Species description: This is an invasive colonial sea squirt that is similar to, but not the same as, Aplidium glabrum. Since the correct name is currently unknown the abbreviation cf (similar to) is used. It should be recorded as Aplidium cf. glabrum. This sea squirt forms thick cushions that are around 1 cm thick and has a disinctive glassy appearance. It can vary in size but is usually 4-8 cm across. It is grey in colour with individual zooids visible as white spots through a semi-transparent matrix.

Habitat: Often on artificial substrata in marinas and harbours, but also found beneath boulders on lower shore in sheltered, silty areas.

Distribution: First record of this species in Northern Ireland was in 2015, and it is now recorded in most marinas and aquaculture sites and in some cases is spreading to the adjacent shore. In Britain and the rest of Ireland it is also being recorded in many marinas, harbours and aquaculture sites and in some cases adjacent shores.

Similar Species: Unlikely to be confused with any other species due to distinctive glassy appearance and grey colouration.

Key Identification Features:

• Distinctive glassy appearance.
• Semi-transparent grey matrix.
• Zooids visible as white spots.

iNaturalist: Aplidium cf. glabrum at iNaturalist World Species Observations database.