Attachment of Myzobdella lugubris (Hirudinea: Piscicolidae) to Logperch, Percina caprodes, and Brown Bullhead, Ictalurus nebulosus

Abstract

Attachment of Myzobdella lugubris to logperch (Percina caprodes) and brown bullhead (Ictalurus nebulosus) is described. Leeches usually are firmly attached to fins with the caudal sucker molded over a fin ray. The leech body is always directed posteriorly over the surface of the fins. Host tissue surrounding the leech attachment site is raised due to epithelial hyperplasia and hypodermal thickening. In brown bullhead, dilated blood vessels and hemorrhage are present around the attachment site, and hemorrhage occurs at the margins of the fin rays where the caudal sucker erodes the dermis. Epithelium is absent at the site of attachment in both fish species. An acellular layer is present between the caudal sucker and host tissues, and apparently is formed from secretions of several types of leech gland cells. The adhesion of the leech at the unprotected site on the fins probably is enhanced by the leech's body orientation which minimizes water resistance, caudal sucker secretions which likely complement suctorial pressure, and close concordance of the caudal sucker with the firm substrate provided by the fin ray. Localization of M. lugubris on the fins of the fishes may be determined in part by the preferred attachment of the caudal sucker to the fin rays. The piscicolid leech Myzobdella lugubris Leidy, 1851 predominantly attaches to the fins of a variety of fresh-water and estuarine fish species (Dechtiar, 1972; Daniels & Sawyer, 1975; Sawyer et al., 1975; Amin, 1981). However, nothing is known of the significance of the site specificity of this leech or the mechanism by which it attaches. Myzobdella lugubris recently was found firmly attached to the fins of logperch, Percina caprodes (Rafinesque), and brown bullhead, Ictalurus nebulosus (LeSueur). This study describes the method of attachment on the fin rays, and describes some caudal sucker secretions of the leech. The possible significance of these features to the usual localization of M. lugubris on the fins of logperch and brown bullhead is discussed. MATERIALS AND METHODS Nineteen logperch, 4.5-9.0 cm long, were collected in July 1980 with a seine along beaches of Lake St. Clair, near Tremblay, Ontario, Canada (42?18'N x 82?31'W). Logperch were placed individually in vials and pre1 Mr. Steve Nepzy and Mr. Kelly Munkittrick kindly provided preserved logperch and live catfish, respectively. Mr. Geoff Black, Mr. John Smith, and Prof. Roy C. Anderson, University of Guelph, reviewed the manuscript. This work was supported by a NSERC Operating Grant to Prof. Roy C. Anderson and NSERC Postdoctoral Fellowships to the authors. TRANS. AM. MICROSC. Soc., 101(2): 135-141. 1982. ( Copyright, 1982, by the American Microscopical Society, Inc. This content downloaded from 207.46.13.20 on Sat, 24 Dec 2016 05:14:24 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC. served immediately in 10% formalin. Twenty-three brown bullheads, 14.625.7 cm long, were collected in April 1981 with a gill net in Hamilton Harbor, Lake Ontario, Canada (43?15'N x 79?51'W). Brown bullheads were examined alive and tissues with leeches attached were preserved in 10% buffered formalin or Gendre fluid (Humason, 1972). Fins of logperch and brown bullheads preserved with 10% formalin were decalcified overnight in 5% formic acid-formalin. All tissues examined histologically were dehydrated in an ethanol series, embedded in paraffin, and sectioned at 6-8 g/m. Sections were stained with hematoxylin and eosin, aqueous and alcoholic periodic acidSchiff (PAS) for possible mucopolysaccharides, Alcian blue (pH 2.5) for acid mucopolysaccharides, Gomori's Millon reaction for protein, and Mallory triple connective tissue stain (Pantin method, Humason, 1972). Specimens examined with SEM were postfixed in osmium tetroxide, dehydrated in an ethanol series, critical-point dried by CO2 substitution, coated with gold-palladium alloy and viewed with an ETEC Autoscan. Leech identification follows Sawyer et al. (1975) where M. morrei (Meyer, 1946) and Illinobdella spp. are treated as junior synonyms of M. lugubris. Voucher specimens have been deposited at the Canadian National Museum of Natural Sciences, Invertebrate Collection, Invertebrate Zoology Division, Ottawa, Ontario K1A OM8 (NMCIC 1981-589, -590, -591).