- Oviposition strategy for superparasitism in the gregarious parasitoid Oomyzus sokolowskii (Hymenoptera: Eulophidae). [Journal Article]
- BEBull Entomol Res 2019; 109(2):221-228
- Superparasitism is an adaptive strategy in solitary parasitoids, yet insufficient evidence confirms this in gregarious ones. We here ask whether the gregarious parasitoid Oomyzus sokolowskii is able …
Superparasitism is an adaptive strategy in solitary parasitoids, yet insufficient evidence confirms this in gregarious ones. We here ask whether the gregarious parasitoid Oomyzus sokolowskii is able to discriminate in attack and progeny allocation between parasitized and unparasitized Plutella xylostella larvae, and how the parasitoid allocates brood size and sex to superparasitized hosts due to some circumstances. We found that female parasitoids preferred unparasitized to parasitized host larvae, and allocated a smaller brood with more males in the later than in the former host. Brood size and sex ratio decreased from superparasitized hosts with a 48 h interval since a previous attack compared with one without an interval; they also declined from the host superparasitized by the parasitoid with oviposition experience compared with one without it. Brood size and sex ratio did not differ between the host superparasitized by the same parasitoid as in the first attack and that by a different one. Our findings suggest that O. sokolowskii females may adjust their oviposition decisions on progeny allocation in response to parasitized P. xylostella larvae to maximize their fitness gains from superparasitism.
- Deciphering the behaviour manipulation imposed by a virus on its parasitoid host: insights from a dual transcriptomic approach. [Journal Article]
- PParasitology 2018; 145(14):1979-1989
- Behaviour manipulation imposed by parasites is a fascinating phenomenon but our understanding is still very limited. We studied the interaction between a virus and the parasitic wasp Leptopilina boul…
Behaviour manipulation imposed by parasites is a fascinating phenomenon but our understanding is still very limited. We studied the interaction between a virus and the parasitic wasp Leptopilina boulardi that attacks Drosophila larvae. Wasps usually refrain to lay eggs into already parasitized hosts (superparasitism avoidance). On the contrary, females infected by the Leptopilina boulardi Filamentous Virus (LbFV) are much more incline to superparasitize. Interestingly, the host-sharing induced by this behaviour modification leads to the horizontal transmission of the virus, thus increasing its fitness at the expense of that of the wasp. To better understand the mechanisms underlying this behaviour manipulation, we studied by RNA sequencing the meta-transcriptome of LbFV and the parasitic wasp both in the abdomen and in the head. We found that the abundance of viral transcripts was independent of the wasp strain but strongly differed between tissues. Based on the tissue pattern of expression, we identified a set of 20 viral genes putatively involved in the manipulation process. In addition, we identified a set of wasp genes deregulated in the presence of the virus either in the abdomen or in the head, including genes with annotations suggesting involvement in behaviour (i.e. Potassium-channel protein). This dataset gives new insights into the behaviour manipulation and on the genetic basis of superparasitism in parasitoids.
- The metabolic costs of fighting and host exploitation in a seed-drilling parasitic wasp. [Journal Article]
- JEJ Exp Biol 2017 11 01; 220(Pt 21):3955-3966
- Oviposition sites may be challenging and energetically costly to access for females in the presence of competitors contesting that resource. Additionally, oviposition sites may be difficult to reach,…
Oviposition sites may be challenging and energetically costly to access for females in the presence of competitors contesting that resource. Additionally, oviposition sites may be difficult to reach, and penetrating a hard substrate can raise energy costs. In the seed-drilling parasitic wasp Eupelmus vuilleti, females actively fight with conspecific competitors over access to hosts. They are often observed laying eggs on already parasitized hosts (superparasitism) living inside cowpea seeds despite the resulting larval competition. Using flow-through respirometry, we quantified the metabolic costs of fighting and of drilling through the seed to access the host, to understand the wasp's fighting strategies and the occurrence of superparasitism. Agonistic interactions such as kicks or pushes generated very small instantaneous costs, but the females that won their contests had higher pre-contest metabolic rates, suggesting a potential long-term cost associated with dominance. We also found that drilling holes through the seed accounted for approximately 15% of a wasp's estimated daily energy budget, and that females can reduce these drilling costs by reusing existing holes. Because exploiting new seeds incurs both drilling costs and the risk of fights, it appears cost effective in some situations for females to avoid confrontations and lay eggs in existing holes, on already parasitized hosts. Our study helps explain the evolution of superparasitism in this system.
- Superparasitism and Population Regulation of the Mosquito-Parasitic Mermithid Nematodes Romanomermis iyengari and Strelkovimermis spiculatus. [Journal Article]
- JNJ Nematol 2017; 49(3):316-320
- Superparasitism is a common phenomenon in mosquito-parasitic mermithid nematodes. Multiple nematodes are needed in a single host to produce males. Host selection behavior and intraspecific competitio…
Superparasitism is a common phenomenon in mosquito-parasitic mermithid nematodes. Multiple nematodes are needed in a single host to produce males. Host selection behavior and intraspecific competition among Romanomermis iyengari and Strelkovimermis spiculatus were investigated against their host, Culex pipiens pipiens in laboratory experiments. In a choice assay between previously infected and uninfected host larvae, infectious preparasites of both nematode species could distinguish not only between infected and uninfected hosts, but even between different parasite loads in showing a strong preference for uninfected hosts or hosts with a low parasite load. Host heart rate declined briefly immediately after parasitism. Superparasitism resulted in increased parasite mortality. Scramble competition within mosquito larvae for limited host nutrients, coupled with a skewed sex ratio favoring males, is assumed to lead to parasite population decline and subsequently toward host-parasite population equilibrium. The ability of mermithid preparasites to accurately assess parasite load likely plays an important role in host population dynamics and regulation.
- Avoidance of parasitized host by female wasps of Aphidius gifuensis (Hymenoptera: Braconidae): The role of natal rearing effects and host availability? [Journal Article]
- ISInsect Sci 2018; 25(6):1035-1044
- Natal rearing experience of animals may affect their behaviors, such as habitat selection and oviposition decision. As part of the overall fitness of insect parasitoids, successful host discriminatio…
Natal rearing experience of animals may affect their behaviors, such as habitat selection and oviposition decision. As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing parasitized hosts from unparasitized hosts) is of paramount importance. In this study we examined whether and how parasitoids' natal rearing experience would affect their host discrimination ability according to host availability. We established separate colonies of Aphidius gifuensis Ashmead by continual rearing on two hosts, Sitobion avenae F. and Myzus persicae (Suzler), and quantified self superparasitism and self superparasitism versus parasitism ratio for the four combinations of parasitoid colonies and host species (S. aveane and M. persicae) at four host densities (30, 50, 100 or 150 per plant). Results showed that self superparasitism of M. persicae by A. gifuensis reared on S. avenae was significantly higher than by those reared on M. persicae, no matter whether the host densities were 30, 50, 100 or 150. Aphidius gifuensis reared on M. persicae significantly superparasitized more S. avenae than those reared on S. aveane only when host density was 30. Self superparasitism versus parasitism ratio of A. gifuensis from both colonies was always lower on natal hosts than on new hosts, and the difference was more pronounced as the host density decreased. These results suggested that natal rearing effects is important on host discrimination and oviposition decision of the parasitoid A. gifuensis. These effects promoted the parasitoid's host adaptation and made them confer greater fitness.
- Intraspecific maternal competition induces summer diapause in insect parasitoids. [Journal Article]
- ISInsect Sci 2018; 25(6):1080-1088
- Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions. According to bet-hedging theory, individuals can reduc…
Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions. According to bet-hedging theory, individuals can reduce variation in fitness outcomes by investing in different strategies at the same time. For arthropods, facultative summer diapause enables survival during dry and hot periods of the year, and can be triggered by a decrease in resource abundance. However, the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors. Using two solitary parasitoid species of cereal aphids as a model system, Aphidius avenae (Haliday) and Aphidius rhopalosiphi (De Stefani-Perez) (Hymenoptera: Braconidae), we tested whether (i) low absolute host density and/or (ii) high levels of parasitoid females' competition lead to maternal-induced summer diapause in parasitoid offspring. Under summer-like climatic conditions, emerging parasitoid females were (i) reared alone and exposed to different host densities (from 5 to 130 aphids), or (ii) reared together with competing females (from 2 to 20 females) and then exposed individually to 50 aphids. For both parasitoid species, low aphid densities did not induce summer diapause. However, the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition experienced by female parasitoids. More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk" strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism. These results provide the first experimental evidence of direct maternal competition-induced diapause in insects, and may change the way we apprehend the evolution of arthropod seasonal ecology, by considering intraspecific competition.
- Egg limitation and individual variation in parasitization risk among hosts in host-parasitoid dynamics. [Journal Article]
- EEEcol Evol 2017; 7(9):3143-3148
- Egg limitation is known to destabilize host-parasitoid dynamics. This study reexamines the effect of egg limitation in light of the individual variation in parasitization risk among hosts (e.g., some…
Egg limitation is known to destabilize host-parasitoid dynamics. This study reexamines the effect of egg limitation in light of the individual variation in parasitization risk among hosts (e.g., some hosts are more likely to be parasitized than others). Previous studies have considered egg limitation (predicted as a destabilizing factor) and individual variation among hosts (predicted as a stabilizing factor) in isolation; however, their interaction is not known. An individual-based model was used to examine the effects of each factor and their interaction. The model-based analysis shows a clear interaction between egg limitation and individual variation in risk among hosts. Egg limitation can both stabilize and destabilize host-parasitioid dynamics depending on the presence and absence of the risk variation. The result suggests that the population-dynamic consequences of egg limitation are more complex than previously thought and emphasizes the importance of the simultaneous consideration of multiple ecological factors (with individual-level details) to uncover potential interactions among them.
- Number of attacks by Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) affects the successful parasitism of Ostrinia furnacalis (Lepidoptera: Crambidae) eggs. [Journal Article]
- BEBull Entomol Res 2017; 107(6):812-819
- In laboratories, the parasitism rate of Ostrinia furnacalis (Güenée) (Lepidoptera: Crambidae) eggs by Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) is low; however, efforts to co…
In laboratories, the parasitism rate of Ostrinia furnacalis (Güenée) (Lepidoptera: Crambidae) eggs by Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) is low; however, efforts to control O. furnacalis with T. dendrolimi in the field have been successful. In this study, the effects of the number of attacks by T. dendrolimi against O. furnacalis eggs and diet of O. furnacalis larva on wasp development were investigated. The results indicated that more attacks increased significantly not only the successful parasitism rate of O. furnacalis eggs by T. dendrolimi, but also the percentage of host eggs that failed to develop into either O. furnacalis larvae or T. dendrolimi. Both the size and female proportion of T. dendrolimi offspring decreased as the number of attacks increased. The number of T. dendrolimi eggs laid in per host egg increased significantly as the ratio of wasps to host eggs increased from 1:5 to 3:5. Host diet also significantly affected the developmental time of immaturity and the emergence rate of adults of T. dendrolimi. These results illustrate how inundative releases of T. dendrolimi can successfully control O. furnacalis despite the fact that pest parasitism by the subsequent wasp generation decreases sharply in the field. The suitability of O. furnacalis eggs to T. dendrolimi and the superparasitism effects on offspring of T. dendrolimi are discussed.
- Effects of superparasitism on immature and adult stages of Diachasmimorpha longicaudata Ashmead (Hymenoptera: Braconidae) reared on Ceratitis capitata Wiedemann (Diptera: Tephritidae). [Journal Article]
- BEBull Entomol Res 2017; 107(6):756-767
- The optimal use of available host by parasitoid insects should be favoured by natural selection. For solitary parasitoids, superparasitism (i.e. the egg-laying of several eggs/host) may represent a d…
The optimal use of available host by parasitoid insects should be favoured by natural selection. For solitary parasitoids, superparasitism (i.e. the egg-laying of several eggs/host) may represent a detrimental phenomenon both in a biological and an applied sense, but under certain circumstances it may be adaptive. Here, we studied the effects of increasing levels of superparasitism (LSPs, number of parasitoid larvae/host) on fitness-related parameters of the immature and adult stages of Diachasmimorpha longicaudata, a solitary endoparasitoid parasitizing Ceratitis capitata. We investigated the moment when supernumerary parasitoid larvae are eliminated and the effects produced by this process, together with its repercussion on female fecundity, parasitism rate, sex ratio, adult survival, flight ability and body size. Complete elimination of competitors occurred soon after larval hatching, before reaching the second larval stage. Elimination process took longer at higher LSPs, although a normal developmental (egg-adult) time was achieved. For LSPs 1, 2, 3 and 5 the effects on parasitoid emergence were mild, but LSP 10 led to the death of all developing parasitoids. Aside from this, to develop in superparasitized hosts did not significantly affect any of the evaluated parameters, and only a female-biased sex ratio was observed at higher LSPs. However, the effects of superparasitism on the adults may have a different outcome under more variable conditions in the field, once they are released for biological control purposes.
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- Superparasitism, immune response and optimum progeny yield in the gregarious parasitoid Palmistichus elaeisis. [Journal Article]
- PMPest Manag Sci 2017; 73(6):1101-1109
- CONCLUSIONS: An optimum number of three clutches laid per host pupa was detected for P. elaeisis. As immune response via haemocyte production, encapsulation and melanisation decreased with the number of clutches laid per host, the higher parasitoid yield and fitness observed is the likely consequence of a compromised immune response coupled with an accommodative (i.e. scramble) larval competitive strategy allowing enough resources for optimum balance of parasitoid number and quality produced. © 2017 Society of Chemical Industry.