Although monogenean systematics is often based on the morphological analysis of sclerotised structures, their variation with size or age is rarely investigated. Two hundred specimens of the monocotylid Dendromonocotyle pipinna Chisholm and Whittington 2004 were studied. In the haptor, the numbers of marginal papillae, of sclerites in the marginal papillae and of sclerites in the septa did not change according to the size; however, the mean interval between the sclerites in the septa increased linearly with body length. This suggests that, at least in certain cases, valuable systematic descriptions can be made on incompletely grown monogeneans.

A blotched fantail ray, Taeniurops meyeni (Müller et Henle, 1841), was captured in New Caledonia, South Pacific, and kept in a tank for quarantine before exhibition at the Nouméa public aquarium. After 24 days, the ray exhibited a heavy infection with two species of skin monogeneans. A freshwater bath allowed the collection of 1,914 monogeneans, including 1,453 capsalids, Neoentobdella taiwanensis Whittington et Kearn, 2009, on the ventral surface, and 461 monocotylids, Dendromonocotyle pipinna Chisholm et Whittington, 2004, on the dorsal surface. More than 300 monogeneans were prepared on slides to allow precise measurements. Capsalids and monocotylids occupied about 6% and 0.2% of the total ventral and dorsal ray surfaces, respectively.