The deutocerebrum of the cockroach Blaberus craniifer burm. Spatial organization of the sensory glomeruli

Abstract

The objective of this work is to describe the glomerular organization of the deutocerebrum in Blaberus craniifer and to test the hypothesis that the glomeruli are identifiable. The problem is studied using the techniques of analytical geometry, i.e., by measuring the location of the glomeruli in cartesian coordinate systems. Computerized geometrical and statistical techniques are described for the three-dimensional reconstruction and quantitative study of these brain structures. The invariance of the glomerular organization, and consequently the identifiability of the glomeruli, is based on three criteria: (1) the number of glomeruli per hemideutocerebrum (hDTC) is a constant (109); (2) the position of the glomeruli is symmetrical in the two sides of one individual and identical in the same side of two individuals, except for small local variations,(3) the dimensions of two positionally homologous glomeruli are statistically equal in the same and in different individuals, except for a macroglomerulus which is found only in the male. The causes of variability, from experimental and biological origin, are discussed and quantitatively evaluated. The interindividual biological variability, not ascribable to differences in size between brains, expressed as a 95% interval, is estimated to be 27 micrometer for the location of glomeruli and 12 micrometer for the diamter of glomeruli.

The Antennal Lobe of Orthoptera – Anatomy and Evolution

“…This is found in a recent phylogenetic tree for the Orthoptera, which is based on small subunit nuclear ribosomal RNA (rRNA) and on mitochondrial rRNA gene sequences Rowell, 1997a, b, 1998]. Because the Blattodea are the sister order of the Orthoptera [Storozhenko, 1997 and references therein; Flook and Rowell, 1998] they can be used as an outgroup for this analysis, particularly because many architectural features of their antennal lobes are well documented [Boeckh et al, 1970;Ernst et al, 1977;Chambille and Masson, 1980;Prillinger, 1981;Rospars and Chambille, 1981;Ignell et al, unpubl. data].…”

“…The glomerular organization of Blattodea [e.g. Boeckh et al, 1970;Ernst et al, 1977;Chambille and Masson, 1980;Prillinger, 1981;Ignell et al, unpubl. ] and of primitive orthopterans (Stenopelmatidae and Tettigoniidae) Rowell 1997a, b, 1998] provide a strong argument for the basal position of unique glomeruli among ancestral orthopterans ( fig.…”

Constancy and variability of glomerular organization in the antennal lobe of the silkmoth

“…As noted in some other insect ALs (Ignell et al 2005), glomeruli in the posterior part of the AL were difficult to identify because, sometimes, the borders between glomeruli were unclear and the shapes of the glomeruli were ambiguous. Previous studies involving glomerular identification have used the following morphological characteristics: (1) relative positions, (2) sizes, and (3) shapes of individual glomeruli (Chambille et al 1980;Rospars and Chambille 1981;Rospars andHildebrand. 1992, 2000;Baier and Korsching 1994;Laissue et al 1999;Galizia et al 1999;Berg et al 2002;Smid et al 2003;Skiri et al 2005).…”

Constancy and variability of identified glomeruli in antennal lobes: computational approach in Spodoptera littoralis

“…LNs are restricted to the AL and connect glomeruli to one another, whereas PNs connect the glomeruli to higher centres, the mushroom bodies and the lateral protocerebrum (for reviews, see Anton and Homberg 1999;Hansson and Anton 2000). A noteworthy feature of insect glomeruli is that they have been shown to be invariant, each glomerulus having the same shape, size and location across individuals of the same species, sex and developmental stage (Chambille et al 1980; for a review, see Rospars 1988; see also references in AL atlases below). This invariance results from several properties of the neuronal processes arborising within the glomeruli.…”