Distribution of chitinase and chitobiase in bacillus

Sixty strains representing 29 taxospecies ofBacillus were assayed for their ability to hydrolyze colloidal chitin. A qualitative estimation of chitinolysis was made from the clear zone produced around colonies in the conventional agar plate method and chitobiase activity by use of the fluorescence of 4-methylumbelliferyl-N-acetyl--d-glucosaminide.Strains positive in the chitin-agar plate method were assayed for production of reducing sugar in liquid culture. Seventeen of 52 strains representing 10 species ofBacillus were chitinolytic. The most chitinolytic species ofBacillus were:B. chitinosporus, B. pulvifaciens, B. alvei, B. Macerans, andB. licheniformis. Seventy-eight percent ofBacillus isolates from chitinenriched soil (AU Y91B1, AU-X (unidentified), and AU B₂–B₈) were chitinolytic. Twenty-three strains representing 15 species gave a positive test for chitobiase. Many strains negative for endochitinase gave a strong positive reaction (4+) for chitobiase.     

Seasonal activities of chitinase and chitobiase in the digestive tract and serum of cod, Gadus morhua (L.)

No statistically significant seasonal variations of chitinase and chitobiase in cod, Gadus morhua , stomach, intestine or serum could be detected. Enzyme activity often varied considerably (up to six-fold) between fish captured at the same time, but no correlation could be detected between the presence of chitin or the amount of prey in the stomach and the activities of chitinase and chitobiase. Lysozyme was absent from all the tissues tested.     

Studies on the gill ciliation of the American oyster Crassostrea virginica (Gmelin)

Latero-frontal, para-latero-frontal, and frontal ciliary tracts on the gill filaments of Crassostrea virginica (Gmelin) were studied with light microscopy and scanning electron microscopy. Latero-frontal cirri are complex structures composed of varying numbers of paired cilia. The multiple pairs of cilia which constitute a single cirrus are closely appressed for a portion of their length; they then branch laterally from the central axis in a plume-like fashion. Latero-frontal cirri of adjacent gill filaments create a filtration sieve which should be capable of retaining particles smaller than 1 μm in diameter. Para-latero-frontal cilia are short, closely spaced cilia arranged as a staggered row along the frontal side of each tract of latero-frontal cirri. Latero-frontal cirri and para-latero-frontal cilia occur on ordinary, principal, and transitional gill filaments. Frontal ciliary tracts of ordinary filaments are divided into a central, ventrally directed coarse tract, flanked on either side by a dorsally directed fine ciliary tract. The coarse tract is covered by cirri which are comprised of five to eight cilia, while the fine frontal tracts are made up of individually functioning cilia. The frontal ciliary tracts of principal and transitional filaments bear only dorsally directed fine cilia. The unique direction of effective beat of the coarse frontal cirri of ordinary filaments, in combination with the action of fine frontal cilia and the strategic location of mucus producing cells, is used to describe a possible mechanism for the sorting of filtered particles.     

Cadmium-dependent oxygen limitation affects temperature tolerance in eastern oysters (Crassostrea virginica Gmelin)

Marine ectotherms, including oysters are exposed to variable environmental conditions in coastal shallow waters and estuaries. In the light of global climate change, additional stressors like pollution might pose higher risk to populations. On the basis of the concept of oxygen- and capacity-limited thermal tolerance in aquatic ectotherms (40), we show that a persistent pollutant, cadmium, can have detrimental effects on oysters (Crassostrea virginica). During acute warming from 20 to 28 degrees C (4 degrees C/48 h) standard metabolic rate (SMR) rose in control and cadmium-exposed (50 microg Cd2+/l) animals, with a consistently higher SMR in Cd-exposed oysters. Additionally, Cd-exposed oysters showed a stronger temperature-dependent decrease in hemolymph oxygen partial pressures. This observation indicates that the effect of temperature on aerobic metabolism was exacerbated due to the additional Cd stress. The oxygen delivery systems could not provide enough oxygen to cover Cd-induced elevated metabolic demands at high temperatures. Interestingly, cardiac performance (measured as the heart rate and hemolymph supply to tissues) rose to a similar extent in control and Cd-exposed oysters with warming indicating that cardiac output was unable to compensate for elevated energy demand in Cd-exposed oysters. Together with the literature data on metal-induced reduction of ventilatory capacity, these findings suggest that synergistic effects of elevated temperatures and cadmium exposure led to oxygen limitation by impaired performance in oxygen supply through ventilation and circulation. Overall, cadmium exposure resulted in progressive hypoxemia in oysters at high temperatures, suggesting that the thermal tolerance window is narrowed in marine ectotherms inhabiting polluted areas compared with pristine environments.     

Copper exposure affects hemocyte apoptosis and Perkinsus marinus infection in eastern oysters Crassostrea virginica (Gmelin)

Dermo disease in the eastern oyster (Crassostrea virginica) is caused by an intracellular protistan parasite Perkinsus marinus. The progression and outcome of this disease is determined by a complex interplay between the host's immunity and parasite's escape mechanisms, both of which can be influenced by environmental pollutants including heavy metals such as copper (Cu). The goal of the present study was to determine the effects of Cu on the levels of apoptosis (which can serve as an important host defense mechanism) in oyster immune cells (hemocytes) in?vitro and in?vivo as well as on the establishment of P.?marinus infections in?vivo. Surprisingly, Cu exerted opposing effects on apoptosis levels of hemocytes in?vitro and in?vivo, stimulating apoptosis in isolated hemocytes but suppressing it during Cu exposure of whole oysters. The mechanisms of this effect are presently unknown and may be related to the different bioavailability of the metal in?vitro and in?vivo. As expected, Cu accumulated in oyster soft tissues during in?vitro exposure. Unexpectedly, this metal also strongly accumulated in hemolymph plasma which is classically considered isoionic with the surrounding seawater, likely reflecting the presence of soluble Cu-binding proteins in oyster plasma. Cu reduced growth of P.?marinus in?vitro and greatly reduced infection levels of hemocytes in?vivo, presumably by direct toxic effects on the parasite. As a possible parasitic counterbalance, Cu accumulation in the hemocytes was reduced by P.?marinus infection, although this reduction was not sufficient to prevent the parasiticidal effects of the heavy metal in?vivo. This effect of Cu may be useful as a potential therapeutic against Dermo disease in aquaculture conditions. Overall, this study provides important new insights into the potential role of environmental metals in host-parasite relationships and disease dynamics in C.?virginica.     

Genetic Analysis of Selected Strains of Eastern Oyster (Crassostrea virginica Gmelin) Using AFLP and Microsatellite Markers

Amplified fragment length polymorphisms (AFLPs) and microsatellite markers were used to examine genetic variation and divergence in 4 selected strains (DBH, NEH, FMF, and CTS) and 1 wild population (DBW) of the eastern oyster Crassostrea virginica Gmelin. Eighty-six AFLP markers (from 3 primer pairs) and 5 microsatellite loci were used for the analysis of 30 oysters from each of the 5 populations. Microsatellite loci were considerably more variable than AFLPs. The observed heterozygosity ranged from 0.560 to 0.640 across populations for microsatellites, and from 0.186 to 0.207 for AFLPs. Both F_st and _PT of microsatellite data and _PT statistics of AFLP data revealed significant divergence between all pairs of populations. There was no significant reduction in heterozygosity in all 4 selected strains; however, the number of alleles per locus was considerably lower in the selected strains than in the wild population. Two strains subjected to long-term selection for disease resistance shared frequency shifts at a few loci, which deserve further analysis to determine if they are linked to disease-resistance genes.     

The effects of photoperiod,A-23187 and PTZ on the habitat salinity adaptation of Crassostrea virginica (Gmelin)

• 1.1. Electrical stimulation and DOPA decarboxylase activities were studied in Crassostrea virginica maintained at 30‰ habitat salinity.
• 2.2. Exposure to light significantly reduced the effectiveness of the electrical stimulation and 30‰ habitat acclimation. However, periods of exposure to darkness had the opposite result. Recovery to the 30‰ habitat ctenidial ciliary rate was significantly faster (more than 2 × ) in animals dissected and then maintained in darkness during the acclimation period.
• 3.3. Acclimation time of dark-dissected ctenidial preparation was significantly increased in the presence of A-23187 (a calcium cell membrane pore facilitator) or PTZ (a cytosomal calcium releasor). The latter treatment exhibited only about a 65% recovery to the control basal rate of beating.
• 4.4. This study elucidates a cytosomal role in the acclimation process via a neuronal regulatory mechanism controlling ciliary activity on the ctenidium. Cytosomes could conceivably furnish an extension of the transport activity of the plasma membrane to bring about a sophisticated microscopic control of solute (i.e. calcium) homoeostasis in the cytosol.

     

The taxonomy and biology of Diadegma chrysostictos (Gmelin) and Diadegma fabricianae sp.n. (Hymenoptera: Ichneumonidae)

Abstract. A combination of morphological and biological evidence is used to separate two species of Ichneumonidae parasitizing Lepidoptera: Diadegma chrysostictos (Gmelin), a parasitoid of phycitine and galleriine Pyralidae, and Diadegma fabricianae sp.n. which parasitizes the choreutid Anthophila fabriciana (Linnaeus). An inbred laboratory culture of D.chrysostictos was found to be atypical with respect to some character states, illustrating the unsuitability of artificially maintained populations for morpho-taxonomic study. A neotype is designated for Ichneumon chrysostictos Gmelin, 1790.     

Numerical quantification of Perkinsus marinus in the American oyster Crassostrea virginica (Gmelin, 1791) (Mollusca: Bivalvia) by modern stereology

Species of Perkinsus are responsible for high mortalities of bivalve molluscs world-wide. Techniques to accurately estimate parasites in tissues are required to improve understanding of perkinsosis. This study quantifies the number and tissue distribution of Perkinsus marinus in Crassostrea virginica by modern stereology and immunohistochemistry. Mean total number of trophozoites were (mean +/- SE) 11.80 +/- 3.91 million and 11.55 +/- 3.88 million for the optical disector and optical fractionator methods, respectively. The mean empirical error between both stereological approaches was 3.8 +/- 1.0%. Trophozoites were detected intracellularly in the following tissues: intestine (30.1%), Leydig tissue (21.3%), hemocytes (14.9%), digestive gland (11.4%), gills (6.1%), connective tissues (5.7%), gonads (4.1%), palps (2.2%), muscle (1.9%), mantle connective (0.8%), pericardium (0.7%), mantle epithelium (0.1%), and heart (0.1%). The remaining 0.6% were found extracellularly. Percentages of trophozoite stages were (mean +/- SE): large, log-phase trophonts, i.e., signet rings, 97.0 +/- 1.2%; meronts, 2.0 +/- 0.9%; clusters of small, log-phase trophonts, i.e., merozoites, 1.0 +/- 0.5%. Levels of infection in hemocytes and Leydig tissue were representative of total parasite intensity. These techniques are a powerful tool to follow parasite distribution and invasion, and to further explore mechanisms of Perkinsus spp. pathogenesis in bivalves.     

Sobolevicanthus transvaalensis n.sp. (Cestoda: Hymenolepididae) from the Cape Teal (Anas capensis Gmelin, 1789)

Summary Sobolevicanthus transvaalensis n.sp. is described from the Cape Teal, Anas capensis Gmelin, 1789, collected in the Republic of South Africa. The new species possesses 8 skrjabinoid hooks 78–88 m long (mean 85 m) and a short claviform cirrus-sac 79–143 m long and resembles S. javanensis (Davis, 1945) and S. terraereginae (Johnston, 1913). It can be distinguished from S. javanensis by its shorter cirrus-sac and smaller cirrus diameter, and by differences in the morphology of the accessory sac and vagina and in their position relative to the cirrus-sac. It can be separated from S. terraereginae on the basis of cirrus length and diameter. The basal diameter of the cirrus in S. terraereginae is three times that in S. transvaalensis. ac]19830414     

Change in lipid composition in eastern oyster (Crassostrea virginica Gmelin) exposed to constant or fluctuating temperature regimes

A temperature decrease usually induces an ordering effect in membrane phospholipids that can lead to membrane dysfunction. Ectotherms typically counteract this temperature effect by remodeling membrane lipids as stipulated in the homeoviscous adaptation theory (HVA). Previous studies mostly focused on the remodeling of membrane lipids during long-term acclimatization or acclimation at constant temperature regimes, whereas in nature, many organisms experience variations in temperature on a daily basis and must react to this changing thermal environment. The objective of this study was to examine the composition of membrane lipids in oysters subjected to long-term acclimation at constant temperatures (12 or 25 degrees C) or to environmentally realistic daily fluctuations in temperature between 12 and 25 degrees C for 7 d. The lipid composition of gill in oysters subjected to long-term acclimation at a constant temperature or to daily temperature fluctuations varied in a way consistent with HVA: oysters adjusted their phospholipid to sterol ratio in response to long-term acclimation to a constant temperature but not to daily temperature fluctuations. In contrast, the unsaturation index of polar lipids in oysters varied in response to both long-term acclimation to a constant temperature and to daily temperature fluctuations, mainly due to changes in 22:6n-3 and 20:5n-3. The 20:4n-6 levels in oyster gills increased as temperature rose, suggesting an increasing availability of this fatty acid for eicosanoid biosynthesis during stress responses.     

Polymorphism in a serine protease inhibitor gene and its association with disease resistance in the eastern oyster (Crassostrea virginica Gmelin)

Serine protease inhibitors (SPIs) are a superfamily of structurally related but functionally diverse proteins found in almost all organisms ranging from viruses to humans. Some of them play important roles in host defense. A recently identified SPI from the eastern oyster (Crassostrea virginica), cvSI-1, has been shown to inhibit the proliferation of the Dermo pathogen Perkinsus marinus in vitro, although direct evidence linking it to disease resistance is lacking. In this study, we identified polymorphism in the cvSI-1 gene and studied its association with improved survival after disease-caused mortalities and in disease-resistant eastern oyster strains. Full-cDNA sequence of cvSI-1 was sequenced in a diverse panel of oysters, revealing 12 single-nucleotide polymorphisms (SNPs) in the 273 bp coding region: five were synonymous and seven non-synonymous. The Dn/Ds ratio, 1.4, suggests that cvSI-1 is under positive selection. Selected SNPs were genotyped in families before and after disease-caused mortalities as well as in disease-resistant and susceptible strains. At SNP198, the C allele consistently increased in frequency after mortalities that are caused primarily by Dermo and possibly also by MSX. Its frequency in the disease-resistant strain is significantly higher than that in the susceptible strains and the base population from which the selected strains were derived. These results indicate that polymorphism at cvSI-1 is associated with Dermo (possibly also MSX) resistance in the eastern oyster. SNP198 is a synonymous mutation, and its association with disease resistance may be due to its close linkage to a functional polymorphism nearby.