Catadromous eels continue to be slippery research subjects

John C Avise

doi:10.1111/j.1365-294x.2011.05012.x

Abstract

As adults, Atlantic eels (Anguilla rostrata in the Americas and Anguilla anguilla in Europe) are tubular slime-covered fish that spend most of their catadromous life-cycle in coastal environs before swimming far out to sea to reproduce, as part of an intergenerational migratory circuit that provides an interesting reversal of the pattern displayed by adult anadromous salmon that live mostly in the ocean but then migrate long distances to spawn in freshwater streams. Earlier genetic findings on Atlantic eels involved specimens collected across their broad continental ranges and generally indicated that conspecifics probably engage in panmictic or quasi-panmictic spawning,from which arise leaf-shaped leptocephaus larvae that then disperse back to coastal locations more or less at random with respect to the widespread geographical origins of the parental genes they carry. In this issue, Alset al. (2011) add exciting information about this peculiar life-history pattern of catadromous Atlantic eels by extending the genetic analyses to eel larvae collected from the Sargasso Sea, the oceanic area where both species spawn. Results help to confirm standard textbook wisdom that these catadromous eels are nearly unique in the biological world by having both broad geographical distributions and yet displaying intraspecific near panmixia.

Highlights

Atlantic eels (Anguilla rostrata in the Americas and Anguilla anguilla in Europe) are tubular slimecovered fish that spend most of their catadromous life cycle in coastal environs before swimming far out to sea to reproduce, as part of an intergenerational migratory circuit that provides an interesting reversal of the pattern displayed by adult anadromous salmon that live mostly in the ocean but migrate long distances to spawn in freshwater streams
Earlier genetic findings on Atlantic eels involved specimens collected across their broad continental ranges and generally indicated that conspecifics probably engage in panmictic or quasi-panmictic spawning, from which arise leaf-shaped leptocephaus larvae that disperse back to coastal locations more or less at random with respect to the widespread geographical origins of the parental genes they carry
Als et al (2011) add exciting information about this peculiar life-history pattern of catadromous Atlantic eels by extending the genetic analyses to eel larvae collected from the Sargasso Sea, the oceanic area where both species spawn

Summary

Catadromous eels continue to be slippery research subjects

Earlier genetic findings on Atlantic eels involved specimens collected across their broad continental ranges and generally indicated that conspecifics probably engage in panmictic or quasi-panmictic spawning, from which arise leaf-shaped leptocephaus larvae that disperse back to coastal locations more or less at random with respect to the widespread geographical origins of the parental genes they carry. In this issue, Als et al (2011) add exciting information about this peculiar life-history pattern of catadromous Atlantic eels by extending the genetic analyses to eel larvae collected from the Sargasso Sea, the oceanic area where both species spawn. Schmidt and many other researchers that followed his lead

History of indirect mating evidence from continental samples

Towards more direct mating evidence from the spawning grounds

Looking forward