Forty-five specimens of Raia montagui Fowler were recently examined for their cestode parasites and twenty-seven of these contained Echeneibothrium maculatum Woodland, 1927, a species which has not been found in any other elasmobranch. In addition to its well-marked specificity to this host there is an indication that E. maculatum prefers to attach itself to a particular region of the intestine. The cestode was not recognized as a valid species by Baylis (1948) and is included as a synonym of E. dubium Van Beneden 1858 in the Plymouth Fauna List (Marine Biological Association, 1957), but Williams (1958a) and Euzet (1959) were not in agreement with these views. For this and other reasons a re-investigation of E. maculatum was undertaken.

Materials And Methods

The specimens of Raia montagui were trawled off Plymouth by R. V. ‘Sula’ during August and September, 1958 and 1959. The rays were kept alive in the large sea-water tanks outside the laboratory and were examined for their cestode parasites as soon as possible, usually within a period of 24 h. This was found to be necessary because elasmobranchs kept alive under these conditions, presumably without food, have shown a strong tendency to lose their intestinal parasites. It is hoped to discuss this phenomenon more fully elsewhere.

The intestines of some of the fishes were removed from the freshly killed hosts and opened with scissors following the course indicated by the arrowed broken lines in Text-figure 2. Having been opened in this manner they could be quickly examined as a flat piece of tissue for their cestode parasites (Text-fig. 3).