Intraspecific Variation of Adult Telorchis bonnerensis (Trematoda: Telorchiidae) in Amphibian and Reptilian Hosts

Abstract

Telorchis bonnerensis Waitz, 1960, previously reported from larval Ambystoma macrodactylum Baird, 1849, and Thamnophis sirtalis Linnaeus, 1758, in Idaho, also parasitizes larval and adult A. tigrinum Green, 1825, in Iowa. This constitutes a new host record for the species. Additional experimental hosts for the adult stage include adult and larval A. tigrinum, adult A. maculatum Shaw, 1802, young Pseudemys scripta elegans Wied, 1838, Chrysemys picta belli Gray, 1831, and Chelydra serpentina Linnaeus, 1758. Developmental rates of experimentally reared adult worms were most rapid in A. tigrinum and A. macrodactylum. In A. maculatum, development is markedly decreased. Among chelonians, development is most rapid in C. serpentina and least in P. s. elegans. The rearing of successive generations of adults in amphibians, then in reptiles, and again in amphibians, results in a pronounced decrease in size and delayed development in the generation reared in reptiles. Resumption of normal size and developmental rate occurs when progeny are reared once again in amphibians. The great morphological variations of adult worms experimentally reared in amphibians and reptiles emphasize that criteria such as anterior extent of vitellaria, position of ovary, extent of cirrus sac, and comparative sizes of suckers are unreliable in delimiting species within the genus Telorchis. Morphological and physiological changes may occur when adult trematodes mature in different species of definitive hosts. The experimental studies of Beaver (1937) on Echinostoma revolutum Froelich, 1802, developing in avian and mammalian hosts, the work of Rankin (1937) on Brachycoelium collected from various species of naturally infected salamanders, and studies by Wharton (1940) on several species of Telorchis collected from naturally infected chelonian and amphibian hosts present evidence for this statement. More recently, Boddeke (1960) studied experimental infections of Prosthogonimus ovatus Rudolphi, 1803, and observed great morphological variations among flukes from different avian hosts. Haley (1962) emphasized the need for additional studies to determine the influence of differing host environments on variations in parasite structure, physiology, and behavior. Telorchis bonnerensis Waitz, 1960, previously reported from larval Ambystoma macrodactylum Baird, 1849, and Thamnophis sirtalis Linnaeus, 1758, in Idaho, is also a natural Received for publication 27 June 1966. * This investigation was supported in part by research grants (G 23597 and GB 2384) from the National Science Foundation. t Present address: Division of Biological Science, Arkansas State University, State College, Arkansas. parasite of larval and adult A. tigrinum Green, 1825, in Iowa. This constitutes a new host and locality record for the species. The experiments discussed in this paper were conducted to study certain morphological and physiological effects on T. bonnerensis when experimentally reared in three species of Ambystoma, namely: A. tigrinum, A. macrodactylum, and A. maculatum Shaw, 1802, and three chelonian hosts, young Pseudemys scripta elegans Wied, 1838, Chrysemys picta belli Gray, 1831, and Chelydra serpentina Linnaeus, 1758. A preliminary report of this study was published by Watertor and Ulmer (1964). MATERIALS AND METHODS Eggs of T. bonnerensis used for experimental feedings were originally obtained from worms in naturally infected larval A. tigrinum. Flukes removed from the small intestine were placed in 0.3% NaCl. After a few hours, eggs released by the worms were fed to laboratory-reared snails (Physa gyrina Say). Forty actively swimming cercariae recovered from such experimentally infected snails were then placed with a laboratory-reared P. gyrina in a small vial. Twenty-four hours or more later, the entire snail was fed to either amphibian or chelonian experimental definitive hosts. Experimental amphibian hosts were collected from nature, or were laboratory-reared or commercially purchased. Chelonian hosts were commercially purchased. All hosts collected from nature and those commercially purchased were maintained in the laboratory at least 1 month before use for experimental purposes. This time period