Postembryonic proliferation in the spiny lobster antennular epithelium: Rate of genesis of olfactory receptor neurons is dependent on molt stage

Olfactory systems undergo continuous growth and turnover in many animals. M any decapod crustaceans, such as lobsters and crayfish, have indeterminate growth, and in these animals, turnover of both peripheral and central compo nents of the olfactory system occurs continuously throughout life. In this study, we examine the dynamics of olfactory receptor neuron (ORN) prolifera tion in the antennule of the Caribbean spiny lobster, Panulirus argus, usin g in vivo incorporation of the cell proliferation marker BrdU, We show that addition of ORNs occurs in a "proximal proliferation zone" (PPZ), which ex ists on the proximo-lateral margin of the existing ORN population. The PPZ is spatially and temporally dynamic in that it travels as a wave in the pro ximal and lateral directions in the antennule, This wave results in continu ous addition of ORNs throughout the molt cycle. The rate of proliferation, as measured by the size and shape of the PPZ, changes depending an the anim al's molt stage. The rate is highest during premolt and lowest during inter molt, ORNs are the most prominent cell-type produced in the PPZ, but other cell types, including glia, are also produced, Patches of proliferating epi thelial cells occur immediately proximal to the PPZ, suggesting that neuron al and glial precursors reside in this region. Possible mechanisms for peri pheral and central modulation of ORN development are discussed, (C) 2001 Jo hn Wiley & Sons, Inc.