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



which combine with foreign protein to enhance 

 the phagocytic process. Although specific im- 

 munoglobulins have not yet been demonstrated 

 in invertebrates, an analogous protein system, 

 of lower specificity but with functions similar to 

 vertebrate immunoglobulins, is suggested. Na- 

 tural (and in some cases, partially specific) ag- 

 glutinins are common in invertebrate body fluids, 

 and their titers in some species may be increased 

 by e.xposure to specific antigens. 



2. Resistance in the vertebrates, and in some 

 invertebrates also, includes the production of 

 bactericidins, lysins, and agglutinins. The ap- 

 pearance of, or the increase in, titers of such 

 factors in certain invertebrates following expo- 

 sure to foreign proteins may account in part for 

 increased resistance to certain pathogens (Mc- 

 Kay and Jenkin, 1969; Bang, 1967b). 



3. Many of the bactericidal, bacteriostatic, 

 lytic, and agglutinating properties seem to be 

 conferred on the hemolymiih of invei-tebrates by 

 release of materials from hemocytes. The sub- 

 stances so released often seem not only less spe- 

 cific in their action than vertebrate antibodies, 

 but also the stimulation of release may be much 

 less specific. For example, the release of a lysin 

 in sipunculids for the ciliate Anophrys can be 

 stimulated by inoculation of certain bacteria 

 (Bang, 1967a), and the release of a hemolysin 

 in Maia sqninado for sheep red blood cells can 

 be induced by injection of sipunculid coelomic 

 fluid (Cantacuzene, 1920a, 1923b). 



4. Immune response in invertebrates, as best 

 exemplified in insects and crustaceans, is often 

 rapid in onset and disappearance — usually a 

 matter of a few days. 



5. As has been observed by a number of 

 authors (Feng and Stauber, 1968; Stewart, 

 Cornick, and Zwicker, 1969), environmental 

 temperature is a critical factor in the host-par- 

 asite relationships of invertebrates. Temper- 

 ature has been found experimentally to exert a 

 significant eflfect on the appearance, degree, and 

 duration of resistance to infection in certain in- 

 vertebrates (McKay and Jenkin, 1969), just as 

 it does in poikilothermic vertel)rates (Bisset, 

 1946, 1947a, 19471), 1948a, 1948b). Tempera- 

 ture affects the rate of growth and i-eproduction 

 of microorganisms, the rate of production of 



toxic metabolites, and the utilization of nutrient 

 derived from the host. Temperature can also 

 affect the rate of phagocytosis and the rate of 

 production of humoral defenses against infec- 

 tion. Thus the progress of infection and the out- 

 come of disease represents a composite of en- 

 hancement or inhibition partly mediated by 

 temperature. 



6. Endotoxin has been found (in the verte- 

 brates) to increase the metabolic rate of phago- 

 cytes and stimulate phagocytosis (Jenkins and 

 Palmer, 1960; Whitby et al, 1961). A similar 

 effect may be produced by endotoxin in the in- 

 vertebrates. Thus, exposure to gram-negative 

 bacteria which are so abundant in the sea (or 

 to their endotoxins) may increase the level of 

 nonspecific resistance to other gram-negative or- 

 ganisms or their endotoxins. This "nonspecific 

 immunity," which is also known in the verte- 

 brates (Rowley, 1956; Landy and Pillemer, 

 1956), may be of great significance in the in- 

 vertebrates — in fact, it may be the basic mech- 

 anism of internal resistance to bacterial path- 

 ogens in the invertebrates. 



7. Handling and ex])erimental procedures 

 rapidly induce bacteremias in a number of in- 

 vertebrates. Rabin (1965), for example, found 

 that almost half of all American lobsters used 

 in his studies had bacteremias upon arrival in 

 the laboratory. Cornick and Stewart (1966) 

 found that about 20 'r of a large sample of lob- 

 sters had bacteria in their hemolymph. Isolates 

 were principally Micrococcus, Pseiidomonas, 

 Brevibacterium, and Achromobacter — bacteria 

 commonly found in the marine envii'onment, and 

 apparently nonpathogenic for lobsters. The acts 

 of capture, transport, and impoundment of these 

 and other marine animals may produce stresses 

 and physiological changes (or mechanical dam- 

 age) that permit entry of microorganisms com- 

 mon in the surrounding sea water. 



8. There is some limited evidence that the 

 process of phagocytosis, fully elaborated in the 

 Protozoa, is enhanced in the vertebrates by non- 

 specific humoral factors which sensitize, agglu- 

 tinate, immobilize, or otherwise increase the 

 susce))tibilily of iiroteins to jihagoc.vtosis by fixed 

 and mobile phagocytic cells. Although the op- 

 sonizing substances of invertebrates have not 



478 



