FISHERY BLLLETIM: VOL. 69. NO. 3 



crabs, and larval cestodes, acanthocephalans, 

 nematodes, and leeches occasionally have been 

 reported from crabs, shrimps, and lobsters 

 (Sindermann, 1970). 



Crustaceans are frequently parasitized by 

 other crustaceans — sometimes with serious ef- 

 fects on the host. Rhizocephalan barnacles are 

 endoparasites of crabs, causing gonad degener- 

 ation and other morphological changes. Epi- 

 caridean isopods may produce similar changes in 

 crabs and shrimps. Copepods sometimes para- 

 sitize crab eggs, as well as the gills of lobsters 

 (Sindermann, 1970). 



INTERNAL DEFENSE SYSTEMS 



Studies of crustacean internal defenses pub- 

 lished during the last decade have augmented 

 earlier studies and have provided additional data 

 to support generalizations and principles ali'eady 

 enunciated, but none has yet provided the factual 

 basis for new or different concejits. Because 

 additional precision in terminology is now avail- 

 able, it is possible to consider the internal defense 

 systems of Crustacea under the following head- 

 ings: cellular (phagoc.\i:ic), bactericidal, lytic, 

 agglutinating, precipitating, phage clearance, 

 antitoxic, and others. It should be obvious that 

 these systems are not mutually exclusive and 

 may often interact or even share components 

 to protect the individual animal from invasion 

 by potential pathogens. Largely for ease of de- 

 scription, the systems will be considered con- 

 secutively, even though many may act either 

 in concert or simultaneously. 



PHAGOCYTOSIS AND OTHER 

 CELLULAR DEFENSES 



The earliest study of lihagoc.vtosis in Crustacea 

 concerned infections of Daphnia by the fungus 

 Monospora hicuspidata (Metchnikoff, 1884). 

 The fungus spores in the haemocoel were i)hago- 

 cytized and digested; the rapidity and vigor 

 with which phagocytosis occurred determined 

 the outcome of the infection. If some spores 

 escaped phagocytosis, germinated, and formed 

 conidia, the infection became generalized and the 



host died in a few da.vs. If all the fungus spores 

 were phagoc>i:ized and destroyed, the infection 

 was arrested. Thus the speed and effectiveness 

 of phagocj-tic action in some individuals, possibly 

 mediated by humoral factors, determined sur- 

 vival. Absence of phagocytosis inevitably led 

 to death. 



Hemocytes of Crustacea were investigated by 

 Cattaneo (1888b), Cuenot (189r5, 1897. 1905), 

 and Bruntz (1907). Cattaneo described the 

 amebocv-tes of Carcinus maenas; Cuenot re- 

 ported blood forming tissues — nodules of lymph- 

 oid cells in the blood sinuses — in decapods and 

 described "jjhagocytic organs" in the hepato- 

 pancreas of decapods and amphipods; and 

 Bruntz published an extensive paper on the 

 hemocj-tes of many of the crustacean groups, 

 distinguishing granular and hyaline hemocytes. 

 Bruntz also described a "i^hagocytic organ" in 

 gammarids; his 1907 paper reviewed an exten- 

 sive series of his own studies (15 reports) pub- 

 lished during the jjeriod 1903-1907 by the Societe 

 Biologique de Paris. Other early studies of crus- 

 tacean hemocytes include those of Hardy (1892) , 

 Tait (1918a, 1918b), and Tait and Gunn (1918). 



Following the classical early studies of Metch- 

 nikoff, Cuenot, Bruntz, and others, which elu- 

 cidated the critical role of phagocytes in the in- 

 ternal defenses against microorganisms, phago- 

 cytic cells have received greatest attention from 

 vertebrate immunologists. General principles 

 that have emerged from the more recent studies 

 of phagoc.\i;osis in vertebrates undoubtedly apply 

 as well to invertebrates. Among the papers that 

 have contributed to understanding of phagoc.v- 

 tosis are those of Wright and Douglas (1903), 

 Wood, Smith, and Watson (1946), Wood (1953), 

 Robineaux and Frederic (1955), Suter (1956), 

 Rowley (1960), Rogers (1960). Evans and 

 Karnovsky (1961), and Spector and Willoughby 

 ( 1963) . Reviews of phagocj-tosis have been pub- 

 lished by Hirsch (1965) and Aarum (1967). 



The mechanism of intracellular degradation 

 of phagocjlized microorganisms has been de- 

 scribed in general terms for the vertebrates 

 (Figure 2). Lysosomes — graiuiles in the cyto- 

 plasm of phagocytes — contain antibacterial sub- 

 stances and hydrolytic enzymes (Cohn, Hirsch, 

 and Wiener, 1963). The lysosome membrane 



460 



