CLUTTER and THEILACKER, PELAGIC MYSID SHRIMP 



whole animals or molts in a muffle furnace at 

 500° C and weighing the residue. Ash determi- 

 nations were made on six samples composed of 

 mixed animals, juveniles, immatures, adult 

 males, and adult females. The samples con- 

 tained from 2.7 to 7.3 mg of dried animals ; 

 the mean ash content was 12.5 % of the dry 

 weight, and the range was 9.4 to 13.3 % . There 

 was no obvious difference between age groups 

 or sexes. This ash content is within the range, 

 but slightly higher than the mean, of values re- 

 ported for other Mysidae: Mysis flexuosa — 

 16 ^f (Hensen, 1887) and 11.9 '^h (Delff, 1912, 

 quoted by Vinogradov, 1953); Neomysis integer 

 — 7.9 % (Raymont, Austin, and Linford. 1964) ; 

 Siriella aequiremis  — 10.2 ^r (Omori, 1969). 



Molts used for ash determinations were col- 

 lected in the laboratory immediately after they 

 were shed. Two samples, weighing 1.1 and 0.6 

 mg, composed of molts from a wide size range 

 of mysids of both sexes had ash contents of 

 44.4 % and 45.7 Sf; the mean was 44.8 %. 

 Lasker (1966) reported a similar value (46 %) 

 for Euphausia pacifica. This high ash content 

 in the molts suggests that a large fraction of 

 the total body ash resides in the integuments of 

 the whole animals. From 10 observations, we 

 have found that the dry weight of the molt is 

 on the average 13 "^r of the dry weight of the 

 animal that sheds the molt. Assuming that the 

 ash content of the molt is the same as the ash 

 content of the integument of the whole animal, 

 we estimate that 47 % of the body ash resides 

 in the integument. 



Ash content of brood pouch young was esti- 

 mated fi-om a large number of specimens taken 

 from live females. A dry sample of 0.6 mg of 

 newly hatched larvae had an ash content of 

 6.1 %. A sample of 1.2 mg of late stage larvae 

 had an ash content of 6.6 ',?  Ash content of 

 eggs was not determined; we assume that the 

 ash content is slightly less than that of the 

 newly hatched larvae, and we have used a value 

 of 6.0 %. 



Nitrogen and Carbon 



Nitrogen content was determined by the 

 micro-Kjeldahl method from three samples of 

 mixed juvenile-adult animals. The dry weights 



of the samples were 12, 24, and 63 mg, and 

 contained 13.1 %, 11.7%, and 11.2 % nitrogen 

 respectively; the mean was 11.5 % of total dry 

 weight. From a large number of determina- 

 tions, Raymont et al. (1964) found a value of 

 11.4 % for Neo?nysis integer. Omori (1969) 

 reported 11.0 % for Siriella aequiremis, and 

 Jawed (1969) found 11.9 % for Neomysis rayii. 



Carbon content was determined with an F 

 and M carbon analyser model 180, described 

 by Lasker (1966). We assume that all organic 

 carbon, including that in chitin, is liberated by 

 this method. 



Three samples of females, without young, that 

 weighed 0.2 to 0.4 mg, had carbon fractions be- 

 tween 35.6 9f and 38.1 % of dry weight; the 

 mean was 36.8 %. This estimate is intermedi- 

 ate among other values reported for mysids: 

 Lophogaster sp. (family Lophogastridae) — 

 46.8 % (Curl, 1962a); Neomysis integer — 

 30.2 % and 29.5 % (Raymont et al., 1964, 1966) ; 

 mixed mysids and euphausids — 40.7 % (Beers, 

 1966); Siriella aequiremis — 42.4 (Omori, 

 1969). From his analysis of several kinds of 

 arthropods, Curl (1962a) found an average of 

 about 38 ':? of the dry weight as carbon. He 

 points out that this is about % of the commonly 

 assumed value of 50 % (Krogh, 1934). 



In our carbon analysis of molts and young, 

 we found that a 0.2-mg sample of fresh dried 

 molts had 23.5 ^'r carbon, a 0.4-mg sample of 

 eggs had 58.0 % carbon, a 0.4-gm sample of 

 midstage larvae had 47.1 % carbon. The carbon 

 contents of the ash-free organic fractions of the 

 material were calculated from these values. 

 Lasker (1966) found 17 % carbon in the molts 

 of Euphausia pacifica and 50 % carbon in the 

 eggs. 



Macromolecular Components 



We assume that the body nitrogen of our spe- 

 cies, Metamysidopsis , is present as protein, free 

 amino acids, and chitin (Raymont, Austin, and 

 Linford, 1968). We made no evaluation of 

 chitin content, but used the value of 7 % de- 

 termined for Neomysis integer by Raymont et al. 

 (1964). The percent "protein" (may include 

 free amino acids) was estimated by the follow- 

 ing relationship, given that 16 % of "protein" 



105 



