FISHERY BULLETIN: VOL. 69, NO. 3 



Table 1. — A proposed hypothesis to explain the course 

 of Gaffkya homari infections in lobsters at 15° C. 



Day 



Development of gaffkaemia in lobsters 



decrease in 

 bacterial 



hemocyte 

 numbers. 



Bacteria gain access to tissues of lobsters as a result of 

 injury which destroys the integrity of exoskeleton (or pos- 

 sibly the gut epithelium). Lobster hemocytes phagocytrze 

 C. homari. 



Phogocytized bacteria may multiply within hemocytes. Hemo- 

 cytes containing engulfed bacteria lodge in capillary ond 

 lacunar areas (heart, hepatopancreos, gills) of the lobster. 

 Hemocytes may be disrupted, releasing C. homari in hemo- 

 lymph. This may result in rapid 

 numbers and logarithmic increase 



Hemolymph stimulates multiplication of released bacteria. 

 Hemocyte numbers seem to be graduolly reduced by con- 

 tinued phagocytosis and disruption of phagocytes. 



Clotting mechanism (release of coogulin from hemocytes) 

 is affected— possibly by reduction of hemocyte numbers— 

 and clotting time is greatly prolonged. 

 Lobsters die from depletion of nutrient stores and utilization 

 of this material by Gafjkya. Injured gaffkoemic lobsters 

 may bleed to death. (The possibility of exotoxin has not 

 been entirely eliminoted, but there is no present evidence 

 to suggest its existence.) 



stimulated, while growth of a Vibrio (nonpath- 

 ogenic to lobsters) was usually inhibited. Serum 

 from lobsters which had been inoculated 24 hr 

 earlier with killed Gaffkya still stimulated 

 growth of the pathogen in vitro. 



Rabin and Hughes (1968) tested resistance 

 to Gaffkya in a variety of studies with lobsters 

 and other marine arthropods. Findings with 

 spider crabs (Lihinia emargivata) , rock crabs 

 (Cancer borealis) , and horseshoe crabs (Limulus 

 pohjphemiis) were that most of the test animals 

 cleared inoculated G. homari. In vitro studies 

 with hemoljTnph disclosed either no apparent 

 effect or only slight inhibition of growth of the 

 pathogen by sera of spider and horseshoe crabs, 

 and a slight stimulation of growth by sera of rock 

 crabs. 



The possible role of exotoxin was tested in 

 lobsters by Rabin and Hughes with inoculation 

 of filtrates of G. homari cultures. The filtrate 

 had no effect when it was injected into the ab- 

 domen, but injection into the major joint of the 

 chela induced autotomy or abnormal movements 

 in over 50 "^r of the lobsters treated. 



FA'idence of resistance to gaffkaemia was 

 noted by Rabin and Hughes in a single lobster, 

 which had been infected naturally before it was 

 brought to the laboratory. Twelve days after 



capture the lobster was free of the pathogen. 

 The animal was inoculated twice with increas- 

 ingly larger dosages of G. homari and cleared 

 the bacteria within 6 days — but died on the 11th 

 day following the second challenge. The reac- 

 tions indicated a partial resistance and an ability 

 in some individuals to recover from gaffkaemia. 

 It is interesting that serum from this presum- 

 ably resistant lobster was similar to that of other 

 lobsters tested in that it did not inhibit growth 

 of G. homari in vitro. 



Rabin and Hughes stated that the presence 

 of Gaffkya infections did not damage the clotting 

 mechanism — an observation quite different from 

 that of Goggins and Hurst (1960), who found 

 that reduction in amebocytes and a much pro- 

 longed clotting time were distinctive features 

 of the disease. Stewart et al (1969) and Stewart 

 and Rabin (1970) clarified these seemingly dis- 

 parate observations by rejjorting that "coagulin" 

 is released to initiate clotting by rujiture of 

 hemocytes and that the "concentration of plasma 

 proteins, including fibrinogen, does not appear to 

 decline significantly in gaffkaemic lobsters." An 

 earlier report by Rabin and Hughes (1968) 

 stated that when extract of lobster muscle was 

 used as a coagulin source, recalcified clotting 

 times were the same in diseased and normal 

 animals. When these facts are combined, it can 

 be concluded that the abnormally and persistently 

 low hemocyte content of the hemolymph results 

 in prolonged clotting time and does not indicate 

 any deficiency in plasma constituents other than 

 coagulin (Figure 3). 



Studies carried on by James Stewart and his 

 associates at the Halifax (Nova Scotia) Lab- 

 oratory of the Fisheries Research Board of Can- 

 ada have extended the work of Rabin and have 

 provided the greatest number of contributions 

 to the literature about the effects of Gaffkya 

 disease on lobsters. In accord with earlier stud- 

 ies, infections usually were fatal, although rare 

 individuals infected with Go//A-i/a-like organisms 

 did survive (Stewart et al., 1966). 



Cornick and Stewart (1968a) provided con- 

 siderable relevant information about the host- 

 parasite relationships of Gaffkya and lobsters. 

 Experimental infections by inoculation, in which 

 dosages as low as approximately 5 bacteria per 



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