Résumé :
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Copepods are very ancient arthropods. They poorly fossilize, and thus it is rare to fi nd such traces of their remains in sediments which could have facilitated the study of their morpho-logical, physiological, and ecological evolution (Frey, 1964; Walossek & Müller, 1997). Only some recent remains have been identifi ed, mainly spermatophores (Frey, 1964; Warner, 1990) and also, diaptomid egg-sacs found from Denmark and West Greenland in Late Quaternary lake sediments (12 000 to 10 000 and 5 000 to 500 14 C years BP respectively) (Bennike, 1998). Zoogeographical data suggest that the copepod fauna of continental waters was already rich and diversifi ed in the Tertiary (Palmer, 1960, 1969; Cressey & Patterson, 1973), such that different species have had ample time to adapt to the conditions of their environment. While numerous species are freeliving, utilizing various preys, others are stenophagous, and some have become parasites or semiparasites at different stages of their development. Copepods are associated with the aquatic environment, although some can permanently tolerate low humidity. In oceans and lakes, they proliferate in pelagic waters as well as on, and even within the sediments (psammic fauna of coarse sand). In freshwaters too, they are present in many different biotopes, as well as in the humid litter of deciduous forests, in decaying leaf-mould of hollow trees, inside ant nests, etc. This book is primarily a practical guide, intended to provide the reader with a general idea of what a freshwater copepod is. It will also serve as a basis for further study, and as an introduction to the literature. The bibliography is not exhaustive, but has been constructed to pave the way for further research. A natural approach is adopted, in which copepods are viewed as active players in the complex network of interactions within communities of organisms. The complexity of copepods is not limited to their morphology. They provide ideal subjects for the study of numerous problems in general biology and cytogenetics as well as physiological processes associated with their feeding behaviour, reproduction, and ecology. All these subjects will be briefl y touched upon.
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