Helminth Abundance Research Articles

Does the body size, sex, and reproductive modes of leaf litter anurans affect the diversity of parasites?

We describe the composition of endoparasites associated with leaf litter anurans from an Atlantic Forest area, in southeastern Brazil. We tested if body size, sex, and reproductive modes of anuran hosts influence endoparasite abundance and richness. We sampled 583 individuals from 11 anuran species and recorded 1,600 helminths from 14 taxa. The helminths that infected the greatest number of anuran host species were the nematodes Cosmocerca parva (8 spp.), Physaloptera sp. (8 spp.), and Cosmocerca brasiliense (7 spp.), and the most abundant helminth species were Physaloptera sp. (14.6%), Cosmocerca brasiliense (13.7%) and Cosmocerca parva (12.6%). Both helminth abundance and richness were positively affected by anuran body size and dependence on water for reproduction. Larger hosts can contain a higher abundance of parasites because they may provide more physical space than smaller ones, or it can simply be a function of age. Besides, parasite species richness can be highly correlated with the amount of time a host spends in association with aquatic habitats, a conservative aspect of both parasite and host natural history. Within host species, there was a positive and significant influence of body size on helminth abundance. Haddadus binotatus females had greater helminth abundance than males, probably due to sex-related differences in behavior and/or in physiology. Our data suggest that reproductive modes could also influence helminth infection parameters in other anuran communities and should be considered in detail in future analyses.

Ranavirus and helminth parasite co-infection in invasive American bullfrogs in the Atlantic forest, Brazil

Emerging infectious diseases threaten amphibian species across the globe. In Brazil, the American bullfrog (Aquarana catesbeiana) is a highly invasive species that can potentially transmit parasites and pathogens to native amphibians. This is the first assessment of co-infection of Ranavirus and helminth macroparasites in invasive populations of bullfrogs in South America. We collected, measured, and euthanized 65 specimens of A. catesbeiana sampled from 9 sites across three states of Brazil in the Atlantic Forest biome. We collected and identified helminth macroparasites and sampled host liver tissue to test for the presence and load of Ranavirus with quantitative PCR. We documented patterns of prevalence, parasite load, and co-infection with generalized linear mixed models, generalized logistic regressions, and randomization tests. Most individual bullfrogs did not exhibit clinical signs of infection, but the overall Ranavirus prevalence was 27% (95% confidence interval, [CI 17–38]). Bullfrogs were infected with helminth macroparasites from 5 taxa. Co-infection of helminth macroparasites and Ranavirus was also common (21% CI [12–31]). Bullfrog size was positively correlated with total macroparasite abundance and richness, and the best-fitting model included a significant interaction between bullfrog size and Ranavirus infection status. We observed a negative correlation between Ranavirus viral load and nematode abundance (slope = −0.22, P = 0.03). Invasive bullfrogs (A. catesbeiana) in Brazil were frequently infected with both Ranavirus and helminth macroparasites, so adult bullfrogs could serve as reservoir hosts for both pathogens and parasites. However, many macroparasites collected were encysted and not developing. Coinfection patterns suggest a potential interaction between Ranavirus and macroparasites because helminth abundance increased with bullfrog size but was lower in Ranavirus infected individuals. Future studies of bullfrogs in the Atlantic Forest should investigate their potential role in pathogen and parasite transmission to native anurans.

Physicochemical Parameters and Abundance of Pathogenic Protozoans and Helminths in Abattoirs within Minna Metropolis, Niger State, Nigeria

Physicochemical Parameters and Abundance of Pathogenic Protozoans and Helminths in Abattoirs within Minna Metropolis, Niger State, Nigeria

Temporal variation in diet and helminth abundance in the spiny-tailed lizard, Strobilurus torquatus Wiegmann, 1834 (Squamata: Tropiduridae) from the Brazilian Atlantic Forest

Spatial and temporal variations can influence the abundance and biology of parasite species and even the transmission process, as well as the diet, reproduction and distribution of hosts. We studied the influence of seasonality on the diet and endoparasites of the lizard Strobilurus torquatus. The lizards were collected during a period of one year, in the Engenho Gargaú Private Reserve of Natural Heritage, located in the municipality of Santa Rita, in the state of Paraíba, Northeast Brazil. Thirty-three lizards were analysed, of which 30 were parasitised (overall prevalence of 90%) with the helminths Physaloptera lutzi (prevalence of 69.6%), Spauligodon loboi (51.5%), Strongyluris oscari (15.1%) and Haplometroides odhneri (3.0%). Our analysis showed that endoparasite abundance was influenced by host body size (R2m: 0.95; R2c: 0.95; Z-value: 11.521; P < 0.0001). Host sex also influenced endoparasite abundance, where males were parasitised more than females (Z-value: 6.260; P < 0.001). When comparing the two seasons (dry and rainy), we observed that the greatest endoparasites abundance occurred during the rainy season (Z- value: -2.422; P < 0.05). Regarding the lizards’ diet, we observed a high niche overlap (overlap index of 0.999), which indicates that males and females of S. torquatus consumed practically the same prey during the analysed period. The life cycle of the endoparasites found in S. torquatus was linked to seasonal variation, and the behavioural and physiological differences between sexes may have influenced the variations in endoparasite abundance.

Parasite-host relations and new reports of helminths for Rhinella dorbignyi (Duméril & Bibron, 1841) (Anura: Bufonidae) from Neotropical region

This study aimed to analyze helminth assemblage in Rhinella dorbignyi regarding host gender, size and mass in two sampling sites in southern Brazil, and to report new parasite associations. Anurans (n = 100) were collected in two localities from Rio Grande do Sul (RS) state, Brazil, from 2017 to 2020. Nineteen taxa (adults and larval forms) belonging to Nematoda, Acanthocephala, Digenea, and Cestoda were found in different infection sites. Cosmocercidae gen. Spp., Physaloptera liophis, Catadiscus sp., and Cylindrotaenia americana were the dominant taxa in helminth assemblage. Female anurans showed higher helminth species richness than males considering the total sample (two localities) or one of the two localities. However, prevalence and mean intensity of infection did not show any significant difference between genders. Mean intensity of infection was significantly higher (19.52) in Laranjal locality. Host body size does not influence helminth abundance, as infections did not show significant correlation snout-vent length (SVL) nor body mass (BM) of anurans. The findings reveal anurans of R. dorbignyi may be intermediate, paratenic and definitive host for these parasites. Plagiorchioidea helminths (Digenea), Physaloptera liophis, larvae of Acuariidae and Spiroxys sp. (Nematoda), and cystacanth of Lueheia sp. (Acanthocephala) constitute new records for R. dorbignyi. Additionally, this is the first record of Cylindrotaenia americana larvae in this host species. Resulting information increases the knowledge on biodiversity and parasite-host relations and may help future conservation programs developed in ecosystems in the extreme south of Brazil.

Temporal variation in helminth infracommunities of the Gafftopsail pompano, Trachinotus rhodopus (Pisces: Carangidae) off the Pacific coast of Mexico.

Temporal variation of the helminth infracommunity structure in the Gafftopsail pompano Trachinotus rhodopus was studied during bi-monthly revisions of samples collected offshore from Puerto Ángel, Oaxaca (Mexican Pacific) in 2018. In total, 110 specimens of T. rhodopus were subjected to a parasitic review. Helminths found were identified to the lowest possible taxonomic level (six species and three genera) by means of morphological and molecular data. Attributes of the helminth infracommunities are described through statistical analyses, showing stability in terms of their richness throughout the year. However, variations were found in helminth abundance related to the seasonality of samplings, which may be associated with the life cycles of the parasites, the host species' gregarious behavior, the availability of intermediate hosts, and/or the diet of T. rhodopus.

Low-cost molecular methods to characterise gastrointestinal nematode co-infections of goats in Africa

BackgroundVeterinary diagnostics aid intervention strategies, track zoonoses, and direct selective breeding programs in livestock. In ruminants, gastrointestinal nematode (GIN) parasites are a major cause of production losses, but morphologically similar species limit our understanding of how specific GIN co-infections impact health in resource-limited settings. To estimate the presence and relative abundance of GINs and other helminths at the species level, we sought to develop a low-cost and low-resource molecular toolkit applied to goats from rural Malawi smallholdings.MethodsGoats were subjected to health scoring and faecal sampling on smallholdings in Lilongwe district, Malawi. Infection intensities were estimated by faecal nematode egg counts with a faecal subsample desiccated for DNA analysis. Two DNA extraction methods were tested (low-resource magbead kit vs high-resource spin-column kit), with resulting DNA screened by endpoint polymerase chain reaction (PCR), semi-quantitative PCR, quantitative PCR (qPCR), high-resolution melt curve analysis (HRMC), and ‘nemabiome’ internal transcribed spacer 2 (ITS-2) amplicon sequencing.ResultsBoth DNA isolation methods yielded comparable results despite poorer DNA purity and faecal contaminant carryover from the low-resource magbead method. GINs were detected in 100% of samples regardless of infection intensity. Co-infections with GINs and coccidia (Eimeria spp.) were present in most goats, with GIN populations dominated by Haemonchus contortus, Trichostrongylus colubriformis, Trichostrongylus axei, and Oesophagostomum columbianum. Both multiplex PCR and qPCR were highly predictive of GIN species proportions obtained using nemabiome amplicon sequencing; however, HRMC was less reliable than PCR in predicting the presence of particular species.ConclusionsThese data represent the first ‘nemabiome’ sequencing of GINs from naturally infected smallholder goats in Africa and show the variable nature of GIN co-infections between individual animals. A similar level of granularity was detected by semi-quantitative PCR methods, which provided an accurate summary of species composition.Assessing GIN co-infections is therefore possible using cost-efficient low-resource DNA extraction and PCR approaches that can increase the capacity of molecular resources in areas where sequencing platforms are not available; and also open the door to affordable molecular GIN diagnostics. Given the diverse nature of infections in livestock and wildlife, these approaches have potential for disease surveillance in other areas.Graphical

Helminths of freshwater turtles in Northeastern Brazil: parasite–host–environment relationships

ABSTRACT The parasitic fauna of reptiles is considered understudied compared to that of other vertebrates and is even less well known than the parasitic fauna of chelonians. Yet parasites are considered one of the main controllers of host populations because they can strongly impact population structure and species diversity. The objective of the present study was to identify the helminth fauna infecting freshwater turtles Phrynops geoffroanus and Mesoclemmys tuberculata, to evaluate the effects of host features (body mass and sex) and seasonality (dry and rainy seasons) on the abundance of parasites, and to compare infection rates in each host species between different biomes (Caatinga and Atlantic Forest) in an area of Northeastern Brazil. We found seven species of helminths that belong to Nematoda (Physaloptera sp., Serpinema amazonicus, Serpinema monospiculatus and Spiroxys figueiredoi), Cestoda (unidentified specimen), Digenea (Echinostomatidae) and Monogenea (Polystomoides brasiliensis). For both freshwater turtle species, we did not find a significant difference in the abundance of helminths related to the maximum carapace length, body mass or host sex; however, males had higher prevalence than females, while females presented greater abundance when infected. We observed significant differences in the infection levels between biomes and between seasons (dry and rainy), where the Atlantic Forest specimens showed higher infection rates compared to the Caatinga and the highest rates occurred in the dry season. The main parasitological parameters observed in P. geoffroanus and M. tuberculata showed that the studied biomes directly influenced the levels of parasitic infection. Variations in habitat characteristics can directly influence patterns of helminth diversity and abundance, and interactions between these characteristics can generate differences in parasitism rates of the same host species in different environments.

How agricultural land use affects the abundance and prevalence of monoxenous and heteroxenous helminths in the generalist lizard Tropidurus hispidus.

Among the forms of anthropogenic disturbance, agricultural land use is one of the main threats to biodiversity. Understanding how interactions between parasites and hosts are affected by agricultural land use allows predictions of how these anthropogenic impacts affect parasites. Although parasitism patterns are affected by agricultural land use, it is noteworthy that different groups of parasites can respond differently to these environmental alterations. While heteroxenous species need more than one host to complete their life cycle and tend to be more harmed by anthropization, monoxenous species, which need only one host to complete their life cycle, tend to be less harmed. In this work, we evaluate how agricultural land use affects the abundance and prevalence of parasitism for monoxenous and heteroxenous helminths in the generalist lizard Tropidurus hispidus in Caatinga Domain, Brazil. We recorded differences in abundance and prevalence of heteroxeneous (higher in conserved areas) and monoxenous helminths (higher in agricultural areas). Heteroxenous helminths that have lizards as definitive hosts are mainly obtained through diet. Tropidurus hispidus predominantly consumes insects, so it is possible that the lower abundance and prevalence of heteroxenous parasites in agricultural areas, beyond habitat simplification, is related to the decrease in the insect population. As monoxenous species do not need an intermediate host, it is possible that this aspect has influenced their greater success in anthropogenic environments than heteroxenous species. This contrasting result reinforces the need for a separate assessment between these groups when evaluating effects of land use.

How to use natural history collections to resurrect information on historical parasite abundances.

Many of the most contentious questions that concern the ecology of helminths could be resolved with data on helminth abundance over the past few decades or centuries, but unfortunately these data are rare. A new sub-discipline - the historical ecology of parasitism - is resurrecting long-term data on the abundance of parasites, an advancement facilitated by the use of biological natural history collections. Because the world's museums hold billions of suitable specimens collected over more than a century, these potential parasitological datasets are broad in scope and finely resolved in taxonomic, temporal and spatial dimensions. Here, we set out best practices for the extraction of parasitological information from natural history collections, including how to conceive of a project, how to select specimens, how to engage curators and receive permission for proposed projects, standard operating protocols for dissections and how to manage data. Our hope is that other helminthologists will use this paper as a reference to expand their own research programmes along the dimension of time.

TESTING THE ENEMY RELEASE HYPOTHESIS IN THE INVASIVE FISH <i>AMATITLANIA NIGROFASCIATA</i> (PERCIFORMES: CICHLIDAE) IN MEXICO

The enemy release hypothesis (ERH) posits that invasive species are released from their natural enemies in their introduced range, which promotes their successful invasion. In this study, we tested the ERH in a population of the convict cichlid Amatitlania nigrofasciata , an invasive species in Mexico. The ERH predicts that the convict cichlid: a) is not infected by specialist helminth parasites in the introduced range; b) has lower infection parameter values, as measured through richness, prevalence, abundance and diversity of helminths, than a native species-the redside cichlid Cichlasoma istlanum ; and c) is not affected in its condition factor by the abundance of helminths it carries. The convict cichlid was infected by two (33%) specialist helminths relative to the six specialist helminths that infect the cichlid in its native range. The convict cichlid had lower helminth richness and diversity than the redside cichlid. However, the prevalence and abundance of the parasite species varied between the host fish. While the prevalence and abundance of the nematode Rhabdochona kidderi was higher in the redside cichlid, the prevalence and abundance of the trematode Uvulifer sp. was higher in the convict cichlid. The condition factor in both host fish was not correlated with helminth abundance. Our results do not agree with the prediction that the convict cichlid is completely released from specialist parasites, nor with the prediction that this invasive species has lower infection parameter values than the native redside cichlid. However, our results agree with the prediction that the abundance of parasite helminths do not affect the cichlid’s condition factor. More studies are necessary to determine the advantages that the convict cichlid could have in the introduced range when it is infected with a low richness and diversity of helminths.

Long term patterns of association between MHC and helminth burdens in the bank vole support Red Queen dynamics.

Major histocompatibility complex (MHC) genes encode proteins crucial for adaptive immunity of vertebrates. Negative frequency‐dependent selection (NFDS), resulting from adaptation of parasites to common MHC types, has been hypothesized to maintain high, functionally relevant polymorphism of MHC, but demonstration of this relationship has remained elusive. In particular, differentiation of NFDS from fluctuating selection, resulting from changes in parasite communities in time and space (FS), has proved difficult in short‐term studies. Here, we used temporal data, accumulated through long‐term monitoring of helminths infecting bank voles (Myodes glareolus), to test specific predictions of NFDS on MHC class II. Data were collected in three, moderately genetically differentiated subpopulations in Poland, which were characterized by some stable spatiotemporal helminth communities but also events indicating introduction of new species and loss of others. We found a complex association between individual MHC diversity and species richness, where intermediate numbers of DRB supertypes correlated with lowest species richness, but the opposite was true for DQB supertypes—arguing against universal selection for immunogenetic optimality. We also showed that particular MHC supertypes explain a portion of the variance in prevalence and abundance of helminths, but this effect was subpopulation‐specific, which is consistent with both NFDS and FS. Finally, in line with NFDS, we found that certain helminths that have recently colonized or spread in a given subpopulation, more frequently or intensely infected voles with MHC supertypes that have been common in the recent past. Overall, our results highlight complex spatial and temporal patterns of MHC‐parasite associations, the latter being consistent with Red Queen coevolutionary dynamics.

Helminths of sigmodontine rodents in an agroforestry mosaic in the Brazilian Atlantic Forest: Patterns and processes of the metacommunity structure.

Phylogenetically or taxonomically related hosts may harbour similar parasite communities due to phylogenetic conservatism. In addition, host attributes may favour their exposure to parasites. This study aimed to characterize the helminth fauna of sigmodontine rodents in an Atlantic Forest area in northeastern Brazil and determine the pattern of the helminth metacommunity structure. The influence of host attributes and host taxonomy on the metacommunity structure was also investigated. The most abundant helminth species were Raillietina sp. and Hassalstrongylus lauroi. Euryoryzomys russatus was the most infected host species for helminth parasites, as approximately 81% (35/43) of the animals were infected by at least one helminth species. The helminth metacommunity structure was coherent at both the infracommunity and the component community scales, indicating that species responded to the same environmental gradient. A quasi-Clementsian pattern was observed for the infracommunities, indicating the occurrence of compartments of parasite species that were substituted along the environmental gradient, which was formed by host individuals. A quasi-Gleasonian pattern was found at the component community scale, showing random boundary clumping, which is consistent with the individualistic responses of parasite species to each host species. These patterns corroborated the high values of beta-diversity observed, indicating high species turnover among communities at both scales. Host taxonomic distance was the most important variable explaining the patterns of the helminth metacommunity structure.

Dietary shifts and social interactions drive temporal fluctuations of the gut microbiome from wild redfronted lemurs

Animals living in highly seasonal environments adapt their diets accordingly to changes in food availability. The gut microbiome as an active participant in the metabolization of the host’s diet should adapt and change with temporal diet fluctuations, but dietary shifts can be short-term and, hence, difficult to detect in cross-sectional studies. Therefore, we performed a longitudinal study combining repeated sampling of fecal samples with observations of feeding behavior in wild redfronted lemurs. We amplified taxonomical marker genes for assessing the bacteria, archaea, protozoa, helminths, and fungi, as well as the active bacterial community inhabiting their gut. We found that the most abundant protozoans were Trichostomatia and Trichomonadida, and the most abundant helminths were Chromadorea. We detected known members of the gut mycobiome from humans but in low abundances. The archaeal community is composed only of members of Methanomethylophilaceae. The predominant phyla in the entire bacterial community were Bacteroidota and Firmicutes while the most abundant genera harbor so far unknown bacteria. Temporal fluctuations at the entire community level were driven by consumption of fruits and flowers, and affiliative interactions. Changes in alpha diversity correlated only with the consumption of flowers and leaves. The composition of the entire and active bacterial community was not significantly different, but the most abundant taxa differed. Our study revealed that monthly changes in the bacterial community composition were linked to fruit and flower consumption and affiliative interactions. Thus, portraying the importance of longitudinal studies for understanding the adaptations and alterations of the gut microbiome to temporal fluctuations.

Ecological risk factors of soil-transmitted helminths infections in Ifedore district, Southwest Nigeria

BackgroundSoil-Transmitted Helminths are a group of parasites that cause gastrointestinal infections in humans and require the soil to develop into their infective forms. Ecological factors such as soil temperature, soil pH and rainfall patterns are, however, important determinants for the successful transmission of soil helminths as they play a major role in their abundance and survival in the soil. The study investigated the ecological factors influencing the transmission of soil-transmitted helminths in Ifedore district, Southwest Nigeria.ResultsOut of the one hundred and ninety-two (192) soil samples from the study area, one hundred and fifty-two 152 (79.2%) were positive for the presence of soil helminths’ larvae and ova. Higher occurrence of soil helminths was recorded during the rainy months (n = 416) than during the months with no records of rainfall (n = 290). Sandy soil had the highest number of soil helminths 285 (40.4%), while clay soil recorded the least 88 (12.5%). Soil temperature showed negative correlations with the occurrence of Ancylostoma duodenale (r = − 0.53) and Strongyloides stercoralis larvae (r = − 0.36), while soil conductivity showed positive correlations with the occurrence of Ascaris lumbricoides (r = 0.28) and A. duodenale (r = 0.34).ConclusionIt is evident from the study that ecological factors played a significant role in the occurrence and abundance of soil-transmitted helminths. This research is important for predicting and monitoring soil-transmitted helminthiasis in endemic countries, and to devise effective control measures.

Helminth fauna of Norops fuscoauratus (D'Orbigny, 1837) (Squamata: Dactyloidae) in the Atlantic Forest, northeastern Brazil.

The composition of macro endoparasites associated with the lizard Norops fuscoauratus (Squamata) was analysed in two localities in the Atlantic Forest on the northeast of Brazil between December 2012 and July 2015. 74 specimens of N. fuscoauratus were examined and five species of helminths were reported, being: (a) for the population of Pernambuco: Cystacanth (Prevalence=37.5%), Physaloptera retusa Rudolphi, 1819 (Prevalence=4.16%), larva of flatworm (Prevalence=2.08%), Rhabdias sp. (Prevalence=2.08%) and Strongyluris oscari Travassos, 1923 (Prevalence=2.08%), and (b) of Alagoas: S. oscari (Prevalence=17.85%) and Rhabdias sp. (Prevalence=3.57%). The differences in the composition of endoparasites in the two populations are attributed to individualities of environments occupied by the lizards. The collection period does not influence the abundance of parasites, but when associated with sex, there was a positive correlation with the abundance of helminths, with more females than males being infected with parasites in the rainy season.

Helminth community structure of Didelphis marsupialis (Didelphimorphia, Didelphidae) in a transition area between the Brazilian Amazon and the Cerrado.

Although the common opossum, Didelphis marsupialis (Didelphimorphia: Didelphidae) is a species widely distributed in South America, knowledge about their helminth parasites and helminth community structure is scarce. The aims of this study were to describe the species composition and analyze the structure of the helminth community of the common opossum in an area of the Amazonian Arc in northern Mato Grosso. The helminths were recovered, counted, and identified in 32 individuals. Overall, 10,198 specimens were categorized into 9 helminths taxa (seven nematodes, one cestode, and one acanthocephalan). The most abundant species were Aspidodera raillieti, Viannaia hamata, and Travassostrongylus orloffi. No statistically significant differences in helminth abundance and prevalence were observed between host sexes. However, young hosts had higher abundance and prevalence of Didelphonema longispiculata, whereas Oligacanthorhynchus microcephalus had higher abundance and prevalence in adult hosts. This was the first study to analyze the helminth fauna and helminth community structure of D. marsupialis in the Amazonian Arc. This is the first report of the presence of A. raillieti, D. longispiculata, T. orloffi, T. minuta, V. hamata, and O. microcephalus in the state of Mato Grosso, Brazil.

Analysis of the helminth community of Notothenia coriiceps (Actinopterygii: Nototheniidae) collected in the water area of the Argentine Islands, West Antarctica

Helminth community of the Antarctic black rockcod, Notothenia coriiceps, was examined using the fish samples collected in 2014—2015 (106 specimens) and 2020—2021 (78 specimens) in the water area of the Argentine Islands, West Antarctica. In total, 30,951 helminth specimens were collected and identified. We analyse the helminth infra- and component communities and investigate possible changes in the main parameters of helminth communities of N. coriiceps during the six-year period. Thirty species of helminths from five taxonomic groups were recorded: one species of Monogenea, 5 of Nematoda, 4 of Cestoda, 9 of Trematoda, and 11 of Acanthocephala. Notothenia coriiceps was found to be the definitive host of 18 helminth species; 12 species parasitize it in the larval stage using N. coriiceps as the second intermediate or paratenic host. The proportion of larval helminths in the samples was lower in 2014—2015 (73.4%) than in 2020—2021 (81.4%). The number of dominant helminth species (infection prevalence >50%) increased from seven in 2014—2015 to nine in 2020—2021. In helminth infracommunities, the species richness was similar in two samples. On the other hand, we found significantly higher helminth abundance in the infracommunities from the sample collected in 2020—2021. In the helminth component community, the diversity indices (Shannon, Simpson, Pielou, Berger-Parker) evidenced higher evenness and lower domination in the sample collected in 2014— 2015 compared to the sample collected in 2020—2021. Lower evenness in 2020—2021 was due to the larger relative abundance of larval Pseudoterranova sp. and Corynosoma spp. We suggest a deeper investigation of the role of separate helminth species in the component community changes, as well as further monitoring of component community parameters as prospective directions for future studies of helminth communities of N. coriiceps in West Antarctica.

HELMINTH DIVERSITY OF GREEN TREEFROGS (HYLA CINEREA) IN THEIR EXPANDED GEOGRAPHICAL RANGE.

There has been a growing interest in characterizing the parasite faunas of species populations as they expand their geographical ranges as a result of climate change. Expanded-range populations often exhibit lower parasite diversity than historical-range populations, and reduced parasitism may, in part, be attributable to expanded-range populations escaping their native range parasites. The present study compares the helminth faunas of green treefrogs (Hyla cinerea) from 4 historical and 4 expanded-range populations to determine whether these latter populations have undergone parasite escape. Results of this study found relatively high degrees of similarity in species composition among helminth assemblages within historical or within range-expansion locations, with marked differences in the composition of helminth faunas between historical and expanded-range populations of these frogs. Because green treefrogs from expanded-range locations exhibited significant decreases in helminth species diversity compared with those from historical sites, they appear to be escaping levels of parasitism typically experienced by these frogs in their native range. Most notably, there was a decrease in the abundance of helminths with direct life cycles and the absence of trematode assemblages with indirect life cycles among expanded-range populations of H. cinerea. The low prevalence of trematode assemblages among historical populations of green treefrogs could limit these parasites' ability to be introduced and propagated in expanded-range locations. However, the lack of trematode assemblages among populations of H. cinerea in its expanded range may also be due to the absence or limited availability of other aquatic hosts that are required to complete the life cycles of these parasites. The reduction in helminth diversity among expanded-range populations of green treefrogs lends some credence to the notion that individuals at the front of a range expansion often invest less energy in reproduction and in doing so allocate more energy to dispersal and other life-history traits, including resistance to parasites. There may, however, be other explanations for differences in parasite species diversity between historical and expanded-range populations of H. cinerea. Because many of the helminths reported from this study are host generalists of amphibians whose recruitment and transmission among intermediate and paratenic hosts are known to be constrained by water and/or soil moisture conditions, we cannot ignore the role of both local amphibian diversity and local abiotic factors in influencing helminth diversity between the 2 population types of green treefrogs. These latter factors would decrease the role of parasite escape or energy trade-offs in driving helminth diversity among populations of H. cinerea and instead would suggest that local conditions play a more prominent role in structuring their helminth communities.

COMUNIDAD DE HELMINTOS DE POLLOS CASEROS (GALLUS GALLUS DOMESTICUS LINNAEUS, 1758) EN SEROPÉDICA, RIO DE JANEIRO, BRASIL

The domestic chicken, Gallus gallus domesticus Linnaeus, 1758, is an important component of the agribusiness segment, and Brazil is one of the world’s largest broiler producers and exporters. The present study aimed to characterize the composition and structure of the helminth community of backyard chickens, G. g. domesticus, in Seropedica, Rio de Janeiro, Brazil. Fifty-five adult chickens were studied. The overall helminth species richness was 12. The nematodes Capillaria sp. and Heterakis gallinarum (Schrank, 1788), recovered from small intestine and cecum, respectively, presented the highest prevalence and mean abundance and were considered central species. In addition, these species presented the highest values of frequency of dominance and Berger. The pairs of helminth species Amoebotaenia cuneata (von Linstow, 1872) – Raillietina tetragona (Molin, 1958); Davainea proglottina (Davaine, 1860) – A. cuneata; and H. gallinarum – Capillaria sp. showed significant positive correlation between their abundance and prevalence. Gongylonema ingluvicola Ransom, 1904 and H. gallinarum showed significant correlation between host sex and helminth abundance, while there was no correlation between host sex and helminths prevalence. The knowledge of helminth community structure in free-range chickens is important to adopt better measures for control and prevention of helminth infections.