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Host-Parasite Relationships of Helminth Parasites in Leeches of the Genus Haemopis. II. Associations at the Host-Species Level

1983; Wiley; Volume: 102; Issue: 3 Linguagem: Inglês

10.2307/3225829

2325-5145

Michael R. Riggs, Martin J. Ulmer,

Bird parasitology and diseases

Specimens of five species of mature enteric trematodes, an unidentified tetracotyle, two species of nematodes, one enteric and one parenteric, and unidentified glossiphonid leeches were recovered from necropsies of 189 specimens of six species of haemopid leeches collected from Iowa and Minnesota, 1976-1979. Statistical analysis indicated that populations of all helminths were significantly overdispersed in their hosts and that the negative binomial distribution provided an adequate fit to most of the observed parasite frequency distributions. Estimated values of the parameter k were <1.0 and, in several cases, they approached zero. The significance of this extreme aggregation of parasites and its possible consequences at the suprapopulation level are discussed. Species-specific differences in habitat and dietary preferences of different species of hosts are compared with observed patterns of prevalence and density of helminths of haemopid leeches reported here and in the literature. The results indicate that Haemopis grandis, H. plumbea, and H. marmorata are primarily aquatic, that H. lateromaculatum and H. kingi are semiaquatic, and that H. lateralis is confined to terrestrial habitats. Dietary diversity, helminth faunal diversity, and relative density of helminths all appeared to decrease with the increase of terrestrial habits in the hosts. An ecologic hypothesis is proposed to explain species-specific differences in the dynamics of haemopid parasites on the basis of habitat and dietary relationships evolved by the different species of hosts. Recently, Vande Vusse et al. (1981) have reported on patterns of prevalence and host-specificity of adult macroderoidid trematodes in hirudinid leeches from the upper mid-west. They assumed abbreviated life cycles (see Riggs & Ulmer, 1983) for all mature flukes and concluded that parasite distribution and host-specificity were determined by strict physiological specificity of penetrating cercariae. Apparently, this specificity was keyed to some unknown physiologic reflection of phylogenetic differences among various species of the host. Bayliss (1938), Stunkard (1970), and Noble & Noble (1976) have cautioned against such phylogenetically based interpretations of hostspecificity and have advised that the habits (particularly as regards food) and environment of the hosts have played a far more important role in de' We thank Drs. Frederick Vande Vusse, Roy T. Sawyer, Marvin Meyer, and L. R. Richardson for contributing their knowledge of and experience with the hirudineans and their parasites. We are especially grateful to Dr. Gerald W. Esch for his careful reviews of the manuscript and his helpful suggestions during its preparation. 2 Publication costs, in part, are being met by a grant from the Spencer-Tolles Fund of the American Microscopical Society. 3 Present address: Department of Biology, Wake Forest University, Winston-Salem, North Carolina 27109, U.S.A. TRANS. AM. MICROSC. Soc., 102(3): 227-239. 1983. (?) Copyright, 1983, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.45 on Wed, 05 Oct 2016 05:28:49 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC. termining their helminth fauna than have their phylogenetic relationships . (Bayliss, 1938). In the present study, attempts were made to provide a more quantitative description of the distribution of mature trematodes in their haemopid hosts. Additional data on abundance and prevalence (prevalence, abundance, and relative density are used in accordance with Margolis et al., 1982) of parenteric helminths in the leeches were considered together with ecological data on hosts' feeding and habitat preferences. Finally, we sought to coordinate all of this information with in situ observations on infected hosts (Riggs & Ulmer, 1983) in the formulation of a more global view of the nature of hostspecificity patterns of helminths in leeches of the genus Haemopis. MATERIALS AND METHODS Aquatic and semi-aquatic leeches were collected from lakes in Iowa and Minnesota; specimens of the terrestrial leech, Haemopis lateralis Forbes, 1890, were dug from the banks of the Iowa River at Marengo, Iowa. All leeches were necropsied within 48 h of collection and the locations of all helminths, enteric and parenteric, in their hosts were recorded. Worms were relaxed in cold distilled water, fixed in AFA or 10% buffered formalin, stained in Mayer's paracarmine, and counter-stained with fast green. The identity of all recognizable food items in the gut was recorded as accurately as possible. Chi-square tests for goodness of fit of observed frequencies of helminths in each species of host to several theoretical distributions including the normal, log-normal, Poisson, binomial, and negative binomial were made using a Fortran program on the HP-3000 computer at Wake Forest University. A modification of Davies' (1971) program for calculating the index of overdispersion (IJ) was employed to measure the degree of overdispersion of helminths. The general formula for ID (Southwood, 1978) is: ID= S2(n1)/X where: n = the number of samples, S2 = the variance, X = the mean, and ID is approximately distributed as Chi-square. Basic statistical analyses were performed using SAS programs on the IBM 360 computer located at the Triangle Universities Computation Center, Raleigh, North Carolina. Limnological and morphometric data on Iowa lakes were obtained from Eickstaedt (1964) and Bachmann & Jones (1974)4. Data on Minnesota Lakes were obtained from the Minnesota Department of Conservation (Minnesota Lake Survey Summary nos. 40-68 and 11-402; Division of Game and Fish Investigational Report no. 317, Minneapolis). These data are summarized in Table I. 4 Bachmann, R. & Jones, R. M. 1974. Water Quality in the Iowa Great Lakes: a Report to the Iowa Lakes Water Quality Control Plan. Unpubl. Available from: Iowa State Univ. Library, Ames, Iowa 50011, U.S.A. 228 This content downloaded from 157.55.39.45 on Wed, 05 Oct 2016 05:28:49 UTC All use subject to http://about.jstor.org/terms