A spatiotemporal wave of turnover and functional maturation of olfactory receptor neurons in the spiny lobster Panulirus argus.

Olfactory receptor neurons (ORNs) of crustaceans are housed in aesthetasc sensilla that are located on the lateral flagellum of the antennule. We used young adult spiny lobsters to examine turnover of aesthetascs and functional maturation of their ORNs after molting. The proliferation zone for new aesthetascs is located in the proximal part of the aesthetasc-bearing region and progressively moves along a distoproximal axis. Older aesthetascs are lost in the distal part of the aesthetasc-bearing region. As a result, an aesthetasc may be shed three to six molts after it differentiates. Taurine-like immunoreactivity is elevated in ORNs of aesthetascs that have yet to emerge on the cuticular surface and thereafter decreases gradually and asynchronously. ORNs from the distalmost-developing aesthetascs lose taurine-like immunoreactivity immediately before sensillar emergence, whereas ORNs from the most proximal and lateral new aesthetascs retain taurine-like immunoreactivity throughout the intermolt stage after sensillar emergence. Furthermore, taurine-like immunoreactivity is inversely correlated with odor responsiveness. These results suggest that taurine-like immunoreactivity reveals immature ORNs and that their functional maturation is not synchronized with molting and may not be completed until many weeks after sensillar emergence. Our data suggest successive spatiotemporal waves of birth, differentiation and functional maturation, and death of ORNs.