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Mushroom Body Evolution - Figure 14 |
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Figure 14: Chelicerate mushroom bodies illustrate the relationship between glomeruli number and mushroom body size and elaboration. Several of the early anatomists thought that the size of the calyx was proportional to the elaboration of the antennal lobe, such as the number of its glomeruli. In chelicerates, this relationship is subtly different. Their mushroom bodies do not have calyces. Yet the elaboration and size of the lobes is proportional to the number of olfactory glomeruli supplied by chemosensory appendages or organs. Olfactory receptor organs are shown in black in the solpugid Eremboates pallipes (A), the amblypygid Tarantula sp. (C), and the pycnogonid Lecythorhyncus hilgendorfii (E). Irrespective of the location of glomeruli (red), mushroom bodies (blue, B, D, F) are located within the protocerebrum. In solpugids, malleoli provide afferents to glomeruli (shaded in B-F) in the first and second opisthosomal (postoral) ganglion. In amblypygids (D), an enormously elongated first leg pair supplies afferents to hundreds of small glomeruli in the first opisthosomal ganglion. Glomeruli are so numerous that they even invade supraoesophageal neuropil. In pycnogonids (F), glomeruli are arranged segmentally in ganglia associated with the legs. In this class of cheliceriformes, the left and right mushroom body lobes are small and are confluent at the protocerebrum's midline.
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