PLEUROXUS-DENTICULATUS (CRUSTACEA, ANOMOPODA, CHYDORIDAE) - A NEW INVADER IN THE DANUBE BASIN

Pleuroxus denticulatus Birge, 1879 is a new invader from Western to Ce ntral Europe. Its occurrence in a Danube inundation (Slovak region) pr obably corresponds with the junction of the Danube and Rhine Rivers. T he species was found among 'the hard macrophytes' of flowing arms and artificial ponds. A large variability was recorded in the number of va lval denticles and in postabdominal denticulation. It is evident that part of the N. American populations is different from European populat ions. P. denticulatus seems to represent two sibling species. Both are characterised by an angular distal postabdominal corner, bearing 3-4 denticles, and by valval denticles on the postero-ventral corner.