Oocyte Numbers as a Diagnostic Character for the Identification of Ammocœte Species

Abstract

THE nature of the relationship between the European brook lamprey L. planeri and the closely related parasitic form, L. fluviatilis, has been the subject of considerable discussion, especially since the classical studies of Weissenberg^1–3 showed that differences between these species are based on biological rather than morphological criteria. The difficulty of finding taxonomic characters for the identification of their larval stages has been a matter of great inconvenience to workers in this field, especially since the two species often occur together in the same river system.