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121.
Local site differences in survival and parasitism of periwinkles (Littorina sitkana Philippi, 1846)
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Mónica Ayala‐Díaz Jean M. L. Richardson Bradley R. Anholt 《Ecology and evolution》2017,7(4):1021-1029
The periwinkle, Littorina sitkana, is found throughout the intertidal zone, often in isolated subpopulations. The majority of trematode parasites use snails as intermediate hosts, and decreased survivorship is often observed in snails infected with trematodes. Sampling L. sitkana from four sites in Barkley Sound, British Columbia, Canada, we test the effects of parasitic infection on snail survival using maximum likelihood and Bayesian approaches using the software MARK and WinBUGS. We found that survival of periwinkles and trematode community composition differed among sites, but survival and trematode prevalence were uncorrelated. WinBUGS performed better than MARK in two ways: (1) by allowing the use of information on known mortality, thus preventing survival overestimation; and (2) by giving more stable estimates while testing the effect of body size on snail survival. Our results suggest that snail survival depends heavily on local environmental factors that may vary greatly within a small geographical region. These findings are important because the majority of experimental studies on survival are done on snails from a single location. 相似文献
122.
Egil Karlsbakk 《Marine Biology Research》2005,1(2):140-148
Marine fish from several locations along the west coast of Norway were examined for leeches. Seven leech species were detected, Calliobdella nodulifera (Malm, 1863) from codfish, flatfish and a ray, Calliobdella lophii van Beneden & Hesse, 1863 from Lophius piscatorius L., Platybdella anarrhichae (Diesing, 1859) on Anarhichas lupus L., Platybdella quadrioculata Malm, 1863 on Symphodus melops (L.), Oceanobdella sp. on Zeugopterus punctatus (Bloch), Malmiana brunnea (Johansson, 1896) on Myoxocephalus scorpius (L.) and Malmiana bubali Srivastava, 1966 on Taurulus bubalis (Euphrasen). Calliobdella nodulifera infected unrelated hosts (euryxenic); the others appeared to be host specialists (oio- or stenoxenic). Details on the occurrence of Calliobdella nodulifera on Enchelyopus cimbrius (L.) during 1 year are given, which together with other observations suggest that its life cycle exceeds a year. A brief account on the morphology of “Platybdella” quadrioculata is provided, justifying its transfer to the genus Oceanobdella Caballero, 1956 as O. quadrioculata comb. nov. With the new additions, the Norwegian marine piscicolid fauna contain 12 species. At least ten additional species, known from adjoining areas, also probably occur along the Norwegian coast. 相似文献
123.
The decay of similarity over geographical distance in parasite communities of marine fishes 总被引:2,自引:0,他引:2
Aim We evaluate, for the first time, the decay of similarity over distance in four species of marine fishes with different vagility: Trachurus murphyi (pelagic, highly vagile), Merluccius gayi (demersal, highly vagile), Sebastes capensis (demersal, low vagility) and Hippoglossina macrops (benthic, non‐vagile). Location We use our own data of the species composition of parasite communities in four host species: T. murphyi (Perciformes), M. gayi (Gadiformes), H. macrops (Pleuronectiformes) and S. capensis (Scorpaeniformes), from the coast of Chile and southern Argentina. Trachurus murphyi, M. gayi and H. macrops in the area studied live closely associated with the cold waters of the Humboldt Current System, while S. capensis in southern Chile is associated with the fjord areas south of c. 43° S, and in Argentina this species lives in close association with the cold water of the Malvinas Current, which mixes with the warm water of the Brazilian Current in the sampled area. Thus, for all four host species there are no known geographical (oceanographic) barriers that interrupt their continuous distributions. Methods Fish were collected and frozen (?18 °C) until examination in the laboratory. After thawing, each visceral organ was dissected separately, washed in running water, filtered using a mesh of 0.25 mm, and examined under a stereomicroscope (20×). For S. capensis, only ectoparasites were included in this study because data on endoparasites for some locations are not available. The approach of Poulin [Journal of Biogeography 30 (2003) 1609] was used. For each host species, we computed similarity in parasite composition using the Bray–Curtis distance on a presence/absence matrix. Similarity between each pair of localities was correlated (linear regression on raw and transformed data) with the distance (in nautical miles) among those sites. Results Among conspecific populations of host fish, there was no correlation between sample size and parasite species richness. The same pattern was evident when all host populations were pooled and treated as a single sample. Except for H. macrops, an important proportion of the geographical ranges of the host species was covered. The decay in similarity of parasite communities over distance was recorded in three of the four hosts analysed. For H. macrops, no relationship between distances and decay of similarity was evident. A linear regression on non‐transformed data provided a good fit, and the regression on log(n + 1) does not change significantly for both r2 and probability, but slopes are smaller for log‐transformed than for non‐transformed data. Main conclusions Three of the four fish parasite systems studied fit well with the expected decay of similarity over distance. The slopes of the relationship between distance and similarity in the marine fishes studied are lower, but significant (three orders of magnitude) than those recorded in freshwater fishes by Poulin (2003) . In our case, Hippoglossina macrops (benthic, non‐vagile host) does not show any relationship, suggesting homogeneity over the geographical area studied for this species. 相似文献
124.
Immune function, parasitization and extended phenotypes in colour polymorphic pygmy grasshoppers 总被引:3,自引:0,他引:3
EMILIO CIVANTOS JONAS AHNESJÖ ANDERS FORSMAN 《Biological journal of the Linnean Society. Linnean Society of London》2005,85(3):373-383
Ecological and evolutionary consequences of host–parasite interactions have attracted considerable attention from evolutionary biologists. Previous studies have suggested that immune responsiveness may be genetically or developmentally linked with colour pattern, such that the evolution of animal colour patterns may be influenced by correlated responses to selection for parasite resistance. We studied interactions between the endoparasitic fly Leiophora innoxia (Meigen) (Diptera: Tachinidae) and its colour polymorphic pygmy grasshopper host Tetrix undulata (Sow.) (Orthoptera: Tetrigidae) to test for morph‐specific differences in parasitization and immune defence, and host‐induced variation in parasite phenotypes. Our results revealed that c. 2 and 30% of adult grasshoppers collected from the same natural population in two subsequent years, respectively were parasitized. Parasite prevalence was independent of host sex and colour morph. Pupae were larger if the parasite had developed in a female than in a male host, possibly reflecting host resource value or a physical constraint on larval growth imposed by host body size. Pupal size was also associated with host colour morph, with individuals that had developed in dark morphs being smaller at pupation compared to those that developed in paler morphs. However, immune defence, measured as the encapsulation response to a novel antigen, did not differ among individuals belonging to alternative colour morphs or sexes. Darker morphs warm up more quickly and prefer higher body temperatures than paler ones. Encapsulation was not influenced by maintenance temperature (15 vs. 30 °C), however, suggesting that indirect effects of coloration on parasite resistance mediated via differential body temperature are unlikely. The dependence of parasite body size on host colour morph may thus reflect plasticity of growth and development of the larvae in response to differential host body temperature, rather than variable host immune defence. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 373–383. 相似文献
125.
Mota Marcelo A. Campos Artur K. Araújo Jackson V. 《World journal of microbiology & biotechnology》2003,19(9):913-916
The biological control of helminth parasites of bovines by nematophagous fungi is an alternative to the use of drugs with the principal objective of reducing the source of infection available on pastureland. The maintenance of predatory activity of the fungal isolates is one of the basic prerequisites to ensure the success of this form of control. In this study behaviour of the isolates I31 of Arthrobotrys robusta and NF34a of Monacrosporium thaumasium was investigated following three storage methods: stored at 4 °C, cryopreserved with or without cryoprotectants or preserved in silica gel. All samples were subsequently passed through the gastrointestinal tract of calves. The latter involved the administration of 20 g of mycelia to the animals. This quantity was sufficient to recover fungal material from the faeces. The peak reduction in the number of infective larvae in the faeces occurred 24 h after administration of the samples (P < 0.05). The storage at 4 °C was the treatment that produced the greatest reduction in larvae for NF34a (81.3%) and I31 (65.1%) isolates. Nf34a isolate was responsible for the highest percentage reduction of larval helminth populations (P < 0.05). Cryopreservation appears to be an efficient method of preserving isolates, although diminished predatory capacity compared to storage at 4 °C was seen only for isolate NF34a (73.2%). Cryopreservation did not interfere in predatory activity of I31 isolate (P < 0.05). Maintenance of isolates in silica gel showed the lowest reduction throughout the experiment (P < 0.05). 相似文献
126.
Effects of elevated CO2 , nitrogen deposition, and decreased species diversity on foliar fungal plant disease 总被引:4,自引:0,他引:4
CHARLES E. MITCHELL PETER B. REICH† DAVID TILMAN JAMES V. GROTH‡ 《Global Change Biology》2003,9(3):438-451
Three components of global change, elevated CO2, nitrogen addition, and decreased plant species richness (‘diversity’), increased the percent leaf area infected by fungi (pathogen load) for much to all of the plant community in one year of a factorial grassland experiment. Decreased plant diversity had the broadest effect, increasing pathogen load across the plant community. Decreased diversity increased pathogen load primarily by allowing remaining plant species to increase in abundance, facilitating spread of foliar fungal pathogens specific to each plant species. Changes in plant species composition also strongly influenced community pathogen load, with communities that lost less disease prone plant species increasing more in pathogen load. Elevated CO2 increased pathogen load of C3 grasses, perhaps by decreasing water stress, increasing leaf longevity, and increasing photosynthetic rate, all of which can promote foliar fungal disease. Decreased plant diversity further magnified the increase in C3 grass pathogen load under elevated CO2. Nitrogen addition increased pathogen load of C4 grasses by increasing foliar nitrogen concentration, which can enhance pathogen infection, growth, and reproduction. Because changes in foliar fungal pathogen load can strongly influence grassland ecosystem processes, our study suggests that increased pathogen load can be an important mechanism by which global change affects grassland ecosystems. 相似文献
127.
Entomo-pathogen parasites typically induce alternative ”parasitogenic” phenotypes in ants and other insects. However, the
basis of generated developmental changes is poorly understood. Parasitic mermithid nematodes also cause the formation of three
discrete and aberrant morphologies within Myrmica ants. These have been called ”worker-like” (”mermithergate”), ”intermorphic” (”gynaecoid mermithergate”) and ”gyne-like”
(”mermithogyne”) and their formation has been attributed to infection of worker- and queen-presumptive larvae, respectively.
In order to better understand the developmental mechanisms that lead to the formation of these alternative parasitogenic phenotypes
we observed allometric patterns of parasitogenic Myrmica gallienii phenotypes in comparison with uninfected workers and gynes from the same nests. It was revealed that the three discrete morphologies
of parasitogenic female phenotypes did not differ significantly from each other in their scaling indicating that these were
trapped in the same developmental pathway. Infected individuals scaled according to basically gyne-like allometry, however
significantly differed from workers in their scaling. Based on the observed scaling patterns we herein raise an alternative
explanation according to which both ”mermithergate”, ”gynaecoid mermithergate” and ”mermithogyne” Myrmica phenotypes develop from the same type of larvae, namely from the queen-presumptive larvae and their formation, therefore,
is rendered as a diverging process. According to the mechanism we propose effect of nematodes may turn out to be the determining
factor in the formation of alternative parasitogenic morphologies.
Received 16 June 2008; revised 15 September and 7 November 2008; accepted 18 November 2008. 相似文献
128.
129.
Parasites are a health concern of many wildlife species, although their effect on reptiles is poorly studied. Here we examine effects of hemogregarine and external parasites on Texas ratsnake Elaphe obsoleta white blood cell (WBC) concentrations, WBC differentials, heterophil/lymphocyte ratios, packed cell volume (PCV), corticosterone concentrations and body condition. We found little evidence that either ectoparasites or hemogregarines affected the health of Texas ratsnakes. We found a seasonal increase in corticosterone, consistent with glucocorticoids priming the snakes to deal with higher predation risks later in the season. We also examined whether the potential stress of carrying a surgically implanted radio-transmitter compounds any parasitic health effects. We found no effect of transmitters on most aspects of health. We did find equivocal evidence that WBC concentrations were higher in snakes with transmitters and that PCV decreased following transmitter implantation. Although our results generally support the view that data collected using radio-telemetry are unlikely to be biased due to adverse health effects of transmitters, the growing importance of telemetry for studies of snakes and other taxa argues for further research on this topic. When possible, researchers should design telemetry studies in such a way that assessing potential heath effects of transmitters is one of the objectives. 相似文献
130.