Dispersal and tributary immigration by juvenile coho salmon contribute to spatial expansion during colonisation

Anadromous fishes are frequently restricted by artificial barriers to movement such as dams and culverts, so measuring dispersal helps identify sites where improved connectivity could promote range expansion and population viability. We used a combination of DNA‐based parentage analysis and mark–recapture techniques to evaluate dispersal by juvenile coho salmon (Oncorhynchus kisutch) in a population in the initial stages of colonisation following installation of fish passage structures at a previously impassable dam on the Cedar River, WA, USA. The spatial distribution of individuals within maternal families revealed that dispersal was common. Among the offspring of radio‐tagged mothers, 28% were collected outside the spawning reach and dispersed up to 6.3 km (median = 1.5 km). Most juveniles captured in a tributary (Rock Creek, where few adults spawned) had immigrated from the Cedar River and represented many different families. Juvenile dispersal therefore provided a secondary phase of spatial expansion following initial colonisation by adults. Consistent with the condition‐dependent dispersal hypothesis, juveniles that dispersed farther upstream in the tributary were larger than fish collected near the tributary mouth. Overall, the results demonstrated widespread dispersal in a system with low coho salmon densities, and this might increase the rate of population growth if it reduces the effects of local density dependence. By implication, juveniles can take advantage of rearing habitats reconnected through barrier removal, even when such areas are located several kilometres from adult breeding grounds.     

Orthopedic Infections in Equine Long Bone Fractures and Arthrodeses Treated by Internal Fixation: 192 Cases (1990–2006)

Objective: To determine the rate of postoperative infection (POI) for internal fixation repaired equine long bone fractures and arthrodeses and identify associated risk factors. Study Design: Case series. Animals: Horses (n=192) with fracture repair of the third metacarpal and metatarsal bones, radius, ulna, humerus, tibia, and femur, or arthrodesis with internal fixation. Methods: Medical records (1990–2006) were reviewed for signalment, anatomic location, fracture classification and method of repair, technique and surgical duration, bacterial species isolated, postoperative care, onset of POI, and outcome. Results: Of 192 horses (171 [89%] closed, 21 [11%] open fractures), 157 (82%) were discharged from the hospital. Infection occurred in 53 (28% horses), of which 31 (59%) were discharged. Repairs without POI were 7.25 times more likely to be discharged from the hospital. Closed fractures were 4.23 times more likely to remain uninfected and 4.59 times more likely to be discharged from the hospital compared with open fractures. Closed reduction and internal fixation was associated with a 2.5‐fold reduction in rate of POI and a 5.9 times greater chance for discharge from the hospital compared with open reduction and internal fixation. Females had a strong trend for increased POI when compared with colts and stallion but not geldings. Conclusions: Overall rate of POI was 28%. Fracture classification, method of repair, gender, and surgical duration were significant risk factors.     

Morphological variability of Atlantic salmon Salmo salar and brown trout Salmo trutta in different river environments

Abstract – The morphologies of sympatric juvenile Atlantic salmon Salmo salar parr and brown trout Salmo trutta parr were compared between Irish rivers with contrasting hydraulic environments – a high‐gradient and a low‐gradient tributary from the River Barrow catchment, south‐east Ireland and a high‐gradient river from the Burrishoole catchment, west of Ireland. The two catchments differ markedly in mean annual precipitation (849.0 mm year^?1 and 1370.3 mm year^?1 for the Barrow and Burrishoole catchments, respectively). Parr of both species demonstrated morphological variation between and within catchments. Changes in metrics such as pectoral fin length, body depth and body length between and within catchments suggest that hydraulic forces were a major determinant of morphological variation. Both species from the Burrishoole catchment had relatively larger pectoral fins, longer heads, larger eyes and shallower bodies than conspecifics from the Barrow catchment. In rivers subject to frequent rainfall‐driven high discharges, such as those in the Burrishoole catchment, a more fusiform body and head shape coupled with larger pectoral fins may reduce the energetic cost of maintaining position in the water column, as well as increase stability and manoeuvrability. The larger eyes in both parr species in the Burrishoole catchment could further be a response to the lower visibility of the more turbid and peat‐stained waters or to the reduced prey availability. The results of this study demonstrate that local adaptation to flow conditions can yield morphologically distinct populations and that multiple species can exhibit parallel phenotypic responses to changing environmental conditions.     

Persistence and binding of DDT and gamma-HCH in a sandy loam soil under field conditions in Delhi,India

Persistence and binding capacity of [¹⁴C]p, p′-DDT and [¹⁴C]y-HCH were studied for one year in a sandy loam soil of Delhi, India, after surface treatment during monsoon, winter and summer seasons under field conditions. Both DDT and HCH dissipated more rapidly under the Indian subtropical climate than reported for temperate regions. In all three seasons, both insecticides dissipated most rapidly during the initial 60 days. However, in the final six months there was very little change in the residue levels. After one year, the final soil burden of DDT varied from 33 to 36% and of HCH from 14 to 15% of the initial concentrations in the different experiments. HCH bound more with the soil as, out of the total residues present after one year, more than 75% of HCH was in bound form compared with only 24% of DDT. The observed time for 50% initial dissipation of DDT ranged from 60 to 120 days, while in the case of HCH it varied from 30 to 45 days. However, the rate of loss of residues which persisted for more than 6 months was equivalent to a half-life of between 500 and 10000 days for DDT, and between 700 and 2000 days for HCH, thus illustrating the very long persistence of aged residues. Since degradation of both insecticides was apparently minimal, the data indicate that dissipation of DDT and HCH was largely due to volatilisation.     

A PCR diagnostic for cyclodiene insecticide resistance in the red flour beetle Tribolium castaneum

A molecular diagnostic was used to examine the conservation of cyclodiene resistance associated mutations between different strains of Tribolium castaneum (Herbst.). An improved insecticide bioassay for discrimination between resistant genotypes was developed and seven resistant strains were established from five different continents. In order to develop a molecular diagnostic a partial cDNA of the cyclodiene insecticide resistance gene Rdl, a γ-aminobutyric-acid-gated chloride-ion channel, was cloned and sequenced. This cDNA spans exon 7, the region containing the resistance-associated mutation, and part of exon 8. An ‘allele-specific’ oligonucleotide primer, carrying the resistance-associated mutation at its 3′ end, was used in combination with a flanking ‘allele-independent’ primer in the polymerase chain reaction to selectively amplify a single resistance-associated mutation from all seven strains collected worldwide. The implications of these findings for the population genetics of insecticide resistance and its management in pest insects via quarantine are discussed.     

Blood chemistry values of juvenile red pacu (Piaractus brachypomus)

Abstract: Blood samples were collected from 29 juvenile red pacu ( Piaractus brachypomus ), ornamental freshwater fish, to establish baseline blood chemistry values. Mean (minimum-maximum) values, obtained by automated bichromatic analysis and ion selective electrode analysis, were as follows: sodium, 150.4 (146–159) mmol/L; potassium, 3.93 (2.7–5.0) mmol/L; chloride, 138.7 (128–150) mmol/L; total CO₂, 7.5 (6–10) mmol/L; albumin, 0.86 (0.5–1.0) g/dL; lactate dehydrogenase, 237.8 (65–692) IU/L; aspartate aminotransferase, 49.1 (0–125) IU/L; creatinine, 0.31 (0.2–0.4) mg/dL; calcium, 10.80 (9.5–12.5) mg/dL; anion gap, 6.89 (1.2–12.5) mmol/L; and phosphorus, 7.29 (4.1–8.9) mg/dL.     

Muscular dystrophy in female dogs

The most common form of muscular dystrophy in dogs and humans is caused by mutations in the dystrophin gene. The dystrophin gene is located on the X chromosome, and, therefore, disease-causing mutations in dystrophin occur most often in males. Therefore, females with dystrophin deficiency or other forms of muscular dystrophy may be undiagnosed or misdiagnosed. Immunohistochemistry was used to analyze dystrophin and a number of other muscle proteins associated with muscular dystrophy in humans, including sarcoglycans and laminin alpha2, in muscle biopsy specimens from 5 female dogs with pathologic changes consistent with muscular dystrophy. The female dogs were presented with a variety of clinical signs including generalized weakness, muscle wasting, tremors, exercise intolerance, gait abnormalities, and limb deformity. Serum creatine kinase activity was variably high. One dog had no detectable dystrophin in the muscle; another was mosaic, with some fibers normal and others partly dystrophin-deficient. A 3rd dog had normal dystrophin but no detectable laminin alpha2. Two dogs could not be classified. This study demonstrates the occurrence of dystrophin- and laminin alpha2-associated muscular dystrophy and the difficulty in clinical diagnosis of these disorders in female dogs.     

Occlusion of the Middle Cerebral Artery: a New Method of Focal Cerebral Ischemia in Rats

The study in Wistar rats attempted to improve the occlusion technique of the middle cerebral artery (MCA) as a precise method for initiating stroke. In a first part it was necessary to study the exact anatomy of blood vessels of the brain in seven rats of 170-410 g body weight by corrosion cast. The lengths and diameters of defined locations of the blood vessels were measured. The temporary as well as the permanent methods were refined or replaced. The first one was completed in main training the physiological blood flow after temporary occlusion, while the permanent occlusion was performed by positioning a silicone cap in the MCA. A filament guide was introduced from the common carotid artery (CCA) via internal carotid artery (ICA) to guide the silicon cap at the branch of the MCA. Histological sections of the brain of rats showed 24 h after the permanent occlusion a reproducible infarct in the brain. This area corresponded very well with the supply of the MCA. The new occlusion method with a silicon cap was compared with the occlusion methods of CCA route and external carotid artery (ECA) route. The total infarct volume was significantly larger in the CCA route and ECA route groups than in the silicon cap group (means: CCA route 261 mm³; ECA route 191 mm³ vs. 128 mm³ silicon cap group; P  < 0,05). It could be demonstrated that the new silicon cap occlusion technique imitates the pathological situation of a cerebral infarct in man. Moreover it is less invasive for the animals and more precise and reproducible regarding the infarcted area in comparison to the other occlusion methods. Based on anatomical measurements of the blood vessels the described silicon cap method can be recommended for rats of a body weight between 340–370 g.