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1.
A. Schopf 《BioControl》1991,36(4):593-604
The endoparasitic development ofG. liparidis was examined in 3 different host stages of gypsy moth larvae. Hatching ofG. liparidis-larvae occurred 3 to 5 days after oviposition in hosts parasitized during their premoulting period, and after 5 to 7 days
in those parasitized in the 3rd midinstar state. The parasites generally moulted to the 2nd larval instar between the 11th and 13th day in the first group, and between the 13th and 15th day in the latter, when they had reached a volume of 0.04–0.05 mm3. The positive correlation between host ecdysis and the ecdysis of 1st stadium larvae to L2 suggested that host moulting influenced the development of the parasitoid larvae. Emergence from the host larvae occurred
at 20°C after 27 days on average, and coincided with the parasites moulting to the 3rd instar. Five to 7 days after spinning their cocoons near the developmentally arrested host larva, the male, and 1 to 2 days
later the female wasps eclosed. Due to the variation in the number of parasites per host, no difference was observed between
the hosts parasitized at various stages; however, a tendency for later parasitized hosts to contain more parasite larvae was
evident. The nutritional conditions of the moth parental generation influenced both host and parasite development. On the
other hand no influence of host age was observed on emergence dates of larvae and wasps.
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2.
Rune Knudsen Per-Arne Amundsen Rune Nilsen Roar Kristoffersen Anders Klemetsen 《Environmental Biology of Fishes》2008,83(1):107-116
The habitat and diet choice and the infection (prevalence and abundance) of trophically transmitted parasites were compared
in Arctic charr and brown trout living sympatrically in two lakes in northern Norway. Arctic charr were found in all main
lake habitats, whereas the brown trout were almost exclusively found in the littoral zone. In both lakes the parasite fauna
reflected the niche segregation between trout and charr. Surface insects were most common in the diet of trout, but transmit
few parasites, and accordingly the brown trout had a relatively low diversity and abundance of parasites. Parasites transmitted
by benthic prey such as Gammarus and insect larva, were common in both salmonid host species. Copepod transmitted parasites were much more common in Arctic
charr, as brown trout did not include zooplankton in their diets. Parasite species that may use small fish as transport hosts,
were far more abundant in piscivorous fish, especially brown trout. The seasonal dynamics in parasite infection were also
consistent with the developments in the diet throughout the year. The study demonstrates that the structure of parasite communities
of charr and the trout is highly dependent on shifts in habitat and diet of their hosts both on an annual base and through
the ontogeny, in addition to the observed niche segregation between the two salmonid species. 相似文献
3.
Crustaceans are important hosts for a number of helminth parasites, and they are increasingly used as models for studying the physiology, ecology and evolution of parasite-host interactions. In ecological studies, this interaction is commonly described only in terms of prevalence and number of larvae per infected host. However, the volume of helminth parasites can vary greatly, and this variation can potentially give important insights into the nature of a parasite-host relationship. It may influence and be influenced, for example, by within-host competition, host size, growth, and life history. Here we present a simple method that allows rapid approximation of the absolute and relative volumes of cestode larvae within copepod hosts of various developmental stages (nauplii, copepodites and adults). The measurements are taken in vivo without much disturbance of the animals, i.e. the technique allows study of growth and development of the parasites in relation to that of their hosts. The principles of this technique can be adopted to other helminth parasites and other crustacean hosts. Using this method in the copepod Macrocyclops albidus infected with the cestode Schistocephalus solidus, we found that the relative parasite size (= `parasite index') ranged from 0.5% to 6.5% of host size 14 days after infection. It was greater in male than in female hosts. With increasing number of parasites per host, the total parasite volume increased while the mean volume of the individual parasites decreased. The magnitude of the observed parasite indices, the large variation that was found within a sample of 46 infected adult copepods, and the observed correlates suggest that this new index can indeed be an important measure of parasite success and its pathogenecity. 相似文献
4.
Parasite modification of host behavior is common, and the literature is dominated by demonstrations of enhanced predation on parasitized prey resulting in transmission of parasites to their next host. We present a case in which predation on parasitized prey is reduced. Despite theoretical modeling suggesting that this phenomenon should be common, it has been reported in only a few host–parasite–predator systems. Using a system of gregarine endosymbionts in host mosquitoes, we designed experiments to compare the vulnerability of parasitized and unparasitized mosquito larvae to predation by obligate predatory mosquito larvae and then compared behavioral features known to change in the presence of predatory cues. We exposed Aedes triseriatus larvae to the parasite Ascogregarina barretti and the predator Toxohrynchites rutilus and assessed larval mortality rate under each treatment condition. Further, we assessed behavioral differences in larvae due to infection and predation stimuli by recording larvae and scoring behaviors and positions within microcosms. Infection with gregarines reduced cohort mortality in the presence of the predator, but the parasite did not affect mortality alone. Further, infection by parasites altered behavior such that infected hosts thrashed less frequently than uninfected hosts and were found more frequently on or in a refuge within the microcosm. By reducing predation on their host, gregarines may be acting as mutualists in the presence of predation on their hosts. These results illustrate a higher‐order interaction, in which a relationship between a species pair (host–endosymbiont or predator–prey) is altered by the presence of a third species. 相似文献
5.
Christen JM Campbell JF Zurek L Shapiro-Ilan DI Lewis EE Ramaswamy SB 《Journal of invertebrate pathology》2008,99(1):35-42
Entomopathogenic nematodes of the family Steinernematidae and their mutualistic bacteria (Xenorhabdus spp.) are lethal endoparasites of insects. We hypothesized that growth of the nematode’s mutualistic bacteria in the insect host may contribute to the production of cues used by the infective juveniles (IJs) in responding to potential hosts for infection. Specifically, we tested if patterns of bacterial growth could explain differences in CO2 production over the course of host infection. Growth of Xenorhabdus cabanillasii isolated from Steinernema riobrave exhibited the characteristic exponential and stationary growth phases. Other non-nematode symbiotic bacteria were also found in infected hosts and exhibited similar growth patterns to X. cabanillasii. Galleria mellonella larvae infected with S. riobrave produced two distinct peaks of CO2 occurring at 25.6–36 h and 105–161 h post-infection, whereas larvae injected with X. cabanillasii alone showed only one peak of CO2, occurring at 22.8–36.2 h post-injection. Tenebrio molitor larvae infected with S. riobrave or injected with bacteria alone exhibited only one peak of CO2 production, which occurred later during S. riobrave infection (41.4–64.4 h post-infection compared to 20.4–35.9 h post-injection). These results indicate a relationship between bacterial growth and the first peak of CO2 in both host species, but not for the second peak exhibited in G. mellonella. 相似文献
6.
John D. Smith 《Environmental Biology of Fishes》1986,16(4):295-308
Synopsis The seasonal transmission ofRaphidascaris acus was studied in two small lakes on Manitoulin Island, Ontario. Dragonfly nymphs and caddisfly larvae, acting as paratenic hosts, contained second-stage larvae. Several fishes, including percids and cyprinids, were intermediate hosts with second, third, and fourth-stage larvae in the liver. Yellow perch,Perca flavescens, was the most important of these. Intensities were up to 928 and increased with length and age of the perch; prevalence was 100%. Abundance ofR. acus tended to be higher in females but was not related to condition of the perch. Second-stage larvae were acquired from invertebrates in summer and developed to the fourth stage by November. They became surrounded by fibrous capsules during the next summer but remained alive for at least another year. The longevity of larvae in the intermediate host may ensure survival of the parasite through periods of low host abundance after winterkill. Northern pike,Esox lucius, was the definitive host. Abundance ofR. acus tended to be greater in larger pike but was not related to sex or condition of the fish. The parasite was acquired in late fall. Prevalence was 100% and mean intensities were over 200 in winter and spring, declining to 64–100% and less than 15, respectively, in summer. Mature worms were present from early spring through summer. Seasonality of infection in the definitive host is not attributable to seasonal availability of larvae in perch. Instead it may be controlled by timing of predation on perch and rate of development and longevity of the parasite. Transmission to pike apparently continues in summer. Low intensity may result from low recruitment rate and rapid turnover of the parasite population. 相似文献
7.
Competition between granulosis virus (GV) and the larval parasite,Sturmiopsis inferens Tns. (Tachinidae: Diptera), was studied in 3rd — and 4th — instar larvae of the sugarcane shoot borer,Chilo infuscatellus Snellen (Crambidae: Lepidoptera), under laboratory conditions. Mortality due to GV infection and parasitization was 76.8 and 47.6 per cent, respectively,
when they were tested separately. But when hosts were infected simultaneously with microfeeding of GV and larval parasite,
a significantly low parasitism (5.5%) was obtained compared to 74.8 per cent mortality by GV infection. When the larvae were
microfed with the GV 6 days after inoculation with parasitic maggots, mortality due to the virus was reduced significantly
to 20.5 per cent, but when the maggot inoculation was preceded by virus microfeeding 6 days before, parasitization was unsuccessful,
while 75% of larvae died of virus. Results obtained from field — collected larvae also showed that significantly more parasite
puparia were recovered from healthy larvae than from virus — infected larvae. Similar differences in parasitization were not
obtained in the case of healthy or virus — infected pupae.
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8.
The prevalence of the microsporidian, Nosema herpobdellae, in the leech, Erpobdella octoculata, collected from a eutrophic English lake, was examined at monthly intervals over two years. The leech has an annual life cycle and, for each cohort, infection appeared in recently recruited animals in early autumn and prevalence levels rose to a peak in late autumn or winter before declining till the cohort died out the following autumn. Prevalence levels never exceeded 9%. The effect of the parasite on young leeches was difficult to assess, but there was some evidence of parasite-induced host mortality in older animals. 相似文献
9.
Michael Stuart Vickie Pendergast Susan Rumfelt Suzanne Pierberg Lisa Greenspan Kenneth Glander Margaret Clarke 《International journal of primatology》1998,19(3):493-512
A literature review of howler parasites provides the basis for an overview of the ecological significance of parasite surveys in primates. Within this framework, we have added insights into the interactions between primate hosts and their parasites from a long-term study in Costa Rica. We collected fecal samples from mantled howlers (Alouatta palliata) over a 9-year period (1986–1994 inclusive) and analyzed them for parasite eggs, larvae, cysts, and oocysts. We found many misperceptions inherent in the typical methodology of primate parasite surveys and in the reporting of the findings. Our work in Costa Rica suggests that a snapshot effect occurs with most surveys. A static view does not reflect the dynamic and changing ecological interaction between host and parasite. We describe some problems with parasite data analyses that emphasize the need for long-term longitudinal surveys in wild primate groups. 相似文献
10.
Y. Hailemichael J. W. Smith R. N. Wiedenmann 《Entomologia Experimentalis et Applicata》1994,71(2):155-166
Xanthopimpla stemmator (Thunberg)(Hymenoptera: Ichneumonidae), a solitary endoparasite of pupae of Old World lepidopteran stalkborers, was recently
imported into Texas as a candidate for biological control of New World stalkborers. Information on host acceptability, host
suitability and cues responsible for host finding were necessary to gain an insight into parasite/host interactions, because
of the absence of a coevolutionary history.Xanthopimpla stemmator females were exposed to laboratory-reared one-to six-day-oldDiatraea saccharalis (F.) pupae. An average of 62% of host pupae were accepted and all ages of pupae were equally acceptable. Host suitability
decreased with host age. One- to five-day-old host pupae averaged 31–37% suitability, whereas only 19% of 6-day-old pupae
were suitable. Successful parasitization, defined as the product of the proportion accepted and the proportion suitable, decreased
from 22–23% for 1-, 2- and 3-day-old pupae to 13% for 6-day-old pupae. Sex ratio (female:male) of the parasite progeny increased
with host age. Females comprised 47% of total parasite progeny of 1-day-old and 84% of 6-day-old pupae. The increase in percent
females was a result of a similar number of females in all age classes, coupled with a decrease in the number of males from
older hosts.Xanthopimpla stemmator superparasitized 61% of acceptedD. saccharalis pupae in the laboratory. On dissection, 73% of host pupae with multiple probe wounds were found to contain parasite eggs
or larvae; these hosts contained up to 10 eggs or 7 first-instar larvae. Increased numbers of probes by the parasites were
associated with an increase in successful parasitization. Host seeking activity inX. stemmator was stimulated by the presence of larval frass, host odor and movement of host pupae. Results suggest thatX. stemmator is a good candidate for biological control ofD. saccharalis and possibly other factitious stalkborer hosts. 相似文献
11.
Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host.
Recent studies have shown that allocation of additional eggs to an already parasitized host may be beneficial under certain
conditions. In the present work, mortality of Microplitis rufiventris wasps was significantly influenced by both host instar of Spodoptera littoralis larvae at parasitism and level of parasitism. In single parasitization, all host instars (first through sixth) were not equally
suitable. Percentage of emergence success of wasp larvae was very high in parasitized first through third (highly suitable
hosts), fell to 60% in the fourth instar (moderate suitable) and sharply decreased in the penultimate (5th) instars (marginally
suitable). Singly parasitized sixth (last) instar hosts produced no wasp larvae (entirely unsuitable), pupated and eclosed
to apparently normal adult moths. The scenario was different under superparasitism, whereas supernumerary individuals in the
highly suitable hosts were almost always killed as first instars, superparasitization in unsuitable hosts (4th through 6th)
had significant increase in number of emergence success of wasp larvae. Also, significantly greater number of parasitoid larvae
successfully developed in unsuitable hosts containing three wasp eggs than counterparts containing two wasp eggs. Moreover,
the development of surplus wasp larvae was siblicidal in earlier instars and nonsiblicidal gregarious one in the penultimate
and last “sixth” instars. It is suggested that the optimal way for M. rufiventris to deal with high quality hosts (early instars) is to lay a single egg, while the optimal way to deal with low quality hosts
(late instars) might be to superparasitize these hosts. 相似文献
12.
Anja C. Winger Marte Kanck Roar Kristoffersen Rune Knudsen 《Environmental Biology of Fishes》2008,83(1):117-123
The seasonal occurrence of the monogenean ectoparasite Gyrodactylus salaris Malmberg infecting Arctic charr, Salvelinus alpinus (L.) in the two rivers Skibotnelva and Signaldalselva in northern Norway was studied in the period from autumn 2003 to autumn
2005. Skibotnelva has been infected with the parasite since 1979, and treated with rotenone twice. Most likely resident Arctic
charr avoided the rotenone treatment in small tributary streams, and thus was the source of the repeated re-infection of this
river. G. salaris was first recorded in Signaldalselva in the year 2000 and it is still untreated. Unlike Atlantic salmon, which is highly
susceptible to G. salaris, Arctic charr can display a wide range of host-responses to G. salaris infections. Arctic charr were sampled by electro fishing with a total sample of 681 Arctic charr. The results from this study
demonstrate an evident seasonal dynamic in G. salaris infection in charr in both rivers. Parasite intensities fluctuated with the rise and fall in temperature through the year,
with an autumn high and spring low. There was a significantly lower prevalence and mean intensity of G. salaris in Skibotnelva than in Signaldalselva. There were also a lower prevalence and intensity of G. salaris in the older than in the youngest charr. The different history of infection and treatment in the two rivers might be the
underlying cause of these observed dissimilarities. The current study indicates that Arctic charr is a good natural host for
G. salaris. 相似文献
13.
Andrea L. Joyce Jocelyn G. Millar Timothy D. Paine Lawrence M. Hanks 《Biological Control》2002,24(3):145
The solitary larval ectoparasitoid, Syngaster lepidus Brullé, parasitizes the cryptic larvae of two wood-boring beetles, Phoracantha recurva Newman and Phoracantha semipunctata F. The objective of this study was to determine how the female parasitoids allocated the sex of progeny when presented with larval hosts of uniform size classes. Host size was directly correlated with age of the Phoracantha larval hosts. Groups of Phoracantha larvae of a single age class (2-, 3-, 4-, or 5-week-old) were exposed to parasitoids, and sex ratios of the resulting parasitoid progeny from each host age class were determined. A significant relationship was observed among the sizes of P. recurva and P. semipunctata hosts and the sex ratio of emerging parasitoids. Parasitized 2-week-old beetle larvae of both Phoracantha spp. produced only male S. lepidus progeny, whereas older larval hosts produced increasing proportions of female parasitoids (up to 80% females from 5-week-old hosts). Two-week-old Phoracantha larvae of both species produced fewer parasitoids than host larvae 3–5-week-old. The size of parasitoid progeny consistently increased with host larval age (size), and female parasitoids were larger than males across all host size classes. Male S. lepidus developed in approximately 25 days from 2-week-old hosts, and 19–21 days in 3–5-week-old hosts. Female S. lepidus developed in 22–25 days, with developmental time increasing with host size. 相似文献
14.
Interaction between an entomopoxvirus (PsEPV) and a gregarious braconid endoparasitoid,Cotesia kariyai,inPseudaletia separatalarvae showed that infection of larvae with PsEPV was deleterious to the development and survival ofC. kariyai.The survival and development ofC. kariyaiin PsEPV-infectedP. separatalarvae depended on the length of time between parasitization and viral infection. No parasitoid larvae emerged from PsEPV-infected hosts when host larvae were exposed simultaneously to parasitization and PsEPV inoculation whereas more than 80% of the hosts produced parasitoids when PsEPV was administered 5 days postparasitization.C. kariyailarvae in PsEPV-infected hosts showed a retarded development, shrank, and died about 8 days after viral exposure. Virion-free plasma from PsEPV-infectedP. separatalarvae was toxic to the parasitoid larvae even up to a dilution level of 32 when it was injected intrahemocoelically into the host larvae. Development of parasitoids in hosts that were simultaneously parasitized and injected with the virion-free plasm never progressed beyond the egg stage. The parasitizedP. separatalarvae injected with the virion-free plasma did not pupate and died within 30 days after injection. 相似文献
15.
Ronald M. Weseloh 《BioControl》1988,33(2):153-161
Artificial and modified natural hosts were exposed to females of the gypsy moth [Lymantria dispar (L.)] hyperparasite,Eurytoma appendigaster (Swederus), to investigate its host recognition behavior on the primary host, which are cocooned larvae of the gypsy moth
parasite,Cotesia melanoscela (Ratzeburg). Material(s) which caused drilling behavior by the hyperparasite on host cocoons were extracted with both polar
and non-polar solvents. However, cocoons washed with large volumes of solvent still caused substantial drilling activities
by females, suggesting that additional cues may be important. Results suggest that host recognition in this hyperparasite
involves a variety of host characteristics.
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16.
Predators have the potential to limit the spread of pathogens not only by selecting infected prey but also by shaping prey demographics. We tested this idea with an epidemiological experiment in which we simulated variable levels of size-selective predation on zooplankton hosts and monitored the persistence of host and parasite populations. In the absence of simulated predation, the virulent protozoan Caullerya mesnili frequently drove its host Daphnia galeata to extinction. Uninfected control populations showed lower extinction rates and higher average densities than infected populations in the absence of simulated predation (all of the latter went extinct or remained infected). With a weak removal rate of the largest hosts, the proportion of populations in which the parasite drove the host to extinction decreased, while the number of populations in which the host persisted and the parasite went extinct increased. Host-parasite coexistence was also observed in some cases. With intermediate levels of removal, most of the parasite populations went extinct, while the host populations persisted. With an even higher removal rate, Daphnia were driven to extinction as well. Thus, variation in one factor, size-selective mortality, resulted in four different patterns of population dynamics. Our results highlight the potential role of predation in shaping the epidemiology and community structure of host-parasite systems. 相似文献
17.
Introduced exotic species have the potential to spread their associated parasites to native species which can be catastrophic if these hosts are immunologically naïve to the novel parasite. The guppy (Poecilia reticulata) has been disseminated worldwide outside of its native habitat and therefore could be an important source of infection to native fish species. Its parasite fauna is dominated by the ectoparasitic monogeneans, Gyrodactylus turnbulli and Gyrodactylus bullatarudis. The current study tested the host specificity of G. bullatarudis by experimentally infecting a range of isolated fish hosts, including temperate species. Surprisingly, the parasite was capable of establishing and reproducing, for several days, on the three-spined stickleback when transferred directly to this host. We also established that G. bullatarudis could be transmitted under aquarium conditions at both 25 °C and 15 °C. At the higher temperature, the parasite was even capable of reproducing on this atypical host. The implications of these findings are discussed in terms of host specificity, host switching and climate change. 相似文献
18.
Fopius arisanus (Sonan) and Diachasmimorpha tryoni (Cameron) are two important solitary endoparasitoids of tephritid fruit flies. The former species attacks host eggs while the latter attacks host larvae, and both species emerge as adults from the host puparium. This study investigated intrinsic competition between these two parasitoids, as well as aspects of intraspecific competition within each species in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Parasitization by F. arisanus resulted in direct mortality of host eggs and prolonged development of host eggs and larvae. Superparasitism by F. arisanus was uncommon when mean parasitism per host patch was <50%, but increased with rising rates of parasitism. Superparasitism by D. tryoni was more common. In superparasitized hosts, supernumerary individuals of F. arisanus were killed through physiological suppression, while supernumerary larvae of D. tryoni were killed mainly through physical attack. In multiparasitized hosts, dissections showed that 81.6% of D. tryoni eggs in the presence of F. arisanus larvae died within 3 days, indicating physiological inhibition of egg hatch. Rearing results further showed that F. arisanus won almost all competitions against D. tryoni. The ratio of D. tryoni stings to ovipositions was lower in hosts not previously parasitized by F. arisanus than in parasitized hosts, suggesting that D. tryoni can discriminate against parasitized hosts. The mechanism that F. arisanus employs to eliminate D. tryoni is similar to that it uses against all other larval fruit fly parasitoids so far reported. The results are discussed in relation to the competitive superiority of early acting species in fruit fly parasitoids, and to a possible competitive-mediated mechanism underlying host shift by D. tryoni to attack non-target flies following the successful introduction of F. arisanus in Hawaii. 相似文献
19.
Bioassay studies were conducted to investigate the influence of Dimilin (diflubenzuron), a chitinsynthetase inhibitor used for insecticidal control of the gypsy moth, Lymantria dispar, on the development and viability of a microsporidian pathogen of L. dispar. Before or after an infection with a Nosema species, L. dispar larvae were fed Dimilin in sublethal dosages. Dimilin fed to L. dispar larvae at 0.65 ng/cm2 diet surface resulted in a total larval mortality of 53%. Although the microsporidian infection alone did not cause high mortality rates (9%), mortality increased to 96% when L. dispar larvae were inoculated with both Dimilin and Nosema spores. When Dimilin was fed to the larvae 24 h before or 6 days after inoculation with the microsporidium, the number of mature spores produced was significantly reduced. When Dimilin was fed to the larvae 24 h after microsporidian inoculation, the number of spores produced was not significantly reduced. Spores that were produced in larvae after Dimilin had been ingested with the diet were less infectious than spores produced in control larvae; the experimental infection rate decreased from 94% when spores obtained from control larvae were used, to 48 or 10% when spores obtained from larvae fed Dimilin 24 h or 6 days after Nosema inoculation, respectively, were used. Mature microsporidian spores washed in Dimilin solution prior to oral inoculation, however, were as infectious as spores stored in liquid nitrogen. We have shown that Dimilin interferes with the establishment of the parasite in its host. In addition, when Nosema sp. succeeds in infecting the L. dispar host despite treatment with Dimilin, the microsporidium does not develop optimally and spore production is reduced. 相似文献
20.
Genetic studies have indicated that some parasite species formerly thought to be generalists are complexes of morphologically similar species, each appearing to specialize on different host species. Studies on such species are needed to obtain ecological and parasitological data to address whether there are fitness costs in parasitizing atypical host species. We examined whether lungworms from two anuran host species, Lithobates sylvaticus and Lithobates pipiens, differed in measures of infection success in L. pipiens recipient hosts. We also determined if the worms from the two host species were sources of genetically resolvable species of morphologically similar nematodes. Sequences of internal transcribed spacer and lsrDNA regions of adult lungworms from each host species indicated that worms from L. sylvaticus matched Rhabdias bakeri, whereas worms from L. pipiens matched Rhabdias ranae. Our work suggested that these morphologically similar species are distant non-sibling taxa. We infected male and female metamorphs experimentally with lungworm larvae of the two species. We observed higher penetration, higher prevalence and higher mean abundance of adult worms in lungs of male and female metamorphs exposed to R. ranae larvae than in lungs of metamorphs exposed to R. bakeri larvae. Furthermore, metamorphs exposed to R. ranae larvae carried larger adult female worms in their lungs. Some variation in infection measures depended on host sex, but only for one parasite species considered. Overall, the differential establishment and reproductive potential of R. ranae and R. bakeri in L. pipiens suggests co-adaptation. 相似文献