Some Aspects of the Biology of Monogenean (Platyhelminth) Parasites of Marine and Freshwater Fishes

Müller [1] was the first to describe a monogenean, collected from the skin of the halibut (Hippoglossus hippoglossus). However, he regarded the parasite as a leech and named it Hirudo hippoglossi. It was not until 1858 that its status as a monogenean was established by van Beneden [2] and named Epibdella (now Entobdella) hippoglossi. Van Beneden published a detailed and accurate description of the parasite and one of his excellent illustrations is reproduced here in Figure 1. Entobdella hippoglossi is one of the largest monogeneans, measuring up to 2 cm in length. It has a smaller relative, measuring 5 to 6 mm in length, which was described by van Beneden and Hesse in 1864 [3] and named Phyllonella (now Entobdella) soleae from the skin of the Dover or common sole, Solea solea (Figures 2 and 3). This parasite is now perhaps the best known monogenean in terms of its biology [4-6].