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We introduce logistic regression procedure and explain how it can be applied for classification of species. This technique is more useful than traditionally used linear discriminant analysis since it does not require multivariate normality in populations being classified. Finally, the proposed approach is illustrated by an example of classification of four species of metacercariae of Diplosomum.
The views on the ways of migration of Diplostomum cercaria from body surface to fish eyeball, among them about the ways of parasites dislocation through the tissues, beginning from the penetration to host body - was presented. The hypothesis on passive in-coming transport of cercaria by the circulatory system of fish was questioned; on the other hand it has been argued active penetration of parasites through tissues, according to the hypothesis of cercaria migration stimulated by the respective concentration of carbonate anhydrasis in host. It has been stated that migrations of cercaria to fish eyeball may be different depending on the penetrations place of parasite on body host.
The objective of the experiment was to compare the growth rate in two groups of Siberian sturgeon fry, one of which was infested with metacercariae of Diplostomum, the infestation degree was from 1 to 160/fish. The fish fed on natural as well as artificial food; the latter was given at the rate sufficient to cover 50% of the fish requirements. The average initial body weight in the control group was 16.8 ± 1.9g, and in the group with Diplostomum - 28.4 ± 3.6 g. During the period of favorable temperatures, viz. for about 90 days, the fry was showed satisfactory growth, but the growth rate becaine inhibited as the temperatures decreased to below 12°C, so that throughout the wintering period the fish weight decreased by some 10%. Fish from the control group showed a higher growth rate than the infested ones, and by the end of the experiment the controls weighted 7.5% more than the infested group in spite of their lower initial weight.
The identification of many Diplostomum species is difficult due to their high morphological similarity. For six species: D. spathaceum, D. parviventosum, D. mergi, D. paracaudum, D. pseudospathaceum and D. baeri phylogenetic analyses based on morphological data and sequences of ITS1 region of the rDNA were conducted. It was demonstrated that the phylogenetic trees obtained for morphological data at cercarial, metacercarial and adult stages, as well as all characters together differ in branch topology from one another. Molecular data support the composition of species in two clusters (D. spathaceum, D. parviventosum, D. mergi and D. paracaudum, D. pseudospathaceum) with D. baeri outside these clusters. The phylogenetic tree derived from the molecular data is most similar to that based on cercarial characters. No differences were observed among sequences of D. spathaceum and D. parviventosum. The comparative analysis of the molecular and morphology-based phylogenies is given.
Siberian sturgeon fry coming from three different ponds has been examined. 1. „Dgał" - fish culture conerete-terrestrial pond beloning to D.O.Z. Dgał Inland Fisheries Institute in Olsztyn supplied with fresh water from Great Dgał Lake; 2. ,,Grzmięca" - fish culture pond terrestrial, natural belonging to fishing farm Grzmięca near Brodnica; 3. ,,Konin" - fish culture pond near Konin supplied with water utilized by near beat and power generating plant. Total of 80 sturgeons fry with parameters: length 17.5 cm - 38.5 cm, weight 21 g- 134 g, age O⁺ ,1⁺ has been examined. The examinated group of sturgenos had metacercariae Diplostomum sp. in their lenses. Prevalence of infection of sturgeon with metacercariae Diplostomum sp. was high in all this three ponds. Intensity of infection was also high in ponds „Dgał" and „Grzmięca", but low in ,,Konin". In ponds ,,Dgał" and ,,Konin" we have obtained high positive correlation (,,Dgał" - r = 0,606, p ≤ 0,05; ,,Konin" - r = 0,743, p ≤ 0,01) between number of metacercariae in sturgeon and temperature of water. Our study confirmed observations other authors susceptibility sturgeon fry on the Diplostomum sp. invasion.
Seasonal changes in prevalence and mean intensity of several parasite species representing four systematic classes, and occurring in four herbivorous fish (common, grass, silver and big head carp) in pond culture were analysed. Frequency of metacercariae of Diplostomum sp. appeared not to be dependent on the season of the year. The seasonal occurrence patterns of two cestode species, Khawia sinensis and Bothrio-cephalus acheilognathi, are described with regard to the process of recruitment of larvae by fish, their maturation and removal of old specimens from fish. Two species of Crustacea (Ergasilus sieboldi and Argulus foliaceus) and two species of Hirudinea (Piscicola geometra and P. pojmanskae) appeared to be most frequent on fish in autumn.
Background. Aparasitological survey was carried out in a shallow, eutrophic Oświn Lake (north-eastern Poland), within the Seven Islands ornithological reserve. We intended to compare the occurrence of eyeflukes in fish from two, distinctly demarcated pools of the lake, differing in environmental conditions. The effect of fish size and sampling season on the infection parameters was analysed and the present state of the parasite faunas was compared to the literature data. Materials and Methods. Within 1998 and 1999, a total of 1091 fishes representing 8 dominant species was examined. Samples were collected four times a year (in May, July, August, and October) simultaneously from the eastern- and western parts of the lake. Results. Diplostomum spp. occurred in all the fish examined, numerously in roach, rudd, white bream, and carp bream. The parasite was less abundant in northern pike, crucian carp, and European perch. Tylodelphys clavata was found in roach and it sporadically occurred in northern pike, rudd, white bream, carp bream, and European perch. The infection rates of rudd and white bream in the eastern part of the lake were significantly higher than the respective values from the western part. The infection with both eyeflukes did not correlate with the fish length. The infection of roach, rudd, white bream, and carp bream with Diplostomum spp. and roach with T. clavata varied significantly in different experimental periods. Conclusion. The eyeflukes as well as P. cuticola were sensitive indicators, reflecting the environmental pressure-both, spatial differences in ecological conditions within the same water body and long-term alterations. Diplostomum spp. did not accumulate with the age of fish. No seasonality was found for Diplostomum spp. or Tylodelphys clavata. Locationdependent occurrence of Diplostomum spp. in rudd and white bream indicated a limited fish interchange between the two pools of the lake.
Throughout 3 years, a total of 721 various fish species, from the Łebsko Lagoon were examined. The most abundant groups of parasites were Digenea and Crustacea. Metacercariae of Posthodiplostomum cuticola (Nordmann, 1832) were found only in Cyprinidae (highest prevalence in rudd – 62.5%, and mean intensity in roach 12.71 indiv.). Metacercariae of Diplostomum spp. and Tylodelphys clavata (Nordmann, 1832), and also copepods Ergasilus sieboldi Nordmann, 1832 occurred in majority of examined fish species. The highest infection with Diplostomum spp. was noted in rudd (prev. 50.0%, int. 11.25 indiv.). T. clavata occurred with highest prevalence in pike (46.15%) and mean intensity amounted to 54.7 indiv. in perch. E. sieboldi was reported mostly from zander with typical for this fish Achtheres percarum (Nordmann, 1832) (prev. 75.0% and 92.86%; int. 6.0 indiv. and 10.92 indiv. respectively). Also nematode Anguillicola crassus (Kuwahara, Niimi and Hagaki, 1974) was noted with high prevalence 76.47% in eel. The remaining parasites species were noted less frequently.
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