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

Abstract

Specimens of six species of leeches of the genus Haemopis were necropsied and examined histologically in an attempt to elucidate the in situ host-parasite relationships between the leeches and their helminths. Specimens of five species of mature trematodes were recovered from the gastrointestinal ceca. The histological organization of the gastrointestinal ceca was found to be quite similar to that of the small intestine of ictalurid fishes, and it is suggested that ancestral macroderoidid parasites of leeches may have been preadapted to the intestinal environment of catfishes. This explanation is proposed to account for the continued existence of members of the genus Alloglossidium in the intestine of both piscine and hirudinean hosts. Extreme interand intraspecific crowding of enteric trematodes also was observed; a possible mechanism for reduction of competition through habitat partitioning is examined. Immature trematodes and nematodes were observed to be encysted along the blood vessels of the gastrointestinal ceca. A nonspecific fibrous encapsulation response to these cysts was observed frequently; in some cases, this host response appeared to induce disintegration of the larval trematodes. Six species of mature digenetic trematodes from leeches of the genus Haemopis Savigny, 1822 have been described recently (Demshin, 1968; Fish & Vande Vusse, 1976; Neumann & Vande Vusse, 1976; Schmidt & Chaloupka, 1969; Timmers, 1979). With the exception of a brief description of the attachment of some of these trematodes to the host intestinal wall (Taft & Kordiyak, 1973), no effort has been made to examine the nature of these unusual host-parasite systems. Therefore, studies were undertaken in an attempt to describe the in situ relationships between helminth parasites, both enteric and parenteric, and leeches of the genus Haemopis. Data on prevalence, abundance, and host-specificity also were obtained and are presented in part II (Riggs & Ulmer, 1983). MATERIALS AND METHODS Leeches were collected at night during late spring and early summer of 1976 and 1977 in the shallows and from marshy shorelines of several lakes 1We would like to 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): 213-226. 1983. () Copyright, 1983, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.180 on Tue, 27 Sep 2016 05:27:58 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC. and ponds located in north-central Minnesota and northwestern Iowa. Necropsies were conducted 24-48 h after collections; gross observations on living worms in tlhe host gut were made using a stereo microscope equipped with 30x and 60x magnification. The techniques of Fried et al. (1970) were employed in the study of encysted metacercariae. The posterior one-third of the intestines of five specimens each of Haemopis marmorata (Say, 1824) Moore, 1901, H. grandis (Verrill, 1874), H. plumbea Moore, 1912 were removed, extended, and fixed in 10% buffered-formalin at 70?C and embedded in paraffin. Sagittal sections of the intestines from two specimens of each host species were cut serially at 10 /m and the remaining intestinal preparations were sectioned tranversely at 15 /um. All sections were stained in Harris' hematoxylin and eosin Y.