Reed C M
Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2UQ, UK.
Cell Tissue Res. 1995 Dec;282(3):503-12. doi: 10.1007/BF00318882.
Squid chromatophores are organs of colour change, consisting of a pigment sac opened by contraction of 10-24 radial muscle fibres. The ultrastructure and innervation of these muscle fibres were examined by electron microscopy and diagramatic reconstructions made on the basis of serial ultra-thin sections. At the proximal end of the fibre, nearest the pigment sac a cortical myofilament zone surrounds 2 cores containing mitochrondria; further along the fibre these merge to form one central core. The myofilament zone forms a groove containing a nerve bundle consisting of 2 to 4 axons per muscle fibre. The axons are surrounded by glial cell processes, and either originate from a neighbouring fibre, or join the fibre at some point along its length. Axons twist around each other, forming a series of synapses with the muscle fibre. As many as 6-37 synapses exist along the length of each muscle fibre; the mean synapse interval is 9.05 microm, but the largest may be 123 microm. At the distal end of the muscles, the nerve is located towards the middle of the fibre, which it penetrates as the muscle splits up. Electron-lucent vesicles are present in all synaptic regions, but electron-dense vesicles are only found towards the distal end of the fibre. There is thus a possibility that more than one neurotransmitter is present in the nerves innervating chromatophores. Electron-lucent and dense-cored vesicles are not colocalised.
鱿鱼色素细胞是颜色变化的器官，由一个色素囊组成，该色素囊通过10 - 24条放射状肌纤维的收缩而打开。通过电子显微镜检查了这些肌纤维的超微结构和神经支配情况，并基于连续超薄切片进行了图解重建。在纤维的近端，最靠近色素囊的地方，一个皮质肌丝区围绕着2个含有线粒体的核心；沿着纤维再往前，这些核心合并形成一个中央核心。肌丝区形成一个凹槽，其中包含一个神经束，每条肌纤维有2至4条轴突。轴突被神经胶质细胞突起包围，要么起源于相邻的纤维，要么在纤维长度的某个点与纤维相连。轴突相互缠绕，与肌纤维形成一系列突触。每条肌纤维的长度上存在多达6 - 37个突触；平均突触间隔为9.05微米，但最大间隔可能为123微米。在肌肉的远端，神经位于纤维的中部，随着肌肉分裂而穿透纤维。在所有突触区域都存在电子透明囊泡，但仅在纤维的远端发现电子致密囊泡。因此，支配色素细胞的神经中可能存在不止一种神经递质。电子透明囊泡和致密核心囊泡并非共定位。
