Evolution and adaptive radiation in the chydoridae (crustacea: cladocera): a study in comparative functional morphology and ecology

Abstract

Abstract (Numbers given in the summary refer to certain key figures in the text which facilitate understanding.) An account is given of the functional morphology, ecology, habits and feeding mechanisms, of a representative series of anomopod cladocerans of the family Chydoridae, embracing some 22 species belonging to 15 genera. Of these genera two are defined as new on the basis of this investigation. Habits, which often depend on anatomical specializations of great complexity, are more diverse than has been supposed, and permit the exploitation of a diversity of ecological niches. The functional significance of many anatomical features is described. Carapace specializations, previously almost unstudied, are extremely important. Fundamental homologies not only within the Chydoridae but within the Anomopoda as a whole, can now be recognized and the feeding mechanism of all species can be related to one original type. By subtle modification of its various components, however, this basic mechanism has been adapted to very different ways of life and to different functions. The various species are described in a sequence which in part illustrates the progressive development of specialized ways of life rather than phylogeny, but light has been thrown on affinities, or lack of affinity, between certain species.