Description: A colonial ascidian forming compact sheets. The zooids are arranged in meandering lines separated by excurrent channels which lead to a few common exhalant openings very like the oscula of sponges. Common colour forms are bright orange, pink or bright yellow, but patterned forms also occur. The exhalant openings collapse and disappear in specimens removed from the water. 4mm thick x 70mm wide sheets.

Habitat: A common ascidian, occurring on seaweeds on the lower shore and in shallow water, and on rock surfaces exposed to water movement.

Distribution: Widespread all round the British Isles.

Similar Species: Separated from Botryllus schlosseri by the meandering, linear arrangement of zooids and few exhalant openings. See also Aplidium nordmanni and Sidnyum elegans.

Key Identification Features:

• Meandering systems of zooids.
• Usually plain colours, orange, yellow, pink.

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

iNaturalist: Botrylloides leachii at iNaturalist World Species Observations database.

GBIF data for Botrylloides leachii

WoRMS: Botrylloides leachii at World Register of Marine Species. Accepted name: Botrylloides leachii (Savigny, 1816). AphiaID: 250081.

Classification: Biota; Animalia; Chordata; Tunicata; Ascidiacea; Stolidobranchia; Styelidae; Botrylloides