Somatic and wing imaginal disk growth during the last larval instar of <i>Manduca sexta</i>.

<p>Vertical dashed line between days 5–6 indicates the transition from the feeding to the wandering phase. (A) Body growth; feeding stops and mass declines during the wandering phase. Each point is the mean of >50 individuals; bars are standard deviations. (B) Semilogarithmic plot of growth in dry mass of the fore wing imaginal disks. The growth rate of the wing disk increases after larvae enter the wandering stage. Lines are exponential regressions. During the feeding phase the growth is given by the exponential equation mass = 0.011e^0.45, r² = 0.93; during the wandering phase growth is given by the exponential equation mass = 0.007e^0.55, r² = 0.97. Each point is the mean of 20–22 individuals; bars are standard deviations. (C) Semilogarithmic plot of the increase in cell number of the fore wing imaginal disk. Cell division stops after day 8. Each point represents the mean of 12 individuals; bars are standard deviations.</p

Metabolic scaling across and within larval instars of <i>Manduca</i>.

<p>Data are plotted for oxygen consumption rates prior to the critical weight in each instar. A) Measured across instars 3 to 5, metabolic rate scales hypoallometrically as mass 0.85. B) Metabolic rates scale differently in individual instars, with an apparent decrease in scaling in successive instars.</p

Effect of starvation on hemolymph glucose and trehalose concentration.

<p>(A) Glucose concentration in larvae starved before (BCW) and after critical weight (ACW). (B) Trehalose concentration in larvae starved before and after critical weight. Values are means of 8–16 independent samples ±SD.</p

Hemolymph glucose and trehalose concentration during the last larval instar.

<p>Values are means of 10–16 individuals ±SD.</p

Quantification of cell proliferation in the forewing imaginal disk.

<p>Cell proliferation was measured as the average number of PH3 positive cells in an area of 0.0875mm² of the wing imaginal disk. Effect of starvation: larvae were starved on day 4 of the feeding phase and PH3 cells in the wing disk were counted 48h later (<i>p</i> = 0.021). Effect of brain removal: the brain was removed the first day of the wandering phase (day 6) and PH3 cells were counted 24h later (<i>p</i><0.001). Effect of abdominal ligation: a ligation was placed between the thorax and the abdomen on day 6 larvae, and PH3 cells were counted 24h later (<i>p</i><0.001). Each bar represents the mean of 10 disks. Error bars SEM.</p

Effect of starvation before and after critical weight on wing imaginal disk growth.

<p>The grey bar represents the mass interval at which 95% of larvae attain the critical weight. Before the critical weight starvation (open triangles) stopped growth. After the critical weight starvation did not stop growth but reduced the growth rate to approximately 66% of control (black circles).</p

The COX activity per unit of protein decreases within an instar, but increases again at the next instar.

<p>However, COX activity per unit mass decreases monotonically across instars, suggesting that intrinsic demand decreases as the larva grows.</p

Midgut as a proportion of total body mass is constant during the 3rd and 4th larval instars and declines during the 5th instar.

<p>Midgut as a proportion of total body mass is constant during the 3rd and 4th larval instars and declines during the 5th instar.</p

The mass-specific metabolic rate decreases within and between instars (although the within instar decrease is not significant in the third instar).

<p>At the beginning of each instar, the supply structures are not constraining, so this decrease is most likely due to a decrease in intrinsic oxygen demand. In the second half of the fifth instar there is a strong drop-off in the size-specific metabolic rate, which suggests that post-critical weight larvae may be oxygen-limited.</p

Effect of mid-thoracic ligation on fore- and hindwing imaginal disk growth.

<p>A ligation was placed between the second and third thoracic segment on the first day of the wandering phase (day 6). The ligation prevented the forewing from receiving most factors coming from the abdominal region, and also prevented the hindwing from receiving brain factors. The relationship between fore- and hindwing sizes for controls fall on a common regression. In ligated larvae (open triangles) the forewing disks grew little in 24 hours, and the hindwings grew about half as much as controls (black circles) The regression lines for control and ligated larvae for fore- vs hindwing disk sizes are statistically different (<i>p</i><0.001).</p