INVITED DISCUSSION 
FREE AMINO ACIDS OF MARINE INVERTEBRATES 
JAMES S. KITTREDGE, DAISY G. SIMONSEN, EUGENE ROBERTS 
AND BOHDAN JELINEK 
Department of Biochemistry, Medical Research Institute, City of Hope Medical Center, 
Duarte, Calif. (U.S.A.) 
We would like to make a brief addendum to Dr. Awapara’s remarks. 
Paradoxically, the comparative biochemistry of marine invertebrates has been 
handicapped by two very fortunate circumstances. The first is man’s position on the 
evolutionary scale, of which the anthropocentric concentration on the Chordata is an 
understandable consequence. The second is the basic similarity of modes of intra- 
cellular metabolism in all forms of life. This similarity, without the recognition of 
which biochemistry today probably would resemble pre-LINNAEAN zoology, has 
permitted biochemists to skip over the entire evolutionary scale and to utilize the 
microorganisms as an expedient tool in biochemical investigations. 
All of us are on the alert for deviations from this similarity such as occur in mutants 
of microorganisms or are reflected in some organ differences in mammals. Few have 
attempted to utilize the wealth of “natural mutants” available. In fact, most bio- 
chemists are only vaguely aware of the extent of this plethora. There are 17 phyla of 
animals, yet we commonly utilize less than a dozen species of one phylum. How many 
ie 
22 
Fig. 1. A dinoflagellate, Gonyaulax polyhedra. y-Aminobutyric acid, 22. 
excursions into “comparative biochemistry” have been limited to this rather small 
phylum? Of the other 16 phyla, six are confined exclusively to the sea and five other 
phyla are almost entirely marine. Why the diversity of marine forms? Probably the 
extremely uniform environmental conditions in the sea have permitted the develop- 
ment and survival of many divergent branches of the evolutionary experiments, al- 
though only a few have mastered the rigors of terrestrial life. 
References p. 186 
