Two closely located areas in the suboesophageal ganglion and the tritocerebrum receive projections of gustatory receptor neurons located on the antennae and the proboscis in the mothHeliothis virescens

Abstract

Sucrose stimulation of gustatory receptor neurons on the antennae, the tarsi, and the mouthparts elicits the proboscis extension reflex in many insect species, including lepidopterans. The sensory pathways involved in this reflex have only partly been investigated, and in hymenopterans only. The present paper concerns the pathways of the gustatory receptor neurons on the antennae and on the proboscis involved in the proboscis extension reflex in the moth Heliothis virescens (Lepidoptera; Noctuidae). Fluorescent dyes were applied to the contact chemosensilla, sensilla chaetica on the antennae, and sensilla styloconica on the proboscis, permitting tracing of the axons of the gustatory receptor neurons in the central nervous system. The stained axons showed projections from the two appendages in two closely located but distinct areas in the suboesophageal ganglion (SOG)/tritocerebrum. The projections of the antennal gustatory receptor neurons were located posterior-laterally to those from the proboscis. Electrophysiological recordings from the receptor neurons in s. chaetica during mechanical and chemical stimulation were performed, showing responses of one mechanosensory and of several gustatory receptor neurons. Separate neurons showed excitatory responses to sucrose and sinigrin. The effect of these two tastants on the proboscis extension reflex was tested by repeated stimulations with solutions of the two compounds. Whereas sucrose elicited extension in 100% of the individuals in all repetitions, sinigrin elicited extension in fewer individuals, a number that decreased with repeated stimulation.

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

“…induced 100% PER when the tarsi or antennae were stimulated (Jorgensen et al, 2006;Ramaswamy, 1987). In our study, the percentage of insects exhibiting PER in response to sucrose at 100mmoll -1 was about 91%.…”

Lifespan behavioural and neural resilience in a social insect

“…However, results suggest that old P. dentata minors do not decline in performing foraging or nursing tasks that differ qualitatively in olfactory social cue and signal arrays. Odorant inputs are transduced to trigger motor output through the SEZ to control the mouthparts [62] and thoracic ganglia to direct leg movements [63]. Our assessment of predation showed no effect of worker age on sensory responsiveness to prey or the motor execution of attack.…”

Effects of two bitter substances on olfactory conditioning in the moth Heliothis virescens

“…Furthermore, during the preexposure phase of experiment 3, 24.6% of the insects showed PER to sinigrin stimulation, whereas only 3.5% showed PER to quinine stimulation, supporting the assumption of a stronger aversiveness to quinine. In previous feeding and proboscis extension experiments, sinigrin has been shown to be nonappetitive for H. virescens (Blaney and Simmonds, 1988;Jørgensen et al, 2006), but the behavioural effect of quinine has not previously been assayed in this moth. The increasing elicitation of PER to sinigrin during the pre-exposure phase could be because of a familiarity of the substance after several exposures to the moths.…”

“…In the gustatory system, the sucrose solution used as US is detected by the GRNs on the antennae and the proboscis, and information is conveyed to the suboesophageal ganglion and the tritocerebrum (Mitchell et al, 1999;Kvello et al, 2006;Jørgensen et al, 2006). In A. mellifera, the suboesophageal-calycal tract is comprised of neurons passing on information directly from the In nature, moths encounter nutritious and toxic substances in plants, and thus have to discriminate between a diversity of tastants.…”

“…The prototypical bitter compound, quinine, is an alkaloid known to act through blocking of certain K + channels in vertebrates or permeate cell membranes directly and activate G-proteins, bypassing the receptor in in vitro preparations (Spielman et al, 1992;Naim et al, 1994). We also chose sinigrin (a glucosinolate) because it was previously found to be non-appetitive in H. virescens (Blaney and Simmonds, 1988;Jørgensen et al, 2006). Analyses of antennal GRN responses to the two substances were performed and their aversive effects were tested in the appetitive context of olfactory conditioning of PER.…”