Dikerogammarus villosus
The Great Dikerogammarus ( Dikerogammarus villosus ), originally as Gammarus marinus var villosa described, but later found in the family of Pontogammaridae, is an up to 20 -mm-long predatory amphipod. He received his German name only after he had immigrated as neozoon in almost all German water systems.
Description
The Great Dikerogammarus is up to 2 cm long and is one of the major representatives of the encountered in Central Europe amphipods. Its coloration is variable, white - yellowish to greenish and often provided with a clear, dark banding. The antennae are reddish brown, his eyes red. Two striking conical cusps on the segments of the spinal end ( Urosom ) were decisive for the German -language designation. The hairs on the flagellum of the second antennae is much longer than the individual members of the flagellum, at the antenna base is the hair loose. These features distinguish the Great Dikerogammarus of his relatives Dikerogammarus haemobaphes and Dikerogammarus bispinosus.
Dissemination
Originally used in the lower reaches of the Black Sea which opens rivers, he settled in the Danube long time only until the middle reaches. The cancer appeared for the first time in 1992 in the German Danube, in 1993 in the Main -Danube Canal, 1994 Main and 1995 in Rhine, over which he achieved in 2002 the lake. In 2007, he had already conquered the Upper Rhine to Stein am Rhein. 1998 Art in the Weser at Minden, in the Mittelland Canal, Elbe Lateral Canal, in the Elbe and the Elbe - Havel Canal has been demonstrated already dominant occurring in many sections of this channel. Today, he is also widely used in the Elbe, more reserves are found in the Havel and Spree. The animal has reached the Oder, in the west already has penetrated into the Rhone system and been proven in the south in Lake Garda. Meanwhile, the killer shrimp is also common in some lakes in the foothills of the Alps, such as the Lake Zurich at high densities. He was discovered here in February 2006 and has previously apparently settled in a few years unnoticed the entire lake. 2010, the species was observed also in the UK.
Habitat
Large individuals are often found under rocks or in crevices where they wedge themselves with their splayed Peraeopoden ( wishbones ) III -V. He is often in colonies of zebra mussels. Smaller individuals colonize the superficial Algenfilz of stones and sheet piling.
Way of life
The Great Dikerogammarus is an omnivore. It feeds as predatory predator Gammarus tigrinus from ( as he himself an amphipod of subordination Gammaridea ) and probably more important predators of Chelicorophium curvispinum. Its rapid spread is due to its great aggressiveness in the biotope, which has already led to a reduction in biodiversity and to local extinction of certain species. In addition to the predatory food captured the Great Dikerogammarus can live on dead plant debris.
Reproduction
The female carries the always larger males before egg laying on her back around with you ( Prekopula ). The female then lays the eggs in a brood chamber on the front side of the abdomen. After fertilization by the male, the eggs remain until hatching of the finished young crabs in the brood chamber. So how do all amphipods also operates the Great Dikerogammarus brood care.