Marine nuisance species: colonial tunicates of the genus Didemnum (a sea squirt)

http://woodshole.er.usgs.gov/project-pages/stellwagen/didemnum/

Occurrence, photos, and characteristics of some species of the colonial tunicate genus Didemnum, nuisance species that reproduce rapidly and foul marine habitats (including shellfish aquacultures and fishing grounds), ship's hulls, and maritime structure

by Valentine, Page C. (Editor)