Koinobiont Parasitoid (koinobiont + parasitoid)

Distribution by Scientific Domains


Selected Abstracts


Age-dependent clutch size in a koinobiont parasitoid

ECOLOGICAL ENTOMOLOGY, Issue 1 2005
Jelmer A. Elzinga
Abstract., 1. The Lack clutch size theory predicts how many eggs a female should lay to maximise her fitness gain per clutch. However, for parasitoids that lay multiple clutches it can overestimate optimal clutch size because it does not take into account the future reproductive success of the parasitoid. 2. From egg-limitation and time-limitation models, it is theoretically expected that (i) clutch size decreases with age if host encounter rate is constant, and (ii) clutch size should increase with host deprivation and hence with age in host-deprived individuals. 3. Clutch sizes produced by ageing females of the koinobiont gregarious parasitoid Microplitis tristis Nees (Hymenoptera: Braconidae) that were provided daily with hosts, and of females ageing with different periods of host deprivation were measured. 4. Contrary to expectations, during the first 2 weeks, clutch size did not change with the age of the female parasitoid, neither with nor without increasing host-deprivation time. 5. After the age of 2 weeks, clutch size decreased for parasitoids that parasitised hosts daily. The decrease was accompanied by a strong decrease in available eggs. However, a similar decrease occurred in host-deprived parasitoids that did not experience egg depletion, suggesting that egg limitation was not the only factor causing the decrease in clutch size. 6. For koinobiont parasitoids like M. tristis that have low natural host encounter rates and short oviposition times, the costs of reproduction due to egg limitation, time limitation, or other factors are relatively small, if the natural lifespan is relatively short. 7. Koinobiont parasitoid species that in natural situations experience little variation in host density and host quality might not have strongly evolved the ability to adjust clutch size. [source]


Dispersal between host populations in field conditions: navigation rules in the parasitoid Venturia canescens

ECOLOGICAL ENTOMOLOGY, Issue 3 2003
E. Desouhant
Abstract. 1. Dispersal is a life-history trait that can have great ecological and evolutionary consequences, however understanding of how insects disperse is limited. 2. Navigation rules of the solitary koinobiont parasitoid of the pyralid moth larvae Venturia canescens (Gravenhorst) were studied in conditions that it is likely to meet when dispersing between host populations and in the absence of cues related directly to the presence of hosts. 3. Mark,release,recapture experiments were conducted in a natural host-free habitat, and letting the animals disperse for different periods. 4. In the presence of vegetation, wasps seemed to disperse rapidly (1 h for an area of ,,1 ha) and capture rates were independent of both dispersal time and distance from the release point. 5. The navigation rules of V. canescens during dispersal between tree stands can be summarised as: move up- or down-wind, avoid or pass through open, sunny areas, and go for shady and dense vegetation. 6. The consequences of the navigation rules for host,parasitoid dynamics are discussed in relation to different spatial scales. [source]


The relationship between host selection behaviour and offspring fitness in a koinobiont parasitoid

ECOLOGICAL ENTOMOLOGY, Issue 4 2000
Ana Rivero
Summary 1. When host quality varies, optimal foraging theory assumes that parasitic wasps select hosts in a manner that increases their individual fitness. In koinobiont parasitoids, where the hosts continue developing for a certain period of time after parasitisation, host selection may not reflect current host quality but may be based on an assessment of future growth rates and resources available for the developing larvae. 2. When presented with hosts of uniform quality, the koinobiont parasitoid Leptomastix dactylopii exhibits a characteristic host-selection behaviour: some hosts are accepted for oviposition on first encounter, while others are rejected several times before an egg is laid in them, a behaviour that is commonly associated with a changing host acceptance threshold during the course of a foraging bout. 3. The fitness of the offspring that emerged from hosts accepted immediately upon encounter was compared with the fitness of offspring emerged from hosts rejected several times before being accepted for oviposition. 4. The pattern of host acceptance and rejection was not related to any of the measured fitness parameters of the offspring emerging from these hosts (development time, size at emergence, sex ratio at emergence, and female offspring egg load). 5. While complex post facto adaptive explanations can be devised to explain the nature of such a time and energy consuming host selection process, it is suggested that physiological constraints on egg production or oviposition may provide an alternative, purely mechanistic, explanation for the results obtained. [source]


Gregarious development of the solitary endo-parasitoid, Microplitis rufiventris in its habitual host, Spodoptera littoralis

JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2005
E. M. Hegazi
Abstract:, Earlier research has shown that the koinobiont parasitoid, Microplitis rufiventris, attacks and can develop on early instars of Spodoptera littoralis larvae with preference to third instars. However, the present study was carried out using the newly moulted sixth instar larvae at two different temperatures (20 1 and 27 1C) to study the developmental interaction between the parasitoid and the last instar host larvae. Parasitoid eggs laid in singly parasitized host larvae invariably died. As the number of parasitoid eggs/host larvae increased, the proportion of eggs that hatched and number of viable parasitoid larvae successfully reached to their final instar increased. The effect of superparasitization seems to be dose (no. of eggs + parasitoid factors)-temperature-dependent. The results demonstrate a kind of ,Allee effect' suggesting that superparasitized last instar S. littoralis larvae provide a better host environment than singly parasitized hosts for the parasitoid, M. rufiventris. This may be due to host's hormone and/or low dose of factors injected with parasitoid eggs. The supernumerary individuals of wasp larvae developed normally to the point of emergence but most did not successfully emerge from the host. The improvement of both hatchability and post-embryonic development of parasitoid wasp was significantly (P < 0.01) greater at 20C than at 27C. The results of the present study are useful in understanding the evolution of life-history strategies and host range in parasitic hymenoptera. [source]


Age-dependent clutch size in a koinobiont parasitoid

ECOLOGICAL ENTOMOLOGY, Issue 1 2005
Jelmer A. Elzinga
Abstract., 1. The Lack clutch size theory predicts how many eggs a female should lay to maximise her fitness gain per clutch. However, for parasitoids that lay multiple clutches it can overestimate optimal clutch size because it does not take into account the future reproductive success of the parasitoid. 2. From egg-limitation and time-limitation models, it is theoretically expected that (i) clutch size decreases with age if host encounter rate is constant, and (ii) clutch size should increase with host deprivation and hence with age in host-deprived individuals. 3. Clutch sizes produced by ageing females of the koinobiont gregarious parasitoid Microplitis tristis Nees (Hymenoptera: Braconidae) that were provided daily with hosts, and of females ageing with different periods of host deprivation were measured. 4. Contrary to expectations, during the first 2 weeks, clutch size did not change with the age of the female parasitoid, neither with nor without increasing host-deprivation time. 5. After the age of 2 weeks, clutch size decreased for parasitoids that parasitised hosts daily. The decrease was accompanied by a strong decrease in available eggs. However, a similar decrease occurred in host-deprived parasitoids that did not experience egg depletion, suggesting that egg limitation was not the only factor causing the decrease in clutch size. 6. For koinobiont parasitoids like M. tristis that have low natural host encounter rates and short oviposition times, the costs of reproduction due to egg limitation, time limitation, or other factors are relatively small, if the natural lifespan is relatively short. 7. Koinobiont parasitoid species that in natural situations experience little variation in host density and host quality might not have strongly evolved the ability to adjust clutch size. [source]


The relationship between host selection behaviour and offspring fitness in a koinobiont parasitoid

ECOLOGICAL ENTOMOLOGY, Issue 4 2000
Ana Rivero
Summary 1. When host quality varies, optimal foraging theory assumes that parasitic wasps select hosts in a manner that increases their individual fitness. In koinobiont parasitoids, where the hosts continue developing for a certain period of time after parasitisation, host selection may not reflect current host quality but may be based on an assessment of future growth rates and resources available for the developing larvae. 2. When presented with hosts of uniform quality, the koinobiont parasitoid Leptomastix dactylopii exhibits a characteristic host-selection behaviour: some hosts are accepted for oviposition on first encounter, while others are rejected several times before an egg is laid in them, a behaviour that is commonly associated with a changing host acceptance threshold during the course of a foraging bout. 3. The fitness of the offspring that emerged from hosts accepted immediately upon encounter was compared with the fitness of offspring emerged from hosts rejected several times before being accepted for oviposition. 4. The pattern of host acceptance and rejection was not related to any of the measured fitness parameters of the offspring emerging from these hosts (development time, size at emergence, sex ratio at emergence, and female offspring egg load). 5. While complex post facto adaptive explanations can be devised to explain the nature of such a time and energy consuming host selection process, it is suggested that physiological constraints on egg production or oviposition may provide an alternative, purely mechanistic, explanation for the results obtained. [source]


Impact of a parasitoid on the bacterial symbiosis of its aphid host

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2003
Conrad Cloutier
Abstract Embryo production in aphids is absolutely dependent on the function of symbiotic bacteria, mainly Buchnera, and the growth and development of koinobiont parasitoids in aphids requires the diversion of nutrients from aphid embryo production to the parasitoid. The implication that the bacterial symbiosis may be promoted in parasitized aphids to support the growing parasitoid was explored by analysis of the number and biomass of mycetocytes, and the aphid cells bearing Buchnera, in the pea aphid Acyrthosiphon pisum Harris (Hemiptera: Aphididae) parasitized by the wasp Aphidius ervi Haliday (Hymenoptera: Braconidae). Aphids hosting a young larval parasitoid bore more mycetocytes of greater total biomass, and embryos of lower biomass than unparasitized aphids. Furthermore, one of the three aphid clones tested, which limited teratocyte growth (giant cells of parasitoid origin having a trophic role), bore smaller mycetocytes and larger embryos, than one or both of the two aphid clones with greater susceptibility to the parasitoid. These data suggest that susceptibility of the aphid- Buchnera symbiosis to parasitoid-mediated manipulation may, directly or indirectly, contribute to aphid susceptibility to parasitoid exploitation. [source]