Three-dimensional antennal lobe atlas of the oriental fruit moth, Cydia molesta (Busck) (Lepidoptera: Tortricidae): comparison of male and female glomerular organization

Abstract

The oriental fruit moth Cydia molesta is an important pest and the behavioural role of olfactory signals such as pheromones and plant volatiles have been studied extensively in both sexes. To understand odour processing further, however, detailed knowledge of the anatomy of the olfactory system is crucial. In the present study, an atlas of the antennal lobe (AL) is presented based on the three-dimensional reconstructions of both ALs of three male and three female brains by means of neuroanatomical and computational approaches. We identified 48-49 "ordinary" glomeruli and one large glomerulus situated at the entrance of the antennal nerve in males, and 49-52 "ordinary" glomeruli and one large glomerulus in the ventro-medial part of the AL in females. Anomalous supernumerary, anomalous missing and sexually dimorphic glomeruli were found in the studied individuals in greater numbers than in other lepidopteran species. Male and female maps were compared with respect to glomerular size and position with 45 glomeruli being matched, indicating a conserved glomerular pattern between the sexes. Three additional glomeruli were sexually dimorphic in size and five male-specific and six female-specific glomeruli were also found. Palp backfills resulted in the staining of a unique glomerulus in both sexes identified as the sexually dimorphic glomerulus 45. This glomerulus was never stained from antennal backfills, which stained the other glomeruli of the AL. The three-dimensional atlas can now be used to elucidate the functional role of individual glomeruli in both sexes of C. molesta.

Morphological characterization of the antennal lobes in the Mediterranean fruit fly Ceratitis capitata

“…In addition to PD1, the other dimorphic glomeruli larger in females than in males might be involved in a sophisticated system for the detection of suitable oviposition sites (Varela et al 2009), while those larger in males could be linked to other odor-driven behaviors, such as the "lekking" strategies where males aggregate in large numbers (Landolt et al 1992;Field et al 2003). These functional aspects, that go beyond the aim of the present study, await clarification.…”

“…Galizia et al 1999;Smid et al 2003), Lepidoptera (e.g. Berg et al 2002;Greiner et al 2004;Huetteroth and Schachtner 2005;Couton et al 2009;Varela et al 2009;Montgomery and Ott 2015;Grabe et al 2015) and Coleoptera (e.g. Dreyer et al 2010;Hu et al 2011).…”

Ordinary glomeruli in the antennal lobe of male and female tortricid moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae) process sex pheromone and host-plant volatiles

“…Once fixed, the brains were washed in Millonig's buffer and then dehydrated and rehydrated in an ethanol series and propylene oxide to make membranes more permeable. The brains were washed again in Millonig's buffer and synapsin-antibody staining was used to reveal the glomerular structure of the AL (for details, see Varela et al, 2009). Neurobiotinstained brains were incubated for 24h at 4°C in a 4:2.5:96 solution of anti-synapsin (Klagges et al, 1996): Oregon Green-Avidin 488 (stock solution 1mgml -1 to visualize Neurobiotin) (Molecular Probes, Cergy-Pontoise, France): Millonig's buffer with 0.25% Triton X-100 and 1% bovine serum albumin.…”

“…For G. molesta males, all stainings of PNs responding to pheromone components revealed ordinary glomeruli. These glomeruli were located in the posterior area of the AL and were identified, using an available AL map (Varela et al, 2009), but are unlikely to form part of a, so far incompletely described, MGC because of their location far from the Cu. Generally it is believed that the number of axons from an ORN population in the antenna is correlated with the size of glomeruli in the AL.…”

“…Antennal stimulation with plant volatiles and the three sex pheromone components of this species, at behaviourally relevant doses, were used in order to investigate how pheromone and plant volatile information are integrated in the AL. Neurobiotin and Lucifer Yellow staining permitted the identification of the recorded neuron types and of target glomeruli with the help of a three-dimensional (3-D) map of the AL (Varela et al, 2009). …”