Sugar receptor response of the food-canal taste sensilla in a nectar-feeding swallowtail butterfly, Papilio xuthus

Abstract

The feeding behavior in nectar-feeding insects is triggered by a sugar-receptor response in contact chemosensilla. The contact chemosensilla are distributed not only on tarsi and the outside of the proboscis but also on the inside of the food canal in Lepidoptera. Although the chemosensilla inside the food canal are assumed to detect sweet taste during the passage of nectar through the food canal, their electrophysiological function has received little attention. In the nectar-feeding Asian swallowtail butterfly, Papilio xuthus (Lepidoptera: Papilionidae), we found 15-to 30-μm-long sensilla neatly lined up along the inside galea wall, which forms the food canal in the proboscis. The receptor neurons of these sensilla responded to sucrose. We hypothesized that starch and sucrose compete with each other for a taste receptor site on the sensilla. When we added starch and sucrose to the food-canal sensilla, the electrophysiological responses of food-canal sensilla were inhibited in parallel with the food-sucking behavior of the butterflies. These results suggest that the food-canal sensilla are involved in the behavioral control of nectar-sucking in this butterfly species.

Tarsal taste neuron activity and proboscis extension reflex in response to sugars and amino acids in Helicoverpa armigera (Hübner)

“…These findings point to the importance of sucrose and fructose in triggering feeding behaviour of lepidopteran adults. However, stimulation of tarsal sensilla in Papilio xuthus (Lepidoptera: Papilionidae) with sucrose (as high as 1000mmoll -1 ) did not trigger food-sucking behaviour although some tarsal trichoid sensilla were sucrose-sensitive (Inoue et al, 2008).…”

Unique function of a chemosensory protein in the proboscis of two Helicoverpa species

“…4A), the distal part did not contain appreciable amounts of the protein, but variability was quite large and we could not detect any significant difference between sexes. Sensilla have also been observed inside the proboscis of the butterfly Papilio xuthus, where they are probably involved in the detection of sugars (Inoue et al, 2009), but their number is relatively small (about 80 sensilla per proboscis) and cannot account for the large amount of CSP4 (several micrograms) that, on the basis of electrophoretic analyses, we judged to be contained in a single proboscis. These results seem to exclude the possibility that CSP4 could be mainly associated with sensilla of any type and consequently with chemodetection.…”

Taste discriminating capability to different bitter compounds by the larval styloconic sensilla in the insect herbivore Papilio hospiton (Géné)

“…The first second of the discharges was chosen as representative of the phasic/phasic-tonic parts of the response (Dethier and Crnjar, 1982;Inoue et al, 2009) and spike sorting and counting were performed by means of the Clampfit 10.0 software, based on earlier studies (Dolzer et al, 2003;Dulcis and Levine, 2005;Pézier et al, 2007;Sollai et al, 2014). By measuring the peak-antipeak amplitude and duration of action potentials we previously showed that each maxillary styloconic sensillum in the larvae of P. hospiton houses four GRNs: S, M1 and M2, L. Three of these are sensitive to bitters: two in the lateral (''lat-L'' and ''lat-M2'') and one in the medial sensillum (''med-M2'') (Sollai et al, 2014).…”

“…To determine if all 3 bitter-sensitive neurons were always activated, we stimulated the lateral and medial sensilla of the gustatory system with 4 bitter substances belonging to different chemical classes: nicotine and caffeine (alkaloids), salicin (b-glucoside) and quercitrin (flavonoid), each at 3 different concentrations: nicotine, caffeine, salicin at 0.1, 1 and 10 mM, and quercitrin at 0.01, 0.1 and 1 mM, chosen on the basis of data in the literature (Dethier and Kuch, 1971;Schoonhoven and van Loon, 2002). Although a higher concentration of salt stimulates deterrent cells and induces aversive behavior, 50 mM KCl was used to dissolve all compounds to optimize recording conditions and signal-to-noise ratio for better spike identification (Bernays and Chapman, 2001;del Campo and Miles, 2003;Glendinning et al, 2006;Inoue et al, 2009;Jørgensen et al, 2006;Sollai et al, 2014;Zhang et al, 2013).…”