Location: Crop Protection and Management ResearchTitle: An acquired distaste: Sugar discrimination by the larval parasitoid Microplitis croceipes (Hymenoptera: Braconidae) is affected by prior sugar exposure Author
Submitted to: Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2014
Publication Date: 5/16/2014
Citation: Makatiani, J.K., Le, H.K., Olson, D.M., Wackers, F.L., Takasu, K. 2014. An acquired distaste: Sugar discrimination by the larval parasitoid Microplitis croceipes (Hymenoptera: Braconidae) is affected by prior sugar exposure. Experimental Biology. 217:1692-1700. DOI:10.1242/jeb.091843. Interpretive Summary: Most adult parasitoids need sugar-rich food such as floral and extrafloral nectar or homopteran honeydew to obtain energy for maintenance and activities. We examined gustatory responses to the 3 major sugars found in nectar and 1 sugar found in honeydew, as well as various concentrations of the sugars, by the adult parasitoid, Microplitis croceipes. When given single sugar solutions of sucrose, glucose, fructose and maltose at concentrations of 0.008, 0.016, 0.031, 0.063, 0.125, 0.25, 0.5, 1 and 2 mol/L, the estimated concentrations at which 50 % of the wasps accepted the sugar were between 0.053 and 0.084 mol/L for sucrose, glucose and fructose and 0.270 mol/L for maltose. The wasps also fed on maltose for a much shorter time and had reduced longevity on this sugar compared to the other sugars. Higher acceptance thresholds and shorter feeding time and reduced longevity of wasps given maltose suggest that this sugar is of lesser quality than glucose, fructose and sucrose for this species. We also found that the reduced feeding on fructose after feeding on glucose persisted for 24 h. In addition, the feeding suppression on fructose occurred in wasps that had fed on 0.031mol/L of glucose, the lowest acceptance threshold. This is the first study to show feeding suppression of fructose and maltose caused by previous feeding on other sugars, but the function and physiological mechanism(s) of this feeding suppression remain unknown.
Technical Abstract: As sugar quality feeding is very important in the lives of adult parasitoids, we examined several feeding responses of Microplitis croceipes to sugars commonly found in nectar. We first examined the relationship between feeding time and consumption of sucrose, glucose, fructose and maltose by Microplitis croceipes solutions by examining the wasp’s weight before and after exposure to the sugar solution. The effect of sugar concentration on the feeding response of female M. crociepes with no prior feeding experience and those with prior feeding experience was also examined. Longevity of M. croceipes adults was also examined for males and females. We found that as feeding time increased, the amount of sugar consumed increased in a linear fashion for all the sugars. However, feeding time was much lower on maltose than on the other sugars, and the wasps had a higher acceptance threshold for this sugar. Prior feeding by male and female M. croceipes on glucose, fructose or sucrose did not affect their subsequent feeding time on these of those sugars. But, prior feeding on glucose or sucrose significantly reduced subsequent feeding time on fructose and maltose and reduced feeding on fructose after feeding on glucose persisted for 24 h. For both sexes, longevity of wasps that fed on maltose was significantly shorter than that of those that fed on the other sugars. Based on these results, glucose, sucrose and fructose are of higher quality than maltose for this species. The mechanism(s) underlying the feeding suppression of fructose and maltose after previous feeding on other sugars will need further examination.