Search results for "Parasitism"
showing 10 items of 200 documents
Immunological and pathological status of gilthead sea bream (Sparus aurata L.) under different long-term feeding regimes
2003
The possible influence of the feeding regime (FR) on the immune system and pathological status of gilthead sea bream was studied. Two growth trials were performed starting at different seasons (trial 1 = March; trial 2 = June) under controlled experimental conditions. In both trials, FR-1 groups received a restricted amount of food, whereas FR-2 groups were fed to visual satiety. The pathology study included parasitological and bacteriological examination, and the immunological traits analysed were respiratory burst activity of head kidney leucocytes, serum lysozyme and alternative pathway complement activity (ACH50). The immunological status of gilthead sea bream not only was not impaired …
Positive density-dependent growth supports costs sharing hypothesis and population density sensing in a manipulative parasite.
2017
SUMMARYParasites manipulate their hosts’ phenotype to increase their own fitness. Like any evolutionary adaptation, parasitic manipulations should be costly. Though it is difficult to measure costs of the manipulation directly, they can be evaluated using an indirect approach. For instance, theory suggests that as the parasite infrapopulation grows, the investment of individual parasites in host manipulation decreases, because of cost sharing. Another assumption is that in environments where manipulation does not pay off for the parasite, it can decrease its investment in the manipulation to save resources. We experimentally infected rainbow trout Oncorhynchus mykiss with the immature larva…
Social interactions modulate the virulence of avian malaria infection
2013
There is an increasing understanding of the context-dependent nature of parasite virulence. Variation in parasite virulence can occur when infected individuals compete with conspecifics that vary in infection status; virulence may be higher when competing with uninfected competitors. In vertebrates with social hierarchies, we propose that these competition-mediated costs of infection may also vary with social status. Dominant individuals have greater competitive ability than competing subordinates, and consequently may pay a lower prevalence-mediated cost of infection. In this study we investigated whether costs of malarial infection were affected by the occurrence of the parasite in compet…
Effect of starvation on parasite-induced mortality in a freshwater snail (Potamopyrgus antipodarum).
1999
The level of host exploitation is expected, under theory, to be selected to maximise (subject to constraints) the lifetime reproductive success of the parasite. Here we studied the effect of two castrating trematode species on their intermediate snail host, Potamopyrgus antipodarum. One of the trematode species, Microphallus sp., encysts in the snail host and the encysted larvae “hatch” following ingestion of infected snails by birds. The other species, Notocotylus gippyensis, by contrast, releases swimming larvae; ingestion of the snail host is not required for, and does not aid, transmission to the final host. We isolated field-collected snails for 3 months in the laboratory, and followed…
Low parasitism rates in parthenogenetic bagworm moths do not support the parasitoid hypothesis for sex
2012
The parasite hypothesis for sex is one of the many theories that have been suggested to solve the mystery of the widespread occurrence of sex despite its high short-term costs. It suggests that sexual lineages have an evolutionary advantage over parthenogens because they can frequently generate new genotypes that are temporarily less prone to coevolving parasites. In this study, we looked for further supporting evidence for the parasite hypothesis of sex in an attempt to understand the coexistence of sexual and parthenogenetic bagworm moths (Naryciinae). The bagworm moths and their parasitoids form one of the few natural host-parasite systems where sexual and parthenogenetic hosts are appar…
High Temperatures Result in Smaller Nurseries which Lower Reproduction of Pollinators and Parasites in a Brood Site Pollination Mutualism
2014
In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the…
Parasites in sympatric populations of native and invasive freshwater bivalves
2021
An increasing threat to local, native freshwater mussels (Unionida)—an ecologically important but globally alarmingly declining group— is the invasion by exotic bivalves. The Enemy Release Hypothesis predicts that introduced species should benefit from enemy-mediated competition because they are less likely to be harmed by natural enemies, such as parasites, than their native competitors. We investigated within-site differences in parasitism between sympatric native (tot. five spp.) and invasive (tot. three spp.) bivalves in eight northern European waterbodies, which harboured totally 15 parasite taxa. In paired comparisons using within-site averages, the mean number of parasite species in …
The effects of parasites on male ornaments and female choice in the lek-breeding black grouse (Tetrao tetrix)
1992
We describe the results of two studies of parasitic infection in the black grouse (Tetrao tetrix). The first deals with our own observations of lekking black grouse in which the parasite levels of two blood parasites, the protozoan Leucocytozoon lovati and microfilaria, probably produced by a nematode worm Splendidofilaria tuvensis, were scored. We also obtained measures of age, survival, number of copulations, body mass and length of the ornamental tail feathers (the lyre) of the lekking males. The second study analysed the data from Lund (1954) which involved eight gut parasites obtained from birds which were killed. In the first study we found higher levels of infection of Leucocytozoon …
Parasitism and queen presence interactively shape worker behaviour and fertility in an ant host
2019
Parasites with complex life cycles regularly alter host traits in their own interest. In social hosts, phenotypic alterations induced by parasites can also affect uninfected group members. The tapeworm Anomotaenia brevis uses Temnothorax nylanderi ants as intermediate hosts, reducing host activity and behavioural repertoire, but increasing life span. Uninfected nestmates are less active and less aggressive and suffer from higher mortality. Next to parasites, the social environment, such as the queen, influences worker behaviour, reproduction and longevity. Here, we studied how tapeworm parasitism interacts with the queen to affect the behaviour and reproductive potential of ant workers. We …
Dactylogyrids on the gills of roach in central Finland: Features of infection and species composition
1991
Monogenean parasites were examined from the gills of 660 roach (Rutilus rutilus) in four interconnected lakes in Central Finland between February and November 1986 and in three of the same lakes between February and December 1988. One of the lakes is eutrophic and polluted due to a paper and pulp mill, one is oligotrophic and in a natural state, and the other two lakes are eutrophic. The prevalence of Dactylogyrus infection was always high. Differences between the lakes and the years were observed in the intensity of infection, which was significantly higher in the polluted lake. The intensity was also higher in older fish. Nine Dactylogyrus species were found, and of these D. crucifer and …