Fine structure of antennal sensilla of the female sphinx moth, Manduca sexta (Lepidoptera: Sphingidae). II. Auriculate, coeloconic, and styliform complex sensilla

Abstract

The antennal flagellum of the female sphinx moth, Manduca sexta, bears eight types of sensilla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. We previously described the fine structure of the trichoid and basiconic sensilla (Shields and Hildebrand 1999). In this paper, we describe one type of auriculate, two types of coeloconic, and one type of styliform complex sensilla. The auriculate (ear- or spoon-shaped) sensillum is a small peg that averages 4 µm in length, is innervated by two bipolar sensory cells, and has structural features characteristic of an insect olfactory sensillum. Each of the two types of coeloconic sensilla is a small peg that averages 2 µm in length and is recessed in a cuticular pit. One type of coeloconic sensillum is innervated by five bipolar sensory cells and has structural features characteristic of an insect olfactory sensillum or olfactory-thermosensillum, while the other is innervated by three bipolar sensory cells and has structural features characteristic of an insect thermo-hygrosensillum. The styliform complex sensillum is a large peg that averages 38-40 µm in length and is formed by several contiguous sensilla, the number of which depends on the location of the peg on the flagellum. Each unit of the styliform complex sensillum is innervated by three bipolar sensory cells and has structural features characteristic of a thermo-hygrosensillum. We also ascertained the number and distribution of each of the eight types of sensilla on a single flagellomere (annulus) about midway along the flagellum of a female antenna. A total of 2216 sensilla were found on the dorsal, ventral, and leading surfaces of that annulus.

Chemosensory Selectivity of Output Neurons Innervating an Identified, Sexually Isomorphic Olfactory Glomerulus

“…4). In Manduca, the male antenna is less sensitive than the female antenna to plant volatiles, including c3HA (Fraser et al, 2003), and has fewer ORCs that respond to plant volatiles (Shields and Hildebrand, 1999). Thus, the differences in the sensitivity threshold might be attributable to differences in the number, but not in the type, of ORCs converging on the glomerulus.…”

Recent advances in insect olfaction, specifically regarding the morphology and sensory physiology of antennal sensilla of the female sphinx moth Manduca sexta

“…Similarly, there are about 3.3 × 10 5 ORCs associated with about 10 5 sensilla in males (Keil, 1989;Lee and Strausfeld, 1990;Oland and Tolbert, 1989;Sanes and Hildebrand, 1976). In both sexes, each annulus bears approximately 2,100 -2,200 sensilla (Lee and Strausfeld, 1990;Shields and Hildebrand, 1999b) and several sensillum types are located…”

“…In other studies, Cuperus (1983) and Cuperus et al (1983) found no sexual dimorphism with respect to the types of antennal sensilla of some Yponomeuta species, but did find a marked difference in the distribution of various types of these sensilla . Shields and Hildebrand (1999b) found that six of the seven types of sensilla (styliform complex not included) are most abundant on the dorsal surface of the female flagellum of M. sexta, (type-A trichoid, type-B trichoid, type-A basiconic, type-B basiconic, type-A coeloconic, and type-B coeloconic; Table 2). Lee and Strausfeld (1990), in contrast, found equal numbers of sensilla in male M. sexta on the ventral and dorsal surfaces ( Table 2).…”

“…The trailing surface in each of B and C, E and F, and H and I are to the left and right, respectively. Reproduced from Shields and Hildebrand, 1999b, with permission of the publisher. Response profiles of 35 olfactory receptor cells (ORCs), associated with 31 type-A trichoid sensilla (from a total of 126 sensilla tested) on antennae of adult female Manduca sexta, to individual odorants and plant-derived odor mixtures.…”

Enhanced Attraction of <I>Plutella xylostella</I> (Lepidoptera: Plutellidae) to Pheromone-Baited Traps With the Addition of Green Leaf Volatiles

“…A transmission electron microscope study in the tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae), suggested that olfactory molecules entered through the grooves in sensilla coeloconica (Shields & Hildebrand 1999). These results are further substantiated as at least some sensilla coeloconica in female P. xylostella appear to be related to oviposition because more sensilla coeloconica were present in female antennae than in male antennae, and a previous study showed that their numbers were highly correlated with oviposition preference (yan et al 2014).…”