IT is well known that the larval trematode “Diplostomum volvens Nordmann, 1832” may cause impaired vision, and even blindness, in certain fishes. Rushton1 and Baylis2 have reported the presence of this diplostomulum in the eyes of rainbow trout in Britain. The presence of 20–40 parasites in the lens of each eye may favour completion of the life-cycle, because the fish then falls an easier prey to water birds. The definitive hosts of this trematode, Diplostomum spathaceum (Rudolphi, 1819), are various species of gulls, and the usual location is the intestines3.