Didemnum vexillum

Didemnum vexillum


Photo credit: Julia Nunn


Habitat: Marine hard surfaces. The colonies have been found at water depths ranging from intertidal to continental shelf depths of 65m (213 ft).


Description: Exact identification of this species is very difficult and can only be undertaken by a trained expert. However, in general native species are not found in large colonies and do not form the candlewax-like dripping structures, as seen in the photographs. Please see the Habitas website on Sponges of Britain and Ireland for more info on native species. 

The invasive form can be describes as long, ropey or beard-like hanging from hard surfaces such as docks, aquaculture facilities, and ship hulls, or may be found as extensive mats covering rocky sea beds (pebbles, cobbles, boulders, and rock outcrops).


Origin and Distribution: Uncertain at present. The species is known from The Netherlands and France in Europe while worldwide the species is now recognised in Asia, Australasia-Pacific, Europe, and North America.  


Impacts: Alter marine habitats. Interfere with fishing, aquaculture, and other coastal and offshore activities. Increased fouling of manmade structures such as docks, moorings, and boat hulls.  Overgrow other organisms such seaweed, scallops, mussels, and oysters that depend on the seafloor for habitat. May impact on underwater archaeological sites such as ship wrecks. Produce noxious substances that deter most fish and other animals.

How did it get here? Uncertain at present. Likely vector is fouling of ocean going vessel and/or contamination of aquacultre produce.


Where is it found in Ireland? Currently confirmed present in Carlingford Lough, Co. Louth, Malahide Marina, Co. Dublin and Galway Bay, Co. Galway. The species was recorded in Strangford Lough, County Down during October 2012 (http://www.bbc.co.uk/news/uk-northern-ireland-19838653)


See the National Invasive Species Database for more information on the distribution of this species in Ireland.


Prevent Spread

Prevent fouling of boats and equipment. Clean all equipment including boats before moving to new waterbodies. Report all sightings.
Invasive Species Ireland

Invasive Species Ireland