Geographic and host-induced variations of Haematoloechus buttensis and a re-evaluation of representatives of the genus in Canada and the United States

Of tie fifteen species of flukes referred to the genus Haematoloechus Looss. 1899, in Canada and the United States, nine are considered to be synonyms of one or another of the six species considered to be valid. Species identification is primarily based on the ratio of the transverse diameter of the oral sucker to the acetabulum (0/A), the anterior extent of the extracaecal loops along the ovary or testes, and orientation of the testes. The species considered valid are: H. longiplexus Stafford. 1902: H. breviplexus Stafford, 1902; H. varioplexus Stafford, 1902 (= H. similipiexus, = H. parviplexus, = H. buttensis, = H. floedae, = H. uniplexus ): H. medioplexus Stafford. 1902: H. complexus (Seely, 1906) (H. coloradensis, = confuses, = H. oxyorchis ); H. kernensis Ingles, 1932 (= H. tumidus ). Flukes are discussed using the name previously considered valid. H. buttensis, experimentally reared in the laboratory, was used to study morphological variations resulting from changes in technical procedures and environment. Techniques used to prepare study specimens of flukes affected some taxonomic characters previously used to separate species. The presence of spines, position of oral sucker, and size of flukes were affected by temperature of fixative, and the use of distilled water. Pressure added to the coverslip affected length and width of ovary, testes, sucker, and body., The size of flukes, experimentally reared in the frog, R. pretiosa, was affected by temperature at which the host was maintained, the numbers of metacercariae fed to frogs, and the age of the worm. Host size and sex had no apparent influence on fluke morphology. Sixty-day-old flukes were experimentally reared in either R. pretiosa, B. boreas, R, clamitans. or R. aurora. The effects of developing in different frog hosts were to alter the anterior extent of the extracaecal uterine loops relative to the posterior testis, the distribution of the vitellaria, and the size and shape of ovary, testes, and size of the body and suckers. The 0/A ratio remained relatively uniform in flukes from all hosts. Flukes recovered from frogs fed infected dragonflies had a larger body size (length and width), larger testes and ovaries, and had extracaecal loops reaching farther along the posterior testis than did flukes recovered from frogs fed infected damselflies. The O/A ratios for H. longiplexus, H. breviplexus, H. complexus, H, buttensis, H. coloradensis, and H. medioplexus did not vary among specimens collected from different localities. No significant difference in this ratio occurred between flukes that had inhabited more than one host. The O/A ratio of H. parviplexus was significantly greater when R. sylvatica was the definitive host than when R. catesbeiana was the host. This ratio also differed significantly between specimens collected from two localities in Nebraska, even though the host in both localities was R. catesbeiana. Pooled data for H. varioplexus and H. similiplexus indicated that flukes from R. catesbeiana. R. clamitans. R. pipiens, and B. woodhousei differed in their 0/A ratios and egg lengths and widths. Ovary and testes may be lobed or unlobed. Uterine loops extend from the posterior portion of the worm to near the anterior border of the anterior testis in H. varioplexus, H. buttensis, and H. parviplexus. The ext r a caeca1 loops reach to the posterior border of the ovary in H. breviplexus and beyond the anterior border of the ovary in H. longiplexus. In flukes containing extracaecal uterine loops, the left loop vas absent in 4.2% of the H. parviplexus and 8.3% of H. varioplexus examined, the right loop was absent in 9.0% of H. buttensis examined. Egg size (length and width) did not vary geographically in H. longiplexus, H. complexus, H. breviplexus, H. buttensis, H. coloradensis, or H. medioplexus. Egg lengths of H. parviplexus differed in flukes from R. sylvatica and R. catesbeiana.Science, Faculty ofZoology, Department ofGraduat