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.