Sandeman R, Clarke D, Sandeman D, Manly M
School of Biological Science, University of New South Wales, Sydney NSW 2052, Australia.
J Neurosci. 1998 Aug 15;18(16):6195-206. doi: 10.1523/JNEUROSCI.18-16-06195.1998.
Freshwater crayfish increase in size throughout their lives, and this growth is accompanied by an increase in the length of the appendages and number of mechanoreceptive and chemoreceptive sensilla on them. We find that in the Australian freshwater crayfish Cherax destructor, neuropil volumes of the olfactory centers increase linearly with body size over the entire size range of animals found in their natural habitat. The number of cell somata of two groups of interneurons associated with the olfactory centers (projection neurons and small local neurons) also increases linearly with the size of the animals. In contrast, axon counts of interneurons that represent a nonolfactory input to the olfactory centers show that these reach a total number in the very early adult stages that then remains constant regardless of the size of the animal. Only the axon diameter of these interneurons increases linearly with body size. Amputation of the antennule and olfactory sensilla reduces the number of projection and local interneurons on the amputated side. No change in the size of the olfactory centers occurs on the unamputated side. Amputation of the olfactory receptor neurons in crayfish therefore leads not only to a degeneration of the receptor cell endings in the olfactory lobe but also to a trans-synaptic response in which the number of higher order neurons decreases. Reconstitution of the antennule and olfactory receptor neurons in small adult crayfish is accompanied by the reestablishment of the normal number of interneurons and neuropil volume in the olfactory centers.
淡水小龙虾在其一生中体型不断增大，这种生长伴随着附肢长度的增加以及其上机械感受器和化学感受器数量的增多。我们发现，在澳大利亚淡水小龙虾澳洲红螯螯虾中，在其自然栖息地所发现的整个体型范围内，嗅觉中枢的神经纤维网体积随体型呈线性增加。与嗅觉中枢相关的两组中间神经元（投射神经元和小型局部神经元）的细胞体数量也随动物体型呈线性增加。相比之下，代表对嗅觉中枢非嗅觉输入的中间神经元的轴突数量显示，这些轴突在成年早期就达到总数，之后无论动物体型大小都保持不变。只有这些中间神经元的轴突直径随体型呈线性增加。切除触角和嗅觉感受器会减少切除侧投射神经元和局部中间神经元的数量。未切除侧的嗅觉中枢大小没有变化。因此，切除小龙虾的嗅觉受体神经元不仅会导致嗅觉叶中受体细胞末梢的退化，还会引发一种跨突触反应，其中高阶神经元的数量会减少。在小型成年小龙虾中重建触角和嗅觉受体神经元会伴随着嗅觉中枢中间神经元正常数量和神经纤维网体积的重新建立。
