The Life History of Brachycoelium obesum Nicoll, 1914, with a Discussion of the Systematic Status of the Trematode Family Brachycoellidae Johnston 1912

Abstract

Up to the present time no life history is known of any members of the genus Brachycoelium (Dujardin, 1845) Stiles and Hassall, 1898, which includes 10 species. Cheng (1958) published an account of this genus and suggested that the systematic status of Brachycoelium, whether in the Plagiorchiidae, Dicrocoeliidae, or Brachycoeliidae, might be resolved by the knowledge of life history patterns. He based his decision on adult morphological characteristics and considered the genera Brachycoelium, Cymatocarpus Braun, 1901, Leptophallus Liihe, 1909, Glypthelmins Stafford, 1905, Margeana Cort, 1919, and Mesocoelium Odhner, 1911, all to be members of the same taxon, the Brachycoeliinae (Dicrocoeliidae). In a later paper (Cheng, 1959) he included the new genus Reynoldstrema Cheng, 1959, but stated that the subfamily Brachycoeliinae should be elevated to familial rank as suggested by Johnston (1912) since such an arrangement seems to be the natural one as based in the life history patterns of Glypthelmins quieta (Stafford, 1900), as reported by Rankin (1944) and Leigh (1946), and Mesocoelium brevicaecum Ochi, 1930, as reported by Ochi (1930). The life history of Brachycoelium obesum represents the first to have been determined in the genus and the third within the family. In all three cases the parasites utilize only 1 intermediate host. Brachycoelium obesum was described by Nicoll (1914) from the intestine of a moribund specimen of the snake, Contia aestiva, in the London Zoological Gardens. Cheng (1958) considered B. ovale Byrd, 1937, a synonym of B. obesum. During the summer and fall of 1956 the author identified over 300 worms as belonging to this species from the small intestines of Plethodon glutinosus and P. cinereus captured at Mountain Lake, Giles County, and Charlottesville, Albamarle County, Virginia. During the summers of 1957 and 1958 over 50 additional specimens were obtained from the same hosts in Albamarle County, Virginia, and in the vicinity of Phoenixville, Chester County, Pennsylvania. Earlier Byrd (1937) reported B. obesum in Desmognathus f. fuscus from Rome, Georgia; in Leiolopisma laterale from New Orleans and Pearl River, Louisiana; and in Plethodon glutinosus from Calhoun Falls, South Carolina. Parker (1941) reported this parasite in Plethodon glutinosus from Reelfoot Lake, Tennessee. Although Rankin (1938) considered all the species of Brachycoelium to be synonymous with B. salamandrae (Fr6olich, 1789), Cheng (1958) has shown that 10 of the species are morphologically distinct.