Description: A dirty brown, wrinkled solitary ascidian. The test is very thick and leathery and is wrinkled even when the animal is fully expanded. It is covered with detritus, algae and other epibionts. The siphons are fairly long when fully expanded, but sensitive to light or disturbance so that they quickly contract on close inspection. They are longitudinally marked with red and white lines, most obvious on the inner surfaces. The openings become square and fluted in partial contraction.

Habitat: In sheltered conditions attached to shells and rocks.

Distribution: Found on western and southern coasts of the British Isles, common.

Similar Species: Similar species are Polycarpa pomaria, Microcosmus claudicans and Pyura squamulosa.

Key Identification Features:

• Wrinkled, thick, leathery test
• Tapering siphons with longitudinal red stripes
• Internal anatomy

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

iNaturalist: Pyura microcosmus at iNaturalist World Species Observations database.

WoRMS: Pyura microcosmus at World Register of Marine Species. Accepted name: Pyura microcosmus (Savigny, 1816). AphiaID: 103851.

Classification: Biota; Animalia; Chordata; Tunicata; Ascidiacea; Stolidobranchia; Pyuridae; Pyura