Parasite Component Communities Research Articles

Specific features of parasite communities of Siberian cisco Coregonus sardinella in polytypic water bodies of the polar regions: species richness.

The article dwells upon characteristics of the species richness of parasite communities in least cisco Coregonus sardinella Valenciennes in Polar water bodies: Kureyskoye Reservoir, Lake Kutaramakan, Khatanga River. The communities consist of parasite species common in coregonids. The main species in all the parasite communities in least cisco are Dibothriocephalus ditremus and D. dendriticus. Triaenophorus crassus plerocercoids dominate in the regulated water body (Kureyskoye Reservoir). To analyze the species richness of the component communities (s), coefficients of the power-law equation s = a × nb were applied, where a is the expected species richness in the first host individual examined, and b is the rate of species accumulation in parasite component communities (s). The resulting curves of species accumulation give statistical rigor to the assessment of differences and similarities of the species richness of the component communities of parasites in least cisco of various ages and habitats. The species richness of infra- and component parasite communities in least cisco was found to be significantly lower in the lake and the storage reservoir than in riverine habitats (Khatanga River). At the same time, the species accumulation rate for parasite communities in least cisco from Lake Kutaramakan was higher than in the reservoir due to a higher diversity of parasite infracommunities.

Parasitos de peixes de um rio costeiro neotropical dentro de um hotspot de biodiversidade

Abstract: Aim We investigated the ichthyofauna parasite component community across a gradient of anthropogenic pressures of the Guaraguaçu River, south Brazil, a Neotropical river of central importance for biodiversity conservation. Methods After fish sampling, all fish were identified, measured, weighed and eviscerated. The viscera and gills were inspected for parasite screening and subsequent identification. Parasite diversity estimators were calculated for the most abundant host species. Results A total of 159 host specimens from 12 species were examined, being 140 (88.05%) found to be infected with at least one parasite, including 14 new parasite occurrences. The most widely distributed parasite was the nematode Contracaecum sp., found in 8 host species. The highest mean infection intensity and mean abundance was observed for the monogenean Aphanoblastella mastigatus, infecting the Silver catfish Rhamdia quelen. The Shannon-Wiener, Jost and Simpson indexes were higher for the more abundant fishes, except for the Trahira Hoplias malabaricus. Most host species harbored parasites in poorly aggregated distribution, according to the discrepancy index. The Berger-Parker index showed monogenean dominance in all hosts except for H. malabaricus. We found little evidence for parasite infracommunity changes across the gradient of the river. Conclusions We described the infection patterns in an important Neotropical river. The new parasite occurrences highlight the contribution of our study. Fish-parasite interactions changed throughout the river stretches, and we argue that it does not necessarily means changes in diversity and abundance of parasite within species, but the rearrange of interactions. Moreover, it seems that parasites are more abundant in most impacted sites, another reason to continue the monitoring.

Metazoan parasites in Colomesus asellus (Pisces: Tetraodontidae) from Amazon River, in Brazil: an ecological, annual and seasonal study

ABSTRACT Our hypothesis is that annual and seasonal variations influence the structure of component communities and diversity of metazoan parasites from Colomesus asellus from the Amazon River. A total of 107 fish were collected during 2020 and 2021, and 932 metazoan parasites were recovered. In 2020, four species of parasites (one Nematoda, two Digenea and one Crustacea) were found; and in 2021, five species (one Nematoda, one Digenea, one Acanthocephala and two Crustacea) were recorded. Ergasilus colomesus was the most dominant throughout the study. Species richness and Brillouin diversity index were higher in 2021 and in the dry season. Some parasite component communities showed differences between years and between seasonal periods. The structure of parasite communities was mainly influenced by rainfall levels, seasonal availability of infective stages in the environment, and body size of the fish host. These facts corroborate the hypothesis that such variables could influence the component communities of parasites. Lastly, this is the first record of Contracaecum sp., Genarchella genarchella, Clinostomum marginatum, Brasacanthus sp. and Argulus pestifer in C. asellus.

Parasites of Perccottus glenii Dybowski, 1877 (Actinopterygii: Odontobutidae) in the native and the introduced host range: Abundance-occupancy and abundance-variance relationships.

The Chinese sleeper Perccottus glenii Dybowski, 1877 is an invasive fish species rapidly expanding in Siberia and Europe. Its native range encompasses the Far East region of Russia, northeastern China and northern North Korea. We studied species composition, prevalence, mean abundance and variance of mean abundance of macroparasites of the Chinese sleeper in the native and the introduced range. The species composition of the parasite component communities differed considerably in the native and the introduced range. The frequency distributions of prevalence, mean abundance and variance of mean abundance of the parasites did not demonstrate any significant differentiation between the two parts of the host range. However, an analysis of the abundance-occupancy and the abundance-variance relationships revealed that the parasite component communities in the two parts of the host range were quite distinct. In the native range, prevalence increased faster and variance increased more slowly with the increasing abundance of the parasites than in the introduced range. These features are mostly associated with considerably increased prevalence, abundance and aggregation of the host-specific cestode Nippotaenia mogurndae in recipient water bodies as compared with the native habitats.

Component communities and annual and seasonal variations of metazoan parasites in Eleotris pisonis (Gmelin, 1789) (Gobiiformes: Eleotridae) in the Amazon River, Brazil.

Our hypothesis for this study was that annual and seasonal variations do not influence the structure of the component communities and the diversity of metazoan parasites of spinycheek sleeper (Eleotris pisonis) in the Amazon River, state of Amapá, Brazil. A total of 164 fish were collected between 2020 and 2021, from which 888 parasites were found. In 2020, five species of parasites were found (one Nematoda, one Digenea, one Acanthocephala, one Arachnida and one Crustacea); and in 2021, five species were also found (three Nematoda, one Digenea and one Crustacea). Larvae of Contracaecum sp. were the dominant taxon throughout the study. The parasite species richness and Brillouin diversity index were higher in 2021, without significant differences between seasonal periods. Some component communities of parasites showed differences between years and between seasonal periods. These facts do not support the hypothesis that such variables would not influence the component communities of the parasites. Lastly, this report provides the first records of Spirocamallanus inopinatus, Genarchella genarchella, Acari, Ergasilus sp., Neoechinorhynchus sp., larvae of Pseudoproleptus sp. and larvae of Contracaecum sp. in E. pisonis.

The Fish Parasite Community in a Hypertid Estuary Penzhina River (Basin of the Sea of Okhotsk)

The species composition of parasites in the estuary of the Penzhina River was studied (114 species). The influence of the specific conditions of the estuary on the parasite fauna was shown. High flow rates, mixing of fresh and sea waters, and the abundance of organic matter determine the predominance among parasites of species with morphological adaptations for reliable fixation on fish tolerant to changes in salinity and associated with benthos in the life cycle. Transitions of parasites to atypical hosts have been noted. The component communities of parasites of most fish species are characterized by high indices of diversity and evenness and low indices of dominance. In the marginal populations of pike and whitefish, they are strongly depleted with pronounced dominants and their change in ontogeny. The Arctic and Pacific elements of the ichthyoparasite fauna testify to the influence of the Arctic and Pacific oceans on its formation.

Host-parasite relationships in invasive species: macroecological framework

Despite considerable research effort, many aspects of the host-parasite relationships and parasite spatial distribution in invasive hosts remain poorly understood due to complex and context-dependent phenomena related to both the bioinvasions and the parasitism. Using macroecological patterns and theory is a useful approach to analyzing parasitological observations, but in practice parasite ecology and classical macroecology are disconnected. We propose a new framework that can use the conventional parasitology sampling data much more effectively. The innovative concept combines the data inferred from populations, infra- and component communities of parasites and the application of a macroecological approach in the analysis of complex and frequently hidden relationships in host-parasite systems. This comparative analysis draws on parasite data across regions and host species at different organizational (population vs. community) and hierarchical (infra vs. component community) levels of parasites. Our framework based on assessing and analysis of parasitological and ecological indexes, including descriptors of parasite species richness (individual and total), infection parameters, parasite aggregation (Taylor´s power law) and macroecological models (abundance-variance and abundance-occupancy relationships), can produce mechanistic explanations of the Enemy Release Hypothesis and unravel host-parasite relationships of an invasive host and its parasites. Moreover, abundance-variance and abundance-occupancy relationships, core-satellite species hypothesis, patterns on the aggregation and the frequency distribution of prevalence, infrapopulation size and individual parasite species richness provide useful tools to distinguish co-introduced and acquired parasites in communities of the invasive host based on quantitative descriptors. We hope that our framework becomes widely applied as it can potentially contribute to enhance future practice and research in biodiversity conservation and control of invasive species.

Helminth communities of Coregonus lavaretus (Salmonidae: Coregoninae) from Lake Kamennoye (Kostomuksha State Nature Reserve, Russia)

Macroecological models are useful for assessing trends in variability for developing monitoring strategies of successional changes and anthropogenic transformation of aquatic ecosystems. Modelling of the relationships of the generalised population indices also makes possible to reveal qualitative differences in the structure of parasite component communities. We analysed helminth communities of Coregonus lavaretus from a natural water body, Lake Kamennoye (Kostomuksha State Nature Reserve, Russia). The component community of metazoan parasites of C. lavaretus was represented by nine helminth species. Infection with cestodes (two species), nematodes (three species), and trematodes (one species) reflects the presence of zooplankton, aquatic insects and molluscs in the diet of fish, while infection with trematode larvae (three species) occurs by percutaneous penetration. The complete ITS1-5.8S-ITS2 cluster of the rRNA gene was sequenced in order to identify trematode larvae. Metacercariae of Diplostomum sp. LIN 5 were the most abundant among them. Using populational approaches, we described the species richness and the diversity of infra- and component communities of the parasites. We also described the species composition and the structure of the component community, the distribution and the accumulation rate of species richness, and the relationships between the infection intensity and the prevalence. Five species (Diplostomum sp. LIN5, Tylodelphys immer, Crepidostomum farionis, Proteocephalus longicollis, and Raphidascaris acus) were considered as the core species of the component community, while other helminths were considered as satellite species. We conclude that infra-communities play a key role in the formation of species richness, structure and abundance of the parasitic component community of C. lavaretus. Infra-communities in younger age groups of C. lavaretus are characterised by the paucity and a relatively high diversity of the species composition of parasites, which is probably a consequence of their diverse diet. In older fish, the species richness of infra-communities increases but the species diversity of the parasites declines, indicating a pronounced dietary specialisation. An analysis of species richness and population characteristics indicates that in Lake Kamennoye, the parasite communities of C. lavaretus are fairly stable, which reflects the stability of the entire lake ecosystem.

Ecology and diversity of metazoan parasites infecting Geophagus altifrons (Cichliformes: Cichlidae) from the Amazon River system in northern Brazil.

The aim of this study was to investigate the ecology and diversity of community and infracommunities of metazoan parasites Geophagus altifrons (Heckel, 1840) in Rio Jari, in the state of Amapá, in the eastern Amazon region. From the total of 31 fish examined, 90.3% were parasitized by one or more species, collecting a total number of 806 parasites. The parasites species identified were: Sciadicleithrum geophagi, Posthodiplostomum sp., Procamallanus (Spirocamallanus) inopinatus, Raphidascaris (Sprentacaris) sp., Genarchella genarchella, Gorytocephalus spectabilis and Ergasilus xinguensis. Most of the parasites showed an aggregate dispersion pattern. Brillouin diversity index, uniformity and species richness of parasites were low. The component community of parasites was constituted by ectoparasites and endoparasites, but with a predominance of ectoparasites. The body size of hosts had a low effect on the parasites infracommunities. This first eco-epidemiological study for G. altifrons reports these parasites in a host, for the first time, with the exception of S. geophagi and E. xinguensis.

Intestinal Helminth Communities of Grey Partridge Perdix perdix and Common Pheasant Phasianus colchicus in Poland.

Simple SummaryThe presence of intestinal parasites such as nematodes, cestodes, and trematodes is a serious problem for programmes for the conservation of partridges and pheasants, mainly involving the breeding of these birds and their release into the natural environment. These parasites can cause disease in these birds, whether farmed or free-living. The aim of this study was to describe the morphology of parasitic worms in the partridge, native to Poland, and the introduced pheasant, and to determine the level of infection of these birds with intestinal parasitic worms. The study showed that partridges are infected with several helminth species that had not previously been recorded in this species in Poland. Pheasants are more often infected by intestinal nematodes than are partridges. These worms can negatively affect the condition of partridges and increase their risk of infection with pathogenic protozoa. The results of parasitological examination should be used to develop programmes for diagnosis and monitoring of parasitic infections in order to keep flocks free of parasites.The aim of this study was to describe the morphology and means of identification of helminths in native partridges (65) and introduced pheasants (32) in Poland and to determine the level of intestinal infection of these birds by helminths using parasitological and ecological indices. The birds were acquired during the hunting season in the years 2015–2017. Nematodes, Capillaria phasianina, cestodes, Railietina friedbergeri, and one trematode, Brachylaima sp. were recorded for the first time in partridges in Poland. Our findings indicate that parasites are more prevalent in pheasants (prevalence 70.4%) than in partridges (prevalence 50.0%). The component community and infracommunity of parasites of partridges are more diverse (Simpson’s diversity index: 0.63 and mean Brillouin diversity index: 0.10 ± 0.17) and less dominated by a single parasite species (Capillaria sp., Berger-Parker dominance index: 0.53) than the pheasant parasite community (Simpson’s diversity index: 0.07, mean Brillouin diversity index: 0.005 ± 0.02, dominant species Heterakis gallinarum, Berger-Parker dominance index: 0.96). There were statistically significant differences between partridges and pheasants in the Brillouin diversity index and in the prevalence of Heterakis gallinarum (55.6% in pheasants vs. 19.0 in partridges). There were significant differences between wild and farmed partridges in the prevalence of infection by Capillaria sp. (4.3% vs. 37.5%) and H. gallinarum (39.1 vs. 6.2%). In conclusion, the pheasant was shown to be a reservoir, carrier, and shedder of nematodes, which may increase the risk of infection in partridges.

Environmental, anthropogenic, and spatial factors affecting species composition and species associations in helminth communities of water frogs (Pelophylax esculentus complex) in Latvia.

We investigated factors affecting species composition and patterns of species associations in parasite communities of water frogs (Pelophylax esculentus complex), applying the distance-based redundancy analysis for component communities (assemblages harboured by host populations) and Markov random fields modelling for infracommunities (assemblages harboured by individual hosts), respectively. We asked (a) What are the relative effects of variation in environmental, land use (i.e., anthropogenic), and spatial factors on the variation in the species composition of component communities (i.e., in a locality)? and (b) What is the dominant pattern of species associations in infracommunities (in a host individual), and how do these associations vary along environmental and/or anthropogenic gradients? In component communities, the greatest portion of variation in helminth species composition was explained by the combined effects of space, anthropogenic pressure, and NDVI, with the pure effect of the spatial predictor being much stronger than the effects of the remaining predictors. In infracommunities, the probability of occurrence of some, but not all, helminth species depended on the occurrence of another species, with the numbers of negative and positive co-occurrences being equal. The strength and/or sign of associations of some species pairs were spatially stable, whereas interactions between other species pairs varied along the gradient of the amount of green vegetation, from negative to positive and vice versa. We conclude that the processes in parasite infracommunities and component communities in frogs are intertwined, with both bottom-up and top-down effects acting at different hierarchical scales.

Susceptibility of Channel Catfish (Ictalurus punctatus), Blue Catfish (Ictalurus furcatus), and Their Commercially Cultured Hybrid to Metazoan Parasite Infection in Earthen Pond Aquaculture

We herein document the metazoan parasite component communities of channel catfish (Ictalurus punctatus), blue catfish (Ictalurus furcatus), and their commercially cultured hybrid (female I. punctatus × male I. furcatus) communally stocked as parasite-free fingerlings into each of 3 experimental earthen ponds (each pond harbored channel catfish, blue catfish, and hybrid catfish). The fundamental objective of this work was to test the hypothesis that hybrid catfish exhibit less susceptibility to infection by metazoan parasites than do their parental species. Fingerlings of each catfish species from each pond were parasitologically examined monthly for 1 yr. A total of 112 channel catfish, 74 blue catfish, and 209 hybrid catfish were necropsied; collectively resulting in the detection of 14 metazoan parasite species. Channel catfish had the most diverse component community (12 species: 3 myxozoans, 2 monogenoids, 3 cestodes, 1 nematode, 1 unionid, and 2 copepods) followed by hybrid catfish (11 species: 3 myxozoans, 2 monogenoids, 2 cestodes, 1 nematode, 1 unionid, and 2 copepods) and blue catfish (6 species: 1 myxozoan, 2 monogenoids, 2 cestodes, and 1 copepod). These results do not support the assertion that hybrid catfish are demonstrably more resistant to parasitic infection than either parental species. New host–parasite records herein comprise Corallotaenia intermedia (Fritts, 1959) Freze, 1965, and Corallotaenia parafimbriata (Befus and Freeman, 1973) Scholz, de Chambrier, Mariaux, and Kucha, 2011 for channel catfish; Henneguya sp., C. parafimbriata, and Neoergasilus japonicus (Harada, 1930) Yin, 1956 for blue catfish; and Henneguya adiposaMinchew, 1977, Henneguya bulbosusRosser, Griffin, Quiniou, Khoo, and Pote, 2014, Ligictaluridus mirabilis (Mueller, 1937) Beverley-Burton, 1985, Ligictaluridus pricei (Mueller, 1936) Beverley-Burton, 1984, Essexiella fimbriata (Essex, 1928) Scholz, de Chambrier, Mariaux, and Kucha, 2011, C. parafimbriata, Spiroxys sp., Pyganodon sp., N. japonicus, and Achtheres sp. for hybrid catfish. To our knowledge, this is the most extensive parasitological study of this particular hybrid catfish, or any hybrid catfish, published to date.

Metazoan Parasite Communities of Three Endemic Cichlid Fish Species from the Upper Grijalva River, Chiapas, Mexico.

SummaryWe recorded the metazoan parasite communities in three endemic cichlids (Chiapaheros grammodes, Vieja breidohri and V. hartwegi) collected between November 2008 and July 2009 in the upper Grijalva River Basin (GRB), Chiapas, Mexico. In total, 6,287 individual parasites belonging to 18 taxa (1 monogenean, 6 digeneans, 1 cestode, 4 nematodes, 2 acanthocephalans, 1 hirudinean, 2 copepods and 1 pentastomid) were found. Eleven metazoans were adult forms and 7 larvae; moreover, 14 were endoparasites and 4 ectoparasites. Sixteen parasite taxa represent new geographical and host records. The helminth community in the three cichlids was characterized by higher number of generalists than specialists, as well as a higher proportion of autogenics than allogenics. The metazoan parasites showed prevalence and mean abundances moderate to high. The infracommunities and component community of metazoan parasites had low diversity, richness, and number of individuals and are similar to those reported for other cichlids in Southeastern Mexico, characterized by the presence of typical parasites of cichlids, with a high number of digeneans and generalist parasites. We report the introduced Asian parasitic copepod Neoergasilus japonicus parasitizing endangered or threatened endemic cichlids in the upper GRB. This copepod have been widespread in other freshwater fish species, mainly in Asia (China, India, Japan, Russia, Taiwan), Europe (France, Hungary, Italy, Turkey), and America (Cuba, Mexico, Peru, United States).

Stable Isotopes and Parasites Indicate Feeding Ecology in Florida, USA, Wading Birds

We assessed δ13C and δ15N profiles and endoparasite community composition in Great Egrets (Ardea alba), Great Blue Herons (A. herodias), and White Ibis (Eudocimus albus) from four wildlife rescue centers (two mainland, two on islands in the Florida Keys) in south Florida, USA to elucidate feeding ecology. We detected among-species differences for δ15N but not δ13C and noted decreased δ13C enrichment in Great Egrets and Great Blue Herons (but not White Ibis) from these centers. Parasite component community and infracommunity species richness were higher in Great Egrets and Great Blue Herons relative to White Ibis, and higher in birds of the same species from mainland centers. Multivariate analysis of parasite infracommunity structure detected co-occurring clusters of parasite taxa characteristic of Great Egrets and Great Blue Herons on the one part, and of White Ibis on the other; mainland Great Egrets and Great Blue Herons had similar parasite communities and clustered separately from conspecifics from the islands. We detected a significant (negative) correlation of infracommunity species richness with δ13C but not δ15N. Lastly, parasite infracommunity Bray-Curtis similarity correlated significantly with stable isotope Euclidean distances. We conclude that the two approaches converge towards similar outcomes, providing complementary and consilient information on host feeding ecology.

Impacts of ontogenetic dietary shifts on the food-transmitted intestinal parasite communities of two lake salmonids.

Ontogenetic dietary shifts are common in fish and often impact trophically transmitted parasite communities. How parasite species composition and relative abundances change among size classes, and at what rate these changes occur, is rarely examined. Hosts with a broad trophic niche are potentially exposed to a large variety of parasite species. The degree of ontogenetic changes in parasite species composition versus changes in parasite abundance should suggestively differ between thropically generalist and specialist host species. In the present study, we explore ontogenetic dietary shifts and their impact on species composition and relative abundance of intestinal parasites in two sympatric salmonid fish species, Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) caught in the littoral habitat of a subarctic lake. Our results highlight a close interplay between ontogenetic dietary niche shifts and alterations in the acquisition of trophically transmitted parasites, leading to host-specific differences in the component community of parasites. Ontogenetic changes in the intestinal parasite community related to dietary niche shifts were distinct but less pronounced in Arctic charr than in brown trout due to a broader and more consistent dietary niche of the former and an ontogenetic shift toward piscivory in the latter. At the component community level, changes in parasite assemblages of both host species were driven by a faster increase in the heterogeneity of parasite relative abundance than in the compositional heterogeneity, a pattern that partly may be related to a rather species-poor parasite community of this subarctic study system. Separating compositional heterogeneity from heterogeneity in relative parasite abundance is important to understand how size-dependent variability shapes parasite communities of host populations.

Variation in Helminth Parasite Component Communities of Gambusia affinis.

In north-central Texas streams, seasonal changes in ambient temperature and rainfall result in dynamic variation in microhabitat structure, affecting the distribution and abundance of hosts. Since the complex life cycles of parasites require the presence and interaction of multiple hosts, the seasonal variations in microhabitats could influence parasite component communities within these ecosystems. Gambusia affinis (western mosquitofish) serves as a host for a variety of larval and adult parasites. Factors that affect helminth component communities in populations of mosquitofish from the Paluxy River were investigated in this study. Gambusia affinis individuals were collected from 3 sites monthly from June 2015 through August 2016. All helminth parasites were collected during necropsy and subsequently identified. From 495 mosquitofish, 5,283 helminths were collected. Component community diversity varied among collection sites and collection dates and was positively influenced by river flow. These results indicate that helminth assemblages infecting mosquitofish in the Paluxy River vary through time and space, as well as in response to environmental variation (i.e., changes in water flow).

Metazoan parasites of Plagioscion squamosissimus (Osteichthyes: Sciaenidae) of two rivers from the eastern Amazon (Brazil).

Plagioscion squamosissimus, commonly known as "white hake" or "corvina", is among the most commercially important fish in the Amazon and host to a great diversity of endoparasites. The aim of the present study was to compare the communities and infracommunities of metazoan parasites that infect P. squamosissimus in two rivers from the eastern Brazilian Amazon. A total of 75 specimens of P. squamosissimus were collected from Lago Grande do Curuái and the mouth of the Tapajós River. Morphological analysis revealed the presence of 16 parasite species, three myxozoans (Myxobolus sp., Ceratomyxa sp., Henneguya sp.), two trematodes (Austrodiplostomum compactum, Digenea gen. sp. (metacercariae), two monogeneans (Diplectanum sp., Euryhaliotrema sp.), three nematodes (Procamallanus (S.) sp., Anisakis sp., Pseudoproleptus sp. (larva), two acanthocephalans (Rhadinorhynchus plagioscionis and Neoechinorhynchus sp.), one Cestoda Ptychobothriidae gen. sp. and three crustaceans (Therodamas sp., Ergasilus sp., Dolops sp.). Six new records of parasites of P. squamosissimus were made, of which three were myxozoan species, one nematode species and two crustacean species. There were differences in the component communities of parasites of both rivers studied and these were discussed.

Parasites as indicators of fish population structure at two different geographical scales in contrasting coastal environments of the south-western Atlantic

Fish parasites are widely used as biological tags of stocks and populations of their hosts at large spatial scales, but less frequently at small geographical scales. The application of this methodology at small scales requires heterogeneity in the availability of infective stages of parasites and hosts with high site fidelity. Here we tested the value of parasite tags at both large and small spatial scales using the Argentine silverside, Odontesthes argentinensis (Valenciennes, 1835) as a model. This is a marine fish that can tolerate a wide range of salinities and has great phenotypic plasticity, which has promoted adaptive divergences at reduced spatial scales across populations, in the absence of geographical barriers isolating them, which could be reflected in their parasite assemblages. A total of 142 specimens were examined for parasites. Samples were collected at two close localities from each of two different biogeographical regions of the south-western Atlantic. The structure and composition of both parasite infracommunities and component communities were analysed through uni and multivariate statistics. All sites were significantly different in their infracommunity structure, even those that were at shorter distances from each other. However, infracommunity composition and component community structure showed higher similarities within each region than between samples from different ones. These results proved that fish parasites are valuable tools to assess fine-scale population structure of their hosts when site fidelity and adaptations to local conditions prevail. The inclusion of parasite indicators as complementary tools in such kind of studies can provide valuable evidence for those resources requiring stock assessments and management at fine-scale, in order to prevent negative impacts over exploited populations.

Сезонная динамика паразитофауны и структуры компонентного сообщества паразитов хариуса <i>Thymallus thymallus</i> (Linnaeus, 1758) из реки Луженьги (бассейн реки Северной Двины)

Развитие учения о паразитарных сообществах позволило оценивать нарушения структуры гидробиоценозов и популяций рыб. Сбор материала произведен с мая по сентябрь 2011 – 2013 гг. из р. Луженьга (Вологодская область). Исследовали 150 экз. хариуса по 10 выборок (61 самка, 89 самцов) по 15 экз. в каждой. Компонентное сообщество паразитов хариуса с мая по сентябрь последовательно проходит 3 стадии развития, обусловленные сменой генераций составляющих его видов. Это формирующееся сообщество в мае — начале июня, сформированное во 2-й и 3-й декадах июня, разрушающееся в июле–начале сентября и вновь формирующееся. У хариуса выявлены 16 видов паразитов. Их число колебалось от 9 в начале июня и до 13 в октябре. У рыбы на протяжении всего периода исследований присутствовали 6 видов паразитов. От мая к началу июня число особей инвадентов и их биомасса упали в 2 раза, к концу июня значения этих показателей выросли в 2,3 раза с последующим резким падением в июле числа особей в 3,7 – 3,8 раза, биомассы — в 1,8 – 2,7 раза. Далее к октябрю идёт плавный рост значений этих показателей. С мая по октябрь в сообществе паразитов лидируют автогенные виды и виды-специалисты.

Interannual and Seasonal Variation in Protozoan and Metazoan Parasite Communities of Hemibrycon surinamensis, a Characid Fish Inhabiting the Brazilian Amazon.

Few studies on the effects of rainy/dry cycle and interannual variation in parasites of Amazonian fish have been carried out. We investigated the influence of interannual variation and seasonality on the community structure and infracommunities of parasites in Hemibrycon surinamensis in a tributary of the Amazon River, in northern Brazil. The fish were examined for the presence of ectoparasites and endoparasites. In 2011, 9 parasite species were found (2 Protozoa, 2 Monogenea, 1 Digenea, 2 Nematoda and 2 Crustacea), and in 2016, 10 parasite species (3 Protozoa, 2 Monogenea, 1 Digenea, 3 Nematoda and 1 Pentastomida). No qualitative or quantitative dissimilarity in the component communities of parasites was observed between 2011 and 2016, but Brillouin Diversity Index, species richness and evenness were higher in 2016, while Berger-Parker dominance was higher in 2011. In both years, Ichthyophthirius multifiliis and Piscinoodinium pillulare were predominated. Some few species of parasites had interannual (P. pillulare and Genarchella genarchella) and seasonal (Trichodina sp., I. multifiliis, P. pillulare and J. hexops) variation patterns. Species richness of parasites was higher in the dry season, but Brillouin diversity, evenness and Berger-Parker dominance were similar between the seasons. Such seasonal variations were due to the host's the availability of infectious stages of parasites with direct life cycle. Variations due to seasonal dry/rainy cycle, which influenced the availability of infective stages of parasites, and host size are the factors causing the changes interannual.