Thompson K J, Roosevelt J L
Department of Biology, Agnes Scott College, Decatur, Georgia 30030, USA.
J Comp Neurol. 1998 Apr 27;394(1):14-28.
A uniquely female behavior in grasshoppers, oviposition, is driven by neural circuitry in the terminal abdominal segments of the female's central nervous system. Because it is known that the embryonic pattern of neuroblasts is sexually monomorphic in these animals, we were interested to know how the central nervous system of adults is organized to support the obvious behavioral dimorphism. Here, we compare three classes of identifiable adult neurons: ovipositor motor neurons, efferent dorsal unpaired median (DUM) neurons, and DUM interneurons in the eighth abdominal neuromere. Cobalt backfills of the eighth tergal nerves revealed identical complements of motor neurons in males and females. Included among these neurons in the male were putative homologues of two sets of ovipositor muscle motor neurons. Whereas these motor neurons supply two ovipositor muscles in the female, they are divided to supply three muscles in males. The eighth abdominal neuromere of both sexes contained seven efferent DUM neurons, but peripheral axon projections varied between males and females in accordance with gender-specific targets. In the eighth neuromere of females, some 22 small cell bodies of DUM interneurons were stained with Toluidine blue, whereas only three male DUM interneurons were found. Male muscle homologues were induced to express a rhythmical motor pattern by experimental methods that activate the oviposition pattern in females. The induced pattern in males is of unknown behavioral significance. Although oviposition normally occurs only after sexual maturity, the motor pattern could be activated at all life stages in females, including embryos, as early as 90% of embryonic development.
在蚱蜢中，一种独特的雌性行为——产卵，是由雌性中枢神经系统腹部末端节段的神经回路驱动的。由于已知这些动物中神经母细胞的胚胎模式在性别上是单态的，我们很想知道成年动物的中枢神经系统是如何组织起来以支持明显的行为二态性的。在这里，我们比较了三类可识别的成年神经元：产卵器运动神经元、传出性背中线上的（DUM）神经元以及第八腹节神经节中的DUM中间神经元。对第八背板神经进行钴逆行填充显示，雄性和雌性的运动神经元组成相同。在雄性的这些神经元中，包括两组产卵器肌肉运动神经元的假定同源物。在雌性中，这些运动神经元支配两块产卵器肌肉，而在雄性中，它们被分开支配三块肌肉。两性的第八腹节神经节都包含七个传出性DUM神经元，但外周轴突投射在雄性和雌性之间因性别特异性靶点而有所不同。在雌性的第八神经节中，约22个DUM中间神经元的小细胞体被甲苯胺蓝染色，而在雄性中仅发现三个DUM中间神经元。通过激活雌性产卵模式的实验方法，诱导雄性肌肉同源物表达一种节律性运动模式。雄性中的诱导模式的行为意义尚不清楚。尽管产卵通常只在性成熟后发生，但在雌性的所有生命阶段，包括胚胎，早在胚胎发育的90%时，这种运动模式就可以被激活。
