Metabolism and elemental composition of aggregate and solitary forms of Salpa thompsoni (Tunicata: Thaliacea) in waters off the Antarctic Peninsula during austral summer 1999

Abstract

Oxygen consumption, ammonia excretion and phosphate excretion rates were measured on the aggregate form (aggregated sexual blastozooid generation) and solitary form (solitary asexual oozooid generation) of Salpa thompsoni sampled from waters off the Antarctic Peninsula from December 1999 to February 2000, in conjunction with body composition analysis (water, ash, carbon, nitrogen and phosphorus). The specific metabolic rates of S. thompsoni were weight-independent. No significant differences between the aggregate and solitary forms were observed for the weight-specific rates with the exception of the oxygen consumption rate on phosphorus weight. Metabolic loss estimated for the aggregate and solitary forms was 3.0 and 3.5% day−1 for body carbon, 1.6 and 1.8% for body nitrogen, 3.9 and 10.6% for body phosphorus, respectively. Contents of carbon (6.0% of dry weight for the aggregate form and 5.1% for the solitary form), nitrogen (1.5 and 1.3%) and phosphorus (0.15 and 0.11%) tended to decrease with the increase of dry weight. All mean values of each body constituent (water, ash, C, N and P) for the aggregate and solitary forms were not significantly different in the same dry weight ranges.