Description
Hexamita (Syn=Hexamitus, Urophagus) have an oval or pyriform cell body (6-35 1-1m), truncated or tapered posteriorly , bearing 6 anterior locomotory flagella and 2 posterior trailing ones (Fig. Sa). They have 2 rounded nuclei closely apposed each other at the anterior end . Each set of flagella is inserted anteriorly on the external side of each nucleus (Fig . 3c). The recurrent flagella traverse the cell to emerge posteriorly as trailing flagella . They are lying in longitudinal canals which open posteriorly forming 2 apertures which are the cytostome of the cell, and the canals are equivalent to cytopharynges (Brugerolle , 1975c) . The fine structure study of Hexamita inflata has shown the diplomonad characters of this genus. The cytostomal canals are lined by stacks of rough endoplasmic reticulum and by 2 microtubular fibers, and the membrane is also reinforced by a dense lamina (Fig. 3d) . Around the posterior cytostomal openings the fibers lining the canals spread or recurve on each side forming a complex 1 1 31 architecture. Additional dense striated fibers are present in this area in some species (Brugerolle , 1991 a) . At least 16 species described . Many species live in freshwater and saltwater rich in organic matter and bacteria . They prefer low oxygen sites. They form cysts. Light microscopic descriptions of various free-living species are given in Klebs ( 1892) , Lemmerman ( 1 9 1 0) , Skuja (1956) , Calaway and Lackey ( 1962) , van Meel (1982) , Mylnikov (1991 ) . Parasitic species occur in insects: H. cryptocerci (Cleveland et al. , 1934) , in oysters H. nelsoni (Schlicht and Mackin , 1968), in salmonid fishes H. sa/monis (Moore, 1922 , Poynton and Morrison , 1990) , in the cloaca of reptiles, in the coecum of rodents H. teres (Kirby and Honigberg , 1949) in monkeys H. pitheci (Wenrich , 1 9 3 3) . The distinction between parasitic Hexamita species and Spironucleus species is difficult. Description and list of species can be found in Grasse ( 1952) and for the species parasitic in vertebrates in Kulda and Nohynkova ( 1 9 7 8) . Electron microscopic study of Hexamita inflata (Brugerolle , 1974) and of Hexamita nelsoni (Papayanni and Vivares, 1987) . showing the anterior flagella, the two trailin g fl age ll a, and an oblique lateral ridg e along the ce ll body. Bar= 10 J.Jm . (photograph from G. Brugerolle)
Type species
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Raw text
Hexamita (Syn=Hexamitus, Urophagus) have an oval or pyriform cell body (6-35 1-1m), truncated or tapered posteriorly , bearing 6 anterior locomotory flagella and 2 posterior trailing ones (Fig. Sa). They have 2 rounded nuclei closely apposed each other at the anterior end . Each set of flagella is inserted anteriorly on the external side of each nucleus (Fig . 3c). The recurrent flagella traverse the cell to emerge posteriorly as trailing flagella . They are lying in longitudinal canals which open posteriorly forming 2 apertures which are the cytostome of the cell, and the canals are equivalent to cytopharynges (Brugerolle , 1975c) . The fine structure study of Hexamita inflata has shown the diplomonad characters of this genus. The cytostomal canals are lined by stacks of rough endoplasmic reticulum and by 2 microtubular fibers, and the membrane is also reinforced by a dense lamina (Fig. 3d) . Around the posterior cytostomal openings the fibers lining the canals spread or recurve on each side forming a complex 1 1 31 architecture. Additional dense striated fibers are present in this area in some species (Brugerolle , 1991 a) . At least 16 species described . Many species live in freshwater and saltwater rich in organic matter and bacteria . They prefer low oxygen sites. They form cysts. Light microscopic descriptions of various free-living species are given in Klebs ( 1892) , Lemmerman ( 1 9 1 0) , Skuja (1956) , Calaway and Lackey ( 1962) , van Meel (1982) , Mylnikov (1991 ) . Parasitic species occur in insects: H. cryptocerci (Cleveland et al. , 1934) , in oysters H. nelsoni (Schlicht and Mackin , 1968), in salmonid fishes H. sa/monis (Moore, 1922 , Poynton and Morrison , 1990) , in the cloaca of reptiles, in the coecum of rodents H. teres (Kirby and Honigberg , 1949) in monkeys H. pitheci (Wenrich , 1 9 3 3) . The distinction between parasitic Hexamita species and Spironucleus species is difficult. Description and list of species can be found in Grasse ( 1952) and for the species parasitic in vertebrates in Kulda and Nohynkova ( 1 9 7 8) . Electron microscopic study of Hexamita inflata (Brugerolle , 1974) and of Hexamita nelsoni (Papayanni and Vivares, 1987) . showing the anterior flagella, the two trailin g fl age ll a, and an oblique lateral ridg e along the ce ll body. Bar= 10 J.Jm . (photograph from G. Brugerolle)