Embryonic Development of the Central Nervous System in the Cricket, Gryllus bimaculatus : I. Segmental Homologies in Early Neurogenesis

概要

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The embryonic neurogenesis of the cricket Gryllus bimaculatus is described with reference the segmental homology of its central nervous system (CNS). The neurogenesis of the cricket embryo starts with the differentiation of neuroblasts (NB_s) from the ventral dermatoblast layer in each segment. NB_s repetitively produce their progenies by unequal division. The columns consisting of NB and its progenies are formed on the dorsal side. This can be demonstrated directly by a horseradish peroxidase injection into the explanted embryo. A set consisting of one NB and the column of its progenies is, therefore, the primary element of the developing CNS. The number and arrangement of NB_s for all segments resemble each other. There are 31 NB_s in the ganglion hemisphere of the gnathal and thoracic segments, and 28 in the abdominal ones. These values are similar to those reported for the locust and grasshopper. Furthermore, the double-rung ladder structure of the axonal processes of the ganglion cells, which are NB progenies, could be observed in all segments as a result of silver staining. The segmental ganglion of the cricket, therefore, consists of homologous neuron sets produced by segmentally homologous NB_s.
社団法人日本動物学会の論文
1983-09-25