Meeting Abstract
P3-150 - Atmospheric oxygen and the growth of a giant Schaefer, CP*; Lynn, S; Zaffino, A; Hubbard, I; VandenBrooks, JM; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ cschae@midwestern.edu
All terrestrial, aerobic animals require oxygen for cellular respiration, but vary in their method of oxygen acquisition and delivery. In insects, oxygen is transported in the gas phase directly to the tissue via tracheae and delivered to the cells via tracheoles. Space in the body cavity taken up by the tracheal network trades off with other physiological structures and there is a “maximal tracheation” achievable before impairing the function of other systems. Therefore, the tracheal system has been hypothesized to be a limiting factor on the maximum size of insects and has been tied to the evolution of insect gigantism during a period of hyperoxia in the past. This unique respiratory system may make insects more susceptible to changes in atmospheric oxygen and larger insects may gain a greater benefit in response to hyperoxia due to the fact they are closer to this potential tracheal limitation. Cockroaches make an ideal model for these questions as they have existed during times of both high and low oxygen levels and span a wide range of body sizes. Previous research on the relatively small Blatella germanica, the German cockroach, showed that while body size was strongly reduced in hypoxia, it was only mildly affected in hyperoxia. Yet, the volume of tracheae was still inversely proportional to developmental pO2 across the entire oxygen range. Here, we tested these hypotheses in Gromphadorhina portentosa, the Madagascar Hissing Cockroach, one of the largest cockroach species, by rearing them in either 12, 21 or 31% O2. Our results show a more pronounced response to hyperoxia than in Blatella in regard to body size, growth rate, development time, lifespan and femoral tracheal volume. These results support the idea that large insect species are more susceptible to hyperoxia and help inform the role of oxygen in the evolution of insect gigantism.