Search

An extensive reexamination of Chedabucto Bay, Nova Scotia, sediments was carried out in the summer of 1976 for comparison with data obtained shortly after the major oil spill in 1970. Only 2 of the 79 sediment samples examined microbiologically had large numbers of hydrocarbon-utilizing bacteria. The bulk of sediments were, with regard to bacterial populations, comparable to areas described as "clean," i.e. no apparent or known contamination with oil. Key words: Chedabucto Bay, hydrocarbon, hydrocarbon-utilizing bacteria, petroleum, sediment

Various degrees of resistance to infection of lobsters Homarus americanus by Aerococcus viridans (var.) homari (formerly Gaffkya homari) were induced by vaccines prepared in different ways. Vaccines consisting of formalin-killed cells of a virulent strain of the pathogen (grown in vitro and in vivo) gave a low level of protection, i.e. the vaccinated lobsters were able to resist challenges of 200 bacteria/kg host body weight. A vaccination approach utilizing a low initial dose of the antibiotic, vancomycin, followed 24 h later by injection of 1 × 106 live pathogen cells/kg body weight produced a high degree of resistance to subsequent challenge at times considerably beyond the clearance times for the antibiotic. Fatal infections in normal lobsters are readily established with 10 pathogen cells/kg body weight whereas treatment of lobsters with the vancomycin-live pathogen combination resulted in an LD50 of 2 × 107 live pathogen/kg body weight. It is suggested that the relative effectiveness of the various vaccines is related directly to the concentrations of cellular components within the pathogen, possibly precursors of cell wall mucopeptides.

The bactericidin of American lobster (Homarus americanus) hemolymph was adsorbed readily by representatives of two bacterial genera: a nonpathogen, Pseudomonas perolens, and the lobster pathogen Aerococcus viridans (var.) homari. Activation of the bactericidin by factor(s) secreted by the hemocytes can occur before adsorption and also after adsorption by bacteria. Although the lobster pathogen A. viridans (var.) homari is unaffected by the activated bactericidin, this lack of effect is not related to adsorption since this bacterium adsorbs the bactericidin as readily and completely as does the susceptible nonpathogen. Key words: lobster, Homarus americanus, plasma bactericidin, adsorption and activation, hemocytic activator, Pseudomonas perolens, Aerococcus viridans (var.) homari

The antibiotics vancomycin, penicillin G, novobiocin, and oxytetracycline were examined for in vivo effectiveness against gaffkemia, the fatal bacterial infection of lobsters (genus Homarus) caused by Aerococcus viridans (var.) homari (formerly Gaffkya homari). Only vancomycin was truly effective against an established infection and then only when given at high levels (25 mg/kg lobster body weight) in the early stages of infection, prior to development of hemolymph bacterial numbers in excess of 3 × 104/ml or coincident hepatopancreatic bacterial levels of 1 × 107/g. Even massive cumulative doses (500 mg vancomycin/kg body weight), when given after establishment of maximum bacterial numbers, failed to impede the infection. Rates for the clearance of vancomycin from lobsters, established by using three different concentrations (25, 10, and 5 mg/kg body weight, respectively), were extremely slow and markedly concentration dependent. Twenty-five milligrams vancomycin/kg body weight injected prior to infection still gave a high degree of protection against challenge with the pathogen 50 days later in lobsters held at 15 C. One milligram vancomycin/kg body weight administered prior to infection gave complete protection against gaffkemia for 15 days after the antibiotic had been administered.

A system for holding lobster hemocytes in a viable state was developed and utilized to study the in vitro phagocytosis of sheep red blood cells (SRBC) by lobster hemocytes.Using SRBC sensitized with the opsonin present in lobster serum, 2% of the hemocytes demonstrated phagocytosis detectable as early as 20 min after the hemocytes and erythrocytes were mixed and held at 15 C. Lower phagocytosis levels were observed with untreated erythrocytes. As with other poiklothermic animals, the temperature affected the rate of phagocytosis, which was first observed at the 60-min sampling in cells held at 4 C.

Conditions required for the extended survival of American lobsters (Homarus americanus) in a recirculating, refrigerated seawater system were investigated with a unit incorporating a biologically "conditioned" sand filter with and without activated carbon. Lobsters held at a temperature of 5 °C and a density of 50g/ℓ of water for periods up to 60 days without water change experienced

The levels of fluorescent material in the hemolymph of lobsters injected with serum proteins from lobster hemolymph labelled with fluorescein remained relatively constant over a 6-day test period; the levels in lobsters injected with bovine serum albumin labelled with fluorescein declined rapidly. A precipitin-like reaction was observed when lobster hemolymph serum was titrated with bovine serum albumin in vitro.

not available

Gaffkya homari did not exhibit lipase, protease, or lecithinase exoenzyme activities. The organism was coagulase and fibrinolysin negative; only lactic acid was produced from glucose. The capacity of whole lobster hemolymph or its components to promote the growth of G. homari was assessed.

Representatives of eight bacterial genera were grown under identical conditions and the harvested, washed cells were analyzed quantitatively for eighteen amino acids using chemical methods. All of the bacteria contained the eighteen amino acids and, although quantitative differences were noted, variation in composition was not great. Cell nitrogen content averaged 11.91% of the dry weight. Some of the nutritional implications of the data are discussed.

Total serum protein values, hemocyte numbers, and muscle weights were determined for 216 intermolt lobsters immediately after their capture, and for 230 others held captive under a variety of dietary and environmental conditions. Average muscle values ranged from approximately 13% to the more normal 20–25% of the live animals' weight, depending upon experimental conditions. The total serum protein up to a level of 55 mg/ml was shown to be a reliable indicator of muscle weights, although the relationship was not identical for all lobster groups. It appeared to be modified chiefly by the areas from which the different groups were taken. Diet was more important than the temperatures (5 to 14 C) in affecting changes in muscle and serum protein values. Starvation caused a greater reduction (50 to 70%) in the size of the hepatopancreas than in the muscle. Histological examination of the hepatopancreatic tissue showed that the lipid content was markedly reduced upon starvation and that a degeneration of this organ was apparent for lobsters fed a beef liver and herring diet. Measurement of serum proteins would appear to be a useful technique in experiments on lobster nutrition and have value, within specified limits, for assessing the physiological condition of wild lobsters.

The mean time to death for lobsters (Homarus americanus) infected with Gaffkya homari and kept at constant temperatures was 2 days at 20 C, 12 days at 15 C, 28 days at 10 C, 65 days at 7 C, 84 days at 5 C, and 172 days at 3 C. The lobsters were unable to mobilize at any of these temperatures systemic defenses adequate to eliminate the pathogen. No deaths that could be attributed to infection with G. homari occurred during the 250-day trial at 1 C; the pathogen, however, was not eliminated at this temperature but remained in the lobsters at low levels with virulence unchanged and gave rise to a fatal infection when the temperature was increased. Further studies showed that infected lobsters were adversely affected by a relatively rapid increase of 10 degrees C but not by a 5-degree C increase; a relatively rapid decrease of 15 degrees C but not 10 degrees C was adverse. Infected lobsters at 15 C were most sensitive to a 5-degree C decrease around the 12th day of the infection.

not available

not available

Among lobsters infected experimentally at 15 C with the pathogen Gaffkya homari, fed animals died much earlier and with higher bacterial numbers than did animals starved for several months. The shorter times to death were attributed to a more rapid development of the pathogen in the fed host, due to the richer nutrient supply in the circulatory system bolstered by substantial reserves. Infected lobsters ate only during the very early stages of infection.

Infection of the lobster Homarus americanus with the bacterium Gaffkya homari invariably proved fatal. Very small numbers of this pathogen introduced into the hemolymph resulted in septicemia and death, i.e., a dose level as low as approximately five bacteria per lobster at a temperature of 15 C was sufficient to kill 90% of the lobsters in 17 days. The mean time to death was virtually constant, regardless of the dose, indicating a general lack of host defense against G. homari.Investigation of the interaction of G. homari with the defense factors apparent in lobster hemolymph (bactericidal, agglutinin, and phagocytic activities) helped to account for its pathogenicity. Gaffkya homari was unique among the microorganisms tested in that (1) it was resistant to the agglutinin (s); (2) its growth was stimulated by the hemolymph serum rather than inhibited or unaffected; (3) although it was phagocytized, the bacterium could overcome this effect and multiply in the hemolymph.

not available

Hemolymph samples drawn from 2035 lobsters captured in five areas off the Canadian Atlantic coast were individually tested for the bacterium Gaffkya homari, using a qualitative, presumptive test, followed by a confirmatory procedure. Ninety-six lobsters, or almost 5% of the total, were confirmed as being infected. The approximate range of G. homari incidence was from 2 to 40% indicating that G. homari is resident in the natural lobster population of this region. Evidence suggested that a high natural incidence can lead to an epizootic among stored, captive lobsters. The possibility that an infection source exists in addition to the G. homari strains resident in the lobster population is discussed.

not available

not available

A rupture of the integument was shown to be essential for the transmission of Gaffkya homari to the lobster Homarus americanus. The acidity of the lobster gastric fluid was bactericidal for G. homari and was an adequate barrier against transmission of gaffkemia by the oral route. Lytic activity associated with the larger protein molecules of lobster gastric fluid, but not with the bactericidal effect of the acid condition, was weakly active against Micrococcus lysodeikticus but was not active against G. homari. The acidity of the lobster stomach is a function of the acidic protein molecules rather than a result of an excess of small, acidic molecules.

The molting incidence for male lobsters (Homarus americanus) subjected to a variety of conditions was compared with that for free male lobsters. The data show that for free western Newfoundland lobsters, molting reached the 90% level by the end of September. During the same period, mildly restrictive conditions reduced the molting incidence to 50% or less, and when lobsters held under these conditions were also tagged or marked the molting incidence was reduced to 30% or less. A reduction in molting, equivalent to or greater than that produced by tagging or marking plus mildly restrictive conditions, was achieved by highly restrictive conditions which enforced a high degree of association between lobsters. The diets used in these experiments did not appear to have any influence on the molting incidence. The data suggested that darkness plus starvation under highly restrictive conditions was even more inhibitory than any of the other conditions applied. Other light intensities tested under the highly restrictive conditions had no apparent effect on the molting incidence; however, stimulation of molting by light could have been negated by the inhibitory effects of this form of captivity.

not available

not available

not available