Grantee Research Project Results

Effects of Body Size and Development on Insect Respiration

EPA Grant Number: U916165
Title: Effects of Body Size and Development on Insect Respiration
Investigators: Greenlee, Kendra J.
Institution: Arizona State University
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $90,273
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Entomology

Objective:

This research project will investigate the following questions:

1. How do the roles of diffusion and convection vary with body size in two distantly related and morphologically divergent species, the American locust, Schistocerca americana, and the tobacco hornworm larva, Manduca sexta?

2. Preliminary experiments showed that in low O2, adult grasshoppers had better respiratory function than juveniles. Are these differences in respiratory function attributed to body size increases or neuromuscular and chemosensory development?

Approach:

I will test the hypothesis that juvenile grasshoppers and caterpillars of all ages rely on diffusion for gas exchange and adult grasshoppers rely on convection. I will experimentally manipulate the oxygen diffusion coefficient and measure the effect on safety margins for gas exchange. As a second probe to quantify the contribution of convection to O2 delivery capacity, I will use an anaesthetic to block muscle contractions and, therefore, prevent convective gas exchange. To test the hypothesis that larger insects have smaller safety margins, I will measure the effect of graded hypoxia on gas exchange in pairs of large and small species from several orthopteran families.

Insects may undergo dramatic increases in body size throughout development. To understand the ecological and environmental challenges presented by these changes, we must understand the underlying physiology. As body size increases (as much as 10,000-fold in some caterpillars), metabolic rate and O2 demand also increase. It is unclear what mechanisms of gas exchange insects use to meet the increased demand for O2 delivery. Preliminary experiments suggest that grasshoppers meet increased O2 demands with increases in convective gas exchange and that juvenile grasshoppers and caterpillars rely on diffusion for gas exchange.

Supplemental Keywords:

fellowship, American locust, Schistocerca americana, Manduca sexta, tobacco hornworm larva, diffusion gas exchange, convective gas exchange, grasshoppers, metabolic rate, oxygen demand.

Progress and Final Reports:

2003

2004

Final