CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP 



Figure 4. — Average growth in length of female Meta- 

 mysidopsis in the laboratory. The lower curve (fine 

 continuous line) was fitted to molt size data (Fig. 2). 

 The steps represent changes in integument size. The 

 upper curve (heavy broken line) represents the average 

 size of the animals, assuming that the addition of body 

 tissue is continuous. 



- alongalion of pleopodi ond or'enna* 1 3B dart I 



Figure 5. — Average gro%vth in length of male Meta- 

 mysidopsis in the laboratory. The lower curve (fine 

 continuous line) was fitted to molt size data (Fig. 3). 

 The steps represent changes in integument size. The 

 upper curve (heavy broken line) represents the average 

 size of the animals, assuming that the addition of body 

 tissue is continuous. 



males grow more slowly. The males develop 

 easily recogriized secondary sexual character- 

 istics at an average age of 38 days and become 

 sexually mature after about 48 days. Average 

 age at maturity was estimated from observa- 

 tions of testes and copulatory behavior in the 

 laboratory as well as from external morphology. 



Average Growth in Weight 



To estimate gro\vth in terms of energy it is 

 necessary to translate growth in length into 

 growth in dry weight. This growth in dry 

 weight is then translated into growth in organic 

 (ash-free) weight and thereafter into calories. 



The dry weights of Metamysidopsis of body 

 lengths ranging from 1.9 mm to 6.5 mm were 

 determined. The animals were captured alive, 

 measured, washed very briefly with distilled 

 water, and dried at 60° C in an oven for 24 hr. 

 They were then weighed individually on a Cahn 

 electrobalance immediately after they were re- 

 moved from the oven. 



The observed relationship between body 

 length and dry weight is shown in Figure 6. 



Figure 6. — Relationship between body length and dry 

 weight of Metamysidopsis. 



The equation for the relationship was deter- 

 mined empirically by fitting a straight line to 

 the logarithms of body length and dry weight 

 by the method of Bartlett (1949). The rela- 

 tionship is: 



log,, (weight) = -5.436 + 2.77 log,, (length) 



or 



weight = 0.00436 (length)^ " 

 where weight is expressed in mg and length in 

 mm. 



It is common to assume that body weight and 

 body volume have a linear relationship, and that 

 body volume is proportional to the third power 

 of length. Therefore dry weight is expected to 



99 



