FISHERY BULLETIN: VOL. 69. NO. 3 



tion of such defenses by exposure to foreigTi 

 antigen exists. This evidence is primarily in 

 form of increased titers following: experimental 

 inoculation. Specific acquired antibodies (im- 

 munoglobulins) have not been demonstrated in 

 invertebrates, but induced antibody-like activity 

 has been demonstrated in a few^ species. The 

 fundamental difference seems to be in degree of 

 specificity of response, which is significantly 

 higher in the vertebrates. It is obvious that the 

 synergistic action of phagocytes and humoral 

 factors in the invertebrates, as well as in the 

 vertebrates, constitutes the significant defense 

 perimeter — but the degree of specificity of the 

 humoral components is lower in the inverte- 

 bi'ates. The master internal defense plan seems 

 to be: foreign protein + humoral factor = 

 recognition of foreignness and phagocytosis. 



Cooper (1969c), concluding a very though- 

 provoking paper, stated: "It seems reasonable 

 to conclude that invertebrates do possess immune 

 systems, although the nature of the mechanisms 

 is decidedly unknown. Reactions may be as 

 numerous as the varied taxonomic groups, as is 

 true of most rigorously studied vertebrates. In- 

 vertebrate cellular immunity may be closer to 

 vertebrate reactions and may represent the 

 more primitive responses. In the absence of 

 classic vertebrate-type immunoglobulin in in- 

 vertebrates, a real dichotomy would be evident 

 in the evolution of immune responses. On the 

 other hand, immunoglobulin precursors may be 

 present." 



Certainly the next decade will prove to be an 

 exciting one in the study of invertebrate internal 

 defense systems. The components of classical 

 vertebrate immunity — present as analogues in 

 invertebrates, and probably varying widely 

 among phyla — provide an excellent background 

 against which new findings may be evaluated. 



ACKNOWLEDGMENTS 



The author would like to acknowledge with 

 thanks the helpful comments of Dr. Harvey 

 Rabin, Institute for Comparative Biology, Zoo- 

 logical Society of San Diego, San Diego, Calif.; 

 Dr. James Stewart, Halifax Laboratory, Fish- 

 eries Research Board of Canada, Halifax, N. S. ; 



and Dr. Marenes Trip]3, Department of Bio- 

 logical Sciences. LIniversity of Delaware, New- 

 ark, Del. Impetus for this review was provided 

 in part by an examination of cellular and hu- 

 moral I'esponses of shrimps and crabs being con- 

 ducted with Dr. Ben Sloan, Carson-Newman 

 College, Jefferson City, Tenn. Elizabeth Leon- 

 ard, Librarian, Tropical Atlantic Biological Lab- 

 oratory, aided immeasurably in assembling 

 copies of the extensive body of literature on 

 which this review is based. 



REFERENCES 



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Aarim, G. R. 



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AUSTREG, J. 



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19'14. Immunite et reactions immunitaires chez les 



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