James E. Stewart

Partial characterization of a natural agglutinin in the hemolymph of the lobster, Homarus americanus

Abstract Partial characterization of a natural agglutinin in the hemolymph of the lobster showed: (1) Calcium ion stabilized the agglutinin against inactivation at moderate (35–45°C) temperatures as well as against a reversible increase in activity at nonphysiological p H levels ( p H 6 and 9). (2) Serum frozen at −20°C in the absence of calcium showed an increase in agglutinin activity. (3) Heat inactivation curves indicated a single component for the agglutinin. (4) Heat inactivation destroyed the ability of the agglutinin to be adsorbed to the erythrocyte antigen. (5) The chemical nature of the antigenic reactive site differed with the species of erythrocyte tested; D -glucosamine blocked or inhibited adsorption of the agglutinin to erythrocytes of most species tested. (6) In vivo the agglutinin is located in the hemocytes.

Lobster (Homarus americanus) hemocytes: Classification, differential counts, and associated agglutinin activity

Abstract Four hemocyte types were recognized in the lobster based on size and refractile nature of the granules, the ratios of cytoplasm to nucleus, and Giemsa stain characteristics. Two hyaline types were designated as prohyalocytes (1.8%) and hyalocytes (64.2%), and two granular types were termed eosinophilic granulocytes (12.2%) and chromophobic granulocytes (21.9%). There was no significant difference in the percentages of the different hemocyte types (differential hemocyte counts) between sexes, but hyalocyte and eosinophilic granulocyte percentages varied significantly between populations of lobsters. The data suggested that the difference in agglutinin activity (HA) between lobsters with the same total hemocyte numbers was due to activity associated with fixed hemocytes or quantitative differences in HA activity associated with one or more hemocyte types, rather than an increase in the percentage of any one particular type in circulation.

Histopathology of Aerococcus viridans var. homari infection (Gaffkemia) in the lobster, Homarus americanus, and a comparison with histological reactions to a gram-negative species, Pseudomonas perolens

Abstract Histological response of lobsters to injection of Aerococcus viridans var. homari , cause of gaffkemia, was followed over a 14-day period. Salient features in infected lobsters, Homarus americanus , were: aggregations of hemocytes occurring in hemal spaces throughout the tissues and increasing in number and size with time; the early phagocytosis of bacteria by the system of fixed phagocytes (FPs) present in hemal spaces of the hepatopancreas; and premature release of differentiating hemocytes from the hemopoietic tissue, so that by 14 days that tissue consisted mainly of large stem cells. Mass release of differentiating hemocytes presumably occurred to replace hemocytes lost from the circulation by their incorporation into aggregations or by lysis of individual cells ruptured through the pressure of phagocytized bacteria that were multiplying in them. Bacteria and their remains were present in FPs at 2 days but not visible in single or aggregated hemocytes until 6 days, when free bacteria were also present in the hemolymph. By 6 days, all bacteria, whether phagocytized or free, appeared normal and were surrounded by nonstaining halos that extended well beyond the stainable capsular material. As predicted earlier in physiological studies, gaffkemia is a nontoxic, noninvasive bacteremia. There was hemal stasis and consequent injury in the antennal gland due to free and aggregated hemocytes that occluded hemal spaces of that organ, but other tissues and organs appeared normal except for depletion of glycogen. Aggregations of hemocytes were present in lobsters 2 and 12 days after injection of a nonpathogenic, Gram-negative bacterium, Pseudomonas perolens . Unlike the case with gaffkemia, necrotic hemocytes were common in the aggregations, presumably in response to damage by endotoxin. A further difference was that aggregations were common in the heart of P. perolens -injected lobsters but rare in the heart of gaffkemic lobsters. Bacteria were not seen in hemolymph, hemocytes, or other cells of P. perolens -injected lobsters.

Induction of Internal Defense Mechanisms in the Lobster, Homarus americanus

Invertebrates in general have the following nonspecific, hemolymph defense mechanisms: (1) bactericidal activity, (2) agglutinin activity, and (3) phagocytic activity which were recently reviewed in depth by Sindermann (1971) for the crustaceans. The overall effectiveness of these mechanisms in nature, together with mechanical barriers to transmission and possibly other intrinsic defenses can be judged only by the limited data available on epizootics occurring among natural stocks. Apparently, the effectiveness is high since more or less constant exposure to relatively large numbers of different microorganisms does not appear to result in epizootics until the exposure includes an infectious agent uniquely suited to overcome the invertebrate’s defenses. In this, the invertebrates compare favorably with other animals.

Paradoxical effects of salinity reductions on lobsters (Homarus americanus) infected with Gaffkya homari

Abstract 1. 1. For lobsters acclimation to reduced environmental salinities (26·1 and 21·5‰) prior to infection with Gaffkya homari shortened the times to death to 9 and 5 days respectively from the 13 days recorded at normal coastal salinities of 31·8‰. 2. 2. In contrast, reduction to a salinity of 26·1‰ after infection increased the times to death progressively from the sixth day of the infection onward. Reduction to a salinity of 21·5‰ at all times after infection increased the time to death to a value of 18–20 days. 3. 3. Hemolymph total carbohydrates, glucose, lactic acid, serum osmolalities and pathogen numbers were measured during the experiments.