ABSTRACT
Evisceration in the dendrochirote holothurian Eupentacta quinquesemita (Selenka) is associated with the sudden breakdown of three autotomy tissues. These tissues were examined before, during and after evisceration to investigate the presence of autotomy related specializations and to elucidate the morphological events associated with autotomy. The tissues are characterized by a preponderance of connective tissue and also contain muscle and nerve. Axon-like processes containing large electron-dense vesicles (LDVs) are found in the connective tissue and in association with muscle cells. These processes are similar to the neurosecretory-like processes described for other echinoderm autotomy tissues. Autotomy is part of the general phenomenon of variable tensility in echinoderm connective tissues and involves a change in the connective tissue matrix. During autotomy, the matrix loses its structural integrity causing collagen fibril disarray and disorganization of associated cells. Some axon membrane and basal lamina disruption occurs, but the vesicles contained in axons and the LDVs appear to remain in tact. The vesicles contained in locally distributed axons do not appear to be the source of agents that effect connective tissue breakdown; an alternate source is discussed.
