A Redescription and Life-History of Gigantocotyle explanatum (Creplin, 1847) Nasmark, 1937 (Trematoda: Paramphistomidae) from India

Abstract

Gigantocotyle explanatum (Creplin, 1847) Nasmark, 1937 is a very common parasite of the domestic ruminants in India and is found in the liver, bile ducts and gall bladder, usually accompanying infection with Fasciola. In the adult stage the parasites are non-pathogenic, or only slightly so, but immature forms when present in large numbers cause amphistomiasis which in the majority of the cases proves fatal to the host. This amphistome has been reported from Bos taurus indicus and Bubalis bubalis from India, Burma, Ceylon, Indo-China and the Philippines (Nasmark, 1937; Dawes, 1946). Except for a short and incomplete account given by Srivastava (1944) and a study of the structure of the miracidium by Ozaki (1951), no account of the life history of Gigantocotyle explanatum is available. Since considerable difficulty was found in the identification of the parasite and there still seems to be some confusion, a short diagnosis of Gigantocotyle explanatum is included here for the sake of convenience and future reference. The redescription is based on a large number of specimens studied as whole mounts and serial sections, collected from buffalo at Lucknow and with which the present work was carried out. As regards the synonymy of the species, reference is made to Fischoeder (1903, 1904), Maplestone (1923), Travassos (1934), Dawes (1936) and Nasmark (1937). For the purposes of the present work Gigantocotyle bathycotyle (Fischoeder, 1901) Nasmark, 1937 is considered a synonym of Gigantocotyle explanatum. MATERIALS AND METHODS The adult amphistomes were obtained from buffalo slaughtered locally and a large number of gravid specimens were always available throughout the year. The gravid specimens were identified and the eggs obtained by teasing the uterus in a small amount of distilled water. When a large number of eggs had thus been collected from several specimens the eggs were freed from debris by decantation and kept in covered petri dishes. During the summer months the water of the dishes was changed twice daily but only once during the winter months. The eggs were kept at laboratory temperature during the summer months and in a constant temperature cabinet at 82? F ? 2 F during winter months. A large amount of material was examined for the study of all the larval stages. Distilled water and 0.3% salt solution were used as mounting media. Usually the larval stages were examined in living condition without staining but the following intra vitam stains were also found useful: Neutral red, brilliant cresyl blue, methylene blue, methyl green and Bismarck brown. For making permanent preparations the material was fixed in warm alcoholic Bouin's fluid or Susa's fluid and stained with Ehrlich's haematoxylin, borax carmine, acetic acid alum carmine and Semichon's carmine. For sectioning, the material was fixed in alcoholic Bouin's fluid, cleared in cedarwood oil, embedded in wax and cut at 6-12 microns. The sections were stained with Ehrlich's haematoxylin and eosin, Heidenhain's iron haematoxylin and Mallory's triple stain. For the study of the cercaria, the ordinary methods gave poor results. Serum of sheep was used as a mountant for cercariae for studying the excretory system. For the study of the genital rudiments Schneider's acetocarmine was found to be an ideal stain and was used as described by Singh (1955). The permanent preparations were, however, not satisfactory.