Description: This isopod has a markedly elongate, slim body with obvious segments aside from the posterior of the animal where the segments are fused. Here the pleon and telson fuse to form the pleotelson, which has two segments and a suture. It has slightly concave sides and a concave tip. Males grow 15-40 mm long while females are slightly smaller. It is usually green or brown with either darker or lighter longitudinal stripes. Females may be darker in colour than the males and have paler markings at the edge of their body. The have two very long antennae and small eyes.

Habitat: Sublittoral, but occasionally found washed up on the shore. Can sometimes be seen swimming at the water’s edge on sandy shores at low tide.

Distribution: Found all around Britain and Ireland but seems to be more commonly recorded in the south.

Similar Species: Quite a distinctive isopod so unlikely to be confused with other species, although there are several that are markedly elongate.

Key Identification Features:

• Markedly elongate slim body.
• Pleotelson has slightly concave sides and concave tip.
• Green or brown with darker or lighter longitudinal striping.
• Very long antennae.

Distribution Map from NBN: Idotea linearis at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Idotea linearis at iNaturalist World Species Observations database.

GBIF data for Idotea linearis

WoRMS: Idotea linearis at World Register of Marine Species. Accepted name: Idotea linearis (Linnaeus, 1767). AphiaID: 119046.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Peracarida; Isopoda; Valvifera; Idoteidae; Idotea