Limnetica 40
Redescription of Acanthocyclops vernalis (Fischer, 1853) and Acanthocyclops robustus (Sars, 1863) from neotypes, with special reference to their distinction from Acanthocyclops americanus (Marsh, 1892) and its invasion of Eurasia
This paper provides a redescription of Acanthocyclops vernalis and A. robustus neotypes collected in their type localities in Russia (Orlov pond, Peterhof) and Norway (a stream outcoming from a lake in Oslo) with a special attention to their morphological differentiation from A. americanus. Due to overmixing of these species throughout most of the last century and fast arrival and spreading of the aggressive planktonic predator A. americanus, all previous indications of A. robustus should be checked and confirmed. More than 200 localities in Valencia region (Spain) and more than 30 localities in Armenia, Belgium, Egypt, Finland, France, Kazakhstan, Norway, Russia, Sweden and Tunisia were checked for the presence of A. americanus. In all these countries the invader was found in large numbers as dominant species often substituting other native Acanthocyclops species in limnetic communities. A brief history and possible explanation of the successful invasion of A. americanus in Eurasia is discussed.
