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1.
    
A surgical technique for the transfer of 3-week old Schistosoma mansoni to the mesenteric veins of mice is described. Parasites grown in a donor C3H/StCrl strain survive on transfer to recipient C57BL/10J mice despite prior immunization with C3H/StCrl cells or skin grafts. The findings indicate that the ‘species-specific’ mouse host antigens associated with adult worms in xenogeneic transfers do not have an allogeneic basis in these two strains.  相似文献   

2.
Parasites are attracting increasing interest from parasite ecologists as potential indicators of environmental quality due to the variety of ways in which they respond to anthropogenic pollution. In environmental impact studies certain organisms provide valuable information about the chemical state of their environment not through their presence or absence but instead through their ability to concentrate environmental toxins within their tissues. Free living invertebrates, notably bivalve molluscs, are commonly employed in this role as `sentinel organisms' to monitor the concentrations of bioavailable metals in aquatic ecosystems. Also certain parasites, particularly intestinal acanthocephalans of fish, can accumulate heavy metals to concentrations orders of magnitude higher than those in the host tissues or the environment. The comparison of metal accumulation capacities between acanthocephalans and established free living sentinel organisms revealed significantly higher concentrations of several elements in Acanthocephalus lucii (Müller) than in the Zebra mussel Dreissena polymorpha (Pallas) which is a commonly used bioindicating organism in Europe. In contrast to the high heavy metal concentrations recorded in adult acanthocephalans, the larval stages in their respective crustacean intermediate hosts show little tendency to accumulate metals. A number of experimental studies demonstrate a clear time dependent accumulation of lead for acanthocephalans in their final hosts. These investigations provide evidence that the extremely high metal concentrations in intestinal acanthocephalans of fish are not the result of a slow process of accumulation but instead a relatively rapid uptake to a steady-state level. Thus, metal concentrations in adult acanthocephalans respond rapidly to changes in environmental exposure of their hosts. The value of parasites for environmental monitoring will be discussed in detail in the present article.  相似文献   

3.
    
Some parasitoid wasps possess soldier castes during their parasitic larval stage, but are often neglected from our evolutionary theories explaining caste systems in animal societies. This is primarily due to the polyembryonic origin of their societies. However, recent discoveries of polyembryonic trematodes (i.e. flatworms) possessing soldier castes require us to reconsider this reasoning. I argue we can benefit from including these polyembryonic parasites in eusocial discussions, for polyembryony and parasitism are taxonomically vast and influence the evolution of social behaviours and caste systems in various circumstances. Despite their polyembryony, their social evolution can be explained by theories of eusociality designed for parent–offspring groups, which are the subjects of most social evolution research. Including polyembryonic parasites in these theories follows the trend of major evolutionary transitions theory expanding social evolution research into all levels of biological organization. In addition, these continued discoveries of caste systems in parasites suggest social evolution may be more relevant to parasitology than currently acknowledged.  相似文献   

4.
    
Host–parasite coevolution is often suggested as a mechanism for maintaining genetic diversity, but finding direct evidence has proven difficult. In the present study, we examine the process of coevolution using a freshwater New Zealand snail ( Potamopyrgus antipodarum ) and its common parasite (the sterilizing trematode, Microphallus sp.) Specifically, we test for changes in genotypic composition of clonal host populations in experimental populations evolving either with or without parasites for six generations. As predicted under the Red Queen model of coevolution, the initially most common host genotype decreased in frequency in the presence, but not the absence, of parasitism. Furthermore, the initially most common host genotype became more susceptible to infection by the coevolving parasite populations over the course of the experiment. These results are consistent with parasite-meditated selection leading to a rare advantage, and they indicate rapid coevolution at the genotypic level between a host and its parasite.  相似文献   

5.
    
Aim We investigated the relationship between host and parasite diversity as well as latitudinal gradients in parasite diversity on a continental scale in European freshwater trematodes. Location European freshwaters. Methods We extracted distributional data for 564 freshwater trematodes across 25 biogeographical regions in Europe from the Limnofauna Europaea and used multiple regression analyses to test for correlations between the diversity of definitive (vertebrates) or first intermediate (gastropods) hosts and that of trematodes, and for latitudinal gradients in trematode diversity. In particular, we investigated patterns in beta diversity among latitudinal bands and between trematode species that parasitize host groups with low (autogenic) and high (allogenic) dispersal capacity. We also tested for a latitudinal gradient in the proportional representation of these two trematode groups within regional faunas. Results Latitude or first intermediate host richness had no effect on trematode richness, but definitive host richness was a strong predictor of trematode richness, among both allogenic and autogenic parasites. We found that beta diversity of trematode faunas within latitudinal bands decreased to the north, with similar values for allogenic and autogenic trematodes. Finally, we observed an increasing proportion of autogenic species toward the north of Europe. Main conclusions The richness of definitive hosts appears to be the driver of trematode diversity at a continental scale. The latitudinal gradient in beta diversity reflects patterns observed in free‐living species and probably results from recolonization in the aftermath of the ice ages. The similar beta‐diversity patterns of allogenic and autogenic trematodes and the increasing proportion of autogenic trematodes with increasing latitude are surprising. We suggest that the geographical scale of our analysis or confounding factors such as differences in habitat utilization and specialization may partly explain these patterns.  相似文献   

6.
    
Abstract

The cercariae and sporocysts (or rediae) of four trematode species are described from the intertidal snail Zeacumantus subcarinatus: a distome xiphidiocercaria assigned to the genus Renicola (family Renicolidae); a monostome xiphidiocercaria belonging either to the genus Microphallus or Megalophallus (family Microphallidae); a magnacercous cercaria of the genus Galactosomum (family Hetero‐phyidae); and a cercaria of the genus Philophthalmus (family Philophthalmidae). The morphological features of these cercariae are compared to previously described cercariae of the same genera. In addition, since the philophthalmid cercaria encysts readily on artificial substrates in the laboratory, the metacercaria of this species is also described. These cercariae are part of a diverse community of at least six digenean species parasitising the snail Z. subcarinatus that, together, have a major impact on the ecology and evolution of this snail.  相似文献   

7.
Variations in the occurrence of gastrointestinal metazoan parasites in flatfish were examined in relation to sewage sludge dumping at an 'accumulating' and two 'dispersing' dump sites in Scottish coastal waters. The gross disturbance of the benthic communities at the Garroch Head disposal site in the Firth of Clyde and absence of the intermediate hosts of particular parasites was not reflected in the parasite fauna of the long rough dab, Hippoglossoides platessoides . Results indicate that this flatfish host is highly mobile and intermixing within the population masked any localized effects of sludge dumping on parasite transmission at the dump site. The common dab, Limanda limanda , is considered to be relatively static at the St Abb's Head and Bell Rock disposal sites off the Firth of Forth where no evidence of effects of sewage sludge dumping on its metazoan parasite fauna was detected. This is consistent with the results of chemical and biological monitoring of the sites. The value of a parasite-based index of the biological effects of sewage sludge dumping is discussed.  相似文献   

8.
    
Understanding host-parasite coevolution requires multigenerational studies in which changes in both parasite infectivity and host susceptibility are monitored. We conducted a coevolution experiment that examined six generations of interaction between a freshwater snail (Potamopyrgus antipodarum) and one of its common parasites (the sterilizing trematode, Microphallus sp.). In one treatment (recycled), the parasite was reintroduced into the same population of host snails. In the second treatment (lagged), the host snails received parasites from the recycled treatment, but the addition of these parasites did not begin until the second generation. Hence any parasite-mediated genetic changes of the host in the lagged treatment were expected to be one generation behind those in the recycled treatment. The lagged treatment thus allowed us to test for time lags in parasite adaptation, as predicted by the Red Queen model of host-parasite coevolution. Finally, in the third treatment (control), parasites were not added. The results showed that parasites from the recycled treatment were significantly more infective to snails from the lagged treatment than from the recycled treatment. In addition, the hosts from the recycled treatment diverged from the control hosts with regard to their susceptibility to parasites collected from the field. Taken together, the results are consistent with time lagged, frequency-dependent selection and rapid coevolution between hosts and parasites.  相似文献   

9.
Potentiation of zinc stress caused by parasitic infection of snails   总被引:2,自引:1,他引:1  
The purpose of this experiment was to determine the effects of parasitism (Schistosomatium douthitti Price and Trichobilharzia sp.) on the tolerance of snails Lymnaea stagnalis (L.) to acutely lethal concentrations of zinc. Significant reduction in tolerance occurred for snails with patent infections at 24 and 75 ppm of Zn++. At two selected prepatent levels of parasite development, significant differences occurred at the higher concentration only.  相似文献   

10.
Technical, biological and socioeconomic factors act as obstacles in the development of fishing activity in the Guaratuba Bay, southern Brazil. Amongst the difficulties registered, the following stand out: there was little variety of fishing gear; the purchasing power of the fishermen was low; there was a lack of regularity in the presence of the target species in the estuary; legislation restricted the use of certain gear at particular times; the size of the individual fish was small when compared to those from the continental shelf. Aquaculture could offer an alternative to the revenue of the fishermen, but cultural tradition and the lack of financial resources make it difficult to introduce aquaculture as an activity for the fishermen. The pessimism encountered in the community indicates that the future of artisanal fishing in this estuary is uncertain.  相似文献   

11.
By-catch is estimated by sampling the whole fishery (February to April 1987) on the basis of a survey of the fishing effort: 16 species of commercial interest are considered, among them 3 species are dominant: Flounder, sprat and brown shrimp (98,4% of the 49,3 million individuals). By-catch consists mainly of very young animals (larval or 0-group stages). An attempt is made to consider the ratio between by-catch and the potential natural mortality of juveniles.  相似文献   

12.
    
The responsible approach to marine stock enhancement is a set of principles aimed at maximising the success and benefits of artificially re‐stocking depleted fisheries. The benefits of such an approach are evident in the 400% increase in survival of stocked striped mullet in Hawaii through refinement of release techniques, however financially or temporally constrained stocking programs in Australia have not adhered to all principles. A pragmatic approach to address these principles is proposed, using international examples and Australian marine finfish pilot stockings of barramundi, mulloway, sand whiting, dusky flathead and black bream. Biological ranking of candidate species by estuarine residency, a low natural‐mortality to growth ratio, a large L and comparison by recreational value and available rearing technologies, show that mulloway, barramundi and sea mullet are ideal species for stocking in Australia. Australian intermittently closed opening landlocked lagoons and recreational fishing havens, especially near cities, provide experimental opportunities to apply this approach and stock suitable species through small‐scale pilot experiments. This would allow evaluation of production and carrying capacity, and density dependent processes with respect to optimal stocking strategies unconfounded by emigration and commercial fishing practices. Twenty per cent of Australians fish each year, and harvest approximately 27 000 t of finfish. Stocking recreationally important species in Australia should give a greater financial benefit, which is spread across a larger cross‐section of the community, compared to stocking to enhance commercial fisheries. The pragmatic application of the responsible approach, and stocking of fast growing estuarine residents into recreational fishing havens would enhance the benefit from marine stocking.  相似文献   

13.
    
Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are \"roundworms\" (nematodes), \"thorny-headed worms\" (acanthocephalans), \"flukes\" (trematodes), and \"tapeworms\" (cestodes). The optimum method for collecting helminths is to examine a host that has been dead less than 4-6 hr since most helminths will still be alive. A thorough necropsy should be conducted and all major organs examined. Organs are washed over a 106 μm sieve under running water and contents examined under a stereo microscope. All helminths are counted and a representative number are fixed (either in 70% ethanol, 10% buffered formalin, or alcohol-formalin-acetic acid). For species identification, helminths are either cleared in lactophenol (nematodes and small acanthocephalans) or stained (trematodes, cestodes, and large acanthocephalans) using Harris'' hematoxylin or Semichon''s carmine. Helminths are keyed to species by examining different structures (e.g. male spicules in nematodes or the rostellum in cestodes). The protocols outlined here can be applied to any vertebrate animal. They require some expertise on recognizing the different organs and being able to differentiate helminths from other tissue debris or gut contents. Collection, preservation, and staining are straightforward techniques that require minimal equipment and reagents. Taxonomic identification, especially to species, can be very time consuming and might require the submission of specimens to an expert or DNA analysis.  相似文献   

14.
P. Bagge  L. Hakkari 《Hydrobiologia》1982,86(1-2):61-65
The composition of the fish stock, food and macroparasites were studied in eleven basins (22–100 m) of Lake Jyväsjärvi and North Päijänne in August–September 1976. The fishing was done by means of a series of nets (meshes 15, 21 and 35 mm) laid on the bottom overnight. No fish were found in the two northernmost basins owing to bad oxygen conditions caused by waste waters. Smelt and burbot were the most abundant fish in the catches in other basins but the vendace was rare. Relict crustaceans and some deep water copepods (e.g. Heterocope borealis) played an important role in the food of fish in all basins.Parasites spreading via relict crustaceans were abundant in smelt and burbot, but absent in vendace and ruffe. The most common parasite in smelt was Cystidicola farionis, in burbot Echinorhynchus borealis, in ruffe Triaenophorus nodulosus and in vendace the gill parasite Ergasilus sieboldi. Females of a relatively rare copepod Salmincola lotae were found in the oral cavity of five burbot (at depths of 50 and 100 m).  相似文献   

15.
    
Aim We used published inventories of trematodes in Littorina littorea (L.) and Hydrobia ulvae (Pennant) in European seas to search for two basic biogeographical patterns in the spatial occurrence of various trematode species: (1) do parasite distribution and richness patterns in the two host snails overlap with known ecoregions of free‐living organisms; and (2) does trematode species richness in the snails follow latitudinal or longitudinal gradients? Location North East Atlantic. Methods We used multidimensional scaling (MDS), analysis of similarity (ANOSIM) and analysis of variance (ANOVA) to test whether there were overlaps of parasite distribution and richness with known ecoregions of free‐living organisms. In addition, we used linear regression analyses to test whether trematode richness in snails (corrected for sampling effort) was correlated with the latitude or longitude of the sampling sites. Results When corrected for sampling effort, mean trematode species richness per site did not differ among the different ecoregions in L. littorea. In contrast, in H. ulvae, mean species richness was much lower for sites from the Celtic Sea compared with sites from the Baltic Sea and the North Sea. Based on the results of MDS analyses, trematode species composition was distinct among ecoregions; in particular, communities from the Baltic Sea differed markedly from communities in the Celtic Sea, for both snail species. Latitude and longitude were not significantly correlated with parasite species richness in either snail species. Most trematode species had restricted distributions, and only three species in L. littorea and five species in H. ulvae occurred at more than 50% of the sites. Main conclusions There is more structure in the large‐scale distribution of trematodes in gastropods than one would expect from the large‐scale dispersal capabilities of their bird and fish final hosts. We propose mechanisms based both on limited dispersal via fish and bird final hosts and on gradients in environmental factors to explain the observed patterns.  相似文献   

16.
The bivalve Scrobicularia plana, which iscommonly found on tidal flats in northwestern Europe,has disappeared from many locations during the pasttwo decades. Its local disappearance has beensuspected to be a result of pollution, but otherfactors such as parasites have also been discussed. The occurrence of Tetrastemma fozensis, a smallhoplonemertine inhabiting the mantle cavity of S. plana,was examined in bivalves from six differentestuaries in northern Spain. The bivalves are easilycollected, and the nemertines leave the bivalves whenplaced in a small jar with seawater for 72 h. Regularexaminations at 6–10 wk intervals of S. planafrom the estuary of Plencia revealed that thepercentage of bivalves containing nemertines T. fozensisdecreased during the summer months, but wasabove 70% during the rest of the year. In mostestuaries about 40–60% of the bivalves containednemertines, but in March 1994, 100% of the bivalvesfrom the estuary of Hendaye were hosts for nemertines.Nemertines were not found in S. plana from thehighly polluted estuary of Bilbao in either March orSeptember 1994. The number of nemertines withinindividual bivalves was positively correlated with thesize of the bivalves in locations where the percentageof bivalves containing nemertines was above 75%. Inone estuary where the nemertines disappeared almostcompletely from the bivalves between March 1994 andSeptember 1994, parasitic copepods appeared withinsome bivalves in September 1994. The ecology of thenemertine T. fozensis still remains largelyunknown, but we suspect that the nemertines may bebeneficial for their hosts.  相似文献   

17.
The quality of water in aquatic systems is subject to temporal and spatial variations due to varying effects of natural and anthropogenic factors. This study assessed the dynamics of water quality in the Boro-Thamalakane-Boteti river system along an upstream–downstream gradient above and below Maun during February, May, September and December 2012. Temperature, conductivity, pH, dissolved oxygen, turbidity, Escherichia coli and faecal streptococci were monitored in the settlements of Boro, Maun, Xobe, Samedupi, Chanoga and Motopi along the river system. Comparisons of water quality among settlements using ANOVA and Tukey's honest significant difference test highlighted a significant decline in water quality from upstream to downstream, indicated by increases in microbial numbers and turbidity. The quality of water improved as the water level rose during the peak flooding season in September and declined thereafter. This study highlights the possible influence of human settlements and associated developments on waterbodies, and lends strong support to management efforts to maintain river water quality to ensure the suitability of the water for various ecosystem uses.  相似文献   

18.
A series of recent studies have been completed by the authors involving: 1) determining the lethal tolerances of 12 oligochaete species classified (from ecological studies) as tolerant, moderately tolerant and intolerant to selected chemical toxicants and environmental factors under defined bioassay conditions with and without sediment; 2) determining lethal tolerances of candidate species to toxicants in combination with a range of abiotic factors; 3) measuring respiratory stress imposed by exposure to individual and combined sublethal concentrations of toxicants and environmental factors; and, 4) determining differences in lethal tolerance and respiratory stress between individual and mixed species. Surprisingly few previous studies have been done in this area considering the importance of oligochaetes as field pollution indicators. The results of the above major studies coupled with histopathological work are reviewed. Data from these studies substantiate the present use of oligochaete species assemblages as indicators of organic pollution and suggest their use in the laboratory for toxicant screening tests. The range of responses of different oligochaete species to individual and combined stress is complex, particularly in mixed species, which provides useful indications of specific stress factors. The application of these experimental laboratory studies to field situations is described.  相似文献   

19.
    
Air pollution is the single largest environmental risk today and is increasing in developing countries. In addition, exposure to air pollution is correlated to poor socioeconomic conditions owing to political processes and cultural and historic occupation of land. Ports have several structures that are potential emitters of pollutants such as large ship engines, diesel trucks, and trains. Owing to the considerable costs of implementing direct monitoring networks, alternatives like biomonitoring are an interesting approach to evaluate the environmental status of a particular area using living organisms or their parts such as bark, even though the use of bark as a biomonitor has several problems such as difficulties in determining the exposure period and its correlation with human exposure. Therefore, the use of a complementary mathematical logic is necessary. This study describes a methodological approach to evaluate the environmental risk from air pollution integrating data on environmental pollutants from tree bark using Fuzzy logic, based in the port city of Paranaguá in the state of Paraná in Brazil, and validated using income indicators. The results indicate that the risk distribution patterns have an inverse relationship with the income indicator, i.e., higher risk levels indicate lower income levels and vice versa. It was concluded that the system was able to identify the distribution of risk and that there is a context of environmental injustice in the region, where the environmental risk related to air pollution is inversely proportional to income levels. This type of information provides a decision making tool for environmental risk analysis from air pollution and can be used in the definition of public policies.  相似文献   

20.
Goran Milbrink 《Hydrobiologia》1994,278(1-3):213-222
Analyses of the oligochaete fauna of two of the deepest lakes in Scandinavia — the Norwegian lakes Mjösa (450 m) and Tyrifjorden (295 m), revealed a totally different species composition in the deep profundal compared with the upper profundal - in contact with the nutrient-enriched epilimnion. In both lakes a pronounced thermal stratification develops in the summer, thus the epilimnion receiving gross organic pollution behaves differently from the profundal. The lakes are each effectively divided into two bodies of water with limited water exchange between them, i.e. one major oligotrophic body and one minor more nutrient-rich. Since the 1950s both lakes have been exposed to heavy pollution of various kinds. In Lake Mjösa in 1975 and 1976 unpleasant algal blooms of the blue-green alga Oscillatoria bornetii fa. tenuis occurred. Bottom samples obtained at the same time revealed that the deep central bottoms of the lake were totally dominated by oligotrophic oligochaete indicators, i.e. by Stylodrilus heringianus and Spirosperma ferox, while the fauna of the upper profundal in the vicinity of domestic and agricultural sewage outfalls, wood processing industries, etc. was dominated by Limnodrilus hoffmeisteri and Tubifex tubifex in great abundance, indicating enriched conditions. Several other species indicative of eutrophy, were absent, most of them belonging to the genus Potamothrix. A fairly similar situation exists in Lake Tyrifjorden, where, for instance, in the shallow bay of Steinsfjorden — heavily eutrophied by agricultural wastes — blooms of blue-green algae have caused problems from time to time. The same oligochaete communities as in Lake Mjösa distinguish the central oligotrophic bottoms from the regionally more enriched upper profundal. The likely reasons for an intact profundal oligochaete fauna are great volumes of oxygen-rich hypolimnic water of low temperature and a high bottom/lake surface area ratio.  相似文献   

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