INTERNAL DEFENSES OF CRUSTACEA: A REVIEW 



Carl J. Sindermann- 



ABSTRACT 



Studies of the internal defenses of Crustacea have a discontinuous history, which began in the late 1800's. 

 Elaborate early studies of phagocytes and humoral factors in the hemolymph have been extended with 

 renewed vigor during the past decade. As is true for other invertebrates studied, phagocytosis of for- 

 eign particles by fixed and mobile cells in the crustaceans is augmented by naturally occurring bacteri- 

 cidins, lysins, and agglutinins. A few instances of experimental enhancement of titers of such hu- 

 moral factors by previous exposure to foreign protein have been reported. Specificity of natural and 

 experimentally enhanced humoral factors is much lower than that of vertebrate immunoglobulins, but 

 probably such factors act synergistically with cellular protective mechanisms, as they do in the vertebrates. 

 Phagocytosis by fixed and mobile cells in gills, pericardial sinus, and sinuses at the bases of appendages 

 seems to be a principal defense perimeter in many crustaceans. EflScac.v of phagocytes in destroying in- 

 vading microorganisms varies, depending on the species of the microorganism, as well as host physiology 

 and environmental factors. Phagocytic activity is enhanced by hemolymph factors, which, in addition 

 to immobilizing and agglutinating the invading organisms, also sensitize them to phagocytosis. 



Hemolymph factors, most of which seem to be of cellular origin, may also have bactericidal or lytic 

 activity, leading to extracellular destruction of microbial invaders. A few recent studies indicate that 

 effects of hemolymph factors may be enhanced e.xperimentally by injection of killed or living micro- 

 organisms. 



The number of known microbial diseases in crustaceans is greater than that known in most other in- 

 vertebrate groups, with the possible exception of the Mollusca and Insecta. The number and depth of 

 studies concerned with internal defense mechanisms of Crustacea are similarly greater than those of 

 most other invertebrate groups — again with the possible exception of the moUusks and insects. One mi- 

 crobial pathogen of Crustacea that has received adequate attention is daffkya hovinri — a gram-positive 

 coccus which causes a fatal septicemia in lobsters and is capable of infecting other decapods. An elab- 

 orate series of studies in several laboratories has elucidated many details of the host-parasite relation- 

 ship and has also provided extensive information about the internal defenses of a number of the larger 

 Crustacea. Gaffkya constitutes a test microorganism of choice for future studies of disease processes 

 in crustaceans. 



Thus the available information about cellular and humoral defenses of Crustacea against invasion 

 by foreign protein constitutes a significant part of what we know about such proces.ses in the inverte- 

 brates. Phagocytosis, augmented by humoral factors with low specificity, seems to be the fundamental 

 means of internal protection in the crustaceans and in other groups of invertebrates as well. 



Investigations of the internal defense mecha- 

 nisms of invertebrates against disease have pro- 

 gressed with renewed vigor in the past decade. 

 Literature has accumuhited to the point where 

 condensation and summarization of information 

 about certain invertebrate groui^s, such as the 

 Crustacea, seem justified. 



' Contribution No. 197, National Marine Fisheries 

 Service, Tropical Atlantic Biological Laboratory, Miami, 

 Fla. 33149. 



" National Marine Fisheries Service, Tropical Atlantic 

 Biological Laboratory, Miami, Fla. 33149. 



The hirge number of jiubUshed reports on in- 

 ternal defenses of Crustacea can provide a good 

 indication of the extent of our knowledge of im- 

 munity ill marine invertebrates. Beginning with 

 the pioneering work on phagocytosis and the en- 

 tire process of inflammation by Metchnikoff 

 (1884, 1893, and 1905), and on humoral factors 

 described in the very extensive (but sometimes 

 poorly documented, in terms of procedux-es and 

 data) work of Cantacuzene (1912-34), the Crus- 

 tacea have often been animals of choice in studies 

 of internal defense mechanisms. A significant 



Manuscript accepted February 1971. 



FISHERY BULLETIN: \0L. 69, NO, 3. 1971. 



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