Conserved, Highly Specialized Olfactory Receptor Neurons for Food Compounds in 2 Congeneric Scarab Beetles, Pachnoda interrupta and Pachnoda marginata

Abstract

Few studies have systematically addressed evolutionary changes in olfactory neuron assemblies, either by genetic drift or as an adaptation to specific odor environments. We have studied the sense of olfaction in 2 congeneric scarab beetles, Pachnoda interrupta Olivier and Pachnoda marginata Drury (Coleoptera: Scarabaeidae: Cetoniinae), which are both opportunistic polyphages, feeding mainly on fruit and flowers. The 2 species occur in dissimilar habitats: P. interrupta is found in dry savannah, and P. marginata in tropical parts of equatorial Africa. To study how these species may have adapted their sense of olfaction to their odor environments, we utilized single-unit electrophysiology on olfactory sensilla with a wide selection of food-related compounds. Despite the differences in habitat, we found that the species shared most of the physiological types of olfactory receptor neurons (ORNs) encountered, although their proportions frequently varied between the species. The high degree of conservation in olfaction between the species implies that a similar sensory strategy is efficient for food search in both habitats. However, shifts in proportions of receptor neuron classes, and slight shifts in response profiles and/or presence of some ORN classes unique to either species, may reflect adaptation to a different set of hosts.

Antennal fine morphology of the threatened beetle Osmoderma eremita (Coleoptera: Scarabaeidae), revealed by scanning electron microscopy

“…The sensory bristles Ch.5, are spread on the external edges of lamellae in O. eremita . Observing the micrographs published in the literature, similar sensory bristles occur on the edges of lamellae in many species: Pachnoda interrupta and P. marginata (Bengtsson et al, ; Stensmyr et al, ), Adoryphorus couloni (McQuillan and Semmens, ), Oryctes elegans (Al‐Dorsay, ), Oryctes rhinoceros (Renou et al, ), Amorphochelus retusus (Romero‐López et al, ), Antitrogus parvulus (Allsopp, ), Dasylepida ishigakiensis (Tanaka et al, ), Lepidiota negatoria (Allsopp, ), Anomala cuprea (Leal and Mochizuki, ), Phyllopertha diversa (Hansson et al, ), Phyllopertha horticola (Ågren, ), Popillia japonica (Kim and Leal, ). The occurrence of these sensory bristles in several groups of Scarabaeidae throughout the continents led us to suggest that this bristle type has a very important function.…”

Functional evolution of Lepidoptera olfactory receptors revealed by deorphanization of a moth repertoire

“…In moths, such specific pathways have been very well described for sex pheromone perception, but it remains unclear whether they also exist for salient plant odorants. Electrophysiological studies performed on S. littoralis and a range of herbivorous insects demonstrate that they are all equipped with numerous sensory neurons narrowly tuned to common plant volatiles162123535455. Although some specialist species detect compounds specific to a narrow range of plant taxa, a majority of herbivorous insects discriminate host from non-host plants through specific combinations of more ubiquitous odorants.…”

Towards an Understanding of Molecule Capture by the Antennae of Male Beetles Belonging to the Genus Rhipicera (Coleoptera, Rhipiceridae)

“…Sensilla placodea in general are considered to be olfactory receptors (Altner, , Table ), and indeed electrophysiological experiments have shown them to have an olfactory function in beetles (Leal and Mochizuki, , Fig. 2; Renou et al, ; Hansson et al, ; Bengtsson et al, ), bees (Lacher and Schneider, ; Lacher, ; Kaissling and Renner, ; Vareschi, ; Akers and Getz, ), a wasp (Hymenoptera, Braconidae; Ochieng et al, ), and aphids (Bromley and Anderson, ; Dawson et al, [Fig. 4]).…”

“…Sensilla placodea in general are considered to be olfactory receptors (Altner, 1977, Table 2), and indeed electrophysiological experiments have shown them to have an olfactory function in beetles (Leal and Mochizuki, 1993, Fig. 2;Renou et al, 1998;Hansson et al, 1999;Bengtsson et al, 2011), bees (Lacher and Schneider, 1963;Lacher, 1964;Kaissling and Renner, 1968;Vareschi, 1971;Getz, 1992, 1993), a wasp (Hymenoptera, Braconidae; Ochieng et al, 2000), and aphids (Bromley and Anderson, 1982;Dawson et al, 1987, 1990). Most importantly, sensilla placodea have been shown to respond to scent associated with female conspecifics (Kaissling and Renner, 1968;Dawson et al, 1987, 1990; Leal and Mochizuki, 1993, Fig.…”