The Scaling of Olfaction: Moths have Relatively More Olfactory Surface Area than Mammals

Abstract

Body size affects nearly every aspect of locomotion and sensing, but little is known how body size influences olfaction. One reason for this missing link is that olfaction differs fundamentally from vision and hearing in that molecules are advected by fluid before depositing on olfactory sensors. This critical role of fluid flow in olfaction leads to complexities and trade-offs. For example, a greater density of hairs and sensory neurons may lead to greater collection, but can also lead to reduced flow through hairs and additional weight and drag due to a larger olfactory organ. In this study, we report the surface area and sensory neuron density in olfactory organs of 95 species of moths and mammals. We find that approximately 12-14 percent of an olfactory system’s surface area is devoted to chemosensors. Furthermore, total olfactory surface area and olfactory sensing surface area scale with body mass to the 0.49 and 0.38 powers respectively, indicating that moths have a higher proportion of olfactory surface area than mammals. The density of olfactory neurons appears to be near the limit, at 10,000 to 100,000 neurons per square mm across both insects and mammals. This study demonstrates the need for future work detailing how scaling of olfaction and other senses vary across taxa.

Oscillations for active sensing in olfaction: bioinspiration from insect antennal movements

“…For instance, lobsters move their antennae to promote a faster fluid circulation around the antenna, which increases the Reynolds number locally and allows the fluid to penetrate between the hairs and to get in contact with sensitive surfaces [8]. Insects also use olfaction to perform many tasks, such as finding food and locating proper habitats, and partners [9,10]. While the functional morphology of antenna has been studied [11,12], the role of insect antennal movements in olfaction is less well understood.…”

Functional fibrillar interfaces: Biological hair as inspiration across scales

“…Arthropods, including spiders [ 144 ], ants [ 145 ], and bees [ 146 ], possess chemical receptors on their limbs and antennae that detect chemicals in their surroundings, enabling them to locate sustenance, recognize their species, and avoid danger [ 147 ]. Moth antennae possess dense arrays of hairs, which have been found to interact with surrounding airflow in order to enhance diffusion of chemicals to the antennae for detection [ 148 ]. Based on this knowledge, bio-inspired, fibrillar chemical sensors have been developed [ 149 – 150 ].…”