Relationship between metabolic rate in vitro and body mass in a marine teleost, porgy Pagrus major

The rate of oxygen consumption of minced whole body was determined volumetrically, as an indication of metabolic rate in vitro (M_{in vitro}), at 20°C in porgy Pagrus major ranging from 0.0002 g (just after hatch) to 2.9 g (67 days old) in body mass. A triphasic relationship was found between M_{in vitro} of individual fish (μl.min^-1) and wet body mass W (g). During the prolarval stage accompanied with the transitional period to the postlarval stage (0.00020-0.00023 g, 0-6 days old), the mass-specific metabolic rate in vitro (M_{in vitro}/W in μl.g^-1.min^-1) increased with age (D in days) as expressed by an equation M_{in vitro}/W = 3.88 + 0.74/D. During the postlarval stage (0.00031-0.003 g, 8-22 days old), M_{in vitro}/W remained almost constant, independent of body mass following an equation M_{in vitro}/W = 5.24 W^-0.085. During the juvenile and adolescent stages (0.0047-2.9 g, 30-67 days old), M_{in vitro}/W decreased with increasing body mass following an equation M_{in vitro}/W = 1.66 W^-0.235. These results correspond with the triphasic relationship between metabolism in vivo and body mass observed in intact porgy of 0.0002-270 g (Oikawa et al. 1991). It is concluded, therefore, that the dependence of mass-specific metabolic rate on body size exists in vitro as well as in vivo, during the early stages in the porgy. Based on these results, factors controlling the metabolism-size relationship are discussed.