Energy and nutrient utilization of juvenile green abalone (Haliotis fulgens) during starvation

Juvenile green abalone Haliotis fulgens (mean length = 65.15 mm; mean weight = 38.77 g) were fed a standard formulated diet for 15 days (acclimation period), and then starved for 27 days. Following the starvation period, wet weight loss was 13.4%. Crude protein and NFE accounted for 69.9% and 31.5%, respectively, of the total net loss in dry weight that was calculated to be a total loss of 3.57 kcal/organism. Lipid content of the tissue increased by 1.0% (dry weight) while protein content remained unchanged. Plasma levels of free amino acid, soluble protein and glucose were determined on days 0, 7, 14, 21 and 27. The level of plasma glucose significantly decreased after the first 7 days, 34 to 10 μm/ml, and then leveled at 15 μm/mL. Soluble protein in the plasma decreased from 3.33 to 2.6 mg per ml during the starvation period. Taurine was the principal free amino acid among the plasma amino acids, comprising approximately 50-65% and showing a net decrease of almost 75% at 27 days. For the essential amino acids, gross levels of histidine and arginine decreased significantly and correspondingly produced substantially higher net decreases. For the non-essential amino acids, plasma levels of alanine, proline, tyrosine, glutamic acid, and serine decreased significantly by day 27 or earlier, but proportional composition remained similar. After starvation, changes in the gross amounts (μg/mg total dry weight) of some essential and non-essential amino acids in the muscle and visceral tissue occurred, but their relative proportions remained essentially unchanged. The ratio of the concentration of non-essential to essential amino acids in both the muscle and viscera (approximately 1.9) did not change after starvation. The mean net change of non-essential amino acid content per abalone (within muscle tissue) was higher (-41.8) than that of the essential amino acids (-8.9). In contrast to all other amino acids, little or no loss of arginine, histidine and threonine occurred. Plasma levels of carbohydrates and protein in starved abalone dramatically decrease within the first two days and then decrease very slowly. Muscle protein is the principal source of energy, and non-essential amino acids are preferentially used. Retention of arginine in the muscle tissue may reflect its need in arginophosphate for muscle contraction. By converting the decrease in weight to energy loss, the amount of energy used for basal metabolism during starvation was estimated to be 2.99 cal g org-1 day-1.