Search results for "fish diseases"
showing 10 items of 232 documents
Host searching in Argulus foliaceus L. (Crustacea: Branchiura): the role of vision and selectivity.
1998
In laboratory experiments, the swimming behaviour of the ectoparasite Argulus foliaceus and its infection rates on juvenile perch (Perca fluviatilis) and roach (Rutilus rutilus) were examined. The highest infection rate and a preference for perch juveniles were obtained in darkness, the lowest infection rate and a lack of preference in the light, when aquaria with glass walls (high reflectivity) were used. In the light, when aquaria were lined with black plastic (low reflectivity) an intermediate level of infection for perch and the highest for roach was recorded. Under such conditions roach were significantly more heavily infected than perch; an attack rate 4 times greater was recorded for…
Perch (Perca fluviatilis L.) parasites reflect ecosystem conditions: a comparison of a natural lake and two acidic reservoirs in Finland.
2000
Parasite communities of perch were studied in a natural lake (Vetamajarvi) and two reservoirs (the Kyrkosjarvi and Liikapuro reservoirs) located in Western Finland. All water bodies studied are small, shallow and humic. However, the reservoirs are more acidic than the lake (pH 5.9 and 5.3 vs. 6.4). Altogether, 18 parasite species were found, but the component communities were reduced in the harsh conditions of the reservoirs (12 and six species) as compared with the lake (17 species). In addition, the mean number of metazoan parasite specimens per fish was markedly lower in the reservoirs (64.3 and 14.3 specimens) than in the lake (116.1 specimens). Our prediction on the depauperation of pa…
Bacteriophage Resistance Affects Flavobacterium columnare Virulence Partly via Mutations in Genes Related to Gliding Motility and the Type IX Secreti…
2021
Increasing problems with antibiotic resistance have directed interest toward phage therapy in the aquaculture industry. However, phage resistance evolving in target bacteria is considered a challenge. To investigate how phage resistance influences the fish pathogen Flavobacterium columnare, two wild-type bacterial isolates, FCO-F2 and FCO-F9, were exposed to phages (FCO-F2 to FCOV-F2, FCOV-F5, and FCOV-F25, and FCO-F9 to FCL-2, FCOV-F13, and FCOV-F45), and resulting phenotypic and genetic changes in bacteria were analyzed. Bacterial viability first decreased in the exposure cultures but started to increase after 1 to 2 days, along with a change in colony morphology from original rhizoid to …
Phage Specificity of the Freshwater Fish Pathogen Flavobacterium columnare
2011
ABSTRACT Flavobacteria and their phages were isolated from Finnish freshwaters and fish farms. Emphasis was placed on finding phages infecting the fish pathogen Flavobacterium columnare for use as phage therapy agents. The host ranges of the flavobacterial phages varied, phages infecting F. columnare being more host specific than the other phages.
Between-population Similarity in Intestinal Parasite Community Structure of Pike (Esox Lucius)—Effects of Distance and Historical Connections
2009
The effect of geographical distance on similarity in parasite communities of freshwater fish has received considerable attention in recent years, and it has become evident that these apparently simple relationships are influenced by, among other things, colonization ability of parasites and degree of connectivity between the populations. In the present paper, we explored qualitative and quantitative similarity in the intestinal parasite communities of pike (Esox lucius) in a particular system where previously interconnected groups of lakes became isolated ca. 8,400 yr ago. Contrary to our expectations, we did not find differences in similarity between the lake groups or a negative effect of…
Random forests, a novel approach for discrimination of fish populations using parasites as biological tags.
2008
Due to the complexity of host-parasite relationships, discrimination between fish populations using parasites as biological tags is difficult. This study introduces, to our knowledge for the first time, random forests (RF) as a new modelling technique in the application of parasite community data as biological markers for population assignment of fish. This novel approach is applied to a dataset with a complex structure comprising 763 parasite infracommunities in population samples of Atlantic cod, Gadus morhua, from the spawning/feeding areas in five regions in the North East Atlantic (Baltic, Celtic, Irish and North seas and Icelandic waters). The learning behaviour of RF is evaluated in …
Association of colony morphotypes with virulence, growth and resistance against protozoan predation in the fish pathogen Flavobacterium columnare.
2014
Many opportunistic pathogens can alternate between inside- and outside-host environments during their life cycle. The opportunistic fish pathogen Flavobacterium columnare is an inhabitant of the natural microbial community and causes significant yearly losses in aquaculture worldwide. The bacterium grows in varying colony morphotypes that are associated with either virulence (rhizoid type) or resistance to starvation and phages (rough type). Rough type strains can arise spontaneously or can be induced by phage infection. To identify the determinants of morphotype fitness, we measured virulence, growth parameters, biofilm-forming ability and resistance to amoeba and ciliate predation of both…
Digenean parasites of the bivalve mollusc Pisidium amnicum in a small river in eastern Finland
1998
The host-parasite relationship between digeneans and a semelparous population of the mollusc. Pisidium amnicum Müller in a small river in eastern Finland was studied during 1992/1993. The parasite prevalence of the population was high. The total prevalence was 45.6% in 1992 (n = 790) and 47.5% in 1993 (n = 160). The dominant digenean, Bunodera luciopercae (34.2% in 1992, 35.0% in 1993), had highest prevalences in July/August and in winter. Two other species, Palaeorchis crassus (7.8% in 1992, 7.5% in 1993) and Phyllodistomum elongatum (4.7% and 5.0%), were rare during the winter. The prevalence of B. luciopercae increased as clams aged, while the other species were most common in middle-siz…
Phenotypic variation in infectivity of Diplostomum spathaceum cercariae within a population.
2007
The present study examined phenotypic variation in infectivity of Diplostomum spathaceum (Trematoda) cercariae within a natural population. Twelve infected Lymnaea stagnalis were collected from the field, and the infectivity of cercariae from individual snails was assessed under constant laboratory conditions. At a water temperature of 16.3 C, the mean infectivity of cercariae from the snails varied between 55.5% and 87.5%. Depending on the source of variation, this may have important ecological and evolutionary implications for both natural parasite populations and those occurring in aquaculture.
Immune depression induced by acanthocephalan parasites in their intermediate crustacean host: consequences for the risk of super-infection and links …
2009
9 pages; International audience; Parasite survival in hosts mainly depends on the capacity to circumvent the host immune response. Acanthocephalan infections in gammarids are linked with decreased activity of the prophenoloxidase (ProPO) system, suggesting an active immunosuppression process. Nevertheless, experimental evidence for this hypothesis is lacking: whether these parasites affect several immune pathways is unknown and the consequences of such immune change have not been investigated. In particular, the consequences for other pathogens are not known; neither are the links with other parasite-induced manipulations of the host. Firstly, using experimental infections of Pomphorhynchus…