Fig. 3.

BrdU labelling in the olfactory pathway of mature animals. ORN, olfactory receptor neuron. (A and B) Clusters of BrdU-labelled cells were not observed either (A) distally or (B) proximally within the olfactory organs of mature animals, though numerous labelled glial cells (*) could be observed. The inset in A shows the elongated nucleus of a labelled glial cell (*) surrounded by the smaller, round nuclei of unlabelled olfactory receptor neurons. (C) BrdU-labelled cells observed in the olfactory organ of a mature crab (n = 1 of 8) (D) Cluster of BrdU-labelled cells in the olfactory organ of a mature crab following aesthetasc ablation, a procedure designed to examine regenerative responses. This cluster was located midway along the olfactory organ. (E) BrdU labelling in soma cluster 10 of a mature animal injected with BrdU both 4 months and 24 h before being killed. Cells labelled by the first injection (arrowheads) are present amongst the other cells in the cluster while those labelled by the second injection (arrow) occur within the proliferation zone, adjacent to the olfactory lobe. (F and G) Clusters of BrdU-labelled cells (arrows) in (F) soma cluster 9 and (G) soma cluster A of mature crabs. (H) BrdU (blue) and crustacean-SIFamide (green) labelling in cluster 10 of a mature crab injected 6 months earlier with BrdU. The arrow identifies the soma of a double-labelled neuron. (I) BrdU (blue) and dextran (green) labelling in cluster 10 of a mature animal 6 months after the injection of BrdU. The dextran dye was applied to the olfactory lobe. The soma of a double-labelled neuron is identified by the arrow and its primary neurite by the arrowheads. Scale bars: 100 μm (A–C and G), 50 μm (D–F), 10 μm (H and I), 20 μm (inset in A).