Ingestion of sugar diets correlates with spike activity in labellar chemosensilla of the flesh‐fly,Neobellieria(=Sarcophaga)bullata

Abstract

Abstract.Female 2‐day‐old Neobellieria (= Sarcophaga) bullata (Parker) (Diptera: Sarcophagidae) were exposed to different concentrations of sucrose, glucose and fructose in a single‐choice potometer, and the volume ingested in the first hour was measured. Nerve spike activity in response to the same sugars was recorded from medium labellar taste hairs of similar flies by tip‐recording. Two classes of chemosensory cells responded to sucrose, glucose and fructose. Cell 1 showed an increasing spike activity with sugar concentration, whereas cell 2 did not; cell 1 was identified as the ‘sugar cell'.For both spike activity in cell 1 and feeding, sucrose was the most stimulatory sugar. The dose–response curves for glucose and fructose crossed over at about 200 mm. At higher concentrations, glucose was more stimulatory for both cell 1 and for feeding, and at lower concentrations, fructose. The pattern of spike activity supports a separate location on the sensory cells of receptors for pyranose and fructose forms of sugar. The strong correlation between volume ingested and spike activity indicates that sugar feeding is controlled by sensory input from the ‘sugar' cells of labellar chemosensilla. Moreover, the results suggest that the flies do not distinguish between these sugars except by apparent ‘sweetness'.