Biometric Relationships Between Organ Indices, Fecundity, Oxygen Consumption and Body Size in Acanthaster Planci (L.) (Echinodermata; Asteroidea)

Crown-of-thorns starfish, Acanthaster planci, range in size from newly settled recruits of approximately 0.5 mm diameter to adults exceeding 500 mm diameter, a linear range of about three orders of magnitude. Many morphological and physiological parameters vary over this size range and to investigate these variations starfish were measured for diameter, whole wet weight and underwater weight, and for the body compartments, stomach, pyloric caeca, gonads and body wall. There are significant increases in the calorific and dry weight indices for the gonad with increasing size and this is offset by decreases in body wall and caecal indices. Thus, larger starfish partition increasingly heavily towards reproduction at the expense of the body wall and caeca. Oxygen consumption was measured in a closed respiration chamber and found to increase regularly with respect to weight. The slope coefficient for In(oxygen consumption) versus In(wet weight) is 0.870. There is no indication that starfish larger than 500 mm diameter are metabolically unique.