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1.
Salinity levels vary spatially in coastal areas, depending on proximity to freshwater sources, and may also be slowly decreasing
as a result of anthropogenic climatic changes. The impact of salinity on host–parasite interactions is potentially a key regulator
of transmission processes in intertidal areas, where trematodes are extremely common parasites of invertebrates and vertebrates.
We investigated experimentally the effects of long-term exposure to decreased salinity levels on output of infective stages
(cercariae) and their transmission success in the trematode Philophthalmus sp. This parasite uses the snail Zeacumantus subcarinatus as intermediate host, in which it asexually produces cercariae. After leaving the snail, cercariae encyst externally on hard
substrates to await accidental ingestion by shorebirds, which serve as definitive hosts. We found that at reduced salinities
(25 or 30 psu), the cercarial output of the parasite was lower, the time taken by cercariae to encyst was longer, fewer cercariae
successfully encysted and encysted parasites had lower long-term survival than at normal seawater salinity (35 psu). The strong
effect of salinity on the replication and transmission of this parasite suggests that there may be sources and sinks of transmission
to birds along coastal areas, depending on local salinity conditions. Also, unless it evolves to adapt to changing conditions,
the predicted reduction in salinity as a consequence of climate change may have negative impact on the parasite’s abundance. 相似文献
2.
Jukka Kekäläinen Yi-Te Lai Anssi Vainikka Ilkka Sirkka Raine Kortet 《Behavioral ecology and sociobiology》2014,68(2):197-204
Despite that the existence of animal personalities is widely recognized, no consensus has been reached on the relative importance of different ecological factors behind their expression. Recently, it has been suggested that parasites may have a crucial role in shaping animal personalities, but only a very few studies have experimentally tested the idea. We infected Eurasian minnows (Phoxinus phoxinus) with the brain-encysted trematode parasite, Diplostomum phoxini, and studied whether infection could modify the personality of their hosts. Our results show that D. phoxini infection did not affect the mean levels of boldness, activity or exploration, but infected minnows showed higher repeatability in boldness and activity, and reduced repeatability in exploration. We also found that D. phoxini may be able to break the associations (behavioral syndromes) between behavioral traits, but that this effect may be dependent on parasite intensity. Furthermore, the effect of D. phoxini infection on personality of the hosts was found to be nonlinearly dependent on infection intensity. Taken together, our results suggest that D. phoxini parasites may shape the personality of their hosts, but that behavioral consequences of ecologically relevant infection levels may be rather subtle and easily remain undetected if only the mean trait expressions are compared. 相似文献
3.
In this study we examined how the variation in the distribution of six species of seabird trematodes was influenced by human
activities along the subarctic Barents Sea coast of northern Norway. This was done by comparing the prevalence of the parasites
in two species of intermediate host (Littorinasaxatilis and Littorina obtusata) on seashores near fishing industry complexes, fish farms and at control sites. In L. saxatilis there were higher prevalences at sites influenced by human activities for three out of five trematode species (Microphallus piriformes, M. similis, Cryptocotyle lingua) which have gulls (Larus spp.) as their predominant final hosts, while in L. obtusata, only M. similis was more common at sites with human activity. For M. pygmaeus, a trematode which has the common eider (Somateria mollissima) as its most predominant final host, the prevalence in L.␣saxatilis tended to be higher at sites with fishing industry, but differences were not significant. No such tendency was found in L. obtusata for this trematode. The overall prevalence in L. obtusata was lower than in L.␣saxatilis. This indicates that the vulnerability to trematode infection differs between the two snail species depending on the variation
in the distribution patterns in the intertidal zone. Gulls tend to concentrate in areas near fishing industry and fish farms
to feed on fish offal, which leads to an increase in the transmission between hosts, and to a higher level of parasite infection,
locally.
Received: 4 May 1998 / Accepted: 18 October 1998 相似文献
4.
Local adaptation of immunity against a trematode parasite in marine amphipod populations 总被引:1,自引:0,他引:1
Resources allocated to defence against parasites are not available for investment in other functions such as growth or reproduction,
resulting in trade-offs between different components of an organism’s fitness. In balancing the cost of infection and the
cost of immunity, selection should only favour individuals that allocate more energy to resistance and immune responses in
populations regularly exposed to debilitating parasites. Here, we compare the ability of amphipods, Paracalliope novizealandiae, to (1) avoid becoming infected and (2) to respond to infection by encapsulating and melanizing parasites, between two natural
populations exposed to different risk of parasitism. One population faces high levels of infection by the debilitating trematode
parasite Maritrema novaezealandensis, whereas the other population is not parasitised by this trematode nor by any other parasite. Under controlled experimental
conditions, with exposure to a standardized dose of parasites, amphipods from the parasite-free population acquired significantly
more parasites than those from the population regularly experiencing infection. Furthermore, a lower frequency of amphipods
from the parasite-free population succeeded at melanizing (and thus killing) parasites, and they melanized a lower percentage
of parasites on average, than amphipods from the parasitised population. These differences persist when individual factors,
such as amphipod sex or body length, are taken into account as potential confounding variables. These results support the
existence of local adaptation against parasites: an amphipod population that never experiences trematode infections is less
capable of resisting infection, both in terms of its first line of defence (avoiding infection) and a later line of defence
(fighting parasites following infection), than a population regularly exposed to infection. 相似文献
5.
Kathleen L Whitney Ryan F Hechinger Armand M Kuris Kevin D Lafferty 《Ecological applications》2007,17(6):1694-1702
An extinction necessarily affects community members that have obligate relationships with the extinct species. Indirect or cascading effects can lead to even broader changes at the community or ecosystem level. However, it is not clear whether generalist parasites should be affected by the extinction of one of their hosts. We tested the prediction that loss of a host species could affect the structure of a generalist parasite community by investigating the role of endangered Light-footed Clapper Rails (Rallus longirostris levipes) in structuring trematode communities in four tidal wetlands in southern California, U.S.A. (Carpinteria Salt Marsh, Mugu Lagoon) and Mexico (Estero de Punta Banda, Bahia Falsa-San Quintin). We used larval trematode parasites in first intermediate host snails (Cerithidea californica) as windows into the adult trematodes that parasitize Clapper Rails. Within and among wetlands, we found positive associations between Clapper Rails and four trematode species, particularly in the vegetated marsh habitat where Clapper Rails typically occur. This suggests that further loss of Clapper Rails is likely to affect the abundance of several competitively dominant trematode species in wetlands with California horn snails, with possible indirect effects on the trematode community and changes in the impacts of these parasites on fishes and invertebrates. 相似文献
6.
Parasite transmission in complex communities: predators and alternative hosts alter pathogenic infections in amphibians 总被引:1,自引:0,他引:1
While often studied in isolation, host-parasite interactions are typically embedded within complex communities. Other community members, including predators and alternative hosts, can therefore alter parasite transmission (e.g., the dilution effect), yet few studies have experimentally evaluated more than one such mechanism. Here, we used data from natural wetlands to design experiments investigating how alternative hosts and predators of parasites mediate trematode (Ribeiroia ondatrae) infection in a focal amphibian host (Pseudacris regilla). In short-term predation bioassays involving mollusks, zooplankton, fish, larval insects, or newts, four of seven tested species removed 62-93% of infectious stages. In transmission experiments, damselfly nymphs (predators) and newt larvae (alternative hosts) reduced infection in P. regilla tadpoles by -50%, whereas mosquitofish (potential predators and alternative hosts) did not significantly influence transmission. Additional bioassays indicated that predators consumed parasites even in the presence of alternative prey. In natural wetlands, newts had similar infection intensities as P. regilla, suggesting that they commonly function as alternative hosts despite their unpalatability to downstream hosts, whereas mosquitofish had substantially lower infection intensities and are unlikely to function as hosts. These results underscore the importance of studying host-parasite interactions in complex communities and of broadly linking research on predation, biodiversity loss, and infectious diseases. 相似文献
7.
Lisa E. Schwanz 《Behavioral ecology and sociobiology》2008,62(8):1351-1358
Parasitized animals may alter their life histories to minimize the costs of parasitism. Organisms are predicted to decrease
investment in current reproduction when parasitism has the greatest impact on current reproductive ability. In contrast, if
parasitism decreases residual reproductive value, hosts should increase current reproductive investment, referred to as fecundity
compensation or terminal investment. In mammalian hosts, parasitic infection most often leads to reductions in current host
reproduction, perhaps attributable to the emphasis on parasites that are unlikely to impact the host’s residual reproductive
value. In this study, the life history response of a rodent, Peromyscus maniculatus, to infection with a parasite that should strongly impact the residual reproductive value of its host (Schistosomatium douthitti, Trematoda) was examined. Infection decreased survival for hosts exposed to a high dose of parasites and was chronic in survivors,
confirming that infection had strong impacts for the residual reproductive value of the host. As predicted, infected mice
increased their reproductive output, producing litters of greater mass due to heavier offspring. However, this increased output
was observed after a greater delay to begin breeding in infected mice and was not observed in animals that suffered early
mortality. The deer mouse S. douthitti system may provide a rare example of fecundity compensation in mammals. 相似文献
8.
Social nesting behaviour is commonly associated with high prevalence and intensity of parasites in intraspecific comparisons.
Little is known about the effects of interspecific host breeding density for parasite intensity in generalist host–parasite
systems. Darwin’s small tree finch (Camarhynchus parvulus) on Santa Cruz Island, Galápagos Islands, nests in both heterospecific aggregations and at solitary sites. All Darwin finch
species on Santa Cruz Island are infested with larvae of the invasive blood-sucking fly Philornis downsi. In this study, we test the prediction that total P. downsi intensity (the number of parasites per nest) is higher for nests in heterospecific aggregations than at solitary nests. We
also examine variation in P. downsi intensity in relation to three predictor variables: (1) nest size, (2) nest bottom thickness and (3) host adult body mass,
both within and across finch species. The results show that (1) total P. downsi intensity was significantly higher for small tree finch nests with many close neighbours; (2) finches with increased adult
body mass built larger nests (inter- and intraspecific comparison); (3) parasite intensity increased significantly with nest
size across species and in the small tree finch alone; and (4) nest bottom thickness did not vary with nest size or parasite
intensity. These results provide evidence for an interaction between social nesting behaviour, nest characteristics and host
mass that influences the distribution and potential impact of mobile ectoparasites in birds. 相似文献
9.
V. Øresland 《Marine Biology》1986,92(1):87-91
The temporal occurrence of parasites in Sagitta setosa J. Müller, caught one to three times a month during 1982 and 1983 off Plymouth, England, was investigated. S. setosa was infected by eight parasitic species: one nematode, five trematodes, one cestode and, possibly, one protozoon. Infection by a single parasite, normally found in the body coelom, was the rule. The nematode Hysterothylacium aduncum, as III-stage larva, was by far the most common parasite (56% of all parasites found), followed by the metacercariae of three non-encysted trematodes: Derogenes varicus, a didymozoid species and a Lecithochirium species. Two trematode species new to Chaetognatha were found. The percentage of infected S. setosa specimens ranged from 0 to 7%. Absence or low numbers of parasites from June to November were correlated to the disappearance of large S. setosa and the appearance of a new S. setosa generation. Trematodes may show great annual and seasonal differences in occurrence in S. setosa. No injuries due to parasites were seen. The reproduction of the S. setosa populations off Plymouth did not seem to be affected by parasite infections during 1982–1983. 相似文献
10.
Frédéric Thomas Jérôme Fauchier Kevin D. Lafferty 《Behavioral ecology and sociobiology》2002,51(3):296-301
Microphallus papillorobustus is a manipulative trematode that induces strong behavioural alterations in the gamaridean amphipod Gammarus insensibilis, making the amphipod more vulnerable to predation by aquatic birds (definitive hosts). Conversely, the sympatric nematode Gammarinema gammari uses Gammarus insensibilis as a habitat and a source of nutrition. We investigated the conflict of interest between these two parasite species by studying the consequences of mixed infection on amphipod behaviour associated with the trematode. In the field, some amphipods infected by the trematode did not display the altered behaviour. These normal amphipods also had more nematodes, suggesting that the nematode overpowered the manipulation of the trematode, a strategy that would prolong the nematode's life. We hypothesize that sabotage of the trematode by the nematode would be an adaptive strategy for the nematode consistent with recent speculation about co-operation and conflict in manipulative parasites. A behavioural test conducted in the laboratory from naturally infected amphipods yielded the same result. However, exposing amphipods to nematodes did not negate or decrease the manipulation exerted by the trematode. Similarly, experimental elimination of nematodes from amphipods did not permit trematodes to manipulate behaviour. These experimental data do not support the hypothesis that the negative association between nematodes and manipulation by the trematode is a result of the "sabotage" hypothesis. 相似文献
11.
Louis Ranjard Michael G. Anderson Matt J. Rayner Robert B. Payne Ian McLean James V. Briskie Howard A. Ross Dianne H. Brunton Sarah M. N. Woolley Mark E. Hauber 《Behavioral ecology and sociobiology》2010,64(11):1915-1926
A variety of bioacoustics distance metrics have been used to assess similarities in the vocalizations of different individuals.
Here, we provide a detailed analysis of several acoustic similarity indices, some of which have been developed with the specific
aim of characterizing the sensory coding of auditory stimuli. We compare different approaches through the analysis of begging
calls of several passerine species and specialist brood parasitic cuckoos that putatively evolved to mimic their hosts. The
different bioacoustics distances did not provide consistently correlated similarity patterns, implying that they are sensitive
to different sound features. However, the encoded spectrogram alignment method was correlated with all other acoustic distance
metrics, suggesting that this method provides a consistent approach to use when the perceptually salient sound parameters
are unknown for a particular species. Our analyses confirm that statistical similarity of begging calls can be detected in
a New Zealand pair of host and specialist parasite species. We also show detectable similarity in two other Australasian host–parasite
pairs and another New Zealand system, but to a more limited extent. By examining phylogenetic patterns in the begging call
diversity, we also confirm that specialist cuckoos have evolved to mimic the begging calls of their hosts but host species
have not co-evolved to modify their calls in response to begging call similarity by the parasite. Our results illustrate that
understanding the function and mechanism of behavioral copying and mimicry requires statistically consistent measures of similarity
that are related to both the physical aspects of the particular display and the sensory basis of its perception. 相似文献
12.
Parasite assemblages are increasingly being used as indicators of their hosts’ biology and ecology, especially for economically important marine species such as the Soleidae. In this study, seven species inhabiting Portuguese coastal waters were examined for external and internal macroparasite infections using standard procedures: Dicologlossa cuneata, Microchirus azevia, Microchirus variegatus, Solea lascaris, Solea senegalensis, Solea solea and Synaptura lusitanica. Despite being closely related, these species present different life history patterns and ecological preferences which were expected to be mirrored by their macroparasite assemblages. The aim of the study was, therefore, to study the variation of these assemblages, within and between host species, along the Portuguese coast in order to evaluate the importance of the hosts’ features and environmental factors in the assemblage compositions. Flatfish were obtained seasonally from commercial fishing vessels operating in three areas (northern, central and southern) along the Portuguese coast. Prevalence and mean abundance were calculated and tested for differences between host sex, areas and seasons. The host specificity index and the importance of the host–parasite relationship were computed based on mean abundance. The total number of parasite individuals, species richness, total prevalence, total mean abundance, diversity and evenness were also calculated. A canonical correspondence analysis (CCA) was performed using prevalence and mean abundance data. A total of 44 macroparasite species were found. No significant differences were observed in prevalence and mean abundance between sexes and sampling seasons but, for three of the parasite species, significant differences were found between areas. The highest values of the parasitological and ecological indices were generally registered in the hosts S. lascaris and S. senegalensis and in the southern area. The CCA using the prevalence data revealed the differentiation of S. lascaris samples, which was mainly related to the total prevalence and to the number of important species of macroparasites. When using mean abundance data, the CCA revealed the differentiation of D. cuneata from the south, S. lascaris from the three areas and S. senegalensis from the south, mainly related to total prevalence and richness. The differences found between infection levels and assemblages’ composition were mainly due to differences in hosts’ diet, namely prey type consumption, given that most macroparasites found were transmitted through the food web. However, environmental factors were also important given that they regulate the distribution of ectoparasites and the availability of prey, and therefore the infections’ pattern. These findings were in agreement with the ones from similar studies performed in other species, revealing the importance of parasites as indicators of their hosts’ ecology. 相似文献
13.
Intensive and incessant arms races between a parasite and its host are generally expected to lead to parasite specialization. Nevertheless, some parasitic species still successfully attack wide spectra of hosts. One of the solutions to the evolutionary enigma of the long-term existence of generalist parasites is their specialization at an individual level, a phenomenon well known, e.g., in European common cuckoo. Over its range, it parasitizes a number of bird species; however, individual females are mostly specialists possessing adaptations to a particular host species. In this study, we test the possibility of individual specialization in generalist cuckoo bees, the insect counterparts of avian cuckoos. Females of cuckoo bees lay each egg into a single brood cell in the nests of other bee species. The host’s offspring is destroyed by the parasitic female or later by her larvae, which feed on pollen supplies accumulated by the host. Both studied cleptoparasitic bees (Sphecodes ephippius and Sphecodes monilicornis) are widely distributed in Europe, where they have been reported to use broad host spectra. We recorded several host species (including some previously unknown) for both cuckoo bee species, and confirmed that these parasites are indeed generalist even at a small local scale. However, we demonstrate that exactly as in the avian cuckoos, each female in both species of generalist bee parasites tends to attack just one host species. 相似文献
14.
Hamilton and Zuk (Science 218:384–387, 1982) supported their influential hypothesis of parasite-mediated sexual selection based on a positive interspecific correlation
between the prevalence of blood parasites and the expression of male displays in birds. However, subsequent studies provided
mixed support for this relationship after considering several confounding factors. Here, we revisit this fundamental prediction
by refining the analyses through implementation of recent methodological advancements. First, we distinguish between prevalence
data obtained through microscopic and molecular tools, as PCR-based detection methods may be more sensitive for detecting
infection. Second, we use quantitative estimates of both acoustic and visual signals of males, in which color measurements
adopt the perspective of avian vision. Third, applying modern phylogenetic comparative approaches, we correct for phylogenetic
inertia as well as heterogeneity in sampling effort. Fourth, we distinguish between prevalence transition states, as we compare
species with and without evidence of infection and also monitor changes in parasite prevalence only in species in which blood
parasites are detected. We show that given the considerable variation among populations, the repeatability of prevalence at
the within-species level is modest. We failed to detect a strong interspecific relationship between the prevalence of blood
parasites and sexual traits. However, we found that an evolutionary increase from zero to non-zero prevalence is likely to
be accompanied by an increase in trait expression in males, but further increase from non-zero prevalence to a higher level
of infection tends to be associated with a reduced degree of trait elaboration. Our results provide some support to the Hamilton
and Zuk hypothesis, but the relationship between blood parasites and male displays varies among traits depending on degree
of infection. 相似文献
15.
Bruce Lyon 《Behavioral ecology and sociobiology》2007,61(3):455-463
Hosts of avian brood parasites use a variety of defenses based on egg recognition to reduce the costs of parasitism; the most important of which is rejecting the parasitic eggs. Two basic recognition mechanisms are possible: “true recognition”, whereby hosts recognize their own eggs irrespective of their relative frequency in the clutch, and minority recognition (or “recognition by discordancy”), whereby hosts respond to the minority egg type. The mechanism of recognition has been experimentally studied in a handful of species parasitized by interspecific brood parasites, but the mechanism used in defenses against conspecific brood parasitism is unknown. I experimentally determined the mechanism of egg recognition in American coots (Fulica americana), a species with high levels of conspecific brood parasitism, egg recognition, and rejection. I swapped eggs between pairs of nests to alter frequencies of host and “parasite” eggs and then used two criteria for recognition: egg rejection and nonrandom incubation positions in the clutch. Eight of 12 nests (66%) given equal frequencies of host and parasite eggs showed evidence of true recognition. In contrast, only one of eight (12.5%) nests where host eggs were in the minority showed evidence of recognition by discordancy. The nonrandom incubation positions of parasitic eggs indicates that birds sometimes recognize parasitic eggs without rejecting them and provides a means of assessing recognition on a per nest basis in species with large clutches. Adaptive recognition without rejection may also be an important evolutionary stepping stone to the evolution of egg rejection in some taxa. 相似文献
16.
Extreme events associated with global change will impose increasing stress on coastal organisms. How strong biological interactions
such as the host–parasite arms-race are modulated by environmental change is largely unknown. The immune system of invertebrates,
in particular phagocytosis and phenoloxidase activity response are key defence mechanisms against parasites, yet they may
be sensitive to environmental perturbations. We here simulated an extreme event that mimicked the European heat wave in 2003
to investigate the effect of environmental change on the immunocompetence of the mesograzer Idotea baltica. Unlike earlier studies, our experiment aimed at simulation of the natural situation as closely as possible by using long
acclimation, a slow increase in temperature and a natural community setting including the animals’ providence with natural
food sources (Zostera marina and Fucus vesiculosus). Our results demonstrate that a simulated heat wave results in decreased immunocompetence of the mesograzer Idotea baltica, in particular a drop of phagocytosis by 50%. This suggests that global change has the potential to significantly affect
host–parasite interactions. 相似文献
17.
In nature, multiple parasite species infect multiple host species and are influenced by processes operating across different spatial and temporal scales. Data sets incorporating these complexities offer exciting opportunities to examine factors that shape epidemics. We present a method using generalized linear mixed models in a multilevel modeling framework to analyze patterns of variances and correlations in binomially distributed prevalence data. We then apply it to a multi-lake, multiyear data set involving two Daphnia host species and nine microparasite species. We found that the largest source of variation in parasite prevalence was the species identities of host-parasite pairs, indicating strong host-parasite specificity. Within host-parasite combinations, spatial variation (among lakes) exceeded interannual variation. This suggests that factors promoting differences among lakes (e.g., habitat characteristics and species interactions) better explain variation in peak infection prevalence in our data set than factors driving differences among years (e.g., climate). Prevalences of parasites in D. dentifera were more positively correlated than those for D. pulicaria, suggesting that similar factors influenced epidemic size among parasites in D. dentifera. Overall, this study demonstrates a method for parsing patterns of variation and covariation in infection prevalence data, providing greater insight into the relative importance of different underlying drivers of parasitism. 相似文献
18.
Johnson PT Preston DL Hoverman JT Henderson JS Paull SH Richgels KL Redmond MD 《Ecology》2012,93(1):56-64
With growing interest in the effects of biodiversity on disease, there is a critical need for studies that empirically identify the mechanisms underlying the diversity-disease relationship. Here, we combined wetland surveys of host community structure with mechanistic experiments involving a multi-host parasite to evaluate competing explanations for the dilution effect. Sampling of 320 wetlands in California indicated that snail host communities were strongly nested, with competent hosts for the trematode Ribeiroia ondatrae predominating in low-richness assemblages and unsuitable hosts increasingly present in more diverse communities. Moreover, competent host density was negatively associated with increases in snail species richness. These patterns in host community assembly support a key prerequisite underlying the dilution effect. Results of multigenerational mesocosm experiments designed to mimic field-observed community assemblages allowed us to evaluate the relative importance of host density and diversity in influencing parasite infection success. Increases in snail species richness (from one to four species) had sharply negative effects on the density of infected hosts (-90% reduction). However, this effect was indirect; competition associated with non-host species led to a 95% reduction in host density (susceptible host regulation), owing primarily to a reduction in host reproduction. Among susceptible hosts, there were no differences in infection prevalence as a function of community structure, indicating a lack of support for a direct effect of diversity on infection (encounter reduction). In monospecific conditions, higher initial host densities increased infection among adult hosts; however, compensatory reproduction in the low-density treatments equalized the final number of infected hosts by the next generation, underscoring the relevance of multigenerational studies in understanding the dilution effect. These findings highlight the role of interspecific competition in mediating the relationship between species richness and parasite infection and emphasize the importance of field-informed experimental research in understanding mechanisms underlying the diversity-disease relationship. 相似文献
19.
The evolution and ecology of consistent behavioural variation, or personality, is currently the focus of much attention in
natural populations. Associations between personality traits and parasite infections are increasingly being reported, but
the extent to which multiple behavioural traits might be associated with parasitism at the same time is largely unknown. Here,
we use a population of great tits, Parus major, to examine whether infection by avian malaria (Plasmodium and Leucocytozoon) is associated with three behavioural traits assayed under standardized conditions. All of these traits are of broad ecological
significance and two of them are repeatable or heritable in our population. Here, we show weak correlations between some but
not all of these behavioural traits, and sex-dependent associations between all three behavioural traits and parasite infection.
Infected males showed increased problem-solving performance whereas infected females showed reduced performance; furthermore,
uninfected females were four times more likely to solve problems than uninfected males. Infected females were more exploratory
than uninfected females, but infection had no effect on males. Finally, infected males were more risk-averse than uninfected
males but females were unaffected. Our results demonstrate the potential for complex interactions between consistent personality
variation and parasite infection, though we discuss the difficulty of attributing causality in these associations. Accounting
for complex parasite-behaviour associations may prove essential in understanding the evolutionary ecology of behavioural variation
and the dynamics of host–parasite interactions. 相似文献
20.
Gabriel G. González Katherina B. Brokordt Federico E. Winkler 《Marine Biology》2010,157(10):2195-2203
Several studies on individual physiological traits assume that past records may predict future performance. Marine mollusks,
as other animals, show a wide range of between- and within-individual variation of physiological traits. However, in this
group, almost nothing is known about the relative influence of genetic factors on that variation. Repeatability (R) is a measure of the consistency of the variation of a trait, which includes its genetic variance and represents the maximum
potential value of its heritability (h
2). Traits that show high inter-individual variation and high repeatability levels could potentially evolve through selection
(natural or artificial). We estimated the repeatability [using intra-class (τ) and Pearson-moment (r) correlation coefficients] of several physiological traits related to energy acquisition and allocation in juvenile Pacific
abalone Haliotis discus hannai, maintained under controlled environment growing systems. In order to estimate the range of the R values and the effect of the time elapsed between measurements on these estimates, we measured these traits monthly during
6 months for each individual. Among the physiological traits, those related to energy allocation like oxygen consumption (standard
metabolic rate, SMR) and ammonium excretion rates, and oxygen/nitrogen ratio (O/N), showed intermediate levels of repeatability
(0.48, 0.55 and 0.39, respectively), when this was estimated by τ coefficient. However, the r estimation showed that SMR and O/N repeatability were significant and high (0.6–0.7 and 0.5–0.7, respectively) during the
first 5 consecutive measurements, decreasing strongly (0.3 and 0.2, respectively) during the last measurement. For ammonia
excretion, although repeatability (r) decreased from 0.8 to 0.5 during the 6 consecutive measurements, they remain significant during the experimental period.
Therefore, our results indicate that for H. discus hannai juveniles, physiological traits like SMR, ammonia excretion and O/N are significantly repeatable (i.e. good predictors of
future measurements) during a period of 4–5 months. These significant repeatability values suggest an important genetic control
upon the phenotypic variation of these physiological traits, and could potentially respond to natural or artificial selection,
and be used in genetic improvement programs. By contrast, those traits related to energy acquisition (i.e. ingestion, absorption
and assimilation) and physiological efficiencies (i.e. net growth and scope for growth) showed very low levels of repeatability
(0–0.07). This indicates that the phenotypic variation of these traits would be more influenced by environment rather than
by genetic factors. 相似文献