Effects of Temperature Stress on Growth and Development of Larval and Adult Telorchis bonnerensis (Trematoda: Telorchiidae)

Abstract

Cercarial development of Telorchis bonnerensis Waitz, 1960, in the intermediate host, Physa gyrina Say, is modified by maintenance at various constant temperatures of 4, 10, 22, 30, and 37 C. The proportion of snails in which infections developed to cercarial emergence was largest and development was most rapid at 30 C. Cercarial emergence was delayed for a period of 152 days at 10 C, but could be modified by transferring the snail host to 30 C where cercariae emerged after 3 days. Growth and developmental rate of adult T. bonnerensis in the definitive host, adult Ambystoma tigrinum Green, 1825, showed similar modification when the host was maintained at constant temperatures of 10, 22, 30, and 34 C. At 10 C, development was delayed and adults increased in size only slightly, after 6 weeks. Growth and developmental rate of worms was most rapid at 30 C. At 34 C, maturation rate was equal to that of worms maintained at 30 C, but overall growth was decreased. The deleterious effects of high temperature were indicated by a decrease in overall size of adult worms, reduced egg size, and degeneration of the reproductive structures. The developmental rate of trematode larvae is known to be directly related to the temperature at which molluscan intermediate hosts are maintained (Stirewalt, 1954; Gumble et al., 1957). Temperature studies with adult trematodes of poikilothermic definitive hosts are limited. Izyumova (1956) reported that variations in water temperature affect development of the monogenetic trematode, Dactylogyrus vastator Nybelin, 1924, a parasite on the gills of fish. Vernberg and Hunter (1961) found the in vitro metabolic-temperature responses of two intestinal trematodes, Saccocoelium beauforti Hunter, 1961, in fishes and Pleurogonius malaclemys Hunter, 1961, in turtles, corresponded closely to the body temperatures of their hosts. McCue and Thorson (1964) observed a positive reaction of the frog lung trematode, Haematoloechus sp., to a thermal gradient. The purpose of this study was to determine the effect on development of larval Telorchis bonnerensis and the effect on morphology, growth, and development of adult T. bonnerensis Waitz, 1960, when the first intermediate host, Physa gyrina Say, and the definitive Received for publication 15 December 1967. *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. host, adult Ambystoma tigrinum Green, 1825, were maintained at various constant temperatures. A preliminary report of this work was published by Watertor and Ulmer (1965). MATERIALS AND METHODS Eggs of T. bonnerensis used for experimental feedings were originally obtained from worms in naturally infected larval salamanders (A. tigrinum). Flukes removed from the small intestine were placed in 0.3% NaCI. After a few hours, eggs released by the worms were fed to laboratoryreared snails (P. gyrina). To determine the effects of varying temperatures on cercarial development, 220 snails were maintained under controlled temperatures of 4, 10, 22, 30, and 37 ? 2 C (44 snails at each temperature). One-half of the snails were exposed to 10 to 20 eggs each and one-half to one egg per snail. The snails were also equally divided into two size groups of 2 to 4 and 6 to 8 mm in length. Metacercariae were obtained by exposing 40 actively swimming cercariae, recovered from experimentally infected snails maintained at 22 C, to a laboratory-reared P. gyrina in a small vial. After 24 hr or longer, the entire snail was fed to experimental amphibian definitive hosts. Experimental amphibian hosts were collected from nature. Before experimental use, all salamanders were maintained in the laboratory at 22 C for at least 1 month, a time sufficient for eggs to appear in the feces of laboratory-reared adult A. tigrinum maintained at 22 C after exposure to metacercariae. Data presented on adult worms are limited to those from hosts showing no evidence of previous infections. Experimental salamanders were approximately the same age and size. Six experimentally infected adult A. tigrinum were maintained in each of six moistened aquaria placed in incubators kept at constant temperatures