Nematomorpha: Gordioidea)
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UNL | Libraries University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln John Janovy Publications Papers in the Biological Sciences 6-2002 Morphometric Analysis of Nonadult Characters of Common Species of American Gordiids (Nematomorpha: Gordioidea) Ben Hanelt University of New Mexico, [email protected] John J. Janovy Jr. University of Nebraska - Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/bioscijanovy Part of the Parasitology Commons Hanelt, Ben and Janovy, John J. Jr., "Morphometric Analysis of Nonadult Characters of Common Species of American Gordiids (Nematomorpha: Gordioidea)" (2002). John Janovy Publications. 17. https://digitalcommons.unl.edu/bioscijanovy/17 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in John Janovy Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. J. Parasitol., 88(3), 2002, pp. 557-562 C American Society of Parasitologists 2002 MORPHOMETRICANALYSIS OF NONADULTCHARACTERS OF COMMONSPECIES OF AMERICANGORDIIDS (NEMATOMORPHA: GORDIOIDEA) Ben Hanelt and John Janovy Jr. School of BiologicalSciences, Universityof Nebraska-Lincoln,Lincoln, Nebraska 68588-0118. e-mail:[email protected] ABSTRACT: The nonadultstages, egg strings, eggs, larvae, and cysts of Gordius robustus,Paragordius varius, and Chordodes morganiare describedmorphometrically. The goal was to documentthe differencesbetween species and to evaluatethe usefulness of morphometricsin species identification.In concert, multivariateanalysis of variance(MANOVA) and univariateanalysis of variance(ANOVA, a posterioricontrasts) statistical tests demonstratedthat each species is morphometricallydistinguishable from all others. Additionally,discriminant function analysis indicatedthat postseptumlength, pseudointestinelength, and stylet width were the most importantvariables in the discriminationof species based on larval characters.Finally, differencesin oviposition behaviorsamong these 3 species were found. It is suggestedthat ovipositioningdifferences may place larvae into distinctniches and may ultimatelylead to the use of differentparatenic hosts by differentgordiid species. Gordiids are the freshwater-inhabiting members of the Nem- (Chandler and Wells, 1989). Gordius robustus adults have been atomorpha. They are parasitic as larvae but free-living as adults. studied using only light microscopy (May, 1919). After mating, females expel egg strings within which larvae Nonadult life cycle stages have been less studied. Larval gor- mature. After hatching, larvae encyst within a variety of aquatic diids of these species have been described using light micros- animals. The life cycle is completed when terrestrial insect copy (Montgomery, 1904), SEM (Bohall et al., 1997; Adrianov hosts consume cysts and become infected. et al., 1998), and transmission electron microscopy (Zapotosky, About 320 species of gordiids have been described globally 1974, 1975). Even though cysts are a critically important part (Bresciani, 1991). Only 14 species have been described from of this life cycle, they have never been thoroughly studied, al- the United States (Chandler, 1985; Smith, 1991, 1994; de Mir- though some investigations have indicated possible size differ- alles and de Villalobos, 1995). Of these, Gordius robustus Lei- ences among species (Poinar, 1991). Studies on the eggs or egg dy, 1851, Paragordius varius Leidy, 1856, and Chordodes mor- strings of these species have also never been conducted satis- gani Montgomery, 1898, are the most widely distributed spe- factorily. Furthermore, none of these studies provide measure- cies in the United States (Chandler, 1985). All 3 of these species ments of these life cycle stages. have been reported from throughout the contiguous United Because adults can be difficult to find, but other life cycle States; from either coast and from southern states, Texas and stages can be encountered frequently (Hanelt et al., 2001), the Florida, to border states with Canada (see Chandler, 1985 and present study was conducted to describe the nonadult life cycle references therein). stages. The focus of this study was on morphometrically de- The phylogenetic placement of the Nematomorpha is still scribing eggs, larvae, and cysts. Also, differences in egg string uncertain. Cladistic analyses based on morphological and be- morphologies and oviposition behaviors are described. Subse- havioral characters places the Nematomorpha sister to the Nem- quently, features of the larvae were identified, using multivar- atoda (Nielsen et al., 1996; Wallace et al., 1996). Using 18S iate analysis to allow for the discrimination of species based on rRNA molecular data to support these findings has proven ex- mensural data. tremely difficult because of the unstable nature of this clade (Aleshin et al., 1998). However, several studies, based on mo- MATERIALSAND METHODS lecular characters, have supported a close relationship between Specimencollection and maintenance the Nematoda and the (Winnepenninckx et al., Nematomorpha Two for each species of gordiid were located and used most strik- populations 1995; Aleshin et al., 1998; Zrzavy et al., 1998). The in this study. Gordius robustuswas collected from Las HuertasCreek ing difference, however, between these 2 phyla is the presence (35016.44'N, 106022.41'W), at Highway 44, Bernallio County, New of a larval stage within the life cycle of the Nematomorpha. Mexico, and 18 km southeast of Stillwater (4609.55'N, 96051.28'W), The larval has and of which the Payne County, Oklahoma.Paragordius varius was collected from the stage pre- postsepta, preseptum women's shower room at Cedar Point Station contains rows of hooks and a retractable Biological (41012.51'N, (2-3) proboscis 101038.80'W),2 km east of Lake McConaughy,Keith County,Nebras- (Schmidt-Rhaesa, 1997/98). Although the larval stage of the ka, and from Millville Creek (40059.61'N, 96033.93'W)at 112th Street, Nematomorpha is unique and has been indicated to be of sub- LancasterCountry, Nebraska. Chordodes morgani was collected from Lancaster stantial importance in some classification schemes (Malakhov, Elk Creek(40053.13'N, 96050.06'W),at Highway34, County, Nebraska,and from Branch Creek (40010.67'N, 9605.33'W) at 1980), little attention has been focused on documenting this life Taylor Highway 4, Pawnee County, Nebraska. Adult worms collected from cycle stage. each populationwere deposited in the Harold W. ManterLaboratory Adult forms of the 3 common American gordiid species have (HWML)collection, Universityof Nebraska-Lincoln(G. robustusmale: been described adequately. Studies of P. varius have included HWML 16557, female: HWML 16556; C. morgani male: HWML HWML and P. varius male: HWML and electron (SEM) as 16555, female: 16554; 16553, light microscopy scanning microscopy female: HWML well as de Villalobos et 16552). sectioning (Montgomery, 1903; al., For each species, worm pairs found copulating were isolated; the 2000). Studies of the structure of adult C. morgani have also remainingworms were randomlypaired and placed in 1,000-ml plastic been done by light microscopy (Montgomery, 1898) and SEM containerscontaining well water, with aeration.Egg strings were col- lected from each mated pair and briefly rinsed in a 1:250 :: Clorox" bleach : well-water solution, as describedpreviously (Hanelt and Jan- Received 9 October 2001; revised 19 December 2001; accepted 3 ovy, 1999). A 60-ml glass jar, rinsed previously with the bleach solu- January2002. tion, was used to keep a stock of larvae from each of the 3 species. All 557 558 THEJOURNAL OF PARASITOLOGY,VOL. 88, NO. 3, JUNE2002 CWwidth* - Stywidth (width; Fig. lA). To measure the thickness of the cyst wall, the maxi- 4- CL width --• mum length and the maximum width of the entire cyst were measured. Subsequently, the length or width of the cyst larva was subtracted from these numbers, respectively, and each resulting number was divided by 2. This calculation provided the average thickness of the cyst wall for the height and the width of each cyst. Because the stylet length is unlikely to change through different life cycle stages, this character was only measured in the larvae, not in the cysts. To obtain cysts, Physa gyrina were exposed to freshly hatched larvae. Groups of 20 snails were exposed to 300-500 larvae in a 90-ml plastic container, using well water or aerated commercial spring water. Snails : At were kept unfed for 5 days, after which the water was changed, and snails were fed flakes of Tetramin' fish food (Tetra Sales, Blacksburg, --4 Virginia) and autoclaved lettuce every other day. Approximately 14-30 days postexposure, snails were examined as previously described (Hanelt et al., 2001). Shells were removed from snails, and the soft tissue was crushed between coverslip and slide. Only those cysts, which lay perfectly flat, were measured. One group of ex- posed snails per gordiid species was used for all cyst data. A. B. PsI width Data analysis * see text abouthow CW lengthand width was calculated The resulting data were contained in 4 separate data sets, egg string, FIGURE1. Morphometric measurements for gordiids. (A) Cyst. (B) egg, larva, and cyst. The questions to be addressed using these analysis Larva. CL, cyst larva; CW, cyst wall; PostS, postseptum;