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1.
A histopathological survey was performed to search for the cause of high mortality in the cockle Cerastoderma edule in northern rias of Galicia (northwestern Spain). From limited sampling, 2 severe pathological conditions with high prevalence were found: disseminated neoplasia and the occurrence of numerous, large foci of heavy haemocytic infiltration. Both conditions were detected in areas affected by high mortality and were absent (foci of haemocytic infiltration) or with lower prevalence (disseminated neoplasia) in an area with unnoticeable mortality that was chosen as a reference. Advanced cases of both pathological conditions were associated with extensive tissue destruction. Because of the severity of the lesions and their high prevalence, both pathological conditions could have contributed to the high mortality.  相似文献   

2.
A haemic neoplasm occurs in populations of the common cockle Cerastoderma edule L. along the coast of Ireland. The morphology, epizootiology and distribution of the disease have previously been described. The aetiology of the neoplasm is unknown. In this study transmission of the neoplasm between cockles was accomplished using both whole neoplastic cells and neoplastic cell-free homogenates which were filtered through 0.45 microm Millipore filters. Successful transmission of the disease has been achieved by both methods. These results indicate that the neoplasm in cockles may have a viral aetiology. Whole neoplastic cell inoculation resulted in a higher level of disease development compared to that of cell-free inoculates. The survival rates of the inoculated groups were compared and a significant decrease in survival was found in those groups which developed the disease.  相似文献   

3.
A study is described concerning the infestation of a laboratory-reared Daphnia magna culture by the fungus Aphanomyces daphniae. The origin of this fungus is Lake Huron, Michigan, the water from which is used in the laboratory to culture daphnids and maintain fishes for toxicological testing. Infestations originate from the Lake during the autumnal and vernal homothermal periods. The fungus is apparently maintained in the laboratory in conjunction with the fishes. Onset of fungal infestations in zooplankton culture apparently is initiated by three types of stress: rising temperatures, declining dissolved oxygen values, and poor nutrition. These infections have been eliminated by separating the daphnid culturing facility from the fish facility, substituting an algal diet for a synthetic one, sterilizing all water, air, and glassware connected with zooplankton culture, and maintaining the daphnids in a constant temperature room with controlled dissolved oxygen levels in the culturing vessels.  相似文献   

4.
Cysts with spores showing different degree of maturity and a single plasmodium were observed in the connective tissue of the turbellarian Paravortex cardii located in the digestive lumen of the cockle Cerastoderma edule. The study of spore morphology by transmission electron microscopy revealed that they correspond to an haplosporidian belonging to the genus Urosporidium. Spore ornaments were similar to those described from Urosporidium spisuli, infecting a nematode parasite of the Atlantic surf clam, Spisula solidissima.  相似文献   

5.
Aspects of the shell morphology of the cockles Cerastoderma edule (L.) and C. glaucum (Poiret) collected from the R. Crouch and R. Roach (Essex, England) are considered with reference to interpretation of the environment of sub-fossil assemblages. Discrimination between the two cockle species is best achieved by assessment of qualitative shell characters, quantitative measurements being of rather limited value. Factors influencing shell rib-number differ in the two species of Cerastoderma; within a common environment C. glaucum has fewer ribs than C. edule . Mean rib-number of C. edule is directly related to salinity over the colonized salinity range 20–36.5%0 whilst in C. glaucum rib-number is lowest in both low (<10%0) and high (>35%0) salinity environments, being maximal where salinities between 20–30%0 occur. Internal shell pigmentation may be absent in C. glaucum from low salinity environments. Magnesium content of whole shells is similar in the two cockle species from a mixed population. In both cockles, however, the prismatic layer contained more magnesium than the nacreous shell layer. The most useful molluscan indicators of brackish water lagoon environments are C. glaucum and Hydrobia ventrosa; these species being absent from areas of only limited wave action. C. edule may be associated with marine or estuarine molluscan indicators.  相似文献   

6.
Epizootiological outbreaks of disseminated neoplasia (DN) have been reported in association with mass mortalities in various bivalve species including the cockle Cerastoderma edule. A flow cytometric (FCM) procedure to study DNA content was successfully adapted and tested in haemolymph cells (haemocytes and neoplastic cells) of the cockle. The FCM results were similar to those obtained by histological analysis (DN diagnosis and haemolymph cell features). FCM analysis revealed differences in DNA content among normal haemocytes (diploid) and neoplastic cells. Four types of cells with abnormal DNA content were found in the haemolymph of affected animals: hypodiploid, hyperdiploid, triploid-sesploid and pentaploid. Our results suggest that the flow cytometric DNA content analysis can be applied to identify neoplastic cell types and to study the association between different cell types and the DN progression or remission in this edible and commercially important bivalve species.  相似文献   

7.
8.
We report the occurrence of the microsporidian parasite Steinhausia sp. in the oocytes of the common cockle Cerastoderma edule in a natural population in France, where high mortalities occurred. Steinhausia sp. appeared primarily as sporocysts containing many small spores, and putative earlier developmental stages were also observed. Both its prevalence and infection intensity were low, and no host defence reaction was recognized, suggesting that Steinhausia sp. had no detrimental effect on C. edule. Its prevalence was higher in cockles lying on the sediment surface, but the significance of this observation could not be explained given the poor knowledge of the Steinhausia life cycle. The present data did not allow specific identification of the parasite, and further studies are required to determine whether Steinhausia sp. in the cockle is a new species, or a microsporidian infecting multiple host species.  相似文献   

9.
Cerastoderma edule is a widely distributed bivalve mollusc, commercially exploited throughout Europe and is also an important food source for birds and crustaceans. Recently, mass surfacing and mortalities of cockles have been observed and reported at sites in Ireland and elsewhere, particularly in the summer months. One such site is Flaxfort Strand, Courtmacsherry Bay, County Cork, Ireland, an important feeding area used by many seabirds during the summer months. For the past few years large numbers of surfaced cockles have been observed at the site in a moribund condition. Samples of cockles from this area were collected over the summer months and their health status assessed. Cockles that had surfaced (moribund) and those still buried in the sediment were quantified and screened: sex, gonadal maturity and size class of cockles were also determined. Disseminated neoplasia and trematodes were observed in screened cockles. The most significant finding during the study was that mortalities and surfacing of cockles was related to a greater incidence of disseminated neoplasia. No neoplasia was observed in the smallest and largest size classes. There was a significantly higher prevalence of neoplasia in moribund cockles than in buried cockles, whereas in both groups a similar concentration of trematode metacercariae was observed in the screened tissues. Also, most of the cockles that had surfaced were either in the process of spawning or were spent. Overall a much larger percentage of moribund cockles exhibited both trematode infections plus neoplasia compared with buried cockles. A combination of the presence of neoplasia and trematodes, along with stress related to spawning, may immunocompromise the cockless, causing the animals to surface and become moribund.  相似文献   

10.
Diversity was studied in 10 communities, including the understory of native oak woodland, planted woodlands (pine and eucalypt), and shrublands in the strict sense (heathlands, broom shrublands, gorse shrublands).In each community, species richness, diversity, dominance and evenness were analysed. Differences were observed among communities with regard to species composition, richness in annual herbs, perennial herbs and shrubs, dominant plant families (Ericaceae, Papilionaceae) and diversification of shrub species.The possible relations between environmental stress and/or human influences on differences in diversity are discussed.  相似文献   

11.
We analyzed the capacity of the common cockle Cerastoderma edule to utilize detrital food particles obtained from three different macrophytes: the vascular plant Juncus maritimus and two green macroalgae (Ulva lactuca and Enteromorpha sp.). We measured feeding and digestive parameters at three concentrations of detritus (0.5, 1.0 and 3.0 mm3 l?1), so that functional relationships between ingestive and digestive processes could be assessed. Increasing concentrations of detritus (food) resulted in a reduction in filtering activity (clearance rate l h?1), but an increase in ingestion rate. Consequently, gut content also increased with increasing food concentration, irrespective of food type. In contrast, the trend followed by absorption efficiency with increasing ingestion rate was determined by food type, being significantly reduced (from 0.63 to 0.11) with Juncus but remaining almost constant with the green macroalgae (0.58 ± 0.07 with Ulva) or only minimally reduced (from 0.66 to 0.48 with Enteromorpha). This differential response had clear consequences for energy uptake: absorption rate increased with increasing particulate organic matter with Enteromorpha but decreased with Juncus. We discuss the possible role of digestive parameters such as digestibility, gut content and gut-residence time in the differential utilization of detrital matter from different vegetal origins by cockles.  相似文献   

12.
Fraxinus pollen data from eight Galician localities (1999-2003), recorded using 7-day Lanzoni VPPS pollen traps, were studied to determine their temporal and spatial distribution. The determination of the chill and heat required to trigger flowering and the start cumulative date were calculated using ten years of pollen data from Ourense. The sum of maximum temperatures from the 55 days before the peak date showed the lowest standard deviation coefficient and the mean quantity of accumulated heat was 741. Temperatures below 0°C and/or rainfall at the beginning of flowering caused a longer period before the peak date was registered. Temperatures recorded in November were very important for chill accumulation and determine the heat requirement needed to trigger Fraxinus flowering in Galicia.  相似文献   

13.
Much of the current knowledge concerning bivalve immunology and immunotoxicology has come from studies on the mussel genus, Mytilus, or from the American oyster, Crassostrea virginica. Following a major oil spill, it was observed that the marine mussel, Mytilus edulis, underwent significant immunosuppression but no oil-induced mortalities, while in contrast, mass mortalities were noted in the edible cockle, Cerastoderma edule, and the razor-shell, Ensis siliqua. A study comparing immune cells and functions in these three species was initiated (i) to assess whether M. edulis was a representative model species and (ii) to provide baseline data on immunity in two common species, which had previously received little or no attention in this respect. While all three species shared similar cell types, their lectin-binding and enzyme cytochemistry differed considerably. M. edulis had significantly different proportions of haemocytes binding with the lectins concanavalin A, wheatgerm agglutinin and Helix pomatia agglutinin and stained positive for eight enzymes, compared with only five in C. edule and three in E. siliqua. In terms of immune function, M. edulis haemocytes were much more active in phagocytosis and superoxide generation than haemocytes of the other two species. The results show that immune cells and functions differed extensively in these three closely related species, with M. edulis showing a much higher level of immunological vigour that may be linked to its considerable resilience to adverse environmental conditions. This suggests that M. edulis may not be particularly representative of the bivalves in terms of immune reactivity and that a wider range of species should be included in studies of molluscan immunotoxicology.  相似文献   

14.
Symbionts and abnormal conditions of razor clam Ensis arcuatus were surveyed in three commercially important natural beds of Galician estuaries (NW Spain). Samples of 15-20 E. arcuatus were collected every 2 months from January 2003 until July 2004 and processed for histological examination. Prokaryote-like colonies, renal coccidians, gregarines, Trichodina sp. ciliates, haplosporidian-like plasmodia, turbelaria, trematode metacercariae, cestode-like larvae and basophilic inclusion bodies were observed in razor clam tissues without causing host damage. Bucephalid digenean sporocysts and germinoma were seen in some samples causing moderate or severe damage to the host depending on the intensity of infection and both could be a cause for concern if prevalence reached epizootic levels in Galician E. arcuatus populations. None of the parasites detected is OIE notifiable and, in general, the commercially exploited beds studied seem to be devoid of serious pathogens.  相似文献   

15.
The feeding rate and behaviour of whelks (Buccinum undatum)offered cockles (Cerastoderma edule) in laboratory experimentswere examined. When presented with cockles in a range of sizes(10–40 mm), 14 B. undatum (34.6–88.3 mm),held individually in aquaria, consumed a wide size range ofcockles. Small whelks (<40 mm) consumed cockles (<23 mm),whereas large whelks, (>60 mm) ate a greater numberof larger cockles (>30 mm) and a wider size range ofcockles (12–40 mm) than smaller whelks. The majority(90%) of the shells of the predated cockles were undamaged andthe few (<10%) that were damaged showed only slight abrasionsto the anterior and posterior shell margin. Filmed observationsof B. undatum feeding on C. edule showed a method of attackthat has not previously been reported and involved the use ofthe whelk's foot to asphyxiate the cockle or to pull the shellvalves apart. No filmed evidence was found for the previouslyreported shell ‘wedging’ technique for prising openthe closed shell valves of C. edule, although 10% of the shellsof consumed cockles in feeding experiments had damaged shellmargins. (Received 4 April 2007; accepted 30 June 2007)  相似文献   

16.
During October 1977, phytoplankton iamples were collected alongwith other hydrographic and biological data from a grid of stationslocated off Galicia (NW of Spain), between the coast and about100 km offshore. Chlorophyll a distribution and phytoplanktoncomposition were studied and related to hydrographic and geographicfeatures of the area. The higher phytoplankton biomasses werefound off the western coast and were conditioned by the presenceof the rias - flooded tectonic valleys of moderate depth functioningas positive estuaries - and the occurrence of coastal upwelling,which allows the injection of nutrient rich water along thebottom of the rias. The qualitative composition of the phytoplanktonreflected principally the influence of the rias but appearedalso to show variability related to the distribution of watermasses. The patterns of circulation of the surface and sub-surfacewaters were likely to reinforce the phytoplankton differencesbetween the northern and western coasts of Galicia.  相似文献   

17.
Zooplankton composition and distribution off the coast of Galicia, Spain   总被引:3,自引:0,他引:3  
During June and September 1984, zooplankton samples were collectedwith other hydrographic and biological data along the Galiciancoast (NW of Spain). In June copepods contributed {small tilde}60%to the total zooplankton community, with larvaceans, siphonophoresand cladocerans also abundant. In September >90% of the zooplanktonsampled were copepods. The dominant species of copepods in bothJune and September were Acartia clausi, Paracalanus parvus andTemora longicornis. The meroplankton was dominated by echinoderms,bryozoans, barnacle larvae and bivalve larvae. In June the averagezooplankton biomass was 31.08 mg C m–3; the Septemberaverage was 41.69 mg C m–3. The relationship between theslopes of the regression equations (biomass versus abundance)suggests that the zooplankton assemblage in June was composedby larger animals than in September. The major concentrationof zooplankton was between 0 and 50 m, with both June and Septemberdaytime surface samples having 6–7 times the amount oforganisms than the lower water column (50–100 m). Therewere no distinct differences in total zooplankton abundancesat the inshore and offshore stations; however, the inshore stationsoften had a higher percentage of meroplankton than the offshorestations. In June zooplankton abundance at the northern transectsand the western transects was similar. In September there weregreater concentrations of zooplankton in the western Galicianshelf as compared with the northern shelf. These differencesin the horizontal distribution of the zooplankton were relatedto upwelling events.  相似文献   

18.
The role of marine currents in shaping population connectivity in the common cockle Cerastoderma edule was investigated in the southern Irish Sea. C. edule is one of the most valuable and exploited shellfish species in the area, yet very little is known about its population dynamics. In the present study, coupled hydrodynamic and particle tracking models are used in conjunction with genetic data collected at twelve microsatellite loci to estimate the influence of the Celtic Sea front on larval transport between the coasts of Britain and Ireland. Genetic analysis highlights the presence of at least three genetic clusters partitioned within locations, suggesting a contact zone between separate subpopulations. Samples collected from the Irish coast are most similar to each other. On the British coast, the Burry Inlet appears genetically isolated while samples collected from the coast of Pembrokeshire show evidence of connectivity between Britain and Ireland. These results agree with the model’s predictions: away from the coastal zone, residual baroclinic currents develop along tidal mixing fronts and act as conduit systems, transporting larvae great distances. Larvae spawned in south Wales are capable of travelling west towards Ireland due to the Celtic Sea front residual current, confirming the action of the Celtic Sea front on larval transport. Sheltered, flood-dominant estuaries such as the Burry Inlet promote self-recruitment. The validation of the model using genetic data represents progress towards a sustainable future for the common cockle, and paves the way for a more effective approach to management of all Irish Sea shellfisheries.  相似文献   

19.
The aim of the present study was to characterize and identify vibrios isolated from cultured clams in Galicia (NW Spain). A total of 759 isolates were obtained, phenotypically characterized, grouped and assigned to the genus Vibrio. Subsequently, the genomic diversity of 145 representative strains was analyzed by means of amplified fragment length polymorphism (AFLP), which revealed a high genetic diversity amongst these isolates. Only 57 out of 145 strains could be identified to the species level, and they were distributed in 13 AFLP clusters. V. cyclitrophicus, V. splendidus and V. alginolyticus were the most abundantly represented species. Eighty-eight isolates remained unidentified, 59 were distributed over 16 clusters, while 29 were unclustered. Sequencing of the 16S rRNA and two house-keeping genes (rpoA and recA) from representative strains belonging to eight unidentified clusters with the highest number of isolates confirmed their assignation to the Vibrionaceae family, and some of these probably represent new species within the genus. The present study confirmed that the phenotypic characterization of vibrios is not sufficient to identify them at the species level. A wide diversity of vibrios was found in cultured clams from all four geographic locations analyzed. In total, more than 12 Vibrio species and at least three potential new species in this genus were identified.  相似文献   

20.
We analysed 30 samples of Galician honey with the aim of quantifying and identifying the fungal spores contained in them. Using an optical microscope, we could identify 40 different types, among them Cladosporium, Penicillium/Aspergillus and the Basidiospores, which were identified in more than 80% of the samples. We calculated the relationship between fungal spores and amount of pollen grains in the samples. The maximum values were obtained in samples 21 (more than 208/100 grains of pollen) and 5 (153 spores/100 grains of pollen).  相似文献   

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