Function and central projections of gustatory receptor neurons on the antenna of the noctuid moth Spodoptera littoralis

Abstract

Chemosensory information is crucial for most insects to feed and reproduce. Olfactory signals are mainly used at a distance, whereas gustatory stimuli play an important role when insects directly contact chemical substrates. In noctuid moths, although the antennae are the main olfactory organ, they also bear taste sensilla. These taste sensilla detect sugars and hence are involved in appetitive learning but could also play an important role in food evaluation by detecting salts and bitter substances. To investigate this, we measured the responses of individual taste sensilla on the antennae of Spodoptera littoralis to sugars and salts using tip recordings. We also traced the projections of their neuronal axons into the brain. In each sensillum, we found one or two neurons responding to sugars: one NaCl-responsive and one water-sensitive neuron. Responses of these neurons were dose-dependent and similar across different locations on the antenna. Responses were dependent on the sex for sucrose and on both sex and location for glucose and fructose. We did not observe a spatial map for the projections from specific regions of the antennae to the deutocerebrum or the tritocerebrum/suboesophageal ganglion complex. In accordance with physiological recordings, back-fills from individual sensilla revealed up to four axons, in most cases targeting different projection zones.

Transgenerational inheritance of learned preferences for novel host plant odors inBicyclus anynanabutterflies

“…In addition, for an odor to be detected by a larva, the adequate chemo receptor genes for the different components of the odor have to be present in the genome, and these genes have to be expressed in sensory cells such as in the olfactory neurons that enervate the sensory sensilla in the larvae antennae or in the mouthparts (Hallem and Carlson ; Popescu et al. ; Gomez‐Diaz et al. ).…”

Morphology and distribution of ovipositor sensilla of female cotton leaf worm Spodoptera littoralis (Lepidoptera: Noctuidae), and evidence for gustatory function

“…The responses found on the ovipositor are in accordance with what has been found for sensilla on antennae and tarsi of S. littoralis (Blaney & Simmonds ; Popescu et al . ), and show a functional similarity between the taste sensilla on the different parts. Contact chemosensory sensilla of the ovipositor in different Lepidoptera have showed responses to some of these tastants, but no moth has been shown to respond to all of the three different modalities of tastants.…”

“…Jönsson & Anderson 1999;Binyameen et al 2012;Zakir et al 2013). Studies have also investigated the response spectra of tarsal and antennal chemosensory sensilla in adult females to behaviorally active non-volatile plant compounds (Blaney & Simmonds 1988Seada 2010;Popescu et al 2013), but there are no studies investigating the sensilla on the ovipositor.…”

Electrophysiological Recording From <em>Drosophila</em> Labellar Taste Sensilla

“…In addition, because of the nature of the tip-recording method one cannot record the basal firing immediately prior to the delivery of a stimulus, as is commonly done in olfactory recordings. Despite these drawbacks, the tiprecording method has been successfully used to elucidate many of the principles of taste coding in Drosophila and other species 8,10,17,19,[21][22][23] .…”

“…The tip-recording method, which measures the response of the neurons with an electrode that simultaneously delivers a tastant, has since become the method of choice 9,16 . It has been utilized to investigate the taste system of Drosophila melanogaster 8,10,17,18 as well as a number of other insect species [19][20][21][22][23] . It has been greatly facilitated by the development of the tastePROBE amplifier, which overcame one of the major drawbacks of the tip-recording method by compensating for the large potential difference between the reference electrode and the insect sensillum, allowing the GRN action potentials to be recorded without excessive amplification or filtering 24 .…”