Functional units of a compound nose: Aesthetasc sensilla house similar populations of olfactory receptor neurons on the crustacean antennule

Abstract

The lateral flagellum of the antennule of the spiny lobster Panulirus argus houses more than 1,000 morphologically similar olfactory sensilla, called aesthetascs. By using a high‐resolution activity labeling technique that depends on entry of agmatine into olfactory receptor neurons (ORNs) through cation channels during odor stimulation, we examined the distribution of different functional types of ORNs within and across mature aesthetascs. A significant number of ORNs in mature aesthetascs are labeled with agmatine during stimulation by single odorants, including adenosine‐5`‐monophosphate, ammonium chloride, cysteine, glycine, proline, and taurine. The percentage of ORNs per aesthetasc that was agmatine labeled during odor stimulation averaged 0.5–1.6% for single compounds and 4.6% for a 33‐component mimic of oyster tissue. For most antennules and antennular regions studied, the percentage of agmatine‐labeled ORNs by stimulation with single or complex odorants was statistically homogeneous across most or all aesthetascs. The extent of heterogeneity among mature aesthetascs was correlated with their age: extensive heterogeneity was observed only in the distal part of the flagellum containing the oldest aesthetascs and their ORNs. Thus, it appears that over most of the length of the aesthetasc‐bearing region of the lateral flagellum, different and distinct functional types of aesthetascs do not exist. Rather, aesthetascs appear to be repetitive morphological and functional units in olfactory coding. However, because odor sensitivity of ORNs can change with the age of an aesthetasc, some development‐related functional heterogeneity exists among aesthetascs. J. Comp. Neurol. 418:270–280, 2000. © 2000 Wiley‐Liss, Inc.

Molecular Cloning and Characterization of Homologs of Achaete–Scute and Hairy–Enhancer of Split in the Olfactory Organ of the Spiny Lobster Panulirus argus

“…Aesthetascs are unique in spiny lobsters and other crustaceans in being innervated only by chemoreceptor neurons (i.e., ORNs) and in that these ORNs have axons that project exclusively into the olfactory lobes. Each aesthetasc of spiny lobsters contains approximately 300 ORNs of various olfactory specificities (Grünert and Ache 1988;Steullet et al 2000a;Derby et al 2003). Aesthetascs and their ORNs are organized along the olfactory organ according to their developmental age ( Fig.…”

Ionotropic Crustacean Olfactory Receptors

“…The cells in each cluster were tested with 2 to 10 odorants applied in random order and the data pooled [25]. As with insect ORNs [26], [27], [28], lobster ORNs showed ligand-specific response patterning (e.g., ORN14, Figure 6B), but here we only considered the total number of cells that responded to a particular odorant.…”

Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods

“…One type of setae which has been dealt with in extreme detail compared with others is the so called aesthetascs, which are putative unimodal chemoreceptors found on antenna 1 of most crustacean taxa including: Decapods (Ghiradella, Case & Cronshaw, 1968a, b; Snow, 1973; Thompson & Ache, 1980; Fontaine, Passelecq‐gerin & Bauchau, 1984; Spencer, 1986; Tierny, Thompson & Dunham, 1986; Hallberg et al. , 1992; Steullet et al. , 2000), Pericarida (Nielsen & Strömberg, 1973; Risler, 1977; Johansson et al.…”

“…So far they are the only assumed unimodal chemoreceptory setae found in crustaceans and they seem to be restricted to antenna 1. They are believed to be the primary site for olfaction (Voigt & Atema, 1992; Derby, 2000; Steullet et al. , 2000; Derby et al.…”