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1.
An A in equilibrium with G transition in exon III is known to differentiate alleles A and B of the cattle beta-lactoglobulin (BLG) gene. A BLG exon III fragment containing the transition site was amplified by the polymerase chain reaction. Temperature gradient gel electrophoresis (TGGE) was then used to detect this transition and hence to genotype cattle: the AT base-pair in allele A was readily distinguished from the GC base-pair of allele B. TGGE can be used to detect any single base-pair substitution, and thus is a powerful method of detecting genetic variability.  相似文献   
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The behaviour of the Sociable Weaver Philetairus socius was studied briefly in South Africa in 1969, and more extensively in aviaries in southern California for over three years (1972-75). The species was bred successfully in captivity, apparently for the first time. Building of the compound nest in nature is reviewed in the light of preceding accounts, both by ourselves and by others. The optimal preference for nest materials was experimentally determined. Male and female appear identical and there seems to have been no previous detailed account of the behaviour of Sociable Weavers based on distinctively colour-ringed individuals of known sex. Among the sex differences in behaviour are the amount and nature of building, dominance, malespecific song, and sex differences in relative share of incubation and in the care of nestlings and fledglings. In addition, we describe in detail for the first time certain rarely observed behavioural acts including precopulatory courtship and copulation. Allopreening and water bathing are very rare in this species, and the birds do not take dust baths.  相似文献   
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We evaluated some products and protocols designed for reliable RNA extraction from minute tissue samples and safe tissue storage at room temperature without RNA degradation. Success of RNA retrieval was compared for varying amounts of tissue (3, 5, 10 hair follicles), stored at different temperatures (room temperature, ?20 °C) for variable durations (1, 3, 6, 12 weeks). We also compared two RNA isolation kits specialized for small samples. RNA was successfully retrieved from as few as 3 hairs stored at room temperature for up to 6 weeks, suggesting the potential for gene expression analyses on minimally invasive samples from natural populations.  相似文献   
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Summary
  • 1 To investigate the carrying capacity and factors affecting growth of rainbow trout in Lake Rotoiti, we employed a bioenergetics model to assess the influence of stocking rates, timing of releases and prey abundance on growth and prey consumption. We hypothesised that stocking rates and prey abundance would affect growth and prey consumption by influencing per‐capita prey availability, and that the environmental conditions encountered by fish at the time of stocking would affect growth and consumption.
  • 2 Prey consumption of stocked rainbow trout was calculated with the Wisconsin bioenergetics model. We calculated growth trajectories of released trout based on data from stocked trout that were released in spring and autumn from 1993 to 2009 and then re‐captured by anglers. Diet, prey energy density, body mass lost during spawning and lake temperature were measured locally.
  • 3 Stocking timing had no effect on return rates to anglers or length or weight of caught fish. Although trout released in autumn were smaller than those released in spring, autumn‐released trout grew at a faster rate and had similar lengths and weights to spring cohorts after 2 years of growth in the lake. Modelled consumption parameters were negatively correlated with trout population size, suggesting that stocking rates (347–809 fish ha?1 year?1) caused density‐dependent effects on growth. Although common smelt (Retropinna retropinna) accounted for 85% of total prey consumption, no significant relationship was found between prey consumption by individual trout and adult smelt abundance, possibly because trout are targeting smaller smelt that our abundance estimate did not account for.
  • 4 Releasing trout in autumn appears to be advantageous for growth, possibly because (i) temperature is more suitable for growth in autumn–winter than in spring–summer and (ii) prey for small trout is abundant in autumn. Mild winter conditions appear to enhance overwinter survival and growth of rainbow trout in warm‐temperate lakes compared to higher latitudes. This implies that moderately productive warm‐temperate lake ecosystems are highly suitable for trout growth in winter, but less so in summer, when lake stratification and high nutrient levels may create conditions suitable for algal blooms and hypolimnetic deoxygenation. High growth rates of trout in warm‐temperate lakes can therefore be supported by timing releases to coincide with favourable winter conditions.
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FOSSIL DIAGENESIS IN THE BURGESS SHALE   总被引:1,自引:0,他引:1  
Abstract:  Current models for the exceptional preservation of Burgess Shale fossils have focused on either the HF-extractable carbonaceous compressions or the mineral films identified by elemental mapping. BSEM, EDX and microprobe analysis of two-dimensionally preserved Marpolia , Wiwaxia and Burgessia identifies the presence of both carbonaceous and aluminosilicate films for most features, irrespective of original lability. In the light of the deep burial and greenschist facies metamorphism documented for the Burgess Shale, the aluminosilicate films are identified as products of late-stage volatilization and coincident mineralization of pre-existing compression fossils, whereas the three-dimensionally preserved gut-caecal system of Burgessia is interpreted as an aluminosilicate replacement of a pre-existing carbonate phase. The case for late diagenetic emplacement of aluminosilicate minerals is supported by the extensive aluminosilicification of trilobite shell and (originally) calcareous veinlets in the Burgess Shale, as well as documentation of other secondarily aluminosilicified compression fossils. By distinguishing late diagenetic alteration from the early diagenetic processes responsible for exceptional preservation, it is possible to reconcile the range of preservational modes currently expressed in the Burgess Shale.  相似文献   
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