THE COST OF ARM AUTOTOMY IN THE STARFISH STICHASTER-STRIATUS

Arm autotomy in asteroids, as tail autotomy in vertebrates, typically occurs when the animal is attacked and appears to facilitate escape. O ne assumes autotomy has a cost, but it rarely has been demonstrated in the field in vertebrates and never demonstrated in asteroids. The con centration of lipid was 40 % less and the amount of kilojoules 85 % le ss in the pyloric caeca of the asteroid Stichaster striatus Muller & T roschel (Echinodermata: Asteroidea) with autotomized arms than in thos e of individuals with intact arms collected in the field. As the pylor ic caeca are used as nutrient reserves, individuals with autotomized a rms would have a lesser capacity to withstand low availability of food and, as the caecal reserves can be used for gametogenesis, a decrease d capacity for reproduction.