Juxtaligamental system of the disc and oral frame of the ophiuroid Amphipholis kochii (Echinodermata: Ophiuroidea) and its role in autotomy

Abstract. The ophiuroid Amphipholis kochii is able to detach its central disc from the underlying oral frame in response to external stimuli. In this article we supply new observations on the microanatomy and ultrastructure of the autotomy plane, and of the juxtaligamental system which is believed to bring about connective tissue changes that underpin the detachment process. We correct previous confusion over the innervation of juxtaligamental nodes involved in disc autotomy, provide evidence that juxtaligamental cells are a population of specialized nerve cells, and present observations on changes in the ultrastructure of juxtaligamental cells during autotomy, which support the view that they are responsible for connective tissue disruption.