OBSERVATIONS ON THE NUTRITION OF MONOGENETIC TREMATODES D. W. HALTON ' AND J. B. JENNINGS J >i'ptirtmcnt of Zoology, The (Jni-rcrsity of Leeds, England Relatively little information is available regarding the general pattern of nutri-tion in the Trematoda Monogenea, but there are indications that the two sub-orders of this class of parasitic flatworms differ considerably as regards the nature of their diet. The Monopisthocotylea so far investigated are reported to feed on the epi-dermal tissues and associated secretions of the host organism, whilst the Polyopis-thocotylea appear to be largely sanguinivorous and take in little host tissue other than blood (Goto, 1895; Heath, 1902; Folda, 1928; Gallien, 1934; Sproston, 1945; Llewellyn, 1954; Jennings, 1956, 1959; Uspenskaya, 1962; Kearn, 1963). Other differences between the two sub-orders, concerned with nutrition, are seen in the cellular structure of the digestive organs. Thus, in the Monopisthocotylea the intestine is lined by a continuous and unpigmented gastrodermis ; but in the Polyopisthocotylea the gastrodermis is typically discontinuous and consists of colum-nar cells, containing varying amounts of brownish or black pigment, interspersed with areas devoid of cells and consisting only of thin basement membrane (Baer and Euzet, 1961). In a number of species the pigment has been identified as hematin, a degradation product of hemoglobin (Llewellyn, 1954; Jennings, 1959). These differences in gastrodermal structure within the Monogenea are pre-sumably related to the differences in diet and they may reflect, also, further differ-ences in the site and course of the digestive process. In the present investigation, therefore, the relationships between diet, gut structure and digestion in the Mo-nogenea have been studied, as part of a comparative survey of nutrition within this class of Trematoda. MATERIALS AND METHODS The following species of Monogenea, listed systematically with details of their hosts and parasitic locations, have been examined : MONOPISTHOCOTYLEA Callcot\le kroyeri Diesing. Cloaca of the thorn-back skate, Raid clavata and the starry ray, Raid radiata. Entobdclla hippoglossi Miiller. Skin and general body surface of the halibut, Hippoglossus hippoglossus. Udonclla calit/oniin Johnston. Egg sacs of copepods (Caligus sp. ) found on the head and in the buccal cavity of the cod, Gadns callarias. 1 Present address : Department of Zoology, The Queen's University, Belfast, N. Ireland. 257
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