Fig. 1: A small crayfish (Orsonectes limosus) between lots of zebra mussels (Dreissena polymorpha). Both species were introduced. The crayfish from North America and the zebra mussel from the Black Sea. — EXIF: Nikon D200; Δt=1/250 s; f=20 mm; f/8.0; ISO 100; 2009-09-16 19:49:24
