FREE AMINO ACIDS IN INVERTEBRATES 161 
a-amino nitrogen per 100 g of fresh tissue®, 7. Intracellular free amino acids are more 
abundant in marine than in fresh water forms! 8. This was shown at least to be the 
case in a comparative study of the North Sea lobster (Homarus vulgaris), the spider 
crab (Mata squinado), the chinese crab (Evriochetr sinensis) and the crayfish (A stacus 
fluvialis) and in a comparative study of tissues of lamellibranch molluscs and some 
worms. A series of experiments were carried out by DUCHATEAU et al.® to define the 
ABE, TT 
FREE AMINO ACIDS IN LOBSTER MUSCLE AND ROOSTER MUSCLE 
Values are expressed in mg/100 g wet wt. 

Rooster Lobster 
Alanine 5.2 133.0 
Arginine 13 178.0 
Glycine E223 1025.0 
Leucine 1.6 9.3 
Lysine 2.5 23.0 
Methionine 1.0 II.0 
Phenylalanine 1.3 5.4 
Proline 4.0 728.0 
Threonine 2.8 8.6 
Valine 18} 22.0 
Total 33-3 2743-3 

conditions under which the concentration of free amino acids vary in relation to 
environment; from a study with the crab Carcinus maenas L. they concluded that 
free amino acid concentration decreases as the salinity of the medium decreases. 
When living in sea water, the crab muscle had a total of 2940 mg/100g of amino 
acids (the sum of 15 amino acids measured microbiologically in the muscle). When 
sea water was diluted 1 : 1 and the animals adapted to the new environment for 2 
TABLE III 
THE NITROGENOUS COMPOUNDS PRESENT IN AQUEOUS EXTRACTS OF LOBSTER MUSCLE AND 
HEPATOPANCREAS* 
Values are expressed in mg/too g wet wt. 


Tixsaie Total a-A mino se eid Betaine Glutamine Volatile 
N zat exile N amide base N 
Muscle 820 358 100 92 2 IO 
Muscle 726 306 104 96 30 8 
Muscle 805 280 106 — — — 
Muscle 749 369 IIo — 26 14 
Hepatopancreas 628 248 17 gI 12 30 
Hepatopancreas 625 233 21 85 19 16 

* From a paper by KERMACK, LEES AND Woop?®. 
References p. 174/175 
