Infracommunity Level Research Articles

Richness and diversity of helminth species in eels from a hypersaline coastal lagoon, Mar Menor, south-east Spain

The composition and diversity of parasite communities and intestinal components, as well as infra-community structure, were assessed in eels Anguilla anguilla, from Mar Menor, a permanent Mediterranean hypersaline coastal lagoon. Data were used to determine whether this helminth community differs in composition and structure from that of eels in lagoons with lower salinity regimes and higher freshwater inputs. A total prevalence of 93% was detected. Specifically, parasites were identified as Deropristis inflata, Bucephalus anguillae, Contracaecum sp., Anguillicoloides crassus and two plerocercoid larvae belonging to theorder Proteocephalidae, the marine species representing 91% of the isolated helminths. In the total community, digenetic trematodes were the dominant group of helminths, and D. inflata, an eel specialist, dominated both the component community and the infra-community. Richness and diversity were low but similar to those reported in other saline lagoons, and maximum species per eel did not exceed four. At the infra-community level, higher abundance than in other brackish or marine Mediterranean environments was detected. The findings provide further evidence of the similarity in composition and structure of helminth communities in eels from various Mediterranean coastal lagoons. Moreover, salinity-dependent specificities are well supported and reflect the life history of individual eels.

Helminth communities in the burrowing toad, Rhinella fernandezae, from Northeastern Argentina

The main goals of this study were to determine the richness and diversity of helminth parasites of Rhinella fernandezae at the component and infracommunity levels and determine the ecological implications of different biotic and abiotic factors. Specimens were collected near the city of Corrientes, Corrientes Province, Argentina. Prevalence of infection was 94% in the specimens examined (n = 65). The helminth component community in R. fernandezae in this area was comprised a total of 22 species. Of all helminth species, only three (Catadiscus inopinatus, Cosmocerca podicipinus and C. parva) were dominant (importance value: I > 1.0) in the community. The most abundant species were B. tetracotyloides (d = 0.43) among the larvae and C. podicipinus (d = 0.09) among adult worms. At the infracommunity level, the mean individual species richness (2.28 ± 1.48) (mean ± SD) was no more than 3 helminth species per infected host; the diversity and equitability of helminths were 0.23 ± 0.21 and 0.48 ± 0.38, respectively. The host body size was the main factor in determining the parasite abundance. Species richness was significantly and positively correlated with host body size. The parasite helminth species predominantly showed an overdispersed pattern of distribution. Helminth species showed two negative and significant pairs of covariation and one significant pair of association (P < 0.05). R. fernandezae has a wide variety of parasites relating to the host microhabitat, mobility and feeding habits.

Patterns of variation in parasite component communities and infracommunities of a littoral fish species from the northern coast of Chile

The structure and similarity of the parasite communities of fish can be evaluated at the component community (CC) and infracommunity (IC) levels. Both hierarchical levels have been used to assess parasite variations in fish at large (biogeographic) scales. However, studies evaluating the consistency between these two hierarchical levels at smaller geographical scales are scarce. In this study, the parasite assemblages of 124 Paralabrax humeralis collected by local fishermen by spear fishing at four sites (El Fierro, EF; P. Angamos, PA; Santa María, ISM; San Jorge, BSJ) in northern Chile were compared to assess the variability (or similarity) of their CCs and ICs at a limited geographical scale using multivariate analysis. At the IC level, discriminant analyses showed that P. humeralis parasite communities varied significantly among sites; 70% of ectoparasite ICs were correctly assigned to each site, but only 55% of helminth parasite ICs were correctly classified. At the CC level, the composition of parasite communities as assessed by correspondence analyses varied significantly between sites. Tagia sp., Neobenedenia sp. and Philometra sp. were associated with BSJ, ISM and PA, respectively; Corynosoma sp. and most digeneans were associated with both ISM and EF. Analysis of similarities (ANOSIM) showed significant variations in the degree of similarity between P. humeralis CCs from different sites, but not between ICs. Variations between CCs from different sites reflect fish population processes (e.g., population age, reproductive segregation) and the particular conditions of their respective habitats, whereas ICs reflect individual host movements. This study demonstrated that, when examined at a limited geographical scale, IC is better than CC at capturing the local pool of parasite assemblages when host populations are spatially segregated. Therefore, in this study, it is demonstrated that at a small geographic scale, CC variations are not reflected by IC, when host population is spatially segregated.

Spatial structure of the helminth parasite communities of the tonguefish, Symphurus plagiusa, from the Campeche coast, southern Mexico

The goals of this paper were to determine whether the helminth communities of the blackcheek tonguefish, Symphurus plagiusa, exhibit a spatial structure and, if so, to determine the relative influence of selected environmental and spatial variables. The parasite communities of tonguefish and environmental data (e.g., temperature, salinity, oxygen) were sampled monthly over a network of 37 stations over 1year (February 2006 to January 2007). Analysis of similarities (ANOSIM), non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) were used. Spatial variables were generated using the analysis of principal coordinates of neighbour matrices (PCNM) method. A total of 1,010 flatfishes and nine helminth taxa were collected. For the environmental variables, hierarchical cluster analyses produced groups of stations associated with the Yucatan dry, rainy and winter seasons. At the infracommunity level, there was no group formation as indicated by ANOSIM and NMDS nor association with environmental or spatial variables. At the component community level, there was significant group formation, and RDA analyses of core, satellite and all species produced significant associations with environmental variables. However, model fit improved substantially (from 17–52% to 49–83% of explained variance) when the spatial variables (variables generated with PCNM method) were added. Thus, the helminth component communities of S. plagiusa were affected by associated environmental variables and unknown ecological processes captured by the spatial variables acting at different spatial scales over time. In contrast, at the infracommunity level there was apparently a very fine spatial grain, where the numerical dominance of core species resulted in biased group formation.

Spatial Structure of Helminth Communities in the Golden Grey Mullet, Liza aurata (Actinopterygii: Mugilidae), from the Western Mediterranean

Ecological investigations regarding the parasite fauna of grey mullets are scarce. The present study provides a detailed description of the helminth communities of Liza aurata in the Spanish western Mediterranean and analyzes the role of spatial, temporal, and host variables in shaping the infracommunities. In total, 204 fish were collected in 2 localities, situated ca. 290 km apart, in spring and fall of 2004 and 2005. A non-metric multidimensional scaling (NMDS) was used to visualize an ordination of the infracommunities according to their relative similarities in parasite abundances. The relationship between infracommunity composition and explanatory variables (host size, locality, year, and season of harvest) was examined by permutational analysis of variance (PERMANOVA) applied to species abundances. Permutational tests for homogeneity of multivariate dispersion were used to test the null hypothesis of no differences in dispersion among groups formed by the factors whose effects were significant in PERMANOVA. A total of 33,241 helminth parasites, belonging to 18 species, was collected, i.e., 12 species of adult digeneans (23% of the parasite specimens), 3 digeneans as metacercariae (68%), 1 acanthocephalan (2.1%), and 2 monogeneans (6.5%). An important part of this helminth fauna is specialized to grey mullets, with a sizable portion of the component community restricted to the Mediterranean and northeast Atlantic. The NMDS ordination indicated high heterogeneity among infrapopulations. However, most differences at both the component and infracommunity level were related to geographic locality. In fact, the PERMANOVA showed that, among the explanatory variables considered, sampling locality accounted for the largest share of variation. The geographical differences observed may be related to local environmental characteristics or to the limited spatial dispersal of the species forming the component community. The latter was supported by the significant portion of variation explained by a 3-way interaction term. Thus, the spatial structure of our helminth infracommunities seems to be determined by a combination of differences in local environmental conditions and the transmission ability of each species at small local and time scales.

Helminth Community Structure in Birds of Prey (Accipitriformes and Falconiformes) in Southern Italy

We compared helminth communities in 6 species of birds of prey from the Calabria region of southern Italy. In total, 31 helminth taxa, including 17 nematodes, 9 digeneans, 3 acanthocephalans, and 2 cestodes, were found. All helminth species were observed in the gastrointestinal tract, except for 3 spirurid nematodes. Most of the parasite species were detected in at least 2 hosts, but 13 helminth species were found in only 1 host. At the infracommunity level, the overall species richness and Brillouin's index of diversity varied by host, with the highest values in a generalist feeder, the Eurasian buzzard (Buteo buteo), and the lowest in a specialist, the western honey buzzard (Pernis apivorus). Species richness was gender dependent only in the sparrow hawk (Accipiter nisus). The helminth communities were characterized by different dominant species, namely, Centrorhynchus spp. (Acanthocephala) in the Eurasian buzzard and common kestrel (Falco tinnunculus), Parastrigea intermedia (Digenea) in the marsh harrier (Circus aeruginosus), Physaloptera alata (Nematoda) in the sparrow hawk, Serratospiculum tendo (Nematoda) in the peregrine falcon (Falco peregrinus), and Strigea falconis (Digenea) in the western honey buzzard. Statistical analyses confirmed a highly significant difference of helminth infracommunity structure among host species. We conclude that in the Calabria region of southern Italy, each of the raptor species studied is distinct in terms of its helminth communities, and more diverse feeding habits of the host correspond with richer helminth communities.

Parasite communities of the neotropical cormorant Phalacrocorax brasilianus (Gmelin) (Aves, Phalacrocoracidae) from two coastal lagoons in Guerrero state, Mexico

The parasite community structure of the neotropical cormorant, Phalacrocorax brasilianus, from two lagoons (Coyuca and Tres Palos) from Guerrero state, México, was examined. Fourteen species of adult helminths (6,391 individuals) from 48 cormorants were identified: 9 digeneans, 1 acanthocephalan, 1 cestode, and 3 nematodes. A total of 11 species were collected in Coyuca Lagoon and 12 in Tres Palos Lagoon. Nine species co-occurred in cormorants of both lagoons but, with the exception of Contracaecum multipapillatum and Drepanocephalus olivaceus, species were not equally common in both lagoons. The prevalence values of six species of helminth and the mean abundance of four species varied significantly between lagoons, and C. multipapillatum was numerically dominant in both lagoons. The qualitative similarity between the two communities at the component level was 64%. All cormorants examined were infected, and parasite species richness was 3-5 in Coyuca and 4-9 in Tres Palos lagoon. The results indicate that both communities presented a similar structure at the component level, probably because the cormorants of both lagoons feed on the same species of fish and thus acquire almost the same species of parasites. Differences observed at the infracommunity level were attributed to variations in the degree of dominance of the particular species.

Seasonality of Parasitic Copepods on Bullseye Puffer, Sphoeroides annulatus (Pisces: Tetraodontidae), From the Northwestern Coast of Mexico

Seasonal occurrence of parasitic copepods in wild bullseye puffer, Sphoeroides annulatus (Pisces: Tetraodontidae), was analyzed in conjunction with variation of biotic and abiotic factors. Eleven samples were taken between February 2007 and February 2008 in Santa María La Reforma lagoon (northwestern coast of México). In total, 337 fish was examined; 5 parasitic copepod species were observed, including Acantholochus zairae , Caligus serratus , Lepeophtheirus simplex , Pseudochondracanthus diceraus , and Parabrachiella sp. The most common species were L. simplex , P. diceraus, and C. serratus (overall prevalence, 59, 53, and 35%, respectively), which significantly varied in prevalence and mean intensity between sampling months. A seasonal pattern was only observed for L. simplex, with higher infection levels in the warmest month than in the coldest month. Statistical analyses indicated that the intensity of L. simplex was positively correlated with water temperature. There were no significant differences in prevalence and intensity of infection among female and male hosts. At the component community level, species richness ranged between 4 and 5 during most of the study period, and no seasonality was observed in the number of individuals, Shannon diversity index, evenness index, or the Berger-Parker dominance index. At the infracommunity level, 4 descriptors used (mean species richness, mean number of individuals, mean Brillouin's diversity index, and mean Berger-Parker index) varied significantly between sampling months, but no seasonality was observed, except for a slight increase in the number of individuals during the warmest month. A significant positive association was detected between number of individuals and water temperature and between host size and both species richness and number of individuals. This is the first account of the ecology of these 5 parasitic copepods. Although no significant association was detected between fish condition factor and the burden of parasitic copepods, given the high occurrence of the caligid copepod L. simplex , we suggest that this copepod could represent a threat for the culture of S. annulatus .

Gill ectoparasites ofBarbus martorelli(Teleostean: Cyprinidae) from a tropical watercourse (Cameroon, Africa): conflict or coexistence?

The structure and stability of parasite communities have been mainly explained by high diversity and strong interactions among parasite species. During 16 months, 558 Barbus martorelli gill infracommunities were studied in a tropical zone to determine whether parasite infrapopulations interact. Three levels were retained: the infracommunity level, the gill filament level, and the filament fraction level. Single species infections in Barbus martorelli were very rare and only concerned the core species: Dactylogyrus bopeleti, D. insolitus, D. simplex and Myxobolus barbi. Mixed infections appeared as a general rule in this fish species. Interspecific interactions at all three levels were statistically non significant. Our results suggest that Barbus martorelli gill parasites are non interactive (isolationist).

Richness and Species Composition of Helminth Communities in Yellowfin Snook (Centropomus robalito) (Centropomidae) from Coastal Lagoons in Guerrero, Mexico

Adult yellowfin snook (Centropomus robalito) were collected between January and May 2008 (dry season), to assess the consistency (repeatability) of the species composition and richness of their helminth communities in 4 coastal lagoons from Guerrero, Mexico. Fifteen species of helminth were identified: 4 Monogenea, 6 Digenea, 1 Acanthocephala, and 4 Nematoda. The helminth communities in the 4 lagoons consisted mainly of marine autogenic species, were poor in richness and diversity, and exhibited low qualitative similarity at the component level (29.5% to 62.1%) and the infracommunity level (0.48 6 0.30 to 0.69 6 0.19), indicating that species composition and richness of the helminth communities of C. robalito are not predictable at a spatial scale. Significant nestedness occurred in the infracommunities of all lagoons, as well as among 2 sampling periods in Tres Palos Lagoon, suggesting a certain degree of structure in species composition in infracommunities in space and time.

Helminth Community Structure of the Mediterranean Gull (Ichthyaetus melanocephalus) in Southern Italy

The helminth community of the Mediterranean gull (Ichthyaetus melanocephalus) from the Calabria region in southern Italy was examined. Ten species of helminths, including 2 cestodes (Alcataenia larina and Tetrabothrius cylindraceus), 4 digeneans ( Aporchis massiliensis , Brachylaima fuscatum, Cardiocephaloides longicollis, and Ornithobilharzia canaliculata), and 4 nematodes (Eucoleus contortus, Capillaria sp., Cosmocephalus obvelatus, and Paracuaria adunca), were found. The Mediterranean gull represents new host records for A. larina, A. massiliensis, B. fuscatum, and E. contortus; all species, except C. longicollis and O. canaliculata, constitute new locality records. The gastrointestinal helminth community of I. melanocephalus consisted of 9 species but, at the infracommunity level, species richness, diversity, and total helminth abundance are among the lowest reported from any gull species. Two cestode species accounted for 81% of all helminth specimens found.

Temporal and between-site variation in helminth communities of bank voles (Myodes glareolus) from N.E. Poland. 2. The infracommunity level

The relative importance of temporal and spatial effects was assessed in helminth communities of bank voles (Myodes glareolus) in 3 woodland sites in N.E. Poland in the late summers of 1999 and 2002. Among common species the rank order of sites in relation to prevalence and abundance of infection was maintained between surveys. Site effects accounted for most of the deviance (in statistical models), and time was less important, so the exact location from which voles were sampled was of critical importance. The only exception was Syphacia petrusewiczi. In contrast, for derived measures such as species richness and diversity, most deviance was accounted for by host age, and the interaction between site and year was significant, implying that rank order of sites changed between years. Temporal effects on derived measures were generated primarily by a combination of relatively small changes in prevalence and abundance of the common, rather than the rare, species between the years of the study. In the medium-term, therefore, helminth communities of bank voles in N.E. Poland had a stable core, suggesting a substantial strong element of predictability.

Determinants of the parasite community of clariid fishes from Lake Victoria, Tanzania

The factors that determine parasite assemblages among the clariid fishes of Lake Victoria, Tanzania were studied between August 2003 and February 2005. Six hundred and fifty-six fish belonging to seven species were necropsied and examined for parasites, from which 31 species of metazoan parasites were recorded. The community was dominated by the nematodes both in species and numbers. Most species were generalists with only two trematodes, Diplostomum mashonense and Tylodelphys species, being specialists of Clarias gariepinus. Ten species were considered core and predictable. Parasite species richness, number of individuals per host and Shannon-Wiener diversity indices were generally high. At the compound community level, a mean number of 7.8 parasites were shared among different species of fish and the maximum number of parasites species per fish at the infracommunity level was seven. Levels of similarity in parasite species richness at the component community level ranged from 29.6 to 61.5%. The study concludes that parasite communities in clariid fishes of Lake Victoria are structured by ecological factors. At the infracommunity level, host size, diet and vagility promoted a richer parasite community. At the compound level, two factors were crucial, namely the intermixing of the waters in the lake and the predominant and mobile C. gariepinus.

Relationships between local and regional species richness in flea communities of small mammalian hosts: saturation and spatial scale

The number of species coexisting in a community may be regulated by local factors (e.g., competitive interactions), or by regional processes (e.g., dispersal from a regional species pool). The relative importance of local and regional processes can be inferred from the shape of the relationship between local and regional species richness. We investigated this relationship in communities of fleas parasitic on small mammals at two spatial scales: between the richness of fleas on individual hosts (infracommunities) and that of fleas on host populations (component communities), and between the richness of component communities and that of the entire regional species pool. We tested linearity (proportional sampling) versus curvilinearity with an asymptote (species saturation) by plotting "local" against "regional" species richness of fleas either among host species or within host species among populations. At the two spatial scales, we found consistent curvilinear relationships between species richness of the more "local" communities and richness of the more "regional" communities. This was true across all host species in the data set and for geographic subsets, even after controlling for the influence of sampling effort on estimates of species richness, and that of host phylogeny in interspecific analyses. We also tested for density compensation in species-poor communities. There was no strong evidence for density compensation at the infracommunity level, although its existence at the component community level appeared likely. Our results suggest that identical patterns in local-versus-regional species richness observed on two different spatial scales arise via different mechanisms: infracommunities appear saturated with flea species most likely because of local processes, such as host immune defenses, whereas component communities are saturated with species through interspecific competition, possibly among larval stages.

Infracommunity level aggregation in the monogenean communities of crucian carp (Carassius carassius)

Aggregation is one of the distinctive features in parasite-host relationships, which has generally been studied at the level of host communities. Parasite aggregation at the infracommunity level may nevertheless be important for intraspecific interactions such as parasite mating success and opportunities for cross-fertilization. In the present paper, we studied the infracommunity aggregation of 3 highly abundant Dactylogyrus (Monogenea) species occurring on the gills of crucian carp (Carassius carassius). In line with the previous work on monogenean communities, we observed no competition between the species. At the species level, parasites were distributed unevenly on the gills showing aggregation in the majority of infracommunities. However, aggregation decreased with increasing parasite abundance, which supports the hypothesis that less aggregation may be needed to ensure successful mating when the distance to a potential mate decreases with increasing number of conspecifics. Lack of interspecific interactions, species specific site selection and the importance of study scale for aggregation patterns in dactylogyrids are discussed.

Intestinal helminth parasites in flounder Platichthys flesus from the River Thames: an infracommunity analysis

An analysis was undertaken of intestinal helminth communities in flounder Platichthys flesus from two sites on the River Thames. A comparison was made between helminth community richness and diversity from these sites at the component and infracommunity levels. At the component community level, a richer and more diverse parasite community was found in flounder from the Tilbury location (marine influence) than that from the Lots Road location (freshwater influence). At the infracommunity level, more parasite species and parasite individuals per host were found at Lots Road and the percentage of similarity values were low at both locations. Helminth species with high prevalence values in the parasite communities of the flounder are the dominant species in any individual fish, harbouring multi-specific infections. The presence of more invertebrate species, which are intermediate hosts in the helminth life cycle in the Thames, fish vagility and the high prevalence and abundance values of Pomphorhynchus laevis in the flounder, may explain the differences between the two locations.

Ecological analysis and description of the intestinal helminths present in dogs in Mexico City

The objective of the present study was to determine the prevalence of parasitoses in stray dogs from Mexico City, as well as to describe the structure of the intestinal helminth communities present in said hosts. One hundred and twenty dog intestines were collected and dissected to evaluate their parasitic load; finding parasites in 102 dogs (85%). The cestodes collected were: Dipylidium caninum in 72 dogs (60%), Taenia hydatigena in three (2.5%), Taenia pisiformis in two (1.6%), Echinococcus granulosus, Mesocestoides vogae and Mesocestoides variabilis in only one animal each (0.83%), the latter two being collected for the first time ever in Mexico City. Nematodes collected were: Ancylostoma caninum in 75 (62.5%) animals, Toxocara canis in 16 (13.3%) and Toxascaris leonina in 5 (4.16%). By age, D. caninum and A. caninum were the most prevalent species in older animals, while T. canis was more prevalent in young animals ( P < 0.05). By season, T. canis was most common in the dry season ( P < 0.05). At the parasitic community level, the diversity value was 0.32, while that of equality was 0.1; the dominant species was M. vogae (Berger–Parker index of 0.95). At the infracommunity level, both diversity and equality were low (0.31 and 0.32, respectively) as compared to that observed in wild canines; the dominant species was A. caninum (Berger–Parker index of 0.37). Qualitative similarity was 33.8%, while quantitative similarity was 32.2%. Based upon the low values for mean diversity, equality and species richness, it is possible to deduce that helminth fauna in dogs from Mexico City is weakened, especially if one compares it to that of other wild canines.

Medium-term temporal stability of the helminth component community structure in bank voles (Clethrionomys glareolus) from the Mazury Lake District region of Poland

The structure of helminth communities in wild rodents is subject to seasonal variation, and is dependent on host age within years. Although between-year variation has been monitored, seldom has it been assessed rigorously by appropriate multifactorial analysis with potentially confounding factors taken into account. In this study we tested the null hypothesis that despite seasonal, host age and sex effects, helminth communities should show relative stability between years. Over a period of 3 years (1998-2000) we sampled bank vole (Clethrionomys glareolus) populations (total n = 250) at 2 points in the year: in spring, at the start of the breeding season, and in autumn, after the cessation of breeding. In spite of seasonal differences and strong age effects, the between-year effects were surprisingly small. Measures of component community structure (Berger-Parker dominance index, the dominant species, S. petrusewiczi) did not vary, or varied only slightly from year to year. The majority of measures of infracommunity structure [Brillouin's index of diversity, prevalence of all helminths combined, prevalence and abundance of H. mixtum (the most prevalent helminth), mean species richness] did not differ significantly between years when other factors such as age, sex and seasonal variation had been taken into account. Some between-year variations were found (at the component community level, Simpson's index of diversity; at the infracommunity level, prevalence and abundance of S. petrusewiczi and abundance of all helminths combined), but even these were modest in comparison to seasonal and age differences, and were primarily attributable to S. petrusewiczi. We conclude that despite dynamic within-year fluctuations, helminth communities in bank voles in this region of Poland show relative stability across years. The sporadic occurrence of individual platyhelminths at low prevalence, makes little difference to the overall structure, which is largely maintained by the key roles played by the dominant intestinal nematodes of bank voles and the rarer species collectively.

Variation in the helminth community structure in spiny mice (Acomys dimidiatus) from four montane wadis in the St Katherine region of the Sinai Peninsula in Egypt.

We compared helminth communities in spiny mice (Acomys dimidiatus) from 4 wadis in the arid montane region of the southern Sinai in Egypt, in a 4-week period in late summer. Total helminth species richness was 14 (8 nematodes, 5 cestodes and 1 acanthocephalan) with 94% of mice carrying at least 1 species and an overall mean species richness of 1.85. The most prevalent parasites were Protospirura muricola (47.8 %) and Dentostomella kuntzi (46.3%). One larval cestode, Joyeuxiella rossicum, represents a new host record. The helminth community was dominated by intestinal nematodes (88.7%) of which 58.2% were arthropod-transmitted heteroxenic species. At the component community level, 70% of the worms were recovered from mice in just two wadis (Gharaba and Tlah) and 48.6 % of intestinal nematodes were from Wadi Gharaba. Although only 7 species of helminths were recorded from Wadi Gharaba, this site gave the highest Berger-Parker dominance index because of P. muricola. P. muricola was also dominant in Wadi El Arbaein whilst Syphacia minuta was the dominant species in Wadis Gebal and Tlah. At the infracommunity level, mean species richness and Brillouin's index of diversity were highest in Wadi Tlah and lowest in Wadi Gebal, and the former was age dependent. Whilst mice from different wadis differed in the nematodes that were most common, those from Wadi Gharaba carried the highest mean number of worms/mouse. The abundance of P. muricola in particular varied markedly between sites: Wadi Gharaba was distinct as the site showing the highest mean worm burden whereas mice from Wadi Gebal were uninfected. None of the directly transmitted oxyuroid nematodes showed significant variation in abundance between wadis, or host sex or age classes. Overall, the single extrinsic factor in the study, site of capture, was more important than the intrinsic factors in explaining variation in helminth communities in the region. We conclude that in the high mountains of southern Sinai, each wadi is distinct in terms of its rodent parasites, and hence we expect spatially different coevolutionary pressures on their hosts, with resultant variation in life-histories.

Parasites of flounder Platichthys flesus (L.) from the German Bight, North Sea, and their potential use in ecosystem monitoring

The analysis of fish-parasite community structure and the use of ecological richness and diversity measurements are commonly used for the evaluation of environmental stress in aquatic ecosystems. As part of an integrated biological-effect monitoring, the parasite community of flounder Platichthys flesus (L.) was investigated for various locations in the German Bight during spring and autumn of 1995–2000, using established ecological methods. Although the parasite-community composition was very similar at the component-community level, the number of component species as well as the species accumulation curves showed clear differences among the sites. On the infra-community level, all of the ecological measurements showed significantly lower values in flounder from the Elbe estuary, the most polluted site, than in flounder from Helgoland. This was seen during a single season or during both seasons. When the data were pooled over the years, gradual differences between the sites, which were seldom detected at individual sampling periods, became evident for different measurements of species richness and species diversity and corresponded to a contamination gradient established between Elbe > Inner Eider, Outer Eider > Helgoland. Despite seasonal variations, which were observed in almost all measurements, these gradual differences were found in both seasons.