Relationship between structure and function of antennal chemo-, hygro-, and thermoreceptive sensilla in Periplaneta americana

Abstract

On the antennae of Periplaneta americana, 25 chemo-, hygro- or thermosensitive sensilla were investigated electrophysiologically and, after marking, by transmission and scanning electron microscopy. A clear-cut relationship of functional types to structural types was observed. Two different stimulus conducting structures were observed: a) pore tubules which are found only in smooth, single-walled sensory pegs and b) secretion-filled canals which occur only in grooved double-walled sensilla. Temperature- and humidity-sensitive receptors occur only in double-walled sensilla with secretion material as the stimulus conducting system. Olfactory sensory cells were found in both types, however, those with a specific sensitivity for short-chain n-alcohols are restricted to single-walled pegs with pore tubules, while those which are most sensitive to short-chain n-acids and amines are found in double-walled sensilla, sometimes together with thermosensitive units. The stimulus conducting systems may control the access of odorous substances to the dendritic membranes and thus contribute to the discriminatory properties of the sensilla.

Ultrastructure and receptor cell responses of the antennal grooved peg sensilla of Triatoma infestans (Hemiptera: Reduviidae)

“…This hypothesis is supported by the responses of the receptor cells in the sw-wp basiconic sensilla on the antenna of T. infestans which are sensitive to long-chain aldehydes and terpenes (Guerenstein, 1999;Guerenstein and Guerin, 2001) whereas the dw-wp GP sensilla receptor cells are sensitive to more polar products such as NH 3 , short-chain carboxylic acids and short-chain amines (this paper). This is comparable to the results reported from the dw sensilla in Aedes responding to lactic acid (Davis, 1977;Davis and Sokolove, 1976), in Locusta to green leaf volatiles such as hexenal, hexanol and aliphatic organic acids with a chain length of 3-8 carbons (Boeckh, 1967;Kafka, 1970), and in Periplaneta to acids with a chain length up to six carbons and to amines (Altner et al, 1977;Altner and Prillinger, 1980). In addition, most receptor cells in the dw-wp sensilla coeloconica from Bombyx responded best to acids and aldehydes (Pophof, 1997).…”

“…Additional functions for some of the olfactory receptor cells (ORCs) in the GP sensilla have been found using single sensillum electrophysiological recordings. The number of adequate stimuli identified is in good agreement with the number of receptor cells in these sensilla and, in addition, support the hypothesis of Altner et al (1977) that receptor cells in the double-walled olfactory sensilla respond preferentially to more polar stimuli.…”

“…The cuticular lipids could originate from the vesicles or droplets of variable electron-density which are present in the proximal part of the outer sensillum-lymph cavity. Comparable inclusions have also been reported from several insects such as Bombyx (Hunger and Steinbrecht, 1998), Periplaneta (Altner et al, 1977), Aedes (McIver, 1974), Drosophila (Shanbhag et al, 1999), Psylliodes (Bartlet et al, 1999), or Carausius (Monteforti et al, 2002). They appear to be released by the trichogen and tormogen cells into the outer sensillum-lymph cavity.…”

“…It was proposed that receptor cells in single-walled wallpore sensilla (sw-wp) might be adapted to respond to more apolar compounds such as long-chain aliphatic mono-and sesquiterpenes, aldehydes, alcohols or esters whereas those in double-walled wall-pore sensilla (dw-wp) would specialize for the perception of more polar and hydrophilic volatiles such as short-chain carboxylic acids (Altner et al, 1977). This difference was associated with the distinct stimulus transport systems reigning in each sensillum type (Steinbrecht, 1997).…”

Olfaction in vector-host interactions

“…Based on the cuticular structure of a sensillum, we are able to discriminate different types of sensilla through microscopic analysis. According to a system suggested by Altner (1977), these types are: (a) wall-pore sensilla, (b) tip-pore sensilla, and (c) aporous sensilla; in which wall-pore sensilla are mainly olfactory and the most abundant type found on the olfactory organs. Wall-pore sensilla may be further divided, based on cuticular structure, into single-walled (including e.g.…”