Torres et al Energetics of larval Saaenops ocellatus 



761 



larvae were lower at 0.05—0.14 nL/ind./h for 21—31 

 \ig fish and 0.26-0.28 ^L/ind./h for 52-68 ng larvae. 

 The regression of absolute oxygen consumption 

 versus mass in larval red drum conformed to the 

 equation Y = aM h (Fig. 1) and had a slope or "6 value" 

 of 1.04 (±0.08), which is greater than the most widely 

 used figure of 0.75 (Schmidt-Nielsen, 1983), and the 

 slope of 0.80 commonly cited for adult fish (Brett and 

 Groves, 1979; Houde, 1983; Prasad, 1986). The slope 

 of 1.04 (±0.08) exhibited by red drum larvae indi- 

 cates that oxygen consumption scaled directly with 

 body mass ( 1.0) rather than with surface area (0.67). 

 It is becoming increasingly apparent that metabo- 

 lism scales isometrically with mass in larval fishes 

 (see review by Giguere et al., 1988); thus, a b value 

 of 1.0 is the norm rather than the exception for lar- 

 val fishes and most likely for larval forms in general 

 (Manahan, 1990). 



Feeding metabolism 



Oxygen consumption rates for two-week-old red drum 

 starved for 24 h declined to about 50% of those for 

 fed individuals (Table 2), which is within the range 

 reported in larval starvation studies with several 

 other species (Holliday et al., 1964; Giguere et al., 

 1988; Tucker, 1989). The reduction of oxygen con- 

 sumption in starved versus fed individuals reflects 

 the decrease in energy expenditure associated with 

 feeding metabolism, otherwise known as specific 

 dynamic action (SDA) (Kleiber, 1961; Ki0rboe et al., 

 1985; 1987; Ki0rboe, 1989). Jobling (1981a, 1983) 

 suggested that SDA represents the energy expendi- 

 ture associated with growth. His arguments may be 

 summarized as follows. Biosynthesis is an energy- 

 requiring process (Lehninger, 1985). As a conse- 

 quence, some fraction of the adenosine triphosphate 



