Susceptibility and immunity to Vibrio anguillarum in post-hatching rainbow trout fry, Salmo gairdneri Richardson 1836.

Rainbow trout fry were tested for their susceptibility to experimental infection with Vibrio anguillarum, and their ability to mount an immune response against it, from the age of 2 weeks post-hatch onwards. Bath challenges were ineffective in inducing vibriosis until 6-8 weeks post-hatch, and then only low levels of specific mortality ensued, even at very high doses. However, at the earliest age tested, 7 weeks post-hatch, the fry were susceptible to infection by an intraperitoneal injection with live organisms. Protective immunity was evident in fry vaccinated by direct immersion as early as 2 weeks post-hatch (at an average weight of 0.14g), when tested by intraperitoneal challenge. By the time the fry reached 0.5g (10 weeks after hatching), protection levels had reached 50% for direct immersion vaccination and 100% for intraperitoneal vaccination. An oral vaccination, from first feeding onwards, proved ineffective in inducing immunity. The results are discussed in relation to the onset and maturation of immunological competence in rainbow trout.

The interactive effects of low pH, toxic metals, and DOC on a simulated temporary pond community.

The effects of pH, potentially toxic metals, and dissolved organic carbon (DOC) on a freshwater, palustrine wetland assemblage (three amphibian species, one mosquito genus, and 18 genera of algae) were examined in 500 liter outdoor mesocosms. The design was fully factorial and exposure levels were set to represent concentrations that occur naturally in temporary ponds in central Pennsylvania, an acid-impacted region of the USA. Water chemistry was precisely regulated by use of an artificial pond water rather than using stream water or well water with partially unknown composition. Jefferson (Ambystoma jeffersonianum) and spotted salamanders (A. maculatum) were negatively impacted by low pH and high metal concentrations. Wood frogs (Rana sylvatica) were negatively impacted by high DOC and low pH. These negative effects included increased time to metamorphosis and decreased survival and wet body mass at metamorphosis. Mosquito emergence was unaffected by pH, metals, or DOC. All three abiotic factors (metals, pH, and DOC) interacted to determine algal taxonomic composition. Hence, abiotic conditions may determine amphibian reproductive success both directly and indirectly, via effects on algae, since a primary food source of salamanders, zooplankton, are affected by changes in algal composition. These complex interactions should be considered in evaluating the possible toxicity of pond waters to fauna and flora. Until now, pH alone has been considered the primary limiting factor for amphibians breeding in temporary ponds.

Vaccination of fish: a practical view.

Commercial vaccines giving protection against three important bacterial fish diseases (enteric redmouth, furunculosis and vibriosis) became available in the United Kingdom in 1983. The degree of protection obtained and the cost effectiveness vary according to the method of presentation (injection, dipping or spraying and oral dosing). These methods and the optimum time for vaccination are described.

Statistical thermodynamics and kinetics of DNA multiplex hybridization reactions.

A general analytical description of the equilibrium and reaction kinetics of DNA multiplex hybridization has been developed. In this approach, multiplex hybridization is considered to be a competitive multichannel reaction process: a system wherein many species can react both specifically and nonspecifically with one another. General equations are presented that can consider equilibrium and kinetic models of multiplex hybridization systems comprised, in principle, of any number of targets and probes. Numerical solutions to these systems for both equilibrium and kinetic behaviors are provided. Practical examples demonstrate clear differences between results obtained from more common simplex methods, in which individual hybridization reactions are considered to occur in isolation; and multiplex hybridization, where desired and competitive cross-hybrid reactions between all possible pairs of strands are considered. In addition, sensitivities of the hybridization process of the perfect match duplex, to temperature, target concentration, and existence of sequence homology with other strands, are examined. This general approach also considers explicit sequence-dependent interactions between targets and probes involved in the reactions. Sequence-dependent stabilities of all perfect match and mismatch duplex complexes are explicitly considered and effects of relative stability of cross-hybrid complexes are also explored. Results reveal several interdependent factors that strongly influence DNA multiplex hybridization behavior. These include: relative concentrations of all probes and targets; relative thermodynamic stability of all perfect match and mismatch complexes; sensitivity to temperature, particularly for mismatches; and amount of sequence homology shared by the probe and target strands in the multiplex mix.

Technical aspects of the administration of vaccines.

The practise of vaccination as a standard part of fish husbandry has led during the last 20 years to the adoption of a number of basic vaccination regimes based on an understanding of the principles involved and how to maximize protection. The strategies adopted depend on the species of fish, its husbandry, the disease against which protection is sought and the optimum timing within the growth cycle so that the predicted duration of protection coincides with the timing of any expected disease challenge. These and other parameters influencing the performance of vaccines are discussed in the context of what is practical and cost-effective in each circumstance and the risks involved in handling and administering vaccine by the different available methods.

Behavioral and physiological responses of the terrestrial life stages of the Jefferson salamander, Ambystoma jeffersonianum, to low soil pH.

Terrestrial metamorphs of the salamander, Ambystoma jeffersonianum, were exposed to four levels of pH on artificial substrates in the laboratory. Short-term exposure (7 d) to pH levels between 3.5 and 5.0 had no effect on total body mass, Na+, K+, Ca2+, and Mg2+ concentrations. However, at 14 d in both laboratory experiments and in field microcosms, whole body water and Na+ concentrations were significantly lower at the lower pH level. Terrestrial metamorphs and adults of the Jefferson salamander preferred artificial substrates that were higher in pH. Ponds not utilized for breeding all had adjacent soil pH below 3.7. Pond water and soil pH were directly and highly correlated. Soil pH may indirectly affect breeding success of Jefferson salamanders by influencing pond pH or directly by physiologically stressing the terrestrial life stages. Laboratory data implicate direct effects on the physiology of terrestrial young of the year salamanders by induction of loss of body water and Na+. Apparently, soil pH is a critical factor not only in the selection of vernal ponds by Jefferson salamander adults for breeding, but in determining the likelihood of reproductive success as judged by recruitment into the adult population.

Chromosome polymorphism in the rainbow trout (Salmo gairdneri Richardson).

Chromosome preparations from lymphocyte cultures of 50 rainbow trout were studied. Diploid chromosome numbers of 59, 60, 61, 62 and 63 were found in different individuals in which the arm number (NF) was 104. Intraindividual polymorphism was found at a low level in 25 of the fish. The results suggest that numerous chromosome polymorphisms exist in rainbow trout.

Co-adaptation of Escherichia coli and coliphage lambda vir in continuous culture.

Populations of the bacterium Escherichia coli and of its phage lambda vir appeared to equilibrate in continuous cultures. The bacterial end-populations were heterogeneous in respect of their resistance to lambda vir and their ability to utilize maltose. The most competitive of the selected bacteria were mutants which had a reduced rate of synthesis of lambda-receptor so as to become highly, but not totally, resistant to the phage. The coexisting phage had an increased affinity for the receptor and an altered antigenic specificity, suggesting adaptation of its adsorption site in response to the evolution of resistance in the bacteria.

Chromosome relationships in the genus Salmo.

Chromosome numbers and polymorphisms in rainbow trout, Atlantic salmon, and brown trout are described. The karyotypes of these three species are compared with each other and with those of other salmonid fish from the genera Salmo, Salvelinus, and Oncorhynchus. Karyotype evolution from a postulated ancestral tetraploid is discussed.

Polychlorinated biphenyl- and mercury-associated alterations on benthic invertebrate community structure in a contaminated salt marsh in southeast Georgia.

The community structure of a benthic macroinvertebrate assemblage in a contaminated salt marsh was evaluated as part of an ecological characterization of a former chloralkali production facility in Georgia. Sample locations were chosen based on a gradient of the primary contaminants of concern, total mercury and polychlorinated biphenyls (PCBs), primarily Aroclor 1268. Sediment concentrations of Aroclor 1268 ranged from 2.3 to 150 mg/kg dry weight, while mercury concentrations ranged from 15 to 170 mg/kg dry weight in the study area. Mercury and PCBs were determined to be co-located in the sediments. Total organic carbon composition of the sediments was negatively associated with PCB and mercury concentrations. A total of 29 benthic taxa was identified in 49 samples; replicate samples were taken at each of five sampling locations. Mean infaunal density across all sampling locations was estimated at approximately 61,000 to 234,000 organisms m(-2). Overall, polychaetes comprised 57% of the infaunal community with Manayunkia aestuarina as the dominant species. Oligochaetes, nematodes, crustacea, insects, and gastropods comprised 23.0, 18.0, 1.0, 0.7, and 0.2% of the overall benthic community, respectively. Density estimates of individual species between sampling locations showed no consistent patterns in response to pollutants. However, an analysis of higher taxonomic levels revealed some general trends. In uncontaminated areas, the benthic community was dominated by nematodes and oligochaetes, whereas moderate to highly contaminated areas were dominated by polychaetes and a smaller percentage of oligochaetes and nematodes. A trophic analysis of the same data set revealed that the community shifted from an evenly distributed percentage of surface and subsurface feeders in the uncontaminated areas to a community dominated by surface feeders in the more contaminated locations. Carnivores comprised from 0.13 to 0.90% of the trophic structure, with the percentage of carnivores generally decreasing with increasing contamination. Mercury and PCBs were bioaccumulating in representative marsh benthic invertebrates, presenting a potential source of contaminants to marsh consumers. Tissue PCB and tissue mercury concentrations were positively related to sediment PCB and mercury concentrations, respectively. A standard 14-day toxicity test using the amphipod Leptocheirus plumulosus showed no acute toxicity across the sampling locations.

Peroxide-inducible catalase in Aeromonas salmonicida subsp. salmonicida protects against exogenous hydrogen peroxide and killing by activated rainbow trout, Oncorhynchus mykiss L., macrophages.

Aeromonas salmonicida subsp. salmonicida expresses a single cytoplasmically located catalase which was found to be inducible by exposure to 20 microM hydrogen peroxide in mid-exponential phase resulting in a 4 fold increase in activity. Subsequent exposure to 2 mM peroxide in late-exponential/early-stationary phase resulted in further induction of catalase activity which increased to 20 fold higher levels than those found in uninduced cultures. Exponentially induced cultures were protected against subsequent exposure to 10 mM peroxide which was lethal to non-induced cultures. Bacteria subjected to induction in mid-exponential and early-stationary phase were resistant to 100 mM peroxide, although viability was greatly reduced. Growth of the bacterium under iron-restricted conditions had no effect on the peroxide induction of catalase. As current evidence indicates, the latter is an iron-co-factored heme catalase, this result suggests that catalase induction has a high priority in the metabolism of iron. Furthermore, exposure to peroxide also induces expression of periplasmic MnSOD. A. salmonicida MT423 was resistant to normal rainbow trout macrophages, but was susceptible to killing by activated macrophages. However, if catalase was induced by prior exposure to 20 microM peroxide during mid-exponential phase, A. salmonicida was resistant to killing by activated macrophages. The ability of A. salmonicida to upregulate periplasmic MnSOD and cytoplasmic catalase production under iron restricted conditions and low level peroxide (conditions expected to exist during the early stages of an infection) may be vital for its ability to withstand attack by phagocytic cells in vivo.