Infracommunity Level Research Articles

Correlates of helminth community in the red-legged partridge (Alectoris rufa L.) in Spain.

Between 1992 and 1996, 587 wild red-legged partridges (Alectoris rufa) from 16 Spanish provinces were examined to study the variations of helminth communities in this game species across a broad geographical area. The survey revealed 13 species of helminth parasites. Dicrocoelium sp.. Rhabdometra nigropunctata, and Cheilospirura gruweli were the most common species, whereas Raillietina bolivari, Choanotaenia infundibulum, Tetrameres sp., and Capillaria anatis were the most rare. Subulura suctoria, Heterakis gallinarum, Heterakis tenuicaudata, Capillaria contorta, Trichostrongylus tenuis, and Raillietina tetragona occurred with intermediate frequencies. The abundance of C. gruweli, S. suctoria, H. tenuicaudata, T. tenuis, and R. tetragona was inversely correlated to latitude and directly correlated to yearly mean temperature, whereas the abundance of Dicrocoelium sp. was directly correlated to latitude and inversely correlated to yearly mean temperature. The abundance of R. tetragona was inversely correlated to latitude and yearly mean humidity. The number of helminths per partridge and the number of helminth species per partridge were lower in young birds than in adults. Partridge body condition was inversely correlated to abundance of C. contorta. Richer infracommunities were linked to richer component communities. At the infracommunity level, total number of helminths per partridge and number of helminth species per partridge were inversely correlated to latitude and directly correlated to yearly mean temperature. At the component community level, both species richness and diversity (Simpson's index) were inversely correlated to latitude and directly correlated to mean temperature. Across the broad geographical range of the study area, the helminth parasite communities of red-legged partridges had marked geographical variation in their structure. Our results suggest that this variation is determined by the distribution of both intermediate and definitive hosts. We discuss the implications of this variation for the hypothesis that supplementary releases of captive-bred partridges for sport hunting can affect the helminth fauna of wild red-legged partridges.

Helmintofauna de Rattus rattus (Linnaeus, 1758) y Rattus norvegicus (Berkenhout, 1769) (Rodentia: Muridae) en el distrito de San Juan de Lurigancho, Lima - Perú

Objective: A research at the component community and infracommunity level of the enteroparasite fauna of two sympatric rat species. Rattus rattus Linnaeus and Rattus norvegicus (Berkenhout)was conducted. Specimen were collected in the low basin of the Rimac river, Lima, Peru, in October 1998. Materials and methods: All the helminthes were collected, processed, identified and quantified employing standarized parasitological procedures. Results: 4 parasite species were found with different prevalence and abundance mean of infection respectively: Hymenolepis diminuta (Rudolphi) (Cestoda) (84 % and 4,3), Protospirura chanchanensis Ibanez (Nematoda) (47 % and 1,2), Syphacia obvelata (Rudolphi) (Nematoda) (6,3 % and 0,09) and Heterakis spumosa Schneider (Nematoda) (3,1 % and 0,03). Hymenolepis diminuta was a core species; P. chanchanensis a secondary species, and finally, S. obvelata and H. spumosa were rare species. H. diminuta had the highest frequency of dominance (65,6 %). No significant relationship between mean intensity and parasite prevalence with body‘s standard length and sex of both hosts was observed. Only the mean abundance of P. chanchanensis was significantly higther in males (average ± DS = 1,4 ± 1,6) than females (average ± DS = 0,33 ± 0,70) rats. The species diversity was low, H‘± DS = 0,08 ± 0,1. There was no significant association between H. diminuta and P. chanchanensis. Conclusion: P. chanchanensis is a new registered helmith for R. rattus. S. obvelata and H. spumosa are new registered helmithes for R. norvegicus in Peru.

A perspective on the ecology of trematode communities in snails.

This paper presents a perspective on the ecology of trematodes in snail hosts based on recent evidence. Because flukes use snails almost obligatorily as first intermediate hosts, we highlight the role of gastropods as keystone species for trematodes and their communities. After reviewing recent developments in the transmission of trematodes to and from snails, we discuss trematode communities within individual snails (infracommunities) and in snail populations (component communities). Results garnered using various protocols at the infracommunity level are reviewed. The few data available, all from marine systems, indicate that low colonization rates characterize infracommunities, suggesting that trematode infracommunities tend to be isolationist in character rather than interactive. The variety of trematode species present in a component community seems to be determined by spatial overlap of definitive hosts. Relative abundance of species in a component community shows little dependence on negative interspecific interactions at the level of the infracommunity. Temporal aspects of trematode communities are related to the life history of the host snail. The component communities of long-lived snails (mostly marine) integrate many infection episodes whereas shorter-lived snails (mostly freshwater) acquire new component communities each time host cohorts turnover.

Variation in the helminth community structure in bank voles (Clethrionomys glareolus) from three comparable localities in the Mazury Lake District region of Poland.

We tested the null hypothesis that populations of hosts trapped in isolated neighbouring locations showing comparable habitat quality, should support similar helminth parasite communities. The study was undertaken in a 2-week period in late summer in NE Poland in a single year, thereby eliminating seasonal and between-year variation in parasite burdens. A total of 139 Clethrionomys glareolus (bank vole) were sampled from 3 forest sites of similar habitat quality. Total species richness was 11 (6 nematodes and 5 cestodes) with 85.6% of the voles carrying at least 1 species and an overall mean species richness of 1.4. At the component community level, the fewest species of helminths were recorded from site 2 (n = 6, compared with 9 at each of the other sites), but site 3 had the lowest Berger-Parker Dominance Index and the highest Simpson's Index of Diversity. At the infracommunity level, site 3 had the highest mean no. of helminth species/vole, the highest mean Brillouin's Index of Diversity but the lowest mean no. of helminths/vole. Voles from sites 1 and 3 differed in the nematodes that were most common (site 1, Heligmosum mixtum-95%; site 3, Heligmosomoides glareoli -79.3%). At site 2 no species exceeded 50% but prevalence of Syphacia petrusewiczi was higher than at the other sites. The prevalence of cestodes was too low to test reliably (12.%), but the highest prevalence of adult cestodes was recorded at site 1 (22.5% compared with 4.9 and 1.7% for sites 2 and 3 respectively). Host sex did not influence infection, but mean species richness increased with age. The different sites were responsible for most of the variation in our data, and the intrinsic factors (sex and age) were less important in shaping the component community structure of helminths. We conclude that even locations in relative close proximity to one another (13-25 km), selected on the basis of similar habitat quality, have rodent populations that differ in their helminth parasite communities, although for reasons other than the factors quantified in the present study.

Nestedness, anti-nestedness, and the relationship between prevalence and intensity in ectoparasite assemblages of marine fish: a spatial model of species coexistence

Nested species subset patterns consist in a hierarchical structure of species composition in related assemblages, with the species found in depauperate assemblages representing non-random subsets of progressively richer ones. This pattern has been found at the infracommunity level in about a third of the fish ectoparasite assemblages studied to date. Here we present evidence for another non-random structural pattern in assemblages of fish ectoparasites, anti-nestedness, which corresponds to situations in which parasite species are always absent from infracommunities richer than the most depauperate one in which they occur. We show that this pattern is exactly as common as nestedness, and that anti-nested assemblages are characterised by significantly lower prevalence and mean intensities of parasites than nested assemblages. In addition, we found a positive relationship between the prevalence and the mean intensity of parasites across the different assemblages. We propose a link between the nestedness/anti-nestedness continuum and the prevalence-intensity relationship that may involve colonisation-extinction processes. The results presented here suggest that, although nestedness may not be common in parasite communities, other departures from random species assembly are possible, and that some form of structure may be present in many communities. The continuum between nestedness and anti-nestedness also has implications for recent models of species coexistence in communities.

The structure of the monogenean community on the gills of Pimelodus maculatus in Río de la Plata (Argentina).

The Monogenea fauna was studied from the gills of the catfish Pimelodus maculatus. Fish were caught from Río de la Plata, in Buenos Aires harbour (Argentina). Five species of Monogenea were found. The structure of the monogenean community was analysed at the component and infracommunity level. The nature of the monogenean community, its possible interactivity, seasonal variation and predictability are also discussed.

Patterns in metazoan parasite communities of some oyster species

Metazoan parasite communities of Crassostrea gigas and Ostrea edulis from Great Britain, Crassostrea virginica from Mexico, and Saccostrea commercialis from Australia are described and summarized in terms of species composition, species richness, total number of individuals and dominance. Metazoan parasite communities in all host species were composed of turbellarians and the metacercarial stage of digeneans, with the exception of S. commercialis where only metacercariae were found. Arthropods, including one copepod and one mite species, were present only in British oyster species. All metazoan parasite communities of oysters had few species and low density of individuals. Richest communities were found in C. virginica at both component and infracommunity level. The least diverse component community occurred in S. commercialis. Infracommunities in O. edulis and S. commercialis never exceeded one species per host. The host response against parasites is suggested as the principal factor responsible for depauperate parasite communities of oysters. Environmental factors characteristic of tropical latitudes are likely to have enhanced both the number of species and the densities of parasites per host in the infracommunities of C. virginica.

Patterns in metazoan parasite communities of some oyster species

Metazoan parasite communities of Crassostrea gigas and Ostrea edulis from Great Britain, Crassostrea virginica from Mexico, and Saccostrea commercialis from Australia are described and summarized in terms of species composition, species richness, total number of individuals and dominance. Metazoan parasite communities in all host species were composed of turbellarians and the metacercarial stage of digeneans, with the exception of S. commercialis where only metacercariae were found. Arthropods, including one copepod and one mite species, were present only in British oyster species. All metazoan parasite communities of oysters had few species and low density of individuals. Richest communities were found in C. virginica at both component and infracommunity level. The least diverse component community occurred in S. commercialis. Infracommunities in O. edulis and S. commercialis never exceeded one species per host. The host response against parasites is suggested as the principal factor responsible for depauperate parasite communities of oysters. Environmental factors characteristic of tropical latitudes are likely to have enhanced both the number of species and the densities of parasites per host in the infracommunities of C. virginica.

Is there a fixed number of niches for endoparasites of fish?

Kennedy and Guégan, based on Cornell and Lawton (J Anim Ecol 1992;61:1–12), found a curvilinear relationship (the fundamental form of the relationship for parasite communities) between infracommunity and component community richness, and interpreted this as meaning that only processes acting within the infracommunities can explain the limitation in the number of parasite species in a given host. The research described here shows that an asymptotic relationship is the consequence of the differential likelihoods of parasite species to appear in an infracommunity as determined by transmission rates and intrinsic lifespans. Processes operating at the infracommunity level are not necessary to explain the curvilinear relationship. Even communities much richer than those found in European freshwater fishes cannot be assumed to be saturated in the sense that further species cannot be added over evolutionary time.

Composition and structure of helminth communities in eels Anguilla anguilla from Italian coastal lagoons

The composition and diversity of total and intestinal helminth component and infracommunities were determined in eels Anguilla anguilla from four shallow coastal lagoons near Rome. The lagoons differed principally in respect of their salinity. Only Lake Burano still received an input of freshwater, and both freshwater and marine helminth species were found in eels. In the other three lagoons all helminth species were marine or euryhaline and communities were dominated by digeneans. At component community level these three lagoons were far more similar to each other than to Lake Burano, but this distinction almost disappeared at infracommunity level. Species richness and diversity declined with increasing salinity at component community level but not at infracommunity level. Despite the changes and differences in helminth community composition, intestinal helminth infracommunity structure was very similar in all four lagoons and to that in eels from freshwater localities in Britain. The findings thus provide further and unexpected support for the view that some factor(s) other than supply side ones must be operating to produce the fundamental structural similarity in helminth communities in eels.

Dactylogyrus (Monogenea) communities on the gills of roach in three lakes in Central Finland

SUMMARYDactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often dominated by Dactylogyrus micracanthus and the similarities between the infracommunities were higher within the lakes than between the lakes. It is suggested that these differences are due to the differing water quality of the lakes. The nature of the monogenean community, its possible interactivity, is also discussed.

The Component Community Structure of Larval Trematodes in the Pulmonate Snail Helisoma anceps

Factors that affected the component community structure of larval trematodes in the pulmonate snail Helisoma anceps in Charlie's Pond, North Carolina, were studied over a 15-mo period using a multiple mark-recapture protocol. Patent infections of 8 species were observed in 1,485 of 4,899 snails examined. Reproductive activity, population size, and survival rate of the snail population were estimated to evaluate the extent of resource availability for the parasites. Antagonistic interactions between trematode species that occurred at the infracommunity level had a neglible effect on the composition and structure of the component community. The patterns observed at this level were related to temporal heterogeneity in the abundance of infective stages (mostly miracidia), differential responses of trematode species to the diverse and constantly changing distribution of snail size and abundance, differential mortality of snails infected with certain trematode species, constant recruitment of 1 trematode species over time, and the existence of predictable disturbances such as the complete mortality of the host population and recruitment of a replacement population during a 6-8 wk period. The last factor operated as a reset mechanism for this snail-trematode system once each year. A model of patch dynamics, with snails as patch resources, best explains the organization and dynamics of this system.

Life history of the reindeer sinus worm, Linguatula arctica (Pentastomida), a prevalent parasite in reindeer calves

Three hypotheses of life cycle have been tested. A direct transmission to reindeer hosts with monoxenous development is the most probable. Abundant parasites are generally thought to have much impact on host populations. When assessing potential damage in reindeer calves, it is essential to look at the total parasitic effect on infracommunity level.

Spatial and temporal variation in the infracommunity structure of helminths of Apodemus sylvaticus (Rodentia: Muridae).

Mean species richness and diversity of the helminth infracommunity of Apodemus sylvaticus in woodland areas of Co. Down, Northern Ireland, varied in time and space. Variation in infracommunity structure among individual hosts, however, always accounted for more than 60% of the variation in the data from different places or different times. Helminth species richness increased with increasing population density, the percentage of the host population 16 weeks old or older, and the proportion of the host population with animal material in their stomachs, at two sites monitored over 33 months. The basis for spatial variation in infracommunity structure is less certain but host dynamics and differences in diet are likely to play some role. It is concluded that analysis at the infracommunity level focuses closely on the potential for species interactions and overlap in resource utilization. Infracommunity structure, at least in the case of A. sylvaticus, varies markedly in time and space and between individual hosts. Such variations should not be ignored in comparative studies.