Sexually Dimorphic and Isomorphic Glomeruli in the Antennal Lobes of the Sphinx Moth Manduca sexta

Abstract

Antennal lobes of adult male and female Manduca sexta were compared in order to investigate the nature and extent of sexual dimorphism of the primary olfactory center of this lepidopteran species. Complete identification of the glomeruli led to the conclusion that all female glomeruli have homologous male counterparts. Thus, there is no sex-specific glomerulus present in one sex and absent in the other. Sexual dimorphism (i.e. glomeruli present but morphologically different in males and females), however, does occur in the three glomeruli composing the male macroglomerular complex. The female homologs of this complex consist of two previously identified 'large female glomeruli' and one newly identified normal-sized glomerulus. The lateral and medial large female glomeruli are interpreted to be homologous to the first two macroglomerular-complex glomeruli-the cumulus and toroid 1. The third male component, the toroid 2, was tentatively identified with a normal-sized spheroidal glomerulus of the female, called here the 'small female glomerulus'. The 60 'ordinary' glomeruli that make up the rest of the glomerular neuropil were found to be homologous in males and females, with the exception of two anomalous (or uncertain) glomeruli. Some variations in relative position and size observed among those glomeruli suggest a diffuse, quantitative kind of sexual dimorphism.

Postembryonic development of sexually dimorphic glomeruli and related interneurons in the cockroach Periplaneta americana

“…As in other insects [8,17,18], the adult male and female P. americana ALs contain almost identical numbers of glomeruli. A female MGC-homolog was located in the antero-lateral region of the AL (Fig.…”

“…In the cockroach B. craniifer and fruit flies, the glomerulus in the female is much smaller [8,17]. In the sphinx moth and tobacco budworm moth, both male and female ALs possess a set of large glomeruli, but their organizational patterns differ [1,18].…”

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

“…At the behavioral level, adult female M. sexta exhibit changing responses to host plant volatiles, depending on age and mating status (Mechaber et al 2002). The underlying principle might be comparable to that in males, since the female glomeruli specialized to host plant odors correspond to the MGC in males (Rospars and Hildebrand 2000).…”

“…The neuropil of the antennal lobe (AL) is organized in globular structures, the so-called glomeruli (n=63±1), which are arranged in a sphere around a central coarse neuropil (Rospars and Hildebrand 2000). This glomerular assembly seems to be a conserved morphological principle among brain regions involved in the initial central processing of olfactory information, since it is, with variable numbers of glomeruli, common in insects and vertebrates (for reviews, see Hildebrand and Shepherd 1997;Strausfeld and Hildebrand 1999;Eisthen 2002).…”

Synthesizing Neurophysiology, Genetics, Behaviour and Learning to Produce Whole-Insect Programmable Sensors to Detect Volatile Chemicals

“…The studies on the experience-dependent plasticity in the AL of M. sexta, a model organism of which the anatomy and physiology of the AL are well known (Christensen et al, 2000;Christensen and White, 2000;Hildebrand and Shepherd, 1997;Kent et al, 1987;Lei et al, 2002;Rospars and Hildebrand, 2000;Tolbert and Hildebrand, 1981), reveal the relationships of behavioural measures of olfactory learning with neuro-physiological measures of odour-evoked ensemble responses in the AL before, during, and after olfactory conditioning Daly and Smith, 2000). As in other insects, an olfactory stimulus followed by food resulted in recruitment of neural units in the AL, and lack of food reinforcement withered the responsive neural units (behaviourally referred to as extinction).…”