Morphological characteristics facilitating stimulus access and removal in the olfactory organ of the spiny lobster, Panulirus argus: insight from the design

Abstract

The olfactory organ (antennule) of the spiny lobster, Panulirus argus, has from 1000–2000 olfactory sensilla (aesthetascs) which are grouped in a dense tuft along the distal portion of the lateral filament. This assemblage of aesthetascs, together with other associated sensilla, forms a substantial boundary layer through which odor stimuli must diffuse in moving to and from the aesthetascs. Periodic flicking of the antennule, a behavior analogous to sniffing in certain vertebrate species, is considered to be a means of reducing the thickness of this boundary layer. In this report we describe the structure of the aesthetasc tuft and examine certain of its dynamic properties. We propose that the unique configuration of the aesthetasces, together with their orientation, serves to channel water flow between these sensilla during a flick, thereby reducing diffusion distances and consequently facilitating the access and removal of odor stimuli in a rapid, synchronized manner. The functional significance of this and other design features of the aesthetasc tuft is considered in light of the current understanding of fundamental olfactory process.