Description: This inconspicuous colonial ascidian consists of small globular heads with short stalks, grouped together in a patch arising from a thin sheet of shared test. It is almost colourless, with a brown or grey overall hue and no obvious markings. Each head is about 5mm in diameter and consists of about 10 zooids arranged around a common central exhalent opening.

Habitat: Found normally in sand-scoured sites with significant tidal streams.

Distribution: Found from Plymouth and Salcombe in southern England north to the Irish Sea and North Channel. Probably under-recorded due to its inconspicuous appearance and small size.

Similar Species: Compare with Synoicum incrustatum and Polyclinum aurantium. These are both bigger colonies than Archidistoma aggregatum.

Key Identification Features:

• Small sand-encrusted colonies with globular heads and short stalks.
• Colourless or with a brown or grey hue and no markings.

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

iNaturalist: Archidistoma aggregatum at iNaturalist World Species Observations database.

WoRMS: Archidistoma aggregatum at World Register of Marine Species. Accepted name: Archidistoma aggregatum Garstang, 1891. AphiaID: 103548.

Classification: Biota; Animalia; Chordata; Tunicata; Ascidiacea; Aplousobranchia; Polycitoridae; Archidistoma