Differential attraction of parasitoids in relation to specificity of kairomones from herbivores and their by-products

Infochemicals are used by foraging parasitoids in the host selection process from habitat preference until host recognition. Kairomones from the herbivore host plays a vital role in the attraction of parasitoids, particularly in the micro-habitat. Parasitoids are specifically attracted to their respective herbivore species even when different herbivores are present on the same plant. Chemicals emitted from different stages of host （eggs, larvae, pupae, adult）, host by-products （e.g., frass, exuviae, mandibular gland secretions, defense secretions etc.）, or intra-specific infochemicals （pheromones） can be main signals for the parasitoids. Parasitoids can differentiate between host and non-host, between different hosts and host stages by perceiving specific volatile and contact kairomones from the host itself, host along with its by-product, by-products alone or intra-specific infochemicals; of which frass （by-product） and intra-specific infochemicals are the most reported ones. Adult and larval parasitoids have been reported to be attracted to kairomones of their target stage or byproduct of their host. Pupal parasitoids have been found to utilize kairomones from the preceding host stage while egg parasitoids are known to exploit a variety of host infochemicals, for example, either from eggs themselves or other non-target host stages, especially adults and adult-related by-products. The kairomonal chemicals identified so far include various groups, but mainly hydrocarbons. A high degree of host specificity and host acceptance is important for the parasitoids as any mistake may result in the loss of fitness.

Changes in phototactic behavior of Daphnia magna clone C_1242 in response to copper, cadmium and pentachlorophenol

In order to develop a sound biotechnique for monitoring water quality that builds on the previous experiments carried out in our laboratory, a specific D. magna clone C 1242 was used to study the effects of pollutants on phototactic behavior. In all experiments, the animals showed a stable and repeatable phototactic index approximated 0.2 in the presence and 0.4 in the absence of fish kairomones, which decreased significantly in response to pollutants. There existed no pollutant×fish kairomone interaction, indicating the changes in phototactic behavior of animals imposed by pollutants were independent of the presence of fish kairomones. The detection limits for changes in phototactic behavior of D. magna clone C 1242 are 0.04 mg/L for copper, 0.02 mg/L for cadmium, and 0.80 mg/L for PCP, respectively, quite lower than LC 50(48 h). The changes in phototactic behavior in presence to pollutants occurred quickly(3 h) compared to the period over whole acute toxicity tests. Therefore, D. magna clone C 1242 could be potentially used to monitor water quality. Moreover, the phototactic behavior did not decrease further in the pollutant mixtures employed in our experiments compared to individual pollutants, except in the Cd-PCP treatment. This fact suggests that the formation of water quality criteria must be based upon pollutant mixture tests.

Screening of morphology-related genes based on predatorinduced transcriptome sequencing and the functional analysis of Dagcut gene in Daphnia galeata

High fish predation pressure can trigger"induced defense"in Daphnia species,resulting in phenotypic plasticity in morphology,behavior,or life-history traits.The molecular mechanisms of defense morphogenesis(e.g.,the tail spine and helmet)in Daphnia remain unclear.In the pres-ent study,the tail spine,helmet,and body of Daphnia galeata under fish and non-fish kairomones conditions were collected for transcriptome analysis.A total of 24 candidate genes related to the morphological defense of D.galeata were identified,including 2 trypsin,one cuticle protein,1 C1qDC protein,and 2 ferritin genes.The function of the Dagcut gene(D.galeata cuticle protein gene)in relation to tail spine morphology was assessed using RNA interference(RNAi).Compared with the EGFP(Enhanced green fluorescent protein)treatment,after RNAi,the expression levels of the Dagcut gene(D.galeata cuticle protein gene)showed a significant decrease.Correspondingly,the tail spines of the offspring pro-duced by D.galeata after RNAi of the Dagcut gene appeared curved during the experiment.In whole-mount in situ hybridization,a clear signal site was detected on the tail spine of D.galeata before RNAi which disappeared after RNAi.Our results suggest that the Dagcut gene may play an important role in tail spine formation of D.galeata,and will provide a theoretical basis for studying the molecular mechanisms of the morpho-logical plasticityin cladocera inthefuture.

The fecal shield is a double-edged sword for larvae of a leaf beetle

Larvae of some leaf beetles carry masses of feces covering parts or all of the body,which is called a"fecal shield'In general,the shield is thought to be a defense structure against natural enemies.However,some studies have suggested that defense effectiveness varies depending on the natural enemy.In this study,we used a fecal retention leaf beetle Ophrida xanthospilota(Coleoptera:Chrysomelidae),and 2 local generalist predators(an ant,Camponotus japonicus(Hymenoptera:Formicidae)and a stinkbug,Arma custos(Hemiptera:Pentatomidael)as a system to test the hypothesis that the fecal shield of O.xanthospilota plays different roles in predation behavior of different predators and can provide multiple chemical communication signals in predator-prey interactions.Prey bioassays showed that the fecal shield of O.xanthospilota larvae repelled the ant C.japonicus while attracting the stinkbug A.custos.The results also strongly demonstrated that hexane extracts of the fecal shield significantly repelled C.japonicus,while dichloromethane(DCM)extracts did not inhibit ant predation.Interestingly,DCM extracts attracted A.custos,but hexane extracts did not.Therefore,we suggest that the fecal shield is a double-edged sword for the larvae of O.xanthospilota.Our results also indicated that the risk-benefit tradeoff of an insect should be estimated at a community level involving multiple enemies(predators and parasites)and herbivores,rather than in a single prey-predator pair.

CONSTRUCTION OF A cDNA LIBRARY OF HOST RECOGNITION KAIROMONE FOR TELENOMUS THEOPHILAE

Based on the kairomone from the accessory gland of female Bombyx mori elicting the parasitoid, Telenomus theophilae, to parasitize artifical beads. A cDNA expression library of enrich kairomone gene was constructed using mRNA rich secretory portion of the accessory glands of B. mori at the 9 day old of pupa. The titer of the unamplified library was 3.29×10 4 pfu/μL with a recombinant rate of 90.05%, and titer of amplified library was 1.56×10 7 pfu/μL. The inserted cDNA fragments of the library ranged from 0.5 to 8.0 kb and concentrated around the 2.5 kb, 1.1kb, and 0.75kb regions. All of the data suggest that the library has appropriate titer and high frequency kairomone gene fragments by using special developing stage and tissue of B. mori to extract mRNA. Directional cloning and λZiplox expression were help to clone the kairomone gene with immunoscreening.

Evidence for a female-produced, long range pheromone of Anoplophora glabripennis （Coleoptera Cerambycidae）

Volatiles from female Asian longhorned beetle （ ALB ）, Anoplophora glabripenhis, were evaluated as candidate sex pheromone components. Previous studies on ALB have revealed several antennally active compounds from virgin females; however the origins and activity of these compounds were not apparent and require further investigation. We tested the hypothesis that one or more of the ALB contact sex pheromones is a precursor that undergoes abiotic oxidation to yield volatile pheromone components, and evaluated the activity of these compounds using laboratory and field bioassays. Gas chromatogra- phy coupled electroantennography detection （GC-EAD） analysis indicated the presence of three antennally active aldehydes （heptanal, nonanal, and hexadecanal） in female cuticular extracts exposed to ozone or UV and visible light. In laboratory bioassays using a Y-tube olfactometer, males were preferentially attracted to ozonized female body washes over crude body washes. Similarly, synthetic formulations of these compounds were preferred over controls in the olfactometer. Field trapping experiments conducted from 2006 to 2008 in Ningxia, China showed that synthetic lures of the three aldehydes formulated in a ratio simulating that of virgin females attracted more beetles compared to controls, and that combinations of these aldehydes, linalool oxide, and host kairomones captured more beetles than controls, and captured significantly more males.

Honeydew volatile emission acts as a kairomonal message for the Asian lady beetle Harmonia axyridis （Coleoptera： Coccinellidae）

The Asian lady beetle Harmonia axyridis Pallas is considered as an invasive species in most territories where it has been introduced. Because aphid honeydew acts as an attraetant for many aphid predators and parasitoids, the objectives of this work were to collect and identify the volatile compounds released from the aphid excretory product to evaluate how these semiochemicals could affect the H. axyridis foraging behavior. Twelve volatile chemicals were identified from the Megoura viciae Buckton honeydew including four alcohols, three ketones, three aldehydes, a pyrazine and a monoterpene. The volatiles 3-methyl-l-butanol and 3-methyl-butanal were highlighted as the two most abundant semiochemicals released from the M. viciae honeydew. Vieia faba L. plants treated with crude honeydew attracted more than 80% of the tested individuals with 40% of attracted beetles located on the plant. Four volatile compounds （3-hydroxy-2-butanone, 3-methyl-butanal, 3-methyl-1-butanol and limonene） were also highlighted to attract more than 75% of the coccinellids toward the odor source and to locate about 35% of them on the plants. Limonene was the most efficient attractant since 89% of the H. axyridis responded to this odor. The use of the identified semiochemicals as well as the composition of an artificial honeydew could certainly be helpful to control the dispersal of the Asian lady beetle H. axyridis.

Influence of cornicle droplet secretions of the cabbage aphid, Brevicoryne brassicae, on parasitism behavior of na＇fve and experienced Diaeretiella rapae

Insects have evolved amazing methods of defense to ward off enemies. Many aphids release cornicle secretions when attacked by predators and parasitoids. These se cretions contain an alarm pheromone that alerts other colony members of danger, thereby providing indirect fitness benefits to the releaser. In addition, contact with cornicle se cretions could also threaten an attacker and could provide direct fitness to the releaser. However, cornicle secretions may also be recruited as a kairomonal cue by aphid natural enemies. In this study, we investigated the effect of the cornicle droplet volatiles of the cabbage aphid, Brevicoryne brassicae （L.）, on the hostsearching behavior of naive and experienced female Diaeretiella rapae （M＇Intosh） parasitoids in olfactometer studies. In addition, we evaluated the role ofB. brassicae cornicle droplets on the oviposition prefer ence of the parasitoid in a twochoice bioassay. Naive females did not exhibit any preference between volatiles from aphids secreting cornicle droplets over nonsecreting aphids, while experienced parasitoids exploited the secretions in their host location. Experienced females were also able to choose volatiles from both secreting and nonsecreting aphids over clean air, while this ability was not observed in naive females. Although secretion of cornicle droplets did not influence the percentage of first attack in either naive or experienced females, the success of attack （i.e. resulting in a larva） was significantly different between secreting and nonsecreting aphids in the case of experienced parasitoids.

EFFECT OF KAIROMONE ON PREDATOR-PREY DYNAMICS -- A DELAY MODEL

In most of the predator-prey systems, prey individuals make transitions between vulnerable and invulnerable states or locations. This transition is regulated by various inducible defense mechanisms. Diel vertical migration （DVM） in zooplankton is the most effective and instantaneous defense observed in zooplankton population. Zooplankton shows downward vertical migration in the daytime in the presence of predators （or predator kairomones） to avoid predation （i.e. refuge use）, and it enters into the surface water again at night to graze phytoplankton. The dynamics of the planktonic ecosystem under DVM of zooplankton along with fish kairomone and the multiple delays due to migration for vulnerable and invulnerable prey and reproduction in the predator population is of considerable interest both in theoretical and experimental ecologists. By developing mathematical model, we analyze such a system. The conditions for which the system enters into Hopf-bifurcation are obtained. Moreover, the conditions for which the bifurcating branches are supercritical are also derived. Our results indicate that DVM along with the effect of kairomone and multiple delays with a certain range are responsible to enhance the stability of the system around the positive interior equilibrium point.