Haemoglobin Polymorphism of the American Fresh Water Eel Anguilla

Abstract

A NEW interest in the problems of taxonomy and migration of Atlantic eels^1–5 was aroused by Tucker¹ when he advocated a hypothesis radically different from Schmidt's generally accepted picture of the natural history of Atlantic eels⁶. According to Schmidt, the American and the European fresh water eels constitute two separate species, Anguilla rostrata and A. vulgaris. These can be distinguished by morphological characters such as the numbers of vertebrae. Both species migrate to spawning areas in the Sargasso Sea. Tucker finds it unlikely that European eels can accomplish the inferred return journey to the remote breeding place. American eels, however, have a much shorter distance to cover and may be guided by favourable sea currents. Thus, Tucker concludes that only American eels contribute to the propagation of the Atlantic eel population, which should therefore be genetically homogeneous and constitute one species. The morphological differences are thought by Tucker to be environmentally induced by differences in water temperature encountered by the early stages of the two groups of larvae that will eventually reach American or European coastal waters.