A comparison of the antigenicity of the extracellular products and whole-cell sonicates from Mycobacterium spp. in rabbits, mice and fish by immunoblotting and enzyme-linked immunosorbent assay

The antigenicity of extracellular products (ECPs) derived from Mycobacterium spp. isolated from snakehead, Channa striata (Bloch), and Siamese fighting fish, Betta splendens (Regan), were examined by immunoblotting and enzyme-linked immunosorbent assay (ELISA) using sera collected from immunized rabbits, mice and fish (rainbow trout). All three species responded to a 65-kDa protein present in both the ECPs and whole cell sonicates (WCSs) from a variety of Mycobacterium spp. Cross-reactivity of anti- M. tuberculosis and anti-human heat-shock protein monoclonal antibodies (MAbs), and the presence of fibronectin binding proteins secreted into ECPs of mycobacteria were also examined. The MAbs against human 60-kDa heat-shock protein cross- reacted with the band at 65 kDa in the ECPs of TB1 (isolated from snakehead fish) and the type strain M. marinum, while the anti- M. tuberculosis MAb F29–47 elicited a strong reaction with a band at 21 kDa with most of the ECPs from mycobacterial strains examined. The major fibronectin-binding proteins were located between 21 and 25 kDa. The 65-kDa protein from ECPs of Mycobacterium spp. proved strongly immunogenic to rabbits, mice and fish. Rabbit antiserum against the 65-kDa protein from strain TB267 reacted with many non- Mycobacterium WCSs, and therefore, the 65-kDa protein from Mycobacterium spp. is believed to be a common protein found in many fish bacterial pathogens.     

Carbonate mineral filtrants with new surfaces reduce alkalinity in seawater and artificial seawater: Preliminary findings

Silica sand (silica), coral (aragonite), and oyster shell (calcite) were ground to similar particle sizes and placed in seawater and artificial seawater (GP2 Medium). Alkalinity and pH values of the artificial seawater decreased substantially over 24 h when in contact with coral and oyster shell; the effects in seawater were minor. Once alkalinity has been reduced, the maintenance of stable pH at values typical of seawater is made more difficult. The data, which are preliminary, have practical application.     

Ecology of larval blue sucker (Cycleptus elongatus) in the Mississippi River

Abstract –  Ecology of larval blue sucker, Cycleptus elongatus , a North American catostomid that has declined throughout its range, is poorly known because larvae have rarely been sampled. A total of 316 young blue suckers (16.0–39.0 mm total length) was captured over 3 years at 14 off-channel sites in Pool 25, Mississippi River. Blue suckers demonstrated distinct temporal and spatial abundance patterns. Blue suckers were only captured in late May/early June, and were more abundant during a year of little flooding. Abundance was correlated with the distance a site was from the main channel, being highest in island borders and island sloughs in proximity to the channel. Fish guts contained a relatively high biomass of chironomids and zooplankton, suggesting islands were providing suitable feeding opportunities. Because of their proximity to flows, slack waters provided by islands were accessible to blue sucker larvae dispersing from channel spawning areas and facilitated their development into rheophilic juveniles.     

Experimental amoebic gill disease of Atlantic salmon, Salmo salar L.: further evidence for the primary pathogenic role of Neoparamoeba sp. (Page, 1987)

Amoebic gill disease (AGD) has been attributed to infection by Neoparamoeba sp. The causal mechanisms for AGD lesion development and the primary pathogenic role of Neoparamoeba sp. require elucidation. Three groups of Atlantic salmon were exposed to viable gill isolated amoebae, to sonicated amoebae, or to sea water containing viable amoebae without direct contact with gill epithelia. Fish were removed 8 days post-exposure and the gills assessed histologically for AGD. AGD occurred only when fish were exposed to viable trophozoites. Consequently, in an accompanying experiment, infection was evaluated histologically at 12, 24 and 48 h post-exposure in three groups of salmon, one group being mechanically injured 12 h prior to exposure. A progressive host response and significant increase (P < 0.001) in the numbers of attached amoebae was apparent over the 48-h duration in undamaged hemibranchs in both treatment groups. There were no significant differences to mucous cell populations. Attachment of Neoparamoeba sp. to damaged gill filaments was significantly reduced (P < 0.05) by 48 h post-exposure. These data further confirm and describe the primary pathogenic role of Neoparamoeba sp. and the early host response in AGD. Preliminary evidence suggests that lesions resulting from physical gill damage are not preferentially colonized by Neoparamoeba sp.     

The type of activated carbon determines how much dissolved organic carbon is removed from artificial seawater

Four granular activated carbons (GACs) made of different materials were tested for removal of dissolved organic carbon (DOC) from artificial seawater of a recirculated aquarium. After 70 days in a continuous flow experiment, comparative removal data (grams of GAC required to remove 1 g of DOC) were coconut shell (491), hardwood (84·4), anthracite (837) and bone char (383), indicating the superior performance of hardwood. Scanning electron microscopy showed that microbial colonization of a sample material (hardwood) was slight and occurred exclusively at the surface. Biological enhancement of GAC was considered to be unimportant as a mechanism for DOC removal.     

PROBIT analysis predicts hatching rates of brine shrimp Artemia sp. cysts

Thirty replicates of San Francisco Bay brine shrimp Artemia sp. cysts from one lot were weighed to 0·01 mg. The mean mass of a single cyst was 2·597 μg (±0·040 μg, 95% confidence level). Batches of 1 g from the same lot were hatched in the laboratory, and fraction hatched versus time data were fitted to a nonlinear curve using PROBIT analysis. Median time of hatch was 24·8 h with a standard error of ±3·92 h. Cysts and nauplii in 1-ml aliquots were pipetted at regular intervals and counted under a dissecting microscope. The number of cysts pipetted at the beginning of the experiment was 19% less than estimates based on the known number per volume of hatching medium, indicating that hatching data derived from pipetting procedures may contain large sampling errors. PROBIT analysis allows fraction hatched to be predicted when a particular lot of cysts is hatched under controlled conditions.     

Amoebic gill disease: sequential pathology in cultured Atlantic salmon, Salmo salar L

Amoebic gill disease (AGD) affects the marine culture phase of Atlantic salmon, Salmo salar L., in Tasmania. Here, we describe histopathological observations of AGD from smolts, sampled weekly, following transfer to estuarine/marine sites. AGD was initially detected histologically at week 13 post-transfer while gross signs were not observed for a further week post-transfer. Significant increases (P < 0.001) in the proportion of affected gill filaments occurred at weeks 18 and 19 post-transfer coinciding with the cessation of a halocline and increased water temperature at the cage sites. The progression of AGD histopathology, during the sampling period, was characterized by three phases. (1) Primary attachment/interaction associated with extremely localized host cellular alterations, juxtaposed to amoebae, including epithelial desquamation and oedema. (2) Innate immune response activation and initial focal hyperplasia of undifferentiated epithelial cells. (3) Finally, lesion expansion, squamation-stratification of epithelia at lesion surfaces and variable recruitment of mucous cells to these regions. A pattern of preferential colonization of amoebae at lesion margins was apparent during stage 3 of disease development. Together, these data suggest that AGD progression was linked to retraction of the estuarine halocline and increases in water temperature. The host response to gill infection with Neoparamoeba sp. is characterized by a focal fortification strategy concurrent with a migration of immunoregulatory cells to lesion-affected regions.     

Allelic losses and gains during translocations of a high conservation value fish,Coregonus lavaretus

1. The use of translocations to establish new or ‘refuge’ populations for species with high conservation value is controversial but widely used in conservation management. One of the risks of this approach is that an establishing population does not adequately capture the genetic diversity of the donor gene pool. This effect, rarely examined, is tested here.
2. In this study the genetic consequences of two conservation translocations after five generations (16 years) of the European whitefish, Coregonus lavaretus, were quantified. Both translocations were made using almost the same genetic groups and thus represent a partly replicated natural study.
3. Analysis of 12 informative microsatellites showed that expected heterozygosity, the mean number of alleles per locus and allelic richness did not differ between donor and translocated populations. There was also no loss of heterozygosity in the translocated populations, nor deviations from Hardy–Weinberg equilibrium expectations, nor signs of linkage disequilibrium.
4. All populations were genetically differentiated but pairwise F_ST values were low, indicating that the magnitude of divergence was small.
5. There was no evidence of inbreeding but there were significant differences in private allelic richness between donor and translocated populations. Of 50 alleles found in the donor population, 16% of the rarer alleles were lost in one translocated population and 8% in the other.
6. Allele loss without a reduction in heterozygosity strongly points to stochastic drift effects having occurred following translocation. The evidence indicates that alleles that were not detected in the donor population have arisen de novo in the translocated populations.
7. It is concluded that conservation translocations comprising even a modest number of propagules can successfully capture a high proportion of genetic variation of the host population, and that reduced genetic variation in the translocated population may be mitigated by the emergence of new variation over short time periods.

     

Assessing common bottlenose dolphin (Tursiops truncatus) population structure in Mississippi Sound and coastal waters of the north central Gulf of Mexico

1. Population structure of highly mobile marine organisms can be complex and difficult to study, but it is important to understand how populations partition themselves within their environment for accurate assessment of both natural and anthropogenic impacts and successful management. The 2010 Deepwater Horizon oil spill negatively impacted common bottlenose dolphins (Tursiops truncatus) within Mississippi Sound and the surrounding north central Gulf of Mexico (GOMx); however, little was known about their underlying population structure in these waters. Thus, it was unclear how many demographically independent populations were affected by the spill.
2. Common bottlenose dolphin samples were collected throughout inshore waters of Mississippi Sound and coastal waters of the north-central GOMx. Mitochondrial DNA control region sequence data and 19 nuclear microsatellite loci were analysed to determine how many populations are present and characterize their range throughout these waters.
3. Bayesian clustering and migration analyses identified two genetically distinct and demographically independent populations: one predominantly inhabiting Mississippi Sound and adjacent coastal waters, and a second population extending generally from offshore of Mobile Bay, Alabama, east along the Florida Panhandle. Neither of these populations align with the currently delineated management stocks previously used to estimate impacts from the oil spill on common bottlenose dolphins in this portion of the GOMx.
4. These results suggest that revisions may be necessary so that management stocks accurately represent the demographically independent populations present in these waters. Furthermore, better comprehension of underlying population structure will enhance impact assessments on common bottlenose dolphins and provide more appropriate baseline data to support future restoration and conservation objectives.