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1.
Studies on the enzymic synthesis of glutamine 总被引:17,自引:9,他引:8
ELLIOTT WH 《The Biochemical journal》1951,49(1):106-112
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SUMMARY. Larvae of Dixa , especially D. puberula Loew., were a significant component of the invertebrate drift in the Walla Brook in southwest England, the Wilfin Beck and the River Duddon in the English Lake District, and the River Estibère in the French Pyrenees. The drifting of the larvae increased markedly at night and showed a definite diel periodicity with maximum numbers usually in the early hours of the night. Seasonal peaks in the density of larvae in the drift frequently occurred in months when adults and especially pupae were present. Most drifting larvae were in the fourth and final instar, and their drift rate usually increased when they were searching for suitable pupation sites. 相似文献
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A comparative study of four dredges used for sampling benthic macroinvertebrates in rivers 总被引:1,自引:0,他引:1
SUMMARY. After considering the large number of dredges described in the literature, four light-weight dredges were chosen for manual operation from a small boat or the bank: Irish triangular dredge, small Fast dredge, medium-sized and large Naturalist's dredges. The dredges were tested in a series of trials at three sites in two rivers. A stratified random sample (number of sampling units, n = 5) was taken at each site and the modal particle sizes at sites 1–3 were 1–2 mm (fine gravel), 64–128 mm (larger stones) and 128–256 mm, respectively. The dredges usually took a similar range of stone sizes at each site but the design of the Fast dredge excluded larger stones (>16 mm). The Irish dredge sometimes failed to operate correctly. Variations in the volume of substrata taken with each dredge were large, both between sampling units in the same sample and between samples. The latter differences were partially due to the increase in the modal size of the stones, especially between sites 1 and 2, the different sampling areas of the dredges and the depth of penetration into the substratum. Penetration depth was probably greatest for the two Naturalist's dredges, smaller for the Fast dredge and smallest for the Irish dredge. In field trials, the relative abundances of major taxa were similar for most dredges at each site; major exceptions were the Fast dredge at site 2 and the Irish dredge at site 3. There was a high variability between sampling units in the same sample and therefore a lack of precision in the estimates of the mean number of invertebrates per sample. Therefore, the dredges cannot be used as quantitative samplers for the estimation of population density. Their adequacy as qualitative samplers for the estimation of total number of taxa per sample varied considerably and maximum estimates of their efficiencies for a small sample (n= 5) were <40% for the Irish and Fast dredges, >57% for the medium-sized Naturalist's dredge and >76% for the large Naturalist's dredge. There was a clear relationship between the number of taxa and the number of invertebrates taken at each site and this relationship was well described by a power law with an exponent within the range 0.18–0.53. The number of sampling units in the sample had no significant effect on the power-law equations for each site. The power-law equation was very similar for most of the dredges at each site, the only major exception being the Fast dredge at site 1. The implications of this relationship are discussed. 相似文献
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M. J. KAISER M. GALANIDI D. A. SHOWLER A. J. ELLIOTT R. W. G. CALDOW E. I. S. REES R. A. STILLMAN & W. J. SUTHERLAND 《Ibis》2006,148(S1):110-128
Offshore wind farms are proposed around the coast of the UK and elsewhere in Europe. These sites tend to be located in shallow coastal waters that often coincide with areas used by over-wintering Common Scoter Melanitta nigra . A large-scale study was undertaken to ascertain the relationship of the spatial distribution of Common Scoter in Liverpool Bay with prey abundance and environmental and anthropogenic variables that may affect foraging efficiency. The highest numbers of Common Scoter coincided with sites that had a high abundance and biomass of bivalve prey species. There was strong evidence that the maximum observed biomass of bivalves occurred at a mean depth of c. 14 m off the Lancashire coast and at c. 8 m off the north Wales coast. This coincided well with the distribution of Common Scoter at Shell Flat, but less well with the distribution of birds off North Wales. Common Scoters were observed in lowest numbers or were absent from areas in which anthropogenic disturbance (shipping activity) was relatively intense, even when these areas held a high prey biomass. Commercial fishing activities did not appear to contribute to this disturbance. 相似文献
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Classification and nomenclature of all human homeobox genes 总被引:2,自引:0,他引:2