A contravention of established principles of interspecific allometric metabolic scaling in developing silkworms, Bombyx mori

Established interspecific metabolic allometric relationships do not adequately describe the complexity and variable physiological states of developing animals. Consequently, intraspecific allometric relationships of oxygen consumption (VO·2) and carbon dioxide production (VCO ·2) as a function of body mass; the respiratory quotient; the function of the silk cocoon; and body composition were investigated for each distinct developmental stage of the silkworm, Bombyx mori.;Whole animal VO·2 in Bombyx ranged from 0.00064 +/- 0.000047 ml O2 ·hr -1 at larval instar I to 0.77 +/- 0.06 ml O2 ·hr -1 in pre-pupal, falling to 0.21 +/- 0.01 ml O2 ·hr -1 in the pupae. Those instars having a significant relationship between VO·2 as a function of body mass, the slope of the line relating VO·2 to body mass varied between 0.99 and 1.02, while across all instars the slope was 0.82. Developmental allometry should be presented for individual developmental stages because the individual allometric exponents of the stages can be significantly different from the overall allometric exponent throughout development and in some cases, the overall allometric exponent can be a statistical artifact.;The first larval instar of Bombyx mori has the lowest cross sectional area of high metabolic tissue of the midgut (27%) and had one of the highest percentages of some metabolically inert tissues (i.e. lipid, 7.5%). Body composition of the first instar does not support the idea that smaller mass animals having the highest VO·2 are composed of a greater percentage of metabolically active organs when compared to larger animals. However, this developmental stage has the highest percentage of the mitochondrial marker cytochrome oxidase, which correlates well with the high VO·2 rate of the smaller mass.;Therefore, established interspecific principles should not be assumed to function as valid models for intraspecific developmental relationships of metabolism as a function of body mass. Developmental allometry should include an analysis of individual stages of development as well as an analysis of development as a whole to gain a comprehensive understanding of the complexity of allometry of the developing animal such as the silkworm.