Figure 2.

A. The left side of a brain of P. clarkii in which dextran was applied to the accessory lobe using the technique of Utting et al. (2000). The dextran (green) enters neurons that have their terminals in the accessory lobe and labels the corresponding cell bodies and axons. From this it is clear that both projection neurons in Cluster 10, and local interneurons in Cluster 9, have their terminals in the accessory lobes and the axons from the projection neurons lie in the olfactory globular tract. B. Cluster 10 cell bodies from an animal that was exposed to BrdU for 12 days and sacrificed 4 months later, at which time dextran fluorescein 3000 MW was applied to the accessory lobe. Cells labeled red indicate that they passed through the cell cycle in the presence of BrdU. Cells labeled green indicate that they have terminals in the accessory lobe but did not pass through a cell cycle in the presence of BrdU. Double-labeled cells (orange) are cells that passed through a cell cycle in the presence of BrdU and have differentiated into neurons with their terminals in the accessory lobe. C. Cluster 10 cell bodies with BrdU (blue) and crustacean-SIFamide (green) labeled six months after being exposed to BrdU. Arrowheads point to double-labeled cells, green (cytoplasm) and blue (nuclei). Crustacean-SIFamide immunoreactivity is known to be expressed in olfactory interneurons in P. clarkii (Yasuda-Kamatani and Yasuda, 2006) and the presence of double labeling indicates that these cells were born in the adult animal and have differentiated into olfactory interneurons. Scale bars: A, 10 μm; B, C, 20 μm; C insert, 10 μm. [From Sullivan et al., 2007b; based on the experiments published in Sullivan and Beltz, 2005]