Gastrointestinal parasites of the guenons of western Uganda

From January 1998 to December 2002, we collected 293 fecal samples from free-ranging individuals of the 4 guenon species of western Uganda, i.e., redtail guenons (Cercopithecus ascanius), blue monkeys (Cercopithecus mitis), l'hoesti monkeys (Cercopithecus lhoesti), and vervet monkeys (Cercopithecus aethiops), to quantify the prevalence of gastrointestinal parasites. Helminth eggs, larvae, and protozoan cysts were isolated by sodium nitrate flotation and fecal sedimentation. Helminth parasites were identified, and infection prevalence was determined for all 4 guenon species. Coprocultures facilitated identification of strongylate nematodes. For the most common species, the redtail guenon, we documented prevalence of protozoan parasites and examined the effect of season and host sex on infection prevalence. Six nematodes (Strongyloidesfulleborni, Oesophagostomum sp., unidentified strongyle, Trichuris sp., Streptopharagus sp., and Enterobius sp.), 1 cestode (Bertiella sp.), 1 trematode (Dicrocoeliidae), and 5 protozoans (Entamoeba coli, Entamoeba histolytica, lodameoba butschlii, Giardia lamblia, and Chilomastix mesnili) were detected. Seasonal patterns of infection were not readily apparent for any parasite species infecting redtail guenons. Although prevalence never differed between male and female guenons, only adult females were infected with Oesophagostomum sp. and S. fulleborni.     

Descriptive epidemiology of intestinal helminth parasites from stray cat populations in Qatar

A total of 488 stray cats, 212 adult and 29 juvenile females plus 235 adult and 12 juvenile males, were examined post-mortem during the winter and summer months of 2006 from five sites in the vicinity of Doha and its outskirts. Five helminths, comprising three nematode and two cestode species were identified and the majority of cats harboured two of these species. The most prevalent was the cestode Taenia taeniaeformis (75.8%), followed by the cestode Diplopylidium sp. (42.8%), and the nematodes Ancylostoma tubaeforme (17.0%), Physaloptera sp. (6.6%) and Toxocara cati (0.8%). All five species were found to be typically overdispersed in their distribution. Using univariate and multivariate analyses, the prevalence and abundance of infections were primarily influenced by host gender and season, with females tending to harbour higher levels of infection during the summer. No significant differences were found relative to site except in the case of Physaloptera sp. Using bivariate Pearson product moment correlations, significant positive co-occurrences were identified between Diplopylidium sp. and T. taeniaeformis and also between A. tubaeforme and T. taeniaeformis. The results are discussed in relation to the effect of environmental conditions on the intestinal helminth infracommunities and their possible interactions in stray cat populations from such a harsh and arid region as Qatar.     

Gastrointestinal parasitism of Iowa coyotes in relation to age

Taenia sp., Physaloptera sp., Ancylostoma caninum, Toxascaris leonina, and/or Trichuris vulpis were recovered from gastrointestinal tracts of 141 and 144 (97.9%) coyotes ranging from 1/2 to 8 1/2 years of age. Ancylostoma caninum exhibited a significant decline in both prevalence and mean number per coyote with increasing age of the host. Taenia sp. appeared with consistently high prevalence in all age classes. Physaloptera sp. and T. leonina showed general reductions in prevalence in all age classes. Physaloptera sp. and T. leonina showed general reductions in prevalence and mean nubmer with increasing host age, although the data were not statistically significant. Coccidia were found in 15 of 58 (25.9%) fecal flotations.     

Tardigrades of the Australian Antarctic Territories: the Windmill Islands, East Antarctica

Six species of tardigrades, Pseudechiniscus suillus, Macrobiotus sp., Hypsibius antarcticus, Ramajendas frigidus, Diphascon chilenense and Diphascon pingue were extracted from mosses and lichens from the ice-free regions of the Windmill Islands near Casey Base, East Antarctica. Significant positive associations were found between the three common species ( Pseudechiniscus suillus, Hypsibius antarcticus, Diphascon chilenense ) and bryophytes, whereas strong negative associations were found between these species and algae and lichens. There were additional interspecific associations between the common species of tardigrades as well as between tardigrades, nematodes and rotifers.     

Helminths of sympatric black-tailed jack rabbits (Lepus californicus) and desert cottontails (Sylvilagus audubonii) from the high plains of eastern New Mexico

Thirty-five desert cottontails (Sylvilagus audubonii) and 35 black-tailed jack rabbits (Lepus californicus), occurring sympatrically near the Clovis-Portales area of eastern New Mexico were infected with four species of Eucestoda (adults of Raillietina salmoni and Raillietina selfi, larvae of Taenia pisiformis and Taenia serialis). Raillietina salmoni and T. pisiformis more commonly infected S. audubonii. Raillietina selfi was found in near equal prevalence in both host species. Taenia serialis was recovered only from L. californicus. Thus, three of the four helminth species were shared by both lagomorphs (Jaccard's coefficient = 75). Female hosts were most heavily infected with R. selfi and Taenia serialis.     

Evidence for the existence of a species closely related to the cereal aphid parasitoid Aphidius rhopalosiphi De Stefani-Perez based on host ranges, morphological characters, isoelectric focusing banding patterns, cross-breeding experiments and sex pheromone specificities (Hymenoptera, Braconidae, Aphidiinae)

Abstract. Host transfer trials with six strains of the cereal aphid parasitoid Aphidius rhopalosiphi De Stefani-Perez revealed the presence of two differing host ranges: three strains parasitized Sitobion uvenae (F.) and S.fragariae (Wlk.) exclusively, whereas the others successfully developed in both Sitobion species and also in Metopolophium dirhodum (Wlk.), M.festucue cerealiurn Stroyan, Rhopalosiphum padi (L.) and Diuraphis muehlei Börner. The two host range groups were poorly distinguishable by means of morphological characters. In con trast, isoelectric focusing proved to be a much better tool for discrimi nation. Reproductive isolation between the two host range groups was clear but not complete, as evidenced by crossing experiments with laboratory-bred and field-collected material. Under field conditions, males showed a specific response to virgin females of the two groups. Hence, the sex pheromones of the females were obviously different. Considering these results, a species ( Aphidius sp. A) closely related to A.rhopalosiphi seems to occur. As a detailed study of morphological characters is still lacking, Aphidius sp. A is not yet formally established here. Due to its dependence upon Sitobion spp., Aphidius sp. A may be an economically important parasitoid of the pest aphid S.avenae .     

Odonates,gregarines and water mites: why are the same host species infected by both parasites?

1. Damselflies and dragonflies are widely parasitised insects and numerous studies have tried to understand this host–parasite relationship. However, most of these studies have concentrated on a single host species, neglecting the larger pattern within the Odonata order. 2. The aim of this paper was to examine different damselfly and dragonfly species for common endo‐ and ectoparasites and whether a general infection pattern can be found. Additionally, the goal was to investigate whether the phylogeny of the host species could explain these possible infection patterns. To this end, a dataset from the existing literature was compiled and the prevalence of endoparasitic gregarines and ectoparasitic water mites was analysed for 46 different odonate species. 3. Three distinct patterns were found: (i) most of the odonate host species had both gregarines and water mites, rather than only either one or neither; (ii) there appears to be a positive association between gregarine and water mite prevalences across host species; (iii) a weak phylogenetic signal was detected in gregarine prevalence and a strong one in water mite prevalence. 4. It is hypothesised that, due to the infection and transmission mechanisms by which water mites and gregarines infect different odonate host species, parasitism is aggregated to common, high‐density species. However, much research is needed in order to fully understand this relationship between odonates and their parasites, especially within the same host populations and host species assemblages.     

Gastrointestinal helminths of Commerson's dolphins Cephalorhynchus commersonii from central Patagonia and Tierra del Fuego.

The stomachs and intestines of 9 Commerson's dolphins incidentally caught in trawl nets in central Patagonia and 23 stranded on beaches in Tierra del Fuego were surveyed for helminth parasites. A total of 267 individuals belonging to 4 species of parasites (1 nematode, 3 digeneans) were found in the dolphins from the first area: Anisakis sp. (larvae type 1 = A. simplex), Braunina cordiformis, Hadwenius sp. and Pholeter gastrophilus. In the Tierra del Fuego dolphins, 142 specimens belonging to 3 species (2 nematodes, 1 digenean, 1 cestode) were found: A. simplex, Hadwenius sp. and Strobilocephalus triangularis. Only 2 of the helminth species were shared in the 2 study areas, A. simplex and Hadwenius sp., and both were more common in central Patagonia. Among the species, A. simplex was most prevalent and abundant in both study areas. In Tierra del Fuego, adults of A. simplex appeared in only 1 host. Hadwenius sp., P. gastrophilus and S. triangularis are new host records for Commerson's dolphin. Species diversity and species richness were low in both study areas. Helminth communities were more diverse in central Patagonia (t = 1.97, df = 258, p < 0.05) and species richness was higher in central Patagonia (S = 4). No differences in diversity were observed between females and males of central Patagonia (t = 1.97, df = 139, p < 0.05) and between females of central Patagonia and Tierra del Fuego. The results may suggest some differences in habitat use, diet and sex between Commerson's dolphin populations in the 2 study areas.     

Factors affecting the helminth community structure of adult collared peccaries in southern Texas

Four species of nematodes (Gongylonema pulchrum, Parabronema pecariae, Texicospirura turki, and Physocephalus sexalatus) and one species of cestode (Moniezia sp.) comprised the helminth fauna of adult collared peccaries (Tayassu tajacu) from the plains in southern Texas. The community structure of the helminth fauna of peccaries from this region was basically dissimilar to that from the more humid Gulf coastal prairies of southern Texas in composition (by the conspicuous absence of certain species) and relative abundance of shared species. The distributions of each of the three common species of helminths (G. pulchrum, T. turki, and P. sexalatus) were overdispersed. The effects of selected habitat variables operating across host subpopulations (delineated by condition and sex) and of the extrinsic variable of season on the dispersion patterns of the three common species of helminths were examined. The hypothesis that heterogeneity within the host population, rather than across the collective host population, is the main factor generating overdispersion in natural parasite populations was not confirmed for the three common species of helminths. Overdispersion in P. sexalatus resulted from seasonal changes across the collective host population, with the greatest abundances occurring during the cool season. Aggregated abundances of G. pulchrum resulted from variation generated across host sex subpopulations, while the dispersion patterns of T. turki appeared to be unaffected by the habitat variables examined in this study.     

Ecological causes of sex-biased parasitism in threespine stickleback

Males and females can differ in levels of parasitism and such differences may be mediated by the costs of sexual selection or by ecological differences between the genders. In threespine stickleback, Gasterosteus aculeatus , males exhibit paternal care and territorial nest defence and the costs of reproduction may be particularly high for males relative to females. We monitored levels of parasitism for 15 years in a population of stickleback infected by four different parasite species. Consistent with general predictions, overall parasite prevalence (total parasitism) was greater in males than in females. However, this excess did not occur for each species of parasite. Males had higher prevalence of a cestode Cyathocephalus truncatus and a trematode Bunodera sp. relative to females, while females had higher prevalence of a cestode Schistocephalus solidus and nematodes. This suggested ecological sources to differences in parasitism rather than reproductive costs and therefore we examined diet of unparasitized stickleback, predicting that differences in dietary niche would influence relative parasitism. This was partially confirmed and showed that female stomach contents had increased frequency of pelagic items, the major habitat for the primary host of S. solidus whereas males exhibited increased frequency of benthic items, the dominant habitat of C. truncatus and Bunodera. Temporal shifts in the extent and direction of differential parasitism among years between the sexes were associated with temporal shifts in dietary differences. Our results, combined with those in the literature, suggest that ecological differences between genders could be a more important component to patterns of parasitic infection in natural populations than currently appreciated.     

Parasitism of Hylodes phyllodes (Anura: Cycloramphidae) by Hannemania sp (Acari: Trombicuudae) in an area of Atlantic Forest, Ilha Grande, southeastern Brazil

We studied some parameters of the parasitism by the mite Hannemonia sp. on the endemic frog Hylodes phyllodes in the Atlantic Forest of Ilha Grande (Rio de Janeiro State, Brazil). Prevalence, mean abundance, mean intensity and total intensity of infestation, body regions infected, and host sexual differences in parasitism rate of the larvae of Hannemania sp. on individuals of H. phyllodes were assessed. Prevalence was 86.5% (N = 37; total of 1,745 larvae of Hannemania sp) for male hosts and 91.7% (N = 12; total of 330 larvae) for female hosts, with no significant difference between the sexes. Overall prevalence of Hannemania sp. on H. phyllodes was 87.7%. Mean intensity of infestation in males (54.5 +/- 42.5; range 1-173 larvae) was higher than in females (29.9 +/- 47.6; range 1-166). We conclude that the rates of intensity, abundance, and prevalence of Hannemania larvae parasitizing Hylodes phyllodes at Ilha Grande were considerably high, suggesting that this species of anuran constitutes a relevant host for this mite species to complete its life-cycle in the area. Differences between males and females in infestation rates probably reflect their differential use of space in the forest.     

Helminth parasites of the wild rabbit Oryctolagus cuniculus near Malham Tarn, Yorkshire, UK

Between 1992 and 1996, 95 rabbits from the immediate locality of Malham Tarn, North Yorkshire, UK were examined for the presence of helminth parasites. All the examinations took place in late September or October. Three species of nematodes, Graphidium strigosum, Passalurus ambiguus and Trichostrongylus retortaeformis and two species of cestodes, Taenia pisiformis and Cittotaenia pectinata were identified. There were no associations between helminth species richness and year of sampling, host weight or sex. A logistic model was fitted to the prevalence data from these helminths as was an over-dispersed Poisson model to the worm burden data. Graphidium strigosum was the most frequently identified species with an average prevalence of 78%. The mean prevalence and intensity of Graphidium infection were significantly effected by sampling year. The lower than normal rainfall recorded at the Tarn during the years 1995 and 1996 may have be one reason for this pattern. The worm burden of G. strigosum was significantly positively associated with rabbit body weight. The intensity of infection with P. ambiguus was significantly higher in female rabbits. There was a significant non-linear relationship between P. ambiguus worm burden and rabbit weight (P = 0.002) with worm burdens being highest in the 1000 g to 1499 g weight cohort. Trichostrongylus retortaeformis was only identified in 1994 and male rabbits harboured significantly higher worm burdens than females (48 vs. 7, P = 0.022). Over the five years, the average Taenia pisiformis prevalence was 31% and there was a significant positive association between worm burden and rabbit weight (P = 0.001). Cittotaenia pectinata had a prevalence of 37% over the whole study period with no interactions between prevalence or intensity and body weight, year of sampling or rabbit sex. All five helminths showed an overdispersed distribution with k values less than 1.     

The role of host traits, season and group size on parasite burdens in a cooperative mammal

The distribution of parasites among hosts is often characterised by a high degree of heterogeneity with a small number of hosts harbouring the majority of parasites. Such patterns of aggregation have been linked to variation in host exposure and susceptibility as well as parasite traits and environmental factors. Host exposure and susceptibility may differ with sexes, reproductive effort and group size. Furthermore, environmental factors may affect both the host and parasite directly and contribute to temporal heterogeneities in parasite loads. We investigated the contributions of host and parasite traits as well as season on parasite loads in highveld mole-rats (Cryptomys hottentotus pretoriae). This cooperative breeder exhibits a reproductive division of labour and animals live in colonies of varying sizes that procreate seasonally. Mole-rats were parasitised by lice, mites, cestodes and nematodes with mites (Androlaelaps sp.) and cestodes (Mathevotaenia sp.) being the dominant ecto- and endoparasites, respectively. Sex and reproductive status contributed little to the observed parasite prevalence and abundances possibly as a result of the shared burrow system. Clear seasonal patterns of parasite prevalence and abundance emerged with peaks in summer for mites and in winter for cestodes. Group size correlated negatively with mite abundance while it had no effect on cestode burdens and group membership affected infestation with both parasites. We propose that the mode of transmission as well as social factors constrain parasite propagation generating parasite patterns deviating from those commonly predicted.     

Patterns of infection by intestinal parasites in sympatric howler monkey (Alouatta palliata) and spider monkey (Ateles geoffroyi) populations in a tropical dry forest in Costa Rica

In primate populations, endoparasite species richness and prevalence are associated with host traits such as reproductive and social status, age, sex, host population density, and environmental factors such as humidity. We analyzed the species richness and prevalence of intestinal parasites in two sympatric primate populations, one of Alouatta palliata and one of Ateles geoffroyi, found in a tropical dry forest in Costa Rica. We identified three species of intestinal parasites (Controrchis sp., Trypanoxyuris sp., and Strongyloides sp.) in these two primate species. We did not find any differences in species richness between the primate species. However, the prevalences of Controrchis sp. and Trypanoxyuris sp. were higher in Alouatta palliata. Similarly, males and lactating females of Alouatta palliata showed higher Controrchis sp. prevalences. We did not observe any differences in parasite richness and prevalence between seasons. Infectious diseases in endangered primate populations must be considered in conservation strategies, especially when defining protected areas.     

Ecological interactions among ants in the genus Linepithema, their phorid parasitoids, and ant competitors

Abstract. 1. Many ant species abandon foraging and retreat underground when parasitoids in the dipteran family Phoridae are present. Although the influence of phorids on ant foraging is well documented, their influence on interspecific competition is less studied. This study examined whether phorids influenced the competitive ability of host ants in the genus Linepithema at two sites in Brazil.
2. The phorid Pseudacteon lontrae attacked Linepithema piliferum at one site, while the phorid Pseudacteon pusillus attacked an unknown Linepithema ( Linepithema sp.) at the other site. Phorid parasitoids of Linepithema were far more common than phorids of other ant species.
3. Despite a high abundance of phorids, it was difficult to conclude that they influenced competition. Captures in pitfall traps indicated that host Linepithema were most active during times of day when phorids were inactive.
4. Camponotus rufipes and Brachymyrmex sp., the most common competitors of Linepithema sp. (60% of all interactions), dominated Linepithema sp. during the day regardless of phorids. Remaining ant species could not be evaluated individually because they interacted with Linepithema sp. infrequently.
5. Ectatomma brunneum was the most common competitor of L. piliferum (58% of all interactions). The high abundance of phorids at this site made it impossible to evaluate interactions between E. brunneum and L. piliferum in the absence of phorids.
6. Phorids seldom influenced exploitative competition by causing host Linepithema to abandon the bait when no ant competitors were present.     

Helminth community composition, structure, and pattern in six dove species (Columbiformes: Columbidae) of South Texas

The helminth community composition and structure of 6 species of columbids residing in south Texas are reported and compared herein. Sixty individuals of the following species, rock pigeons (Columba livia [RP]), mourning doves (Zenaida macroura [MD]), Eurasian collared-doves (Streptopelia decaocto [ECD]), white-winged doves (Zenaida asiatica [WWD]), and common ground doves (Columbina passerina [CGD]), and 48 Inca doves (Columbina inca [ID]) were collected during the summer of 2006 and examined for helminths. Twelve helminth species were found (9 nematodes and 3 cestodes), representing 486 individuals. Nematodes numerically dominated the component community in all host species. Overall, helminth prevalence was similar among host sex within all dove species. However, prevalence of Skrjabinia bonini and Hymenolepis sp. in RPs was significantly different among host age groups (P = 0.01, P = 0.0002, respectively). Likewise, prevalence of Killigrewia delafondi was higher (P = 0.0001) in adult WWDs. Based on percent similarity and Jaccard's coefficient of community indices, helminth component communities were dissimilar, and the number of shared helminth species varied among host species. Data from this study suggest that the environment surrounding preferred host habitat and foraging strategies of each host species is the driving force behind helminth component communities. This study emphasizes the importance of examining co-occurring hosts at both local and regional scales to elucidate helminth community structure and patterns.     

Metazoan parasite fauna of the bigeye flounder, Hippoglossina macrops, from Northern Chile. Influence of host age and sex.

The metazoan parasite fauna of Hippoglossina macrops (n = 123) from northern Chile (30 degrees S) is quantitatively described for the first time, and the role of host age and sex was evaluated. Twelve parasite species were recovered, including 5 ectoparasites (2 Monogenea, 2 Copepoda and 1 Piscicolidae) and 7 endoparasites (1 Digenea, 3 Cestoda, 2 Acanthocephala, and 1 Nematoda). The copepod Holobomolochus chilensis, the monogenean Neoheterobothrium sp., the adult acanthocephalan Floridosentis sp. and the hirudinean, Gliptonobdella sp. are new geographical and host records. The most prevalent ectoparasitic species were the monogenean, Neoheterobothrium sp. and the copepod, H. chilensis. Among endoparasites, the acanthocephalans Floridosentis sp. and Corynosoma australe were most prevalent and abundant. Prevalence and mean intensity of infection for most parasitic species were not affected by host sex, however the prevalence of Floridosentis sp. was significantly greater in males. Intensity of infection was positively correlated with host age for Neoheterobothrium sp., and negatively correlated for Floridosentis sp. and H. chilensis. The helminth species richness of the host H. macrops was lower compared to related flatfishes from the Northern Hemisphere. The relationship of the helminth fauna of H. macrops, its feeding habits and ecological habitats are discussed.     

Helminth infections in Apodemus sylvaticus in southern England: interactive effects of host age, sex and year on the prevalence and abundance of infections.

Helminth parasites were studied in the wood mouse, Apodemus sylvaticus, in southern England in September of each of four successive years (1994-1997). Nine species of helminths were recorded: five nematodes (Heligmosomoides polygyrus, Syphacia stroma, Pelodera strongyloides, Trichuris muris, Capillaria murissylvatici), two cestodes (Microsomacanthus crenata, Taenia taeniaeformis) and two trematodes (Corrigia vitta, Brachylaemus recurvum). In total, 134 mice were examined and 91.8% carried at least one species of helminth. The majority of mice carried two to three species (60.5%) and the highest combination was six of the nine species recorded in the study. The patterns of between-year variations in the prevalence and abundance of infection were different for each of the six species for which sufficient quantitative data were available to enable statistical analysis. For H. polygyrus, the most important source of variation arose from between-year differences, host age and the interaction of these factors: abundance increased with host age but in 1995 the age pattern was markedly different from that in the remaining years. The abundance of C. vitta also varied significantly between years but additionally there was a strong independent age effect. For M. crenata, the year x age interaction was significant, indicating that abundance among different age cohorts varied from year to year but there was also a weak significant main effect of age arising from the youngest age cohort carrying no parasites and the oldest age cohort the heaviest infections. For P. strongyloides the only significant factor was between-year variation with 1995 being a year of exceptionally low prevalence and abundance of infection. No significant between-year variation was detected for S. stroma but there was a strong sex effect (males carrying heavier infections) and an age effect (older mice of both sexes carrying heavier infections). The abundance of Trichuris muris varied only in relation to host age, worm burdens growing in intensity with increasing age, but there was also a significant interaction between year and host sex with respect to prevalence. For the remaining three species, the prevalence of infections was too low (< 8.2%) to enable any meaningful interpretation. This analysis emphasizes the need for carefully controlled statistical procedures in aiding the interpretation and the prioritization of the factors affecting worm burdens in wild rodents.     

Dynamics of Amoebophrya parasites during recurrent blooms of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides in Korean coastal waters

During the bloom events of the harmful dinoflagellate Cochlodinium polykrikoides in August and October, 2012, infections by two different Amoebophrya species were observed in Korean coastal waters. To investigate the dynamics of the two parasites and their relative impact on the host populations, a quantitative real-time PCR (qPCR) method was applied to detect and quantify the parasites in the free-living and parasitic stages. Each specific primer set of the target species, Amoebophrya sp. 1 and sp. 2 was designed on the large subunit (LSU) and the first internal transcribed spacer (ITS1) of ribosomal RNA (rRNA) gene, respectively. Dynamics of the two Amoebophrya species via qPCR assay showed distinct patterns during the C. polykrikoides bloom events. Amoebophrya sp. 1 showed peaks during both bloom events in August and October with relatively low copies (10⁶ to 10⁷ copies L⁻¹), while Amoebophrya sp. 2 appeared only during the bloom event in October with very high copies (10⁹ to 10¹⁰ copies L⁻¹). Overall, the qPCR measurements for the dynamics of two Amoebophrya species in the parasitic stage (> 5 μm fractions) were consistent with parasite prevalence through microscopic observations. Amoebophrya sp. 1 infections were observed during both bloom events in August and October with relatively low parasite prevalence (0.1–1.5%), while Amoebophrya sp. 2 infections were detected only during the bloom event in October with high prevalence (up to 45%). Taken together, Amoebophrya sp. 1 may be a generalist and C. polykrikoides may not be its primary host, while Amoebophrya sp. 2 may be a specialist which can substantially impact host population dynamics.     

Influence of host sex and age on infracommunities of metazoan parasites of Prochilodus lineatus (Valenciennes, 1836) (Prochilodontidae) of the upper Paraná River floodplain, Brazil

149 specimens of Prochilodus lineatus were collected on the upper Paran6 River floodplain. Of these, 121 (82.1%) were parasitized. 33 species of metazoan parasites were recorded. Rhinonastes pseudocapsaloideum was classified as secondary, while all other species were classified as satellites. Ergasilus sp. and Tereancistrum curimba were positively associated and their abundances were positively correlated. Saccocoelioides magnorchis and S. nanii were positively associated and their abundances were positively correlated. The mean diversity in the infracommunities of P. lineatus was H = 0.6875 +/- 0.4398. Host standard length was not correlated with parasite diversity (rs = 0.1726; p = 0.0533). The abundances of T. curimba and Kritskyia boegeri, and S. magnorchis and S. nanii were significantly correlated with host length. Correlation between fish age and parasite prevalence was not significant. The abundances of Amplexibranchius sp., K. boegeri and S. magnorchis were significantly different among host age classes. For Amplexibranchius sp., the three-year old age class had more parasites. For K. boegeri, the intermediate age classes had the most numerous parasites. Only Tereancistrum curimba showed significant difference in the prevalence between the sexes, with females being more parasitized.