The gammarid amphipod Eucarinogammarus wagi, a large (~5 cm) species in the endemic family Acanthogammaridae of Lake Baikal, Siberia, the world's oldest and largest lake.  Lake Baikal is home to a spectacular radiation of gammarids (among other groups), containing hundreds of ecologically and morphologically diverse species -- perhaps 20% of the world's freshwater amphipod species live only in Baikal.