FISHERY BULLETIN: VOL. 69, NO. 1 



The mean for the six nonsupplemented sam- 

 ples is 5,240 cal/g (shown as 5.24 cal/mg in 

 Table 3). No significant differences in energy 

 content among developmental stages nor be- 

 tween sexes were found. 



This mean calorie content estimate is some- 

 what lower than those reported for other Crus- 

 tacea. Slobodkin and Richman (1961) gave 

 values of 5.4 to 5.6 cal/ash-free mg; Lasker 

 (1965) reported a range of 4.9 to 5.4 cal/mg (in- 

 cluding ash) for two species of copepods. Our 

 mean value is also lower than the value that can 

 be calculated from the information on body 

 composition, together with reported average 

 values of the calorie content of animal pi-otein, 

 fat, and carbohydi'ate. Conversion factors given 

 by Horowitz (1968) are: protein, 5.5 cal/mg; 

 fat, 9.3 cal/mg; and carbohydrate, 4.1 cal/mg. 

 Since chitin is glucosamine, we have assumed 

 that it, like carbohydrate, has a calorie content 

 of 4.1 cal/mg. From these conversion factors 

 and the composition data given in Table 3, we 

 calculated an expected value of about 5.77 

 cal/ash-free mg. 



We use the empirical value, 5.24 cal/ash-free 

 mg, in our subsequent energy budget calcula- 

 tions. We consider this to be a conservative 

 estimate, because it assumes that the mysid pro- 

 tein has an energy content of only 4.8 cal/mg. 

 This lower than expected estimate may be re- 

 lated to the empirical observation that the mysid 

 protein contains only 36 9^ carbon, rather than 

 about 50 % as is commonly assumed for animal 

 protein. 



The juvenile and adult Metamysidopsis con- 

 tained 12.5 % ash; therefore, the energy in the 

 whole dry body of an adult or juvenile is esti- 

 mated to be: (4.6 cal/mg) x (dry weight, 

 mg). 



Molts 



We estimated the energy content of molts in- 

 directly, because it was difficult to obtain enough 

 material for calorie measurements. The ash- 

 free fraction (55 '.i ) of the molts was estimated 

 to be composed of 44 % chitin and 56 9ir protein. 

 By assuming that chitin has an energy content 

 of 4.1 cal/mg, and that the mysid protein has 

 an energy content of 4.8 cal/mg, we calculate 



that the ash-free fraction of the molts has an 

 energy content of 4.5 cal/mg. 



From a sample of 10 animals and their molts 

 we found that the dry weight of molts is on 

 the average 13 % (range 9-19 /r) of the dry 

 weight of the animals that shed them. Lasker 

 (1964, 1966) and Jerde and Lasker (1966) 

 found that the dry molts of a euphausiid were 

 about 10 % of the dry weight of the animals 

 that produced them (range 4-14 %). 



The energy lost by molting Metamysidopsis 

 is thei'efore proportional to the size of the 

 animal: 



(0.13) (0.55) (4.5 cal/mg) 



X (dry weight of animal, mg) 

 or 



(0.32 cal/mg) x (dry weight of animal, mg). 



Eggs and Larvae 



We estimated that eggs were 6 ^r ash, 35 % 

 protein, and 59 % lipid. The energy content of 

 an egg is estimated to be: (0.35) (4.8 cal/mg) 



+ (0.59) (9.3 cal/mg) = 7.16 cal/mg. A 

 sample of 140 eggs was dried and weighed; the 

 mean dry weight per egg was 0.0055 mg. The 

 energy content per egg is tlierefore 0.039 cal- 

 orie. 



We estimated that, just before being released 

 from the brood pouch, the larvae are about 6 % 

 ash, 61 '"r protein, 29 Sr lipid, and 4 ''/c chitin. 

 The energy content of a late stage larva is esti- 

 mated to be: (0.61) (4.8 cal/mg) + (0.29) 



(9.3 cal/mg) + (0.04) (4.1 cal/mg) = 5.78 

 cal/mg. The mean dry weight per larva, esti- 

 mated from 110 individuals, was 0.0051 mg. 

 The energy content per larva is therefore 0.029 

 calorie. 



ENERGY BUDGET AND 

 EFFICIENCY OF ENERGY TRANSFER 



From the data on average growth, age-spe- 

 cific fecundity, respiration rate, and energy con- 

 tent we have calculated cumulative curves of 

 energy use by individual mysids in attaining 

 various stages of development. Data on age- 

 specific natural mortality rates (Fager and Clut- 

 ter 1968) were used to estimate Ix (probability 



108 



