軟絲大腦視葉對體色的神經調控機制

Neural organization of the optic lobe for controlling body patterns in oval squids Sepioteuthis lessoniana

劉璁翰(Tsung-Han Liu)

指導教授 ： 焦傳金

國立清華大學/生命科學院/分子醫學研究所/博士(2017年)

摘要

在自然界中，頭足類擁有快速改變體色的能力，牠們利用改變體色來進行快速的偽裝或是作為同物種間的溝通方式。在牠們的神經系統中，大腦視葉被認為是控制色素細胞進而產生多樣體色變化的重要角色。然而，我們對於視葉的功能性組織與如何運用神經控制所產生的各種體色變化仍舊所知甚少。在本研究中，我們利用電刺激軟絲(萊氏擬烏賊)大腦視葉的方式探究其體色變化的神經控制。從我們的實驗結果得知，視葉控制同側色素細胞變化的現象只發生在控制體胴上的色素細胞，而非頭部或是腕部。除此之外，視葉控制體表色素細胞面積的大小與給予的電刺激強度以及電刺激視葉的深度有正相關。這結果顯示，視葉主要為同側的體色控制並且在其功能性的組織上，有著垂直聚集的特性。我們更進一步分析14種因電刺激所產生的體色基本單元以及它們各自在視葉中的電刺激點位，發現每一種體色基本單元都能透過刺激視葉中不同的區域而誘發。而在一個刺激點位裡，也可以同時誘發不止一種體色基本單元被呈現。這個發現顯示，軟絲的每個體色基本單元，在其視葉中都具有多個運動單元在控制。而這些運動單元，則是以一種鑲嵌的型式在其視葉中分佈。在頭足類大腦視葉裡，這種重複且多樣組合的運動單元正好反映了頭足類生物能產生各種體色基本單元的組合，進而產生各式各樣的體色變化。

關鍵字

色素細胞 ； 動態體色變化 ； 電刺激 ； 運動單元 ； 軟絲

並列摘要

Cephalopods have highly dynamic skin coloration changes that allow rapid camouflage and intraspecies communication. The optic lobe is thought to play a key role in controlling the expression of the chromatophores that give rise to their diverse body patterns. However, the functional organization of the optic lobe and neural control of the various body patterns by the optic lobe are largely unknown. We applied electrical stimulation within the optic lobe to investigate the neural basis of body patterning in the oval squid, Sepioteuthis lessoniana. Most areas in the optic lobe mediated predominately ipsilateral expression of chromatophores present on the mantle, but not on the head and arms; furthermore, the expanded areas after electrical stimulation were positively correlated with an increase in stimulating voltage and stimulation depth. These results suggest a unilaterally dominant and vertically converged organization of the optic lobe. Furthermore, analyzing 14 of the elicited body pattern components and their corresponding stimulation sites revealed that the same components can be elicited by stimulating different parts of the optic lobe and that various subsets of these components can be coactivated by stimulating the same area. These findings suggest that many body pattern components may have multiple motor units in the optic lobe and that these are organized in a mosaic manner. The multiplicity associated with the nature of the neural controls of these components in the cephalopod brain thus reflects the versatility of the individual components during the generation of diverse body patterns.

並列關鍵字

chromatophores ； dynamic skin coloration ； electrical stimulation ； motor units ； oval squids

參考文獻

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