Taxonomy of the Freshwater Eels, Genus Anguilla Schrank, 1798

Abstract

The freshwatereels of the genus Anguilla Schrank, 1798, are widely distributed in the world and have unique characters such as a catadromous life history strategy, a long spawning migration, and a long leptocephalus larval period. Although there have been a large number of studies on their ecology and physiology, there have been relatively few studies on their taxonomy. Comprehensive revisions of the genus Anguilla using most or all the presently recognized species were done by Kaup (1856), Gunther (1870), and Ege (1939) with morphological analysis. However, relatively little work has been done after the milestone study of Ege (1939). This lack may have been due to the extensive nature of his study, in which he carefully examined a large number of specimens of all the species of the genus Anguilla from throughout the world. As a result, it may have been generally thought that all the problems of the taxonomy of the genus Anguilla were completely solved. However, the freshwatereels have several groups of species that have very similar morphological features, making them difficult to distinguish, and a recent reexamination of Ege’s (1939) study found that there were still several important problems remaining in the present taxonomy of the freshwatereels. The purpose of this chapter is to introduce the history of the taxonomy of the freshwatereels, to evaluate the presently accepted taxonomy, and to propose a new taxonomy to solve the problems of Ege’s (1939) study.