Patterns of host specificity among the helminth parasite fauna of freshwater siluriforms: testing the biogeographical core parasite fauna hypothesis

Host specificity plays an essential role in shaping the evolutionary history of host-parasite associations. In this study, an index of host specificity recently proposed was used to test, quantitatively, the hypothesis that some groups of parasites are characteristics of some host fish families along their distribution range. A database with all published records on the helminth parasites of freshwater siluriforms of Mexico was used. The host specificity index was used considering its advantage to measure the taxonomic heterogeneity of the host assemblages and its appropriateness for unequal sampling data. The helminth parasite fauna of freshwater siluriforms in Mexico seems to be specific for different host taxonomic categories. However, a relatively high number of species (47% of the total helminth fauna) is specific to their respective host family. This result provides further corroboration for the biogeographic hypothesis of the core helminth fauna proposed previously. The statistical values for host specificity obtained herein seem to be independent of host range. However, the accurate taxonomic identification of the parasites is fundamental for the evaluation of host specificity and the accurate evolutionary interpretation of this phenomenon.     

How Many Parasites Species a Frog Might Have? Determinants of Parasite Diversity in South American Anurans

There is an increasing interest in unveiling the dynamics of parasite infection. Understanding the interaction patterns, and determinants of host-parasite association contributes to filling knowledge gaps in both community and disease ecology. Despite being targeted as a relevant group for conservation efforts, determinants of the association of amphibians and their parasites in broad scales are poorly understood. Here we describe parasite biodiversity in South American amphibians, testing the influence of host body size and geographic range in helminth parasites species richness (PSR). We also test whether parasite diversity is related to hosts’ phylogenetic diversity. Results showed that nematodes are the most common anuran parasites. Host-parasite network has a nested pattern, with specialist helminth taxa generally associated with hosts that harbour the richest parasite faunas. Host size is positively correlated with helminth fauna richness, but we found no support for the association of host geographic range and PSR. These results remained consistent after correcting for uneven study effort and hosts’ phylogenic correlation. However, we found no association between host and parasite diversity, indicating that more diversified anuran clades not necessarily support higher parasite diversity. Overall, considering both the structure and the determinants of PRS in anurans, we conclude that specialist parasites are more likely to be associated with large anurans, which are the ones harbouring higher PSR, and that the lack of association of PSR with hosts’ clade diversification suggests it is strongly influenced by ecological and contemporary constrains.     

Parasite assemblages of Australian species of Pseudomys (Rodentia: Muridae: Murinae)

The parasite fauna of many Australian rodents is poorly known. The ectoparasite and helminth faunas of Pseudomys delicatulus, Pseudomys desertor, Pseudomys gracilicaudatus, and Pseudomys hermannsburgensis were determined and compared. In total, 12 species of arthropods, 2 cestodes, and 13 nematodes were found. Species richness of parasites was highest in P. hermannsburgensis and lowest in P. desertor. Despite the sampling effort, the number of parasite species discovered did not reach an asymptote for any of the host species, indicating that the full parasite fauna was not examined. Helminth species richness was highest in the insectivorous P. hermannsburgensis and lower in the obligate herbivores. The structure of parasite component communities was influenced by the social structure of the host species, not surprisingly, with the most highly social species having the highest richness of parasites. Habitat preferences also provided contrast between the helminth component communities, with heligmonellid nematodes occurring in damp woodlands and dominating the parasite fauna of P. gracilicaudatus. Oxyurid nematodes dominated the component communities of the 3 other species, all of which inhabit drier habitats.     

Community structure of helminth parasites of the tuna, Euthynnus affinis, from the Visakhapatnam coast, Bay of Bengal

An analysis is made of the community structure of the helminth parasites of the tuna Euthynnus affinis collected off the coast of Visakhapatnam, Bay of Bengal. The helminth fauna comprised 23 species, consisting of two monogeneans, 18 digeneans, one larval cestode, one nematode and one acanthocephalan. Didymozoids, represented by 14 species, were the dominant members of the parasite spectrum. The parasite assemblage is characterized by species richness as well as a high diversity. Most of the parasites found, the didymozoids in particular, were host specialists, exhibiting a high degree of host specificity. The fauna comprised three core species, four satellite species and many secondary species, with no potential for interaction among them but the degree of predictability is high in that each infracommunity comprised two or three core species superimposed by a few secondary species. Many host factors such as the varied diet, high vagility, long life span and endothermy appear to have contributed to the development of the species rich and diverse parasite communities in the tuna. There was evidence for a decrease in parasite density and an increase in diversity with increase in host size, indicating that host size has a profound influence on the component community structure.     

Helminth infracommunities in Litoria genimaculata (Amphibia: Anura) from Birthday Creek, and upland rainforest stream in Northern Queensland, Australia

The helminth fauna of Litoria genimaculata, a rainforest frog from northern Queensland, was quantified from 53 adult male frogs collected at monthly intervals between April 1990 and March 1991. The helminth fauna of this species was depauperate (6 species: Mesocoelium sp., Parapolystoma bulliense, Austraplectana sp., Onchocercidae gen. sp., Cosmocerca sp. and an unidentified nematode larva). The most commonly encountered species was P. bulliense, but the intestinal infracommanity was dominated by the digenean Mesocoelium sp. Fifty-five per cent of frogs were infected with only 1 helminth species and only 1 frog had more than 2 species, resulting in low diversity values. These results support previous studies which indicate that amphibians have depauperate helminth communities.     

Helminth community structure of sympatric eastern American toad, Bufo americanus americanus, northern leopard frog, Rana pipiens, and blue-spotted salamander, Ambystoma laterale, from southeastern Wisconsin

One-hundred twelve amphibians, including 51 blue-spotted salamanders, Ambystoma laterale, 30 eastern American toads, Bufo americanus americanus, and 31 northern leopard frogs, Rana pipiens, were collected during April-October 1996 from Waukesha County, Wisconsin and examined for helminth parasites. The helminth compound community of this amphibian assemblage consisted of at least 10 species: 9 in American toads, 8 in leopard frogs, and 3 in blue-spotted salamanders. American toads shared 7 species with leopard frogs, and 2 species occurred in all 3 host species. Although there was a high degree of helminth species overlap among these sympatric amphibians, statistically significant differences were found among host species and percent of indirect or direct-life cycle parasites of amphibian species individual component communities (chi2 = 1,015, P < 0.001). American toads had a higher relative abundance of nematodes, 59%, than larval cestodes, 31%, and larval and adult trematodes, 10%, whereas leopard frogs had a higher relative abundance of larval cestodes, 71.3%, and larval and adult trematodes, 25.3%, than nematodes 3.4%. This is related to ecological differences in habitat and dietary preferences between these 2 anuran species. Helminth communities of blue-spotted salamanders were depauperate and were dominated by larval trematodes, 94%, and few nematodes, 6%. Low helminth species richness in this host species is related to this salamander's relatively small host body size, smaller gape size, lower vagility, and more fossorial habitat preference than the other 2 anuran species. Adult leopard frogs and toads had significantly higher mean helminth species richness than metamorphs, but there was no significant difference in mean helminth species richness among adult and metamorph blue-spotted salamanders. Considering adult helminths, the low species richness and low vagility of caudatans as compared with anurans suggest that local factors may be more important in structuring caudatan helminth communities of salamanders than of anuran hosts. Helminth species infecting salamanders may be more clumped in their geographic distribution as compared with anurans, and the role of other hosts and their parasites at the compound community level may be important in structuring helminth communities of salamanders.     

Body size,trophic level,and the use of fish as transmission routes by parasites

Within food webs, trophically transmitted helminth parasites use predator–prey links for their own transfer from intermediate prey hosts, in which they occur as larval or juvenile stages, to predatory definitive hosts, in which they reach maturity. In large taxa that can be used as intermediate and/or definitive hosts, such as fish, a host species’ position within a trophic network should determine whether its parasite fauna consists mostly of adult or larval helminths, since vulnerability to predation determines an animal’s role in predator–prey links. Using a large database on the helminth parasites of 303 fish species, we tested whether the proportion of parasite species in a host that occur as larval or juvenile stages is best explained by their trophic level or by their body size. Independent of fish phylogeny or habitat, only fish body length emerged as a significant predictor of the proportion of parasites in a host that occur as larval stages from our multivariate analyses. On average, the proportion of larval helminth taxa in fish shorter than 20 cm was twice as high as that for fish over 100 cm in length. This is consistent with the prediction that small fishes, being more vulnerable to predation, make better hosts for larval parasites. However, trophic level and body length are strongly correlated among fish species, and they may have separate though confounded effects on the parasite fauna exploiting a given species. Helminths show varying levels of host specificity toward their intermediate host when the latter is the downstream host involved in trophic transmission toward an upstream definitive host. Given this broad physiological compatibility of many helminths with fish hosts, our results indicate that fish body length, as a proxy for vulnerability to predators, is a better predictor of their use by helminth larvae than their trophic level based on diet content.     

Host-parasite relationships of longnose dace, Rhinichthys cataractae, from the Ford River, Michigan.

A total of 1,115 longnose dace, Rhinichthys cataractae (family Cyprinidae), were examined for parasites from May 1983 through October 1986 from 3 localities in the Ford River in Michigan's Upper Peninsula. Thirteen parasite species (1 Monogenea, 2 Digenea, 2 Cestoda, 4 Nematoda, 1 Acanthocephala, 3 Protozoa) infected dace. The parasite faunas of dace, taxonomically and in species number, were similar between localities. Posthodiplostomum minimum minimum, Neascus sp., and Rhabdochona canadensis were the most common helminths infecting dace from each locality. The first 2 species did not exhibit consistent seasonal infection patterns between years, whereas the prevalence and mean intensity of R. canadensis in dace from the downriver locality were higher in summer 1983, 1984, and 1985. The intensity of infection of each of these helminth species significantly increased with host length. The prevalences and mean intensities of P. m. minimum, Neascus sp., and R. canadensis as well as the helminth infracommunity diversity were highest in dace from the upriver locality. The major factors that influenced parasite intensity were environmental factors that occurred when and where a fish began its life, the sequence of events that occurred in each habitat the fish encountered during its life, and the length of exposure (age of fish). Dace have isolationist helminth infracommunities arising from factors including ectothermy, a simple enteric system, restricted vagility, and being gape-limited. Allogenic helminths with indirect life cycles predominate in the depauperate helminth fauna of dace.     

Biogeography of helminth parasites of freshwater fishes in Mexico: the search for patterns and processes

Aim To uncover and describe patterns of biogeography of helminth parasites in freshwater fishes of Mexico, and to understand processes that determine them. Three predictions about host‐specificity, faunal exchange in transitional areas, and the biogeographical ‘core’ fauna, are evaluated, all of which follow from a fundamental hypothesis: that parasites show characteristic associations with particular host clades. The parasite fauna of the southern Mexican cichlids and of the fishes of the Mesa Central are examined as case studies that reflect Neotropical and Nearctic historical influences. Location The region covered in this study includes most of Mexico, with emphasis on six biogeographical areas: the Yucatán Peninsula (area 1), the Grijalva‐Usumacinta drainage (area 2), the Papaloapan and Pánuco drainages (area 3), the Balsas drainage (area 4), the Lerma‐Santiago drainage (area 5), and the Bravo drainage (area 6). Methods A parasite data base containing all the records of helminth parasites of freshwater fishes of Mexico was filtered to extract records of adult helminth parasites in freshwater fishes from the six biogeographical areas designated in this study. Jaccard's similarity coefficients and cluster analyses (using upgma ) were used to analyse the extent of faunal similarity between the designated biogeographical areas and between host (fish) families. Taxonomic composition of parasite assemblages in different host groups was also qualitatively compared from summary data. These data were used to test the three main predictions. Results To date, 184 species of helminths (120 as adults) have been recorded from 127 freshwater fishes in Mexico (almost 33% of the total fish diversity of Mexico). Of these parasite species, 69 are digenetic flukes, 51 are nematodes, 33 are monogeneans, 25 are tapeworms, and only six are acanthocephalans. The data and analyses from the six biogeographical areas corroborate the predictions that: (1) the adult parasite fauna is largely circumscribed by higher levels of monophyletic host taxa (families, orders, etc.), and that this pattern is independent of areas; (2) areas within a certain biogeographical region, and consequently with similar fish composition (e.g. areas 1, 2 and 3) have more similar parasite faunas compared to areas with less similar fish faunal composition; and (3) ‘core’ parasite faunas persist to some extent in transitional areas with limited host‐sharing. Main conclusions Helminth biodiversity in Mexican freshwater fishes is determined by the historical and contemporary biogeography of their hosts. Host lineage specificity, mainly at the level of the host family, appears to be an important factor in the distribution of the parasites. Most fish families (Characidae, Cichlidae, Pimelodidae, Ictaluridae, Catsotomidae, Goodeidae, Atherinidae) possess their own characteristic ‘core’ helminth fauna, with limited host‐sharing in transitional areas (e.g. areas 3 and 4). A re‐evaluation of the helminth fauna of Mexican cichlids questions the hypothesis that cichlids lost parasites during the colonization of Mexico from South America. The evidence supports the idea that they acquired new parasites by host switching, possibly from marine or brackish‐water percomorphs. In contrast, the parasite fauna of the Mesa Central remains enigmatic and reflects the region's history of endemicity with historical marine and Nearctic connections.     

The parasites of Anolis lizards in the northern Lesser Antilles

Summary The helminth communities from ten species of lizard on seven islands in the Caribbean were sampled by collecting one hundred specimens of each species. Nine genera of parasites were identified; these included six nematodes, two digeneans and an acanthocephalan. No relationship was discernible between parasite density or abundance and island area or altitude, although dry islands tend to have fewer species of parasites. Anolis lizards of the bimaculatus and wattsi series share similar parasites with four out of nine species common to both series. The parasite community of lizards on these islands is depauperate with respect to similar surveys on the larger islands of the Greater Antilles.On three of the islands lizards were sub-sampled by collecting from moist woodland and more xeric habitats. These data suggest that differences between habitats are as significant as differences between islands in determining parasite burdens. Worm burdens of the commonest parasite species, T. cubensis, increased monotonically with host body size and no evidence was found to suggest that these parasites affect either host survival or fecundity. The sex-ratio of this species correlated with mean abundance of the parasite, with females the dominant sex on islands or in habitats where the parasite was common. This pattern may reflect haplodiploid sexual determination in this species.     

Helminth parasites of Madeiran rockpool fishes,with a redescription of Schikhobalotrema longivesiculatum Orecchia & Paggi, 1975 (Digenea: Haplosplanchnidae), and some comments on their zoogeographical relationships

Seven species of Madeiran rockpool fishes were examined for their helminth parasites. Only two of these harboured helminth parasites. The most frequently encountered parasite was the digenean Schikhobalotrema longivesiculatum Orecchia & Paggi, 1975 from Parablennius parvicornis; this species is redescribed and discussed. The paucity of the parasite fauna of Madeiran rockpool fishes and the zoogeographical relationships of the digenean fauna of Madeiran marine fishes are commented upon.     

Helminths of sympatric striped, hog-nosed, and spotted skunks in west-central Texas

Twenty-eight hog-nosed skunks (Conepatus leuconotus), 23 striped skunks (Mephitis mephitis), and nine spotted skunks (Spilogale gracilis) from an area of sympatry in west-central Texas were examined for helminth parasites. Shared helminth species among all three host species were one nematode (Physaloptera maxillaris), two acanthocephalans (Pachysentis canicola, Macracanthorhynchus ingens), and one cestode (Mathevotaenia mephitis). Two nematodes (Gongylonema sp. and Filaria taxidaea) occurred in both the striped and hog-nosed skunks. One nematode (Filaroides milksi) and one acanthocephalan (Oncicola canis) were collected only from C. leuconotus. The most common helminth infections for striped and hog-nosed skunks were P. maxillaris and P. canicola. Helminth species richness was highest in hog-nosed skunks, but striped skunks had the highest prevalences and intensities of all the common helminth species. The helminth fauna of spotted skunks was markedly depauperate in terms of species richness and helminth abundance compared to the other two host species. Differences in helminth communities across these three sympatric skunks may be related to differences in their relative abundance, behavior, food habits, and geographic range.     

The Evolution of Taxonomic Diversity in Helminth Assemblages of Mammalian Hosts

Several studies have searched for the key forces behind the diversification of parasite assemblages over evolutionary time. All of these studies have used parasite species richness as their measure of diversity, thus ignoring the relatedness among parasite species and the taxonomic structure of the assemblages. This information is essential, however, if we want to elucidate which processes have caused an assemblage of parasites to acquire new species. Here, we performed a comparative analysis across 110 species of mammalian hosts in which we evaluated the effects of four host traits (body mass, population density, geographic range, and basal metabolic rate) on the diversity of their assemblages of helminth endoparasites. As measures of diversity, we used parasite species richness, as well as the average taxonomic distinctness of the assemblage and its variance; the latter measures are based on the taxonomic distance between two parasite species, computed across all possible species pairs in an assemblage. Unlike parasite species richness, both the average taxonomic distinctness and its variance were unaffected by the number of hosts examined. These two measures of parasite diversity also proved highly repeatable among host populations of the same mammalian species; in contrast, parasite species richness was unreliable as a species character, as it varied as much within a host species than among different host species. Using phylogenetically independent contrasts, and correcting for potential confounding variables, we found that host population density correlated positively with parasite species richness. There were, however, no other relationships between any of the four host traits investigated and either of our measures of parasite diversity. The processes facilitating the taxonomic diversification of parasite assemblages thus remain unclear, but their elucidation will be necessary if we are to fully understand parasite evolution.     

Coexistence of helminth species in Lysapsus limellus (Anura: Pseudidae) from an Argentinean subtropical area: influence of biotic and abiotic factors

The need for studies on helminth communities of South American amphibians was addressed by examining changes in composition and population dynamics of the helminth component and infracommunities in the frog Lysapsus limellus Cope, 1862, from 1994 to 1996. Two pond types were considered, one permanent and one semipermanent. The main goals of this study were (1) to investigate the relationships between pond type, season, study time, frog body size, and frog sex and the presence-absence and counts of helminth parasite species in the frog host, L. limellus, and (2) to examine the co-occurrence of the different parasite species in the frog host in terms of the structure, assembly, and dynamics of the helminth infracommunity. Parasite presence and absence were analyzed using logistic regression and parasite counts were analyzed using log-linear modeling. To examine the association between parasite species, a principal components analysis was carried out on the correlation matrix for the counts. The pattern of co-occurrences was also examined through a randomization test. The main results were as follows: (1) five parasite species were found in the infracommunity; (2) the pond type and the host size class were the principal factors related to the presence and absence of parasites for the three dominant species, while the year of study and the host sex were only important for one of the species; (3) for the parasite counts, many more factors were significant, with body size class and pond type always important factors for the three core species of the infracommunity, with season, year of study, and sex also sometimes important, and (4) strong associations were observed between some helminth species of the host from the permanent pond, but the same species did not co-occur in frogs in the semipermanent pond. The life histories of the five species can be considered as opportunistic or "r strategists."     

Checklist of the helminth parasites of vertebrates in Costa Rica

Helminth parasites of vertebrates have been studied in Costa Rica for more than 50 years. Survey work on this group of parasites is far from complete. We assembled a database with all the records of helminth parasites of wild and domestic vertebrates in Costa Rica. Information was obtained from different sources such as literature search (all published accounts) and parasite collections. Here we present a checklist with a parasite-host list as well as a host-parasite list. Up to now, 303 species have been recorded, including 81 species of digeneans, 23 monogeneans, 63 cestodes, 12 acanthocephalans, and 124 nematodes. In total, 108 species of vertebrates have been studied for helminths in Costa Rica (31 species of fishes, 7 amphibians, 14 reptiles, 20 birds, and 36 mammals). This represents only 3.8% of the vertebrate fauna of Costa Rica since about 2,855 species of vertebrates occur in the country. Interestingly, 58 species (19.1 %) were recorded as new species from Costa Rica and most of them are endemic to particular regions. Considering the valuable information that parasites provide because it is synergistic with all the information about the natural history of the hosts, helminth parasites of vertebrates in Costa Rica should be considered within any initiatives to accomplish the national inventory of biological resources. Starting with this compilation work, the Colección de Helmintos de Costa Rica (CHCR), hosted at the Facultad de Microbiología, Universidad de Costa Rica, has re-emerged and it is our hope that it will have the standards of quality to assure that it will become the national depository of helminths in the country.     

Helminth fauna of Talpa spp. in the Palaearctic Realm

The helminth fauna of the genus Talpa in the Palaearctic Realm is reviewed. Several helminth species reported in Talpa spp. by a number of authors are discussed, with reference to host specificity, parasite biology, and host ethology, ecology and phylogeny. Twelve species of cestodes were found, two of which exhibit stenoxenous specificity (Staphylocystis bacillaris and Multitesticulata filamentosa). Only three species of trematodes, Ityogonimus lorum, Ityogonimus ocreatus and Combesia macrobursata, are exclusive parasites of Talpa spp. The largest group are nematodes, with 37 species. Species of Tricholinstowia are parasites of holarctic talpids and several species of distinct genera, such as Capillaria, Soboliphyme and Trichuris, are found only in Talpa spp. Only acanthocephalans of the genus Moniliformis have been reported in moles of the genus Talpa. On the basis of these helminthological findings, the close phylogenetic relationship between moles (Talpidae) and shrews (Soricidae) supports the separation of the ordinal levels Soricomorpha and Erinaceomorpha.     

Helminth communities in five species of sympatric amphibians from three adjacent ephemeral ponds in southeastern Wisconsin

Representatives of 5 amphibian species (313 individuals), including eastern American toads (Bufo americanus), wood frogs (Rana sylvatica), spring peepers (Pseudacris crucifer), blue-spotted salamanders (Ambystoma laterale), and central newts (Notophthalmus viridescens louisianensis), were collected from 3 ephemeral ponds during spring 1994, and they were inspected for helminth parasites. The component communities of anurans were more diverse than those of caudates. Infracommunities of all host species were isolationist and depauperate, due mostly to host ectothermy and low vagility. Toad infracommunities were dominated by skin-penetrating nematodes, and they had the highest values of mean total parasite abundance, mean species richness, and overall prevalence. This was likely due to their greater vagility compared with other host species. Infracommunities of wood frogs and blue-spotted salamanders had intermediate values for these measures of parasitism, whereas spring peeper and newt infracommunities had the lowest values. In addition to relative vagility, feeding habits and habitat preference were likely important in helminth community structure. Body size also seemed to play a role because mean wet weight of host species followed the same general trend as values of parasitism. However, effects of size were variable within host species and difficult to separate from other aspects of host ecology.     

Helminths of the San Diego alligator lizard, (Gerrhonotus multicarinatus webbi) (Anguidae)

Necropsy of 96 specimens of the San Diego alligator lizard (Gerrhonotus multicarinatus webbi) from Los Angeles County, California (USA) revealed the presence of two nematodes (Physaloptera sp. and Oswaldocruzia pipiens) and a cestode (Oochoristica sp.). Both O. pipiens and Oochoristica sp. represent new host records. Prevalence of helminth infection (all species) was only 4/96 (4%) indicating the lack of a helminth community and a depauperate helminth fauna in this host.     

Helminth communities of the lesser sandeel Ammodytes tobianus L. off the west coast of Ireland

The helminth parasites present in 412 lesser sandeels (Ammodytes tobianus) taken from June 1996 to May 1997 from the Aran Islands on the west coast of Ireland were examined. Ten helminth parasite species were recorded, and more than 92% of the sandeels were infected with at least 1 helminth species. Seven of the species were digeneans, including Brachyphallus crenatus, Hemiurus communis, Derogenes varicus, Lecithaster gibbosus, Opechona bacillaris, Cryptocotyle lingua, and Galactosomum lacteum; 2 nematodes, including Hysterothylacium sp. and Contracaecum sp.; and 1 cestode, Scolex pleuronectis. Three of the 7 digenean species were either larvae or immature. Only 2 species, the digeneans G. lacteum and H. communis, had prevalences greater than 50%. The dominant species was G. lacteum, accounting for 67% of all parasites present. The relationship between spawned groups, host length, and season versus the abundance, prevalence, species richness, and the total number of parasites in the infracommunities was investigated. No difference was found between the parasite communities of the 2 spawning races of the host population. Mean abundance and prevalence of the different parasite species showed seasonal variation. Numbers of parasite species and numbers of parasites increased with fish length. The role of A. tobianus as an intermediate host for helminths was assessed; it was determined that most were infectious to birds or mammals, with the majority of the parasite species being autogenic (infectious to fish). The mean number of parasites per fish was nearly a quarter of the value recorded for A. tobianus in the North Sea, where a much higher intensity of infection was recorded.     

Structure of parasite component communities of didelphid marsupials: insights from a comparative study

The parasite fauna of the gray four-eyed opossum, Philander opossum (Linnaeus, 1758), and the common opossum, Didelphis marsupialis Linnaeus, 1758, in Camp du Tigre, French Guiana, is characterized. Nine species from the gastrointestinal system were recovered from both species, which shared 80% of their parasites. The parasite fauna comprised several monoxenous species (63%) and was dominated by Aspidodera raillieti Travassos, 1914, which exhibited high levels of prevalence and abundance in both communities. Only 2 species (Moennigia sp. and Spirura guianensis) had been recorded in other species of mammals. Both species richness and taxonomic composition at the level of component communities from this locality were compared against 11 communities present in the Virginia ( Didelphis virginiana ), white-bellied (Didelphis albiventris), and common opossum from Argentina, Brazil, Mexico, and the United States. Neither host phylogeny nor taxonomy accounted for statistical differences in species richness. There was no statistical difference among species richness values among the 9 localities studied. Taxonomic similarity was analyzed by means of the Jaccard's similarity index, including all, and only common species (occurring in prevalence >10%). The results suggest that sympatric species of marsupials share more species of parasites than parasite communities occurring in conspecific marsupials from different localities. As a consequence, taxonomic composition of these parasite communities varied depending on the locality. Probably, marsupials of the monophyletic Didelphini offer the same compatibility toward their parasites, by presenting them with similar habitats. Subtle differences in lifestyles of the marsupials may determine the chance of encounter between the symbionts and prevent some parasites from completing their life cycles. Further and more rigorous tests are necessary to determine the roles of encounter and compatibility filters, as well as the role of chance, in the structuring of parasite communities in marsupials.