Sessile Organisms Plate data

Diplosoma listerianum is a colonial tunicate that forms extensive thin encrusting sheets. It was first described from the English Channel in 1841 by Milne-Edwards, but similar species were subsequently found and given many different names around the world, most of which were eventually reduced to synonyms. However, D. 'listerianum' is almost certainly a global complex of an unknown number of different species, to which some of these submerged names may apply. Because of this confusion, and the fact that it was already established in much of its range when researchers began surveying for tunicates, we consider it cryptogenic (of unknown origin) in many regions where it is present. However, it appears to be a definite introduction to the Northeast Pacific (British Columbia to California), the Northwest Atlantic (Maine to Cape Hatteras, North Carolina), Hawaii, New Zealand, and South Africa. Diplosoma listerianum can foul cultured shellfish and aquaculture equipment, and outcompete other colonial tunicates and benthic invertebrates for space.

https://invasions.si.edu/nemesis/calnemo/SpeciesSummary.jsp?TSN=159099 less ↑

Didemnum vexillum, the carpet sea squirt, is a species of colonial tunicate in the family Didemnidae. Believed to be native to the waters around Japan, it has been reported as an invasive species in a number of places in Europe, North America and New Zealand. It is sometimes given the nickname "D. vex" because of the vexing way in which it dominates marine ecosystems when introduced into new locations. less ↑