Meeting Abstract

P3.31  Tuesday, Jan. 6  The calculation of the body surface areas of Manduca sexta larvae using serial sections followed by image reconstruction and the creation of parametric body surface models. FRUTIGER, A.E.*; HOLDENER, J.A.; ITAGAKI, H.; Kenyon College; Kenyon College; Kenyon College itagaki@kenyon.edu

We have attempted to calculate the body surface areas (BSA) of 2nd, 3rd and 4th instar larvae of the sphinx moth, Manduca sexta, of various body weights (BW). The larvae were reared from eggs on a prepared diet, then frozen and embedded in Histoprep along with four external orientation markers to serve as reference points between sections. A cryostat was used to make transverse serial sections of each larva at 50um. Each section was digitized using a stereomicroscope equipped with a digital camera and polarization optics. The images of the sections were then imported into the NIH Image J program for analysis. The distances between each of the 4 orientation markers was measured and used to estimate the centroid of each section. A line drawn between the centroid and the upper left marker dot served as the reference axis between sections. For each section, 36 radius measurements were taken from the centroid to the surface in 10^o increments. Each set of radii values was imported into MAPLE, in which a parametric model of the boundary curve was constructed from 10 sections in the 2nd instar, 30 sections in the 3rd instar, and 28 sections in the 4th instar. A second program in MAPLE was then used to create a parametric model of the body surface for each instar in addition to finding the surface area; the centroid for each section was used to determine a space curve that served as the generating curve for the body surface. These calculated surface areas were then divided by the body weights to find the BSA/BW values for each instar: 2nd instar, 18.8 cm²/g (BW = 0.039g); 3rd instar, 8.5 cm²/g (BW=0.309g); 4th instar, 7.6 cm ²/g (BW=0.787g). This work was supported by the Kenyon College Summer Science Scholars Program.