Parasitism-induced effects on host growth and metabolic efficiency in Plutella xylostella larvae parasitized by Cotesia vestalis or Diadegma semiclausum

The nutritional physiology of the diamondback moth, Plutella xylostella, larvae was examined after parasitization by the solitary endoparasitoids Cotesia vestalis or Diadegma semiclausum. Examinations were performed in two phases, one was examined at the time point of 24 h post-parasitization, and the other was done at the end of the 4th instar larvae of host. Rates of growth, food consumption, assimilation, excretion, and respiration were calculated as well as approximate digestibility and the rate ratios ECI （percent efficiency of conversion of ingested food to body substance）, and ECD （percent efficiency of conversion of digested food to body substance）. Parasitization by C. vestalis resulted in significant decrease in the rates of growth, feeding, excretion, assimilation, and respiration, but the final dry rate of respiration at the end of last larval stadium was elevated. The ECI and ECD were also reduced as the result of parasitization, but digestibility was increased. All these parameters in the larvae parasitized by D. semiclausum at 24 h post-parasitization were also significantly changed compared to the control; however, these differences were quantitatively, but not qualitatively before pupation, similar to those resulted from parasitization by C. vestalis. In spite of the similarities of the parasitism-induced effects caused by these endoparasitoids, the final metabolic rate, that is, the rate of intake of nutrients required to compensate for metabolism, was much lower in the larvae parasitized by C. vestalis than that of the larvae parasitized by D. semiclausum. All of the results discussed here will contribute toward explaining the different ways these two wasps regulate the parasitoid-host relationship.

Expression and functional characterization of odorant-binding protein genes in the endoparasitic wasp Cotesia vestalis

Odorant-binding proteins(OBPs)are crucial in insect's olfactory perception,which participate in the initial step of odorant molecules transporting from the external environment to olfactory receptor neurons.To better understand the roles for OBPs in olfactory perception in Cotesia vestalis,a solitary larval endoparasitoid of diamondback moth,Plutella xylostella,we have comprehensively screened the genome of C.vestalis,and obtained 20 CvesOBPs,including 18 classic OBPs and two minus-C OBPs.Motif-pattern analysis indicates that the motifs of C.vestalis OBPs are highly conserved in Hymenoptera.The results of tissue expression analysis show that five OBPs(CvesOBP1/11/12/14/16)are highly expressed in male antennae,whereas six other OBP genes(CvesOBP7/8/13/17/18/19)are significantly transcriptionally enriched in female antennae.The results of RNA interference experiments for three most highly expressed OBP genes(CvesOBP17/18/19)in female antennae demonstrate that they are likely involved in parasitic processes of female wasps,as the wasps take a longer time to target the hosts when they are knoc ked down.