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

Abstract

SUMMARYIn adult female Helicoverpa armigera (Hübner), the fifth tarsomere of the prothoracic legs bears 14 gustatory trichoid chemosensilla. These chemosensilla were characterized through electrophysiological experiments by stimulating with sucrose, glucose, fructose, maltose, myo-inositol and 20 common amino acids. In electrophysiological recordings from nine sensilla, responses were obtained to certain compounds tested at 100mmoll -1 , and the response spectra differed from broad to narrow. The four sugars excited the same receptor neuron in sensillum a and sensillum b; sucrose and myo-inositol, sucrose and lysine, myo-inositol and lysine excited two different receptor neurons respectively in sensillum a; fructose and lysine excited two different receptor neurons in sensillum n. Furthermore, the four sugars, myo-inositol and lysine all elicited concentrationdependent electrophysiological responses. These six compounds also induced the proboscis extension reflex (PER) followed by ingestion of the solution when they were applied on the tarsi. Lysine and sucrose caused the strongest electrophysiological responses. However, sucrose had the strongest stimulatory effect on the PER whereas lysine had the weakest. Mixtures of sucrose with the other sugars or with lysine had a similar stimulatory effect on the PER as sucrose alone. The electrophysiological and behavioural responses caused by a range of sucrose concentrations were positively correlated. We conclude that the tarsal gustatory sensilla play an essential role in perceiving sugars available in floral nectar and provide chemosensory information determining feeding behaviour. Tarsal taste-receptor-neuron responses to lysine are implicated in oviposition behaviour. Supplementary material available online at

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

“…a similar morphology was observed in Bactrocera where it was related to detection of chemical substances and odours (Zhang et al 2012). As concerns chemosensilla, in Helicoverpa armigera, Zhang et al (2010) reported that the fifth tarsomere showed two clusters of 14 TS. In Rhagoletis pomonella, another Tephritidae, Crnjar and Prokopy (1982) identified three (B, C and D) of the four types of tarsal sensilla proposed by Grabowski and Dethier (1954).…”

How to know which food is good for you: bumblebees use taste to discriminate between different concentrations of food differing in nutrient content

“…However, we do not know which compounds are actually used for discrimination. Insects are generally able to perceive tastes similar to humans and have receptors for bitter and sweet substances as well as for several amino acids (Zhang et al, 2010;Toshima and Tanimura, 2012; for bees, see Linander et al, 2012), glycerol and water (as reviewed for Drosophila by Liman et al, 2014). Bees are even able to sense very small amounts of sugar (de Brito Sanchez, 2011).…”

A Molecular and Cellular Context-Dependent Role for Ir76b in Detection of Amino Acid Taste

“…Studies in blood-feeding tsetse flies identified neurons in tarsal taste hairs that are exquisitely sensitive to several individual amino acids, as well as to a mixture of amino acids that are found in human sweat (van der Goes van Naters and den Otter, 1998). Amino acid-sensing neurons have also been described in cabbage butterflies (Van Loon and Van Eeuwijk, 1989) and Helicoverpa moths (Zhang et al, 2011; Zhang et al, 2010). …”