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.     

Effects of additive iron on growth,tissue distribution,haematology and immunology of gilthead sea bream, <Emphasis Type="Italic">Sparus aurata</Emphasis>

The comparative effects of iron-supplemented levels on growth, tissue distribution, haematology and immunology of gilthead sea bream, Sparus aurata (2 g) were investigated, using four organic (50, 100, 200, 300 mg ORG/kg diet) and one inorganic iron source (200 INOR mg/kg diet). Fish were treated for 12 weeks with the experimental diets and maintained at a water temperature of 19–22°C. Growth (final weight and specific growth rate), tissue distribution (spleen, liver and muscle), haematological parameters (red blood cells, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration) and non-specific immune indexes (respiratory burst activity and antibacterial activity of serum) were analysed. No significant differences were found in growth and iron tissue distribution among the tested groups. Red blood cell counting was statistically higher in fish given 50 ORG, 100 ORG, 200 ORG and 200 INOR feeds. However, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration were not significantly affected by increasing dietary iron. Fish receiving the 100 ORG diet had the best performance with respect to the respiratory burst activity and significantly higher values for antibacterial activity of serum were obtained in fish fed with the 300 ORG diet. The present findings provided no clear evidence of the optimum iron concentration. However, there was adequate indication that iron supplementation enhanced the performance of gilthead sea bream, mainly from a haematological and immunological point of view.     

Ultraviolet light and mating behaviour in domestic broiler breeders

1. The perception of UVA light (320 < lambda < 400 nm) by domestic fowl may be an adaptation to naturally lit habitats and may still be functional in farmed varieties, although not utilised owing to the absence of these wavelengths in commercial house lighting. One function may be the mediation of sexually related signalling or communication. 2. In experiment 1, two groups of 41 adult broiler breeders (four cockerels, 37 hens) were kept under conventional fluorescent light, with or without fluorescent UVA supplementation amounting to 16.9% of the total spectral power output of the luminaires. Each light environment was approximately iso-illuminant as perceived by the birds. The two groups were exposed to the light environments alternately for five 2-day periods in a cross-over design. Mating behaviour, production measures and time budgets were recorded on the second day of each period. 3. A UVA-enriched environment increased the number of attempted matings (1.27 vs 0.99 matings/cockerel.h) and locomotion (5.3 vs 3.7 min/bird.hour). 4. In a second experiment, 10 hens were allowed to choose between four cockerels lit under different power levels of UVA (1.6%, 14.6%, 43.5%, 57.5% of the total spectral power output of the luminaires) in a four-armed maze. Again, each light environment was approximately iso-illuminant as perceived by the birds. Each hen was allowed to make one choice per day over four days, with the position of the cockerels and the UVA levels interchanged each day. This schedule was repeated with the same hens for two other groups of four cockerels. 5. At a distance of no less than 60 cm from the cockerel, the hens spent most time inspecting whichever cockerel was lit by 1.6% or 14.6% UVA (1.33 vs 1.37 vs 1.22 vs 1.16 log seconds/hen.choice, respectively for increasing UVA level). Similarly, when allowed to approach closer to the cockerels, the hens spent most time in the arm which contained a cockerel lit by 14.6% UVA light, (1.62 vs 1.88 vs 1.69 vs 1.51 log s/hen.choice, respectively for increasing UVA level). 6. UVA is clearly implicated in the transmission of sexual signals or communication which may have implications for the welfare and production of broiler breeders.     

Differential responses of Equus caballus and Equus asinus to infection with two pathogenic strains of equine infectious anemia virus

Most in vivo studies with equine infectious anemia virus (EIAV) have been performed in horses and ponies (Equus caballus) with little published information available detailing the clinical responses of donkeys (Equus asinus) to infection with this virus. Consequently, donkeys were inoculated with two strains of EIAV (EIAV(PV) and EIAV(WY)) which have been documented to produce disease in E. caballus. Four ponies, 561, 562, 564 and 567 and two donkeys, 3 and 5 were infected with EIAV(PV) and one horse (94-10) and one donkey (4) were infected with EIAV(WY). Although the horse and ponies all experienced clinical signs of disease, which in some cases were severe, the donkeys remained asymptomatic throughout a 365-day observation period, except for mild transient reductions in platelet counts. The results from serological assays, virus isolation from plasma and detection of plasma-associated viral RNA by RT-PCR, indicated that initial replication of EIAV(PV) and EIAV(WY) was lower in donkeys than in horses and ponies. This conclusion was confirmed using competitive RT-PCR, in which viral RNA levels in the plasma of EIAV(PV)-infected ponies was up to 100,000-fold higher than in infected donkeys during the first 20 days post-infection (dpi). Similar results were obtained in the EIAV(WY)-infected animals, in which viral RNA burdens in the donkey at 20 dpi were 1000-fold less than in the horse. However, infection of donkey and horse monocyte-derived macrophage cultures with EIAV(PV) demonstrated that these cells in vitro were equally susceptible to virus-induced cytopathic effects and yielded similar levels of progeny virus. This result suggests that factors other than host cell permissiveness mediate the clinical differences observed between horses and donkeys infected with EIAV(PV) or EIAV(WY).     

MAGNETIC RESONANCE IMAGING APPEARANCE OF SUSPECTED ISCHEMIC MYELOPATHY IN DOGS

Ischemia and infarction of the spinal cord is a known cause of acute spinal injury in dogs. Currently, the diagnosis of spinal cord infarction in small animals is based on history, clinical signs, and the exclusion of other differentials with radiography and myelography. It is a diagnosis only confirmed through necropsy examination of the spinal cord. The aim of this paper is to describe the Magnetic resonance imaging (MRI) findings of the spinal cord of dogs with suspected spinal cord infarcts to utilize this technology for antemortem support of this diagnosis. This retrospective study evaluated the spinal MR examinations of 11 dogs with acute onset of asymmetric nonpainful myelopathies. All patients except one (imaged at 2 months) were imaged within 1 week of clinical signs and managed conservatively with minimal medical and no surgical intervention. They were followed clinically for a minimum of 4 months after discharge. MR findings in all dogs were characterized by focal, intramedullary, hyperintense lesions on T2-weighted images with variable contrast enhancement similar to what is reported in humans. Though it could not be used to diagnose spinal cord infarction definitively, MRI was useful in excluding extramedullary spinal lesions and supporting intramedullary infarction as a cause of the acute neurologic signs. Together with the history and clinical examination findings, MRI is supportive of a diagnosis of spinal cord infarction.     

Evaluation of PCR,IEF and ELISA techniques for the detection and identification of potato cyst nematodes from field soil samples in England and Wales

Effective management of potato cyst nematodes (PCNs) requires simple, rapid and accurate identification and quantification of field populations. Soil samples from a survey of 484 fields in potato rotations in England and Wales were used to compare the identification and quantification of PCNs using IEF, PCR, ELISA and bait plant tests. The cyst counts and bait plant test revealed that 64.3% of field samples contained PCNs. Bait plant tests increased the detection rate of PCNs in field samples by 4–6.4%. This means that some infestations are cryptic and would not normally be detected by standard counts. IEF, PCR and ELISA methods distinguished between Globodera rostochiensis and G pallida and were able to register mixed populations; however they were not in full agreement. All methods suggested that G pallida is the dominant species in the field samples tested. The PCR results indicated that 66% of field samples contained pure G pallida, 8% contained pure G rostochiensis and 26% contained mixtures of the two species. Estimates of the relative process times taken per sample in the PCR, IEF and ELISA techniques are given. © 2001 Society of Chemical Industry     

Resistance to foliage-feeding insects in conifers: implications for pest management

The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence.