Contribution to the taxonomy and distribution of Cyclops abyssorum Sars (Crustacea,Copepoda) in several lakes and ponds of central Italy

A preliminary study has been carried out on the taxonomy and distribution of Cyclops abyssorum Sars in several deep and shallow lakes and in long lasting ponds of central Italy.A morphological and morphometric analysis of material from Lake Albano has shown that its cyclopoids belong to the praealpinus-group of C. abyssorum. This group has also been found in lakes Vico, Martignano, and Bracciano. All these populations have continuous reproduction and do not show any seasonal variation in size.In some of the long lasting Latial ponds forms of the mixed group divulsus have been found. They are characterized by a marked seasonal polymorphism and their life-cycles vary according to whether the basin is filled with water continuously or is subject to desiccation from time to time. The analysis of a population recently collected in Lake Montepulciano (Tuscany) resulted in the identification of an ecotype similar to that described as C. a. apenninae in other eutrophic lakes of the Apennine region.Causal environmental factors responsible for the distribution of these different types of C. abyssorum are discussed.