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21.
The diatom Phaedactylum tricornutum Bohlin forms blooms in the south arm of the Great Salt Lake, Utah, during cool months. This represents the first report of this taxon from Utah and the first from nonmarine waters in the United States. 相似文献
22.
The soil algae in the Tintic Mountains, Juab County, Utah, was studied over a one-year period in 1982 and 1983. Fluorescence microscopy was used to measure algal density in samples directly from the field. A total of 30 algal taxa was observed, blue-green algae being most abundant both in terms of density and number of species. Algal density showed peaks in late fall and late spring. Minima were present in September 1982 and July 1983. Several weak correlations between algal density and climatic data existed. In general algae correlated positively with precipitation and negatively with temperature. A combination of low precipitation and hot temperatures was likely responsible for the low density observed in July. The Chrysophyta followed slightly different trends than the other algal groups, having minima in early October 1982 and late August 1983. Field observations indicated that the degree of algal crusting varied noticeably over a period of one year, with highest abundance of hummocking in spring. Heavy summer thunderstorms destroyed algal crusting during July and August of 1983, though absolute density of algae increased during this time in response to the extra moisture. 相似文献
23.
The increase in the size of goldfish (Carassius auratus) liver following hypophysectomy is due to a net accumulation of glycogen and the addition of water to maintain a constant proportion with no change in the absolute amount of either protein or lipid. 相似文献
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25.
G. B. Bourne J. R. Redmond K. Johansen 《Cellular and molecular life sciences : CMLS》1977,33(11):1453-1453
Summary Blood pressure recordings from the vena cava, afferent branchial and efferent branchial veins inNautilus showed that a significant increase in pressure of the gill circulation was achieved by the rhythmic contractions of the renal appendages and pericardial glands.We thank the Wilson Vailoces family and the other kind people of Bindoy, Negros Oriental, The Philippines for their unlimited generosity. This research was supported by NSF grant OCE 74-02888 to the Scripps Institution of Oceanography and BMS 75-01149 to Iowa State University, J. R. Redmond, principal investigator. 相似文献
26.
The relationship between soil surface cryptogamic crusts and seed banks was investigated in the shrubsteppe in the Lower Columbia Basin. Seventy-four percent of the seeds in a disturbed bunchgrass community were found in crevices bordering cryptogamic crust polygons. In a sagebrush/bunchgrass community, 89% of the seeds were found in crevices. In a disturbed bunchgrass community, Bromus tectorum seeds were found in both the seed bank and aboveground vegetation communities. Bromus tectorum seeds were located in the seed bank of a sagebrush/bunchgrass community, although it had a minor presence in the aboveground community. Seeds of Artemisia tridentata Nutt. were not found in either the bunchgrass or sagebrush/bunchgrass communities. The high number of seeds found in crevices bordering the cryptogamic crust suggests that crevices play a role in determining the small-scale distributional pattern of shrub-steppe plants at the Fitzner-Eberhardt Arid Lands Ecology Reserve. 相似文献
27.
Star B Nederbragt AJ Jentoft S Grimholt U Malmstrøm M Gregers TF Rounge TB Paulsen J Solbakken MH Sharma A Wetten OF Lanzén A Winer R Knight J Vogel JH Aken B Andersen O Lagesen K Tooming-Klunderud A Edvardsen RB Tina KG Espelund M Nepal C Previti C Karlsen BO Moum T Skage M Berg PR Gjøen T Kuhl H Thorsen J Malde K Reinhardt R Du L Johansen SD Searle S Lien S Nilsen F Jonassen I Omholt SW Stenseth NC Jakobsen KS 《Nature》2011,477(7363):207-210
Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC)?II is a conserved feature of the adaptive immune system of jawed vertebrates, but we show that Atlantic cod has lost the genes for MHC?II, CD4 and invariant chain (Ii) that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions. We find a highly expanded number of MHC?I genes and a unique composition of its Toll-like receptor (TLR) families. This indicates how the Atlantic cod immune system has evolved compensatory mechanisms in both adaptive and innate immunity in the absence of MHC?II. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates. 相似文献
28.
Jack D. Brotherson William E. Evenson Samuel R. Rushforth John Fairchild Jeffrey R. Johansen 《西北部美国博物学家》2011,45(1)
Vegetation patterns in Navajo National Monument, Arizona, were studied over a five-year period from 1977 to 1981. Twelve distinct plant community types occur within the boundaries of the park. These communities are characterized and the dominant plant species of each are recorded. The relationships of parent material, soils, and moisture to plant communities are also discussed. It appears that discrete communities occupy soils of different characteristics, particularly with respect to amount of weathering of parent material. 相似文献
29.
Morphological variability and cell wall composition of Phaeodactylum tricornutum (Bacillariophyceae)
Jeffrey R. Johansen 《西北部美国博物学家》2011,51(4)
Five isolates of Phaeodactylum tricornutum Bohlin were examined in light and transmission electron microscopes. Although isolated from widely separated sites including both coastal marine and inland saline habitats, the morphology of the siliceous frustules of all isolates was very constant. The fusiform and triradiate forms, which have been reported as being non-siliceous in the past, were found to have an amorphous particulate nature in TEM. These forms were examined using EDAX SEM elemental analysis and were found to contain silica in their cell walls. 相似文献
30.
Microbial spatial heterogeneity and bacterial composition of homogeneous surface soils showing evident microbiotic crust development located under Utah juniper canopies in Colorado National Monument were studied. Four distinct homogeneous sampling sites positioned along a 12-m transect were compared on the basis of bacterial density and taxa composition. Bacterial densities showed a range differing by several orders of magnitude. In comparisons of adjacent soil samples or samples taken from two different sampling sites within close proximity, adjacent samples showed no more similarity to each other on the basis of bacterial density or taxa composition than did more widely separated samples. The bacterial composition of these soils included members of the genera Bacillus , Micrococcus , and Arthrobacter . Actinomycetes were also prevalent. 相似文献