Evisceration behaviour and the seasonal incidence of evisceration in the holothurianEupentacta quinquesemita(Selenka)

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Abstract
Evisceration of the dendrochirote holothurian Eupentacta quinquesemita (Selenka) results from softening of three autotomy structures, the P-L tendon, the intestine-cloacal junction and the introvert. The internal organs are expelled anteriorly through rupture of the introvert. Visceral autotomy occurs under natural conditions and is seasonal. Evisceration started in September and continued through November. By November 1982, 76% of the holothurians at one site and 49% at a second site had eviscerated. Specimens collected in the following winter months had regenerating or newly functional digestive tracts. Regeneration under natural conditions takes approximately 2–4 weeks. The extent of annual evisceration appears to be variable from year to year. Seasonal evisceration may serve as an economic autotomy excretory mechanism, whereby waste-laden digestive tracts are discarded after an active summer of feeding. The induction of autumnal evisceration is probably a complex interaction of internal and environmental factors. During the spring and summer the incidence of evisceration decreased or was absent and its occurrence during these months may be in response to asteroid predation.