CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP 



mysid protein is calculated as: 



% C 



(0.08) (0.50) -(0.11) (0.77) 



L[0.42 



-0.79 



— (0.02) (0.40)] 



= 0.364 



= 36.4 % 



This is considerably less than the average value 

 of 52 '( carbon in protein given by Hawk, Oser, 

 and Summerson (1954), but similar to an esti- 

 mate of 37 % made from the data of Lasker 

 (1966), and higher than an estimate of 23 Sr 

 made from the data of RajTiiont et al. (1964). 

 The second step in finding the relationship 

 between chitin and protein in the molts was to 

 estimate the chitin fraction from the following 

 relationship: 



(chitin fraction) (9f C in chitin) 



+ (protein fraction) (9f C in pi-otein) 

 = (% C in molt) 



where 



chitin fraction + protein fraction 



1.0. 



The chitin fraction calculated from this rela- 

 tionship is 44 % for the organic molt. The 

 protein fraction is therefore estimated to be 

 56 ^,x . This result suggests that a large fraction 

 of the chitin may be reabsorbed by the animals 

 before molting. This seems reasonable because 

 in Crustacea the new endocuticle is formed dur- 

 ing the intermolt period (between 2 % and 46 % 

 of the time between molts, according to Passano, 

 1960). 



To estimate the protein content of eggs and 

 larvae, we have made some arbitrary assump- 

 tions that seem reasonable, and that do not 

 measurably affect our energy calculations in any 

 event. We have assumed that the eggs do not 

 contain a measurable amount of carbohydrate, 

 and that they contain little or no chitin because 

 the integument is not yet formed. Therefore, 

 we have assumed that the organic fraction of 

 the eggs is either protein or lipid. For late 

 stage larvae we have also assumed that carbo- 

 hydrate is absent, but that some chitin is pre- 

 sent because they form integument and molt 



once before they are released. We have as- 

 sumed that the organic fraction of the larvae 

 contains half the amount of chitin as the adults, 

 or 4 %. 



The protein-lipid composition of the eggs was 

 calculated from the carbon content of the ash- 

 free fraction. We have estimated (above) that 

 36.4 % of the mysid protein is composed of 

 carbon, that 77 % of the lipid is carbon, and 

 that 61.8 '~r of the ash-free egg is carbon. By 

 using these values we calculate that the organic 

 fraction of the eggs is 62.5 % lipid and 37.5 % 

 protein. The carbon content of intermediate 

 age brood pouch young (about 5 days old) was 

 less than that of eggs and more than that of 

 late stage larvae. For these intermediate age 

 young we calculate a lipid content of 43 %. 



ENERGY CONTENT 



Juveniles - Adults 



The ash-free calorie content of Metamysidop- 

 sis was determined in a Parr non-adiabatic cal- 

 orimeter. The data, converted to ash-free 

 values, are given in Table 4. Three of the 

 samples contained so little material that Nujol 

 supplement had to be added to raise the heat of 

 combustion to a measurable level. All three of 

 these measurements fell outside the 95 % con- 

 fidence limits of the six determinations made 

 without the Nujol supplement. The variability 

 among the three supplemented determinations 

 can be attributed to the ± 2 % variation of the 

 caloric content of the Nujol supplement (10,791 

 ± 200 cal/g) , because the weight of the supple- 

 ment greatly exceeded the weight of the sample 

 material in each case. 



Table 4. — Ash-free' caloric content of Metamysidopsis. 



Specimens 



Dry 

 weight 



Calorie 

 content 



^ Ash content 12.5 % used in all calculations. 

 2 Nujol supplement used in determinotions. 



107 



