Two Asian fresh water shrimp…

The river Erft and its tributary Gillbach in western Germany are thermally polluted, and harbour exotic plant and animal species introduced  by aquarium hobbyists. Here, we report for the first time the occurrence of two species of fresh water shrimp, Neocaridina davidi (Bouvier,  1904) and Macrobrachium dayanum (Henderson, 1893), from these heavily modified waters. We briefly discuss their taxonomy and provide 
characters for distinguishing the species. Due to its dependence on warm waters, it is unlikely that M. dayanum populations will persist permanently beyond the range of the thermal pollution. In contrast, N. davidi is able to tolerate much colder temperature regimes, and might disperse further into the Rhine drainage. Known parasites of N. davidi are however rather specific, and do most likely not pose a threat to 
native or other introduced crustacean species.