Anguilliformes

Article By:

Boschung, Herbert T. Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.034600

The true eels, a large order of actinopterygian fishes, also known as the Apodes. The order Anguilliformes is related to Saccopharyngiformes (sackpharynx fishes), Elopiformes (tarpons), and Notacanthiformes (spiny eels and halosaurs); all members have a leptocephalous (slender and transparent) larval stage in development. The chief characteristics of the Anguilliformes include the following: an elongate body with numerous vertebrae; a pectoral girdle that, when present, is free from the head; absence of a pelvic girdle and pelvic fins in extant adults; dorsal and anal fins that are confluent with the caudal fin (the caudal fin is absent in some ophichthids); loss of skeletal parts, especially those about the head (for example, the orbitosphenoid, posttemporal, and symplectic bones, as well as the gular plate, are absent); mesocoracoid and postcleithra are absent; swim bladder is present, usually physostomous (that is, having a connection to the esophagus); restricted gill openings; no fin spines; scales are usually absent or, if present, cycloid and embedded in the skin; and 6–49 branchiostegal rays. See also: Actinopterygii; Eel; Elopiformes; Notacanthoidei; Saccopharyngiformes; Swim bladder

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