• Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Crustacea
  • Class: Malacostraca
  • Subclass: Eumalacostraca
  • Superorder: Peracarida
  • Order: Isopoda
  • Suborder: Valvifera
  • Family: Idoteidae
  • Scientific name: Idotea balthica
  • Norwegian: tanglus


The male can reach a length of 4 cm. The female is smaller and usually darker. The coloration can be yellow, green or brown with small white spots on the back. It can be distinguished from other members of the Idotea genus by the shape of the tale segment, telson, which is dorsally keeled, with more or less straight sides. It ends in a distinct spine.


The Baltic isopod is usually feeding on algae in the subtidal zone.


This is a cosmopolitan and widespread in Europe and along the entire Norwegian coast.