An accessory olfactory pathway in Lepidoptera: the labial pit organ and its central projections in Manduca sexta and certain other sphinx moths and silk moths

Abstract

In the hawkmoth, Manduca sexta, the third segment of each labial palp contains a pit, which houses a densely packed array of sensilla. We have named this structure the labial pit organ (LPO). The sensilla within the pit are typical of olfactory receptors, characterized by a grooved surface, wall pores, and pore tubules. Axons arising from receptor cells that innervate these sensilla project bilaterally to a single glomerulus in each antennal lobe. We have compared this central projection with that in three other species of Manduca (M. quinquemaculata, M. dilucida, and M. lanuginosa) and in the silkmoths Antheraea polyphemus and Bombyx mori. A bilateral projection to a single glomerulus in each antennal lobe is present in all cases. We suggest that the LPO serves as an accessory olfactory organ in adult Lepidoptera.

Coding and interaction of sex pheromone and plant volatile signals in the antennal lobe of the codling moth Cydia pomonella

“…The ALs of these species show some homologies, including, for example, a large glomerulus in the ventro-medial region of the AL of males and females (OGs 47 and 37). These large glomeruli do not receive afferent innervation from the antennae in either species and are probably analogous to the 'labial pit organ glomerulus' described in other moths (Kent et al, 1986;Rospars and Hildebrand, 2000).…”

Standard three-dimensional glomeruli of the Manduca sexta antennal lobe: a tool to study both developmental and adult neuronal plasticity

“…2E,E′,F,F′, 3), which lies posteromedial to the MGC (Rospars and Hildebrand 1992), the LPOG (yellow glomerulus in Figs. 2D,D′,E,E′, 3), which corresponds to G64 and has been extensively described by Kent et al (1986Kent et al ( , 1999 and Guerenstein et al (2004), and two anteriorly located glomeruli that we have named disc and discbase, which might correspond to G27/28 and G22/29 (dark red and green glomeruli, respectively, in Figs. 2A,A′, B,B′, 3).…”

Antennal transcriptome of Manduca sexta

“…We identified 54 receptor fragments from our transcriptomic dataset, compared with 73 unique glomeruli. However, we must consider that some neuron populations innervating glomeruli in Manduca may be derived from the maxillary palp (20,21,66,67). With current knowledge on antennal physiology, we suspect the missing transcripts are expressed in very few cells, resulting in very low overall expression levels.…”