Difference in benthic invertebrate communities of headwater streams can be detected using a short elevation gradient

International Aquatic Research - Communities of benthic invertebrates from a series of intermittent headwater streams spanning over a short elevation gradient (i.e.,...     

Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B‐cell lymphoma

An 11‐year‐old, 443‐kg Haflinger mare was presented to the North Carolina State University Veterinary Teaching Hospital with a 2‐week history of lethargy and a 3‐day duration of anorexia, pyrexia, tachycardia, and ventral edema. Severe pitting edema, peripheral lymphadenopathy, and a caudal abdominal mass were noted on physical examination. An extreme leukocytosis (154.3 × 10³/μL) and microscopic hematologic findings suggestive of myelomonocytic leukemia were observed. Serum protein electrophoresis revealed a monoclonal gammopathy and urine protein electrophoresis revealed a monoclonal light chain proteinuria. Necropsy and histopathology confirmed widespread neoplastic infiltration in many organs with a heterogenous population of cells; there was no apparent evidence of bone marrow involvement. Immunohistochemistry confirmed presence of a majority of B cells with a limited antigen expression, admixed with a lower number of T cells. Molecular clonality analysis of IgH2, IgH3, and kappa‐deleting element (KDE, B cell) on whole blood and KDE on infiltrated tissues revealed clonal rearrangements, and the KDE intron clones that amplified in blood and in infiltrated tissue were identical. In contrast, the clonality analysis of T‐cell receptor γ revealed no clonality on blood cells and infiltrated tissues. In conjunction with the histopathologic changes, the lesion was interpreted to be composed of neoplastic B cells with a reactive T‐cell population. Polymerase chain reaction testing for equine herpes virus 5 was negative. The final diagnosis was diffuse large B‐cell lymphoma with a marked hematogenous component.     

Rotation-end financial performance of vegetation control on Eucalyptus smithii in South Africa

Control of competing vegetation during eucalypt regeneration is important but the cost-benefit of varying levels of control is not well understood. A trial was initiated to quantify the impact of five vegetation control treatments on Eucalyptus smithii R.T.Baker. to determine the potential loss in growth and differential costs against which this growth loss could be linked. Five treatments were developed to suit the predicted vegetation load at the site and varied according to weeding intensity (high, moderate and low weeding) or area around the tree that was weeded (no vegetation control, a 2 m row weeding and complete vegetation control). The vegetation control treatments were imposed at planting and maintained until canopy closure (16.4 months). Tree growth was monitored throughout the rotation and this, together with the cost of the various establishment and weeding operations, were used to make treatment comparisons. Weed growth was rapid following planting, with competition-induced divergence in tree growth occurring from 52 d. Rotation-end volume for the Weedfree check (414 m³ ha^?1) and Row weeding treatment (394 m³ ha^?1) were significantly different from the Weedy check (319 m³ ha^?1), with the Moderate (374 m³ ha^?1) and Low (371 m³ ha^?1) weeding intensity treatments intermediate but not significantly different from each other, nor from the other treatments. The financial performance (expressed as bare land value [BLV] with 6% discounting) of the Weedfree check outperformed the other treatments and was 37% higher than the Weedy check. The BLVs of the Moderate and Low weeding intensity treatments were similar to each other, indicating that these treatments were both feasible in terms of financial performance. However, the 2 m Row weeding had c. 10% higher BLV than the Moderate and Low weeding intensity treatments, and could be considered as a viable alternative to the Weedfree check. Sensitivity analysis conducted on the data in terms of local or exogenous risks indicated that between the treatments, differences in response to either local or global market risks were minor. Thus, small changes in cost and price levels, or larger changes in applicable discount rate, would not alter the ranking of the vegetation control treatments, with the Weedfree check (High weeding intensity) being the best in terms of financial performance, and the Weedy check the worst.     

Alternative eucalypts for commercial pulpwood production at moderately dry sites in the warm temperate zone of KwaZulu-Natal,South Africa

During 2001, a series of four site–taxa interaction trials was established in the warm temperate (mean annual temperature range 16–19 °C) forestry climatic zone of KwaZulu-Natal (KZN), South Africa. The main objective was to investigate the commercial forestry potential of a range of alternative Eucalyptus and Corymbia taxa for moderately dry (mean annual precipitation < 850 mm) sites within the zone. At rotation end, all trials received final standing tree measurements. At one of the sites (Rockvale), trees of eight promising alternative taxa were felled, stem measurements and wood samples taken, and wood and fibre productivities determined. On the basis of tree growth and wood and fibre production, C. citriodora subsp. variegata, C. henryi, E. badjensis, E. benthamii and E. dorrigoensis (listed alphabetically) demonstrated the greatest potential as commercial alternatives for moderately dry sites in the KZN warm temperate zone. The majority of these taxa showed strong site specificity. Eucalyptus benthamii was the only taxon showing high growth adaptability to the entire range of site conditions applied in the series. The non-susceptibility of C. citriodora subsp. variegata and C. henryi to the current topical insect pests Thaumastocoris peregrinus, Leptocybe invasa and Glycaspis brimblecombei elevates the appeal of these taxa as potential alternative planting choices for moderately dry sites within lower altitude (<1 100 m asl) areas of the climate zone. The matching of the most promising alternative taxa in the series to the range of sites encountered in moderately dry areas of the KZN warm temperate forestry zone is discussed in this paper.     

Magnitude of mitral valve closure plays a pivotal role in enhancing the forward blood flow during cardiac massage in dogs with ventricular fibrillation

Motion of mitral valve during cardiac massage was examined using beagle dogs with ventricular fibrillation (n=4). Active compression-decompression cardiac massage (ACD-CM) exhibited greater peak aortic pressure than standard cardiac massage (S-CM), reverse of which was true for peak pulmonary capillary wedge pressure in each animal. Accordingly, peak aortic pressure was greater than peak pulmonary capillary wedge pressure with ACD-CM, whereas its reverse was true with S-CM. Transesophageal echocardiography revealed that mitral valve was incompletely closed with S-CM with showing regurgitation. The valve was more effectively closed during ACD-CM. These results indicate that effective closure of mitral valve during cardiac massage may increase forward blood flow, supporting “cardiac pump theory” rather than “thoracic pump theory” as a principle in dogs.     

Fate of Dwarf Bunt Fungus Teliospores During Milling of Wheat into Flour

Wheat contaminated with teliospores of Tilletia controversa Kühn (TCK) was mixed with uncontaminated wheat and processed through the Kansas State University pilot mill. Two 50-bu lots of the contaminated mixture were cleaned, tempered, and milled. Approximately 500 samples of wheat, cleanings, and mill fractions were collected and examined for the presence of intact and broken TCK teliospores. Whole wheat samples (50 g) were washed, sieved through a 60-μm nylon sieve, and pelleted by centrifugation. Contents of the pellet were examined microscopically for the presence of TCK spores. The procedure was modified as needed to accommodate cleanings and mill fractions. Levels of spore contamination in whole wheat samples decreased at each step during the handling process, and large numbers of spores were found in materials that were sieved or aspirated from the grain. Very few spores were found in bran, germ, and shorts; none were detected in red dog or straight-grade flour. The results showed that a high percentage of spores can be removed from wheat by mechanical cleaning but that it is not feasible to remove all of them.     

How fast is too fast? Water velocity differentially affects growth of four Gila River,native cyprinids

Understanding trade-offs associated with occupying various aquatic habitats provides a mechanistic understanding of habitat needs that can be used to evaluate the consequences of habitat loss or alteration. We used instream enclosures and field observations to identify how velocity affects the growth rates of four native species in the upper Gila River basin: longfin dace (Agosia chrysogaster) and speckled dace (Rhinichthys osculus), two species of no conservation concern, and loach minnow (Tiaroga cobitis) and spikedace (Meda fulgida), two federally endangered species. Elevated velocity was predicted to increase food delivery through drift or stimulation of benthic primary production. Energetic costs of high-velocity habitat were predicted to vary with morphology and behaviour and be lowest for speckled dace and loach minnow because they are adapted to occupy interstitial spaces of the substrate in riffles. Spikedace and longfin dace should perform best in moderate velocities, where the trade-off between exposure to drifting macroinvertebrates outweighs the energetic costs of maintaining position in the water column. Growth rates of loach minnow and speckled dace increased in higher velocities, but contrary to our initial predictions, spikedace growth rates also increased in high-velocity habitats while longfin dace grew fastest in low-velocity habitats; similar to the locations these species occupied based on field observations. These results indicate that for spikedace, the increased abundance of drifting macroinvetebrates in high-velocity habitats outweighs the energy expenditure, but for longfin dace the energetic costs of occupying moderate to high-velocity habitats outweigh the benefit to increased food availability. Our experiment provides a mechanistic understanding of habitat requirements across species and may inform predictions on how modifications or restoration of riverine ecosystems influence native fish diversity.     

High and dry in days gone by: Life-history theory predicts Appalachian mountain stream fish assemblage transformation during historical drought

Understanding the ecological dimensions of drought is critical for predicting how humans and nature will be affected by the expected increased prevalence of drought in the future. We tested life-history-based predictions for fish assemblage responses to drought using retrospective analysis of long-term (1986–2003) fish surveys from two streams in the Appalachian Mountains of North America. We hypothesised that (1) fish assemblage composition would correlate with wet and dry hydrologic conditions as assemblages fluctuated within a loose equilibrium and (2) life-history traits of fishes would correlate with dry versus wet periods such that opportunistic life-history strategists would dominate during drought. Results showed fish assemblage changes in Little River and Cataloochee Creek correlated with drought severity measured one year prior to fish surveys. Fish assemblages at all three sampling sites in Little River and two sites in Cataloochee Creek fluctuated within a loose equilibrium, while the remaining two sites in Cataloochee Creek indicated directional change. Life-history traits for fishes in Cataloochee Creek correlated with one-year time lag fluctuations in drought caused by opportunistic species being dominant during drought and periodic/equilibrium species dominant during wet periods. Time series plots of fish abundances aggregated by life-history strategy revealed dominance of opportunistic species emerged at the onset of a multi-year drought spanning 1998–2004, particularly for the two sites undergoing directional change. Our work provides empirical evidence for theoretical linkages between life history and environmental fluctuations and can ultimately be used to predict stream fish community response to future drought regimes.