Abstract
The postembryonic development of antennal lobes was examined at the neuronal and glomerular levels in the cockroach, Blaberus craniifer (Dictyoptera : Blaberidae). The deutocerebral neurons are approximately constant in number (340 ± 50, as derived from nuclear counts). They are congregated in 2 groups, containing respectively 80% and 20% of cells, which slightly vary in location during development. The complement of glomeruli is also almost constant (106 ± 1). Their ontogenetic stability is shown by 23 glomeruli that were identified morphologically at all stages. Moreover, almost all glomeruli found in the adults were identified at mid-development (stage L5) according to their relative locations: only 3 adult and one L5 glomeruli were unmatched. A quantitative study of L5 lobes showed that most of the homologous glomeruli have the same location and size. The proportion of glomeruli, which are not identically located in different lobes (20%), is equal at L5 and adult stages, suggesting that the positional variability is already present at hatching and does not increase during postembryonic development. However, L5 lobes are not scale models of adult lobes. First, 12% of glomeruli are displaced between these 2 stages (i.e. one-fourth between L1 and adults) according to a precise spatiotemporal pattern of development. Second, the glomerular sizes are not well correlated between L5 and adults: e.g. a small adult glomerulus may correspond to a bulky nymphal one. Third, glomerulus 106, identified as early as hatching, is not sexually dimorphic in nymphs but only in adults (male macroglomerulus).
Published Version
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