harper Collins.
Robins, C.R. 1989. The phylogenetic relationships of the anguilliform fishes. Orders Anguilliformes and Saccopharyngiformes. Fishes of the Western North Atlantic, vol. 1 (ed. E.B. Böhlke), pp. 9–23. New Haven, CT: Sears Foundation for Marine Research.
Tsukamoto, K., Nakai, I. & Tesch, F.W. 1998. Do all freshwater eels migrate? Nature 396: 635–636.
Tsukamoto, K., Aoyama, J. & Miller, M.J. 2002. Migration, speciation, and the evolution of diadromy in anguillid eels. Can. J. Fish. Aquat. Sci. 59: 1989–1998.
Tsukamoto, K., Miller, M.J., Kotake, A., Aoyama, J. & Uchida, K. 2009. The origin of diadromous fish migration: the random escapement hypothesis. In Challenges for diadromous fishes in a dynamic global environment, vol. 69 (eds A. Haro et al.), pp. 45–61. Bethesda, MD: American Fisheries Society.
Wouthuyzen, S., M.J. Miller, J. Aoyama, G. Minagawa, Y.H. Sugeha, S. Suhartati et al. 2005. Biodiversity of anguilliform leptocephali in the central Indonesian Seas. Bull. Mar.Sci. 77: 209-224.