MYER, Bonnie L.*; BURGGREN, Warren ; University of North Texas: ALLOMETRY AND SCALING OF METABOLIC RATE OF DEVELOPING SILKWORMS, BOMBYX MORI

Allometry purportedly determines physiological rates in developing as well as adult animals. Yet, the tissues and organs of developing animals must switch from hyperplastic differentiation to hypertrophic growth, and allometric principles may not apply during this transition (Burggren, 2005). We tested the allometry of VO2 and heart rate in developing silkworm larvae from 1st-5th instar and in pupae to determine if conventional interspecific allometric principles predict intraspecific VO2. VO2 at 25oC was 1.2+0.04 mlO2/mg/h in 1st instar larvae (mass 0.3mg-0.8mg, n=25), falling to 0.98+0.17 mlO2/mg/h in the 2nd instar (mass 0.3mg-1.6mg, n=8) and 0.44+0.02 mlO2/mg/h in the 5th instar (mass 780mg�2200mg, n=8). VO2 in pupa was considerably lower at 0.18+0.02 mlO2/mg/h (mass 760 mg �1800 mg, n =25). Importantly, the relationship between mass-specific VO2 and body mass differed between instars: sharply negative slopes relating VO2 to body mass in instars 1-3; slightly positive slopes for instars 4-5; and no significant relationship in pupae. These data suggest that intraspecific allometric predictions for developing animals, especially in insects showing marked internal reorganization associated with metamorphosis, may depart from those derived from interspecific allometric data based on adults.