The hungry caterpillar: an analysis of how carbohydrates stimulate feeding inManduca sexta

Abstract

SUMMARY In most insects, the taste of carbohydrates stimulates an immediate appetitive response. The caterpillar of Manduca sexta is an exception to this general pattern. Despite eliciting a strong peripheral gustatory response, high concentrations of carbohydrates (e.g. glucose or inositol)stimulate the same intensity of biting as water during 2-min tests. We suspected that the lack of feeding stimulation reflected the fact that prior studies used single carbohydrates (e.g. sucrose), which M. sextawould rarely encounter in its host plants. We hypothesized that the feeding control system of M. sexta responds selectively to carbohydrate mixtures. To test this hypothesis, we ran three experiments. First, we stimulated the two taste sensilla that respond to carbohydrates (the lateral and medial styloconic) with a battery of carbohydrates. These sensilla responded exclusively to sucrose, glucose and inositol. Second, we determined the response properties of the carbohydrate-sensitive taste cells within both sensilla. We found that one class of carbohydrate-sensitive taste cell responded to sucrose, and two other classes each responded to glucose and inositol. Third, we examined the initial biting responses of caterpillars to disks treated with solutions containing single carbohydrates (sucrose, glucose or inositol) or binary mixtures of these carbohydrates. The only solutions that stimulated sustained biting were those that activated all three classes of taste cell (i.e. sucrose+inositol or sucrose+glucose). We propose that the brain of M. sexta monitors input from the different classes of carbohydrate-sensitive taste cell, and generates protracted feeding responses only when all three classes are activated.

Chemical composition of horse-chestnut (Aesculus) leaves and their susceptibility to chestnut leaf miner Cameraria ohridella Deschka & Dimić

“…An important factor which stimulates larvae to feed is the abundance of nutrients in leaves (Bede et al 2007). Insects more willingly select leaves that are rich in amino acids and carbohydrates (Glendinning et al 2007). The level of amino acids in the leaves may be an important factor affecting the size of the phytophagous population.…”

“…Plant amino acids are a key source of nitrogen, which is a significant factor in egg production (Cahenzli and Erhardt 2013). Carbohydrates, which are also an important component in the diet of many Lepidoptera, cover energy requirements and provide carbon skeletons for somatic development, fitness and reproductive output (Glendinning et al 2007;Marchioro and Foerster 2013). High activity of amylase, maltase and saccharase which was found in the midgut of C. ohridella suggests that starch, maltose and saccharose are primary carbohydrate components of their diet (Stygar et al 2010).…”

Morphological and electrophysiological analysis of tarsal sensilla in the medfly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae)

“…The first second of the discharges was selected as representative of the phasic/phasictonic portion of the response (Glendinning et al 2001(Glendinning et al , 2007; our data were reported as mean values of spike firing frequency ± standard error of the mean (S.E.M.). Spike sorting and counting were performed by means of Clampfit 10.0 software (Axon Instruments Inc, USA).…”

Nutrient Selection in the Absence of Taste Receptor Signaling

“…Therefore, it is possible that postingestive effects, acting independently of taste quality, function as physiological reinforcers, ultimately leading to increased sugar intake (Sclafani, 2001;Glendinning et al, 2007). Here we tested the hypothesis that D-glucose will be consumed at higher levels compared with a free L-amino acid even when gustatory influence is eliminated and that such an effect is associated with nutrient-specific responses in brain dopamine systems.…”