Summary
Despite the evident efficiency with which ophiuroids discard their arms, there has been no attempt to understand how the arm is equipped anatomically to achieve and recover from autotomy. A light microscope study of the breakage plane ofOphiocomina nigra revealed a series of features which can be interpreted as adaptations for the process of autotomy. The epidermis splits at a constriction which acts as a pre-determined line of least resistance and which serves to leave lateral flaps for the protection of the retained wound surface. The radial nerve breaks at a level where its cross-sectional area is least and which avoids the ectoneural ganglion; at this point the nerve is attached to the floor of the epineural canal by a collagenous structure which may facilitate its rupture. The lateral compression of the radial haemal canal at the breakage plane is believed to assist its closure after autotomy. The sphincters of the radial water vascular canal are described and it is suggested that since they occur just proximal to the breakage plane, one of their functions may be to seal off the canal after autotomy.
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I would like to thank Professor N. Millott for his enthusiastic supervision of my work which was supported by a N.E.R.C. research studentship. I am also indebted to Dr. S.J.F. Gorzula whose herpetological interests first brought my attention to the possibility of analogies between the autotomy planes of lizards and ophiuroids
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Wilkie, I.C. Functional morphology of the autotomy plane of the brittlestarOphiocomina nigra (abildgaard) (ophiuroidea, echinodermata). Zoomorphologie 91, 289–305 (1978). https://doi.org/10.1007/BF00999817
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DOI: https://doi.org/10.1007/BF00999817