SINDERMANN: INTERNAL DEFENSES OF CRUSTACEA 



DATS AITIR INJKTION 



Figure 3. — Relations of hemocyte counts, clotting time, 

 and bacterial numbers to time from experimental ex- 

 posure of lobsters to Gaffkyn. (Redrawn from figures 

 in Stewart, Arie, Zwicker, and Dingle (1969) and Stew- 

 art and Rabin, 19V0.) 



lobster at 15° C were used, killed 90 ^^ of the 

 test animals within 17 days. The absence of 

 an effective host defense against Gaffkya was 

 strongly indicated by the fact that the mean 

 time to death was almost constant, regardless 

 of dosage (Figure 4). Cornick and Stewart's 

 studies disclosed additional facts that help to ex- 

 plain the pathogenicity of the bacterium to lob- 

 sters: Gaffkya resisted digestion in phagocytes 

 and multiplied in the hemolymjih; growth of 

 Gaffkya was stimulated in vitro by serum of 

 lobsters while growth of several other bacteria 

 was inhibited; and Gaffkya was not agglutinated 

 by lobster serum, though all other bacteria tested 

 were agglutinated. 



Presence in lobster hemolymph of effective de- 

 fenses against bacteria other than G. homari was 

 indicated by clearance within 30 days of inocu- 

 lated suspensions of Micrococcus conglomeratus. 

 M. sedentarius, Achromobacter thala^sius, and 

 Gaffkya tetragena. Since several of these bac- 

 teria are closely related to G. homari (which was 

 not cleared), some specificity of the phagocytic 

 or humoral protective mechanisms is strongly 

 indicated. 



Natural agglutinins in lobster serum were 

 demonstrated against all bacteria tested (six 



genera), except for all strains of G. homari. 

 Such agglutinins were of low titer, nondialy- 

 sable, inactivated at .56° C, and seemed to be non- 

 specific (as suggested by the limited observation 

 that a single absorption of serum by Flavobac- 

 teriuTn marinum removed agglutinins for all 

 other bacteria tested except Brerihacterium sp.) . 

 Cornick and Stewart's observations on phago- 

 cytosis of G. homari are interesting and war- 

 rant further investigation. They found no 

 phagocytized bacteria in hemolymph prepara- 

 tions 15 min after inoculation, but they did find 

 fluorescent-dye-labelled bacteria in hemoc>i;es in 

 heart, liver, and gill tissues of experimental lob- 

 sters soon after inoculation. Circulating hemo- 

 cyte numbers were reduced significantly with- 

 in 15 min after bacterial inoculation but returned 

 to normal levels after 5 hr. These data are in 

 agreement with the statements of Maynard 

 (1960). that phagocytes which have engulfed 

 foreign material lodge in capillary and lacunar 

 areas of the crustacean body, resulting in re- 

 duction in numbers of circulating hemocytes. 

 Bang (1956) observed in tissues of Limulus in- 

 jected with gram-negative bacteria a similar re- 

 duction in circulating hemocytes. In Cornick 

 and Stewart's study long-term infections of lob- 

 sters were characterized by the presence of black 

 nodules containing G. homari in tissue cells in 

 the gills, swimmerettes, and ventral abdominal 



^ 20- 

 < 



< 15- 



LOG DOSE (BAOERIA / KG WEIGHT) 



Figure 4. — Relation of dosage of Gaffkya to mean time 

 to death (MTD) in lobsters (calculated line of best fit 

 for mean time to death, using experimental groups of 

 10 lobsters each). (From Cornick and Stewart, 1968a.) 



473 



