Los crustáceos del plancton de los embalses españoles

The planktonic crustacea of the spanish reservoirs. — The limnological study of one hundred Spanish reservoirs has been an excellent oportunity to collect crustaceans of the majority of our regions and of almost all the hydrological basins. This study is intended to contribute to the poorly-known crustacean fauna of this area. 
For this reason, some systematic aspects of the identified species are considered. The intraspecific systematics are considered in some cases and the differences between morphologically similar species are discussed.
The abundance of each species in the reservoirs, its geographical distribution and the more important ecological factors in distribution are also discussed.
Spain is a country practically without lakes, but in a few years more than 700 reservoirs have been constructed. The colonization of these reservoirs by planktonic species is hindered by the lack of natural lakes in many areas, and the migration of species from other neighboring areas (Central Europe, Africa) is then possible. This factor contributes also in increasing the
proportion of heleoplanktonic species in our reservoirs. A total of 64 species have been identified, of whom 35 (54,6 %) are heleoplanktonic and 8
(12,5 %) are new records for the Iberian Península.
Among the cladocera (40 species) the genera Daphnia and Ceriodaphnia are the most frequent, and many of its species are euplanktonic. The
presence of ciclomorphotic species of Daphnia (D. cucullata, D. galeata and D. hyalina hyalina)
and others whose geographical distribution did not inelude Spain (D. párvula, Ceriodaphnia
cornuta), shows the possible migration paths of these species to the Península.

The Diaptomidae (7 species), a very frequent group in the European lakes, are poorly represented in Spanish reservoirs, and appear only
in 44 of them (41,9 % of the studied reservoirs). Many of the species are characteristic of temporary waters and withstand dessication (Lovenula alluaudi, Arctodiaptomus wierzejskii, A. salinus and Diaptomus castaneti); only Copidiaptomus steueri is euplanktonic. Distribution of all these species shows a good correlation with the more important environmental factors of our reservoirs (mineralization and eutrophy), and can be used as biological indicators.
The fauna of Cyclopidae (13 species) is similar to that of Diaptomidae, in that only Acanthocyclops robustus and Cyclops sp. pl. are euplanktonic. In general, they are less correlated with environmental characteristics, and seem more dependent on the absence of direct competitors. 

Other groups are poorly represented, and the Harpacticoida (Canthocampus staphylinus) and Ostracoda (Candona, Cypria and Cypridosis) are associated with the sediment or the shore. .