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1.
Sediment samples collected during the expedition “Arctic Ocean `96” with the Swedish ice-breaker ODEN were investigated to
estimate for the first time heterotrophic activity and total microbial biomass (size range from bacteria to small metazoans)
from the perennially ice-covered central Arctic Ocean. Benthic activities and biomass were evaluated analysing a series of
biogenic sediment compounds (i.e. bacterial exoenzymes, total adenylates, DNA, phospholipids, particulate proteins). In contrast
to the very time-consuming sorting, enumeration and weight determination, analyses of biochemical sediment parameters may
represent a useful method for obtaining rapid information on the ecological situation in a given benthic system. Bacterial
cell numbers and biomass were estimated for comparison with biochemically determined biomass data, to evaluate the contribution
of the bacterial biomass to the total microbial biomass. It appeared that bacterial biomass made up only 8–31% (average of
all stations = 20%) of the total microbial biomass, suggesting a large fraction of other small infaunal organisms within the
sediment samples (most probably fungi, yeasts, protozoans such as flagellates, ciliates or amoebae, as well as a fraction
of small metazoans). Activity and biomass values determined within this study were generally extremely low, and often even
slightly lower than those given for other deep oceanic regions, thus characterizing the seafloor of the central Arctic Ocean
as a “benthic desert”. Nevertheless, some clear trends in the data could be found, e.g. generally sharply decreasing values
within the sediment column, a vague tendency for declining values with increasing water depth of sampling stations, and also
differences between various Arctic deep-sea regions.
Received: 16 May 1997 / Accepted: 28 August 1997 相似文献
2.
Lemmings are involved in several important functions in the Arctic ecosystem. The Arctic fox (Vulpes lagopus) can be divided into two discrete ecotypes: “lemming foxes” and “coastal foxes”. Crashes in lemming abundance can result
in pulses of “lemming fox” movement across the Arctic sea ice and immigration into coastal habitats in search for food. These
pulses can influence the genetic structure of the receiving population. We have tested the impact of immigration on the genetic
structure of the “coastal fox” population in Svalbard by recording microsatellite variation in seven loci for 162 Arctic foxes
sampled during the summer and winter over a 5-year period. Genetic heterogeneity and temporal genetic shifts, as inferred
by STRUCTURE simulations and deviations from Hardy–Weinberg proportions, respectively, were recorded. Maximum likelihood estimates
of movement as well as STRUCTURE simulations suggested that both immigration and genetic mixture are higher in Svalbard than
in the neighbouring “lemming fox” populations. The STRUCTURE simulations and AMOVA revealed there are differences in genetic
composition of the population between summer and winter seasons, indicating that immigrants are not present in the reproductive
portion of the Svalbard population. Based on these results, we conclude that Arctic fox population structure varies with time
and is influenced by immigration from neighbouring populations. The lemming cycle is likely an important factor shaping Arctic
fox movement across sea ice and the subsequent population genetic structure, but is also likely to influence local adaptation
to the coastal habitat and the prevalence of diseases. 相似文献
3.
G. F. Camoin M. Colonna L. F. Montaggioni J. Casanova G. Faure B. A. Thomassin 《Coral reefs (Online)》1997,16(4):247-259
The sedimentological and chronological study of Holocene reef sequences recovered in drill cores through modern reefs of
Mauritius, Réunion Island and Mayotte allows the reconstruction of sea level changes and reef growth patterns during the Holocene.
The branching-coral facies systematically predominates over coral head facies throughout the Holocene reef sequences, and
Acropora is the main frame builder among the branching forms. The reconstructed sea level curves, based both on identification of
coral assemblages and on radiometric U/Th ages, are characterized by a rapid rise between 10 and 7.5 ky BP, followed by a
clear inflection between 7.5 and 7 ky BP. The stabilization of sea level at its present level occurred between 2000 and 3000
years ago, probably without a higher sea level stand. Rates of vertical reef accretion range between 0.9 and 7 mm. y-1. In Mauritius, and also probably in Réunion Island, the reef first tracked, then caught-up to sea level to reach an equilibrium
position (“catch-up” growth), while the barrier reef margin off Mayotte has been able to keep pace with rising sea level (“keep-up”
growth).
Accepted: 1 March 1997 相似文献
4.
Jiirgen -Friedrich Hake Ulrich Landwehr Andrea Schreiber 《The International Journal of Life Cycle Assessment》1998,3(4):182-183
In January 1997, the German Research Association (DFG) established a special research programme for an integrated analysis
of metallic resource flows. The programme is a joint interdisciplinary effort of the Technical University of Aachen and of
the Research Centre Jiilich. Apart from many other activities, a series of conferences is organised within this programme.
In October 1997, a first conference was held on “The Economics of Resource Flows: The Case of Aluminium”. In December 1997,
a second conference took place on “Life Cycle Assessment of Aluminium: Methods and Applications”. In April 1998 the third
workshop was held entitled “Methodological Aspects of a Resource-oriented Analysis of Material Flows”. The next conference
is planned for December 1998 on “Environmental related Aspects of Aluminium Production”. Finally, a conference on “Methods
for an Integrated Evaluation of Material Flows” is under consideration for 1999. 相似文献
5.
Masayoshi Maehata 《Ichthyological Research》2002,49(2):202-205
Mating behavior of the Far Eastern catfish, Silurus
asotus (Siluriformes: Siluridae), was observed in a ricefield system facing the shore of Lake Biwa in mid-May to early June in 1990–1997.
A set behavioral sequence similar to those of two other silurid fishes, S. biwaensis and S. lithophilus, both endemic to the Lake Biwa system, was observed: “chasing,”“clinging,”“enfolding” while “squeezing” by the male, and
“circling” by the spawning pair. This form of mating behavior is quite different from that of S. asotus reported from the Ooi River system in Kyoto Prefecture, which mainly spawns in running water in ditches.
Received: April 10, 2001 / Revised: November 5, 2001 / Accetped: November 20, 2001 相似文献
6.
Zooplankton composition and distribution were investigated on the Laptev Sea shelf, over the continental slope and in the
adjacent deep Nansen Basin during the joint German-Russian expedition “Arctic 93” with RV Polarstern and Ivan Kireyev in August/September 1993. In the shelf area biomass decreased from west to east with the lowest values in the area influenced
by the Lena river runoff. A gradual increase of biomass from the shallow to the deep area correlated with water depth. Total
biomass ranged between 0.1 and 1.5 g m−2 on the shelf and 4.7 and 7.9 g m−2 in the adjacent Nansen Basin. On the shelf Calanus glacialis/finmarchicus dominated overall. The contribution of brackish-water taxa was low in the west, where high salinity and southward currents
from the Arctic Basin supported a marine neritic community, but on the southern and eastern Laptev shelf, in the areas of
freshwater influence, brackish-water taxa contributed up to 27% of the total biomass. On the slope and in deep areas a few
large Arctic copepod species, Calanus glacialis, C. hyperboreus and Metridia longa, composed the bulk of biomass and determined the pattern of its vertical distribution. The export of Calanus species from the Nansen Basin onto the Laptev shelf appears to be of great importance for the shelf communities. In turn,
the eastern outer shelf and slope area of the Laptev Sea are thought to have a pronounced effect on the deep basin, modifying
the populations entering the central Arctic.
Received: 25 March 1997 / Accepted: 18 July 1997 相似文献
7.
The effectiveness of a specific fertiliser (INIPOL EAP 22) addition on bioremediation of oil-contaminated Antarctic coastal
seawater was determined in the “Terre Adelie” area. Mesocosm studies were conducted to evaluate the effects of “Arabian light”
crude oil contamination on coastal bacterioplanktonic communities. After oil addition, regular surveys of the bacterial changes
of the oil-contaminated seawater were performed during 5-week periods during the austral summer of 1992/1993 and 1993/1994.
All results (total, saprophytic and hydrocarbon-utilising bacterial abundance) clearly revealed a significant response of
Antarctic bacterial communities to hydrocarbon contamination. A 1 order of magnitude increase of bacterial microflora occurred
in seawater after crude oil contamination. A concomitant enrichment in oil-degrading bacteria was generally observed, from
less than 0.001% of the community in uncontaminated samples to up to 50% after 3 weeks of contamination. Addition of fertiliser
(INIPOL EAP 22) induced clear enhancement of both saprophytic and hydrocarbon-utilising microflora. Chemical analysis of the
residual hydrocarbon fractions confirmed that fertiliser application increased the rate of oil biodegradation.
Received: 27 March 1997 / Accepted: 20 October 1997 相似文献
8.
Atmospheric culturable bacteria associated with meteorological conditions at a summer-time site in the mid-Willamette Valley,Oregon 总被引:1,自引:0,他引:1
Bruce Lighthart Brenda T. Shaffer A. Shelby Frisch Dorothea Paterno 《Aerobiologia》2009,25(4):285-295
A set of simultaneously collected quantitative measurements of 12 meteorological and 6 culturable atmospheric bacterial (CAB)
variables was made over a grass seed field during several early, mid, and late summer days. The observation site was located
between the Cascade and Coastal Mountain Ranges near Corvallis in the Willamette Valley, Oregon. Principal component analysis
identified those meteorological variables that had the highest loadings in six eigenvectors that account for 95.9% of variation
in the data factors, i.e., temperature @ 6.3 m above ground level (AGL), wind velocity @ 10.0 m AGL, wind velocity difference
@ 1.7–10.0 m, barometric pressure, wind direction standard deviation, and wind direction. When these variables were used in
a cluster analysis, they formed three statistically distinct meteorological variable clusters with means at ca. “midnight”,
ca. “midday”, and ca. “evening.” The highest mean density of CAB (i.e., 153.4 ± 162.5 CFU/m3) was associated with the “midday” meteorological Cluster-1 that had warm, dry “gentle breezes” from the southeast, in the
relatively bacteria loaded Willamette Valley air. The lowest mean density of CAB (i.e., 35.5 ± 24.1 CFU/m3) was associated with meteorological Cluster-3 in the late afternoon and “evening” occurring during the hottest and driest
part of the day with “fresh breezes” coming from the north northwest in air off the Pacific Ocean. Finally, the last cluster,
Cluster-2 occurred about midnight and had an intermediate density of CAB (74.2 ± 76.2 CFU/m3) in “light air” coming from the northwest, perhaps off the Pacific Ocean. The CAB associated with each of the three meteorological
clusters was only partially statistically distinct. Partially because the CAB in both the Pacific Ocean derived air masses
of the “evening” Cluster-3 and “midnight” Cluster-2 were not statically separable, though both were statistically separable
from the midday, Willamette Valley derived Cluster-1. Further indicating their common source, both Pacific Ocean derived air
masses had very similar percentages of pigmented bacteria, which were dissimilar to the pigmented bacterial population density
in the Willamette Valley air masses. In short, it is speculated that “midnight” atmosphere may simply contain the settling
concentrated residual bacterial particles in the abated fresh Pacific Ocean breezes after sundown. It is clearly shown that
with the methods employed, it is possible to associate the uniqueness of the quantity, and to a lesser extent the quality,
of the CAB population with the atmospheric conditions reported herein. From this project comes speculation that the strategies
relating the quasi-conservative bacterial populations associated with distinct but nonconservative air mass properties can
help to better understand more of the bacterial dynamics found in such situations. And to a further extent, molecular biological
methods could be applied to identify bacterial taxa in specific air masses. 相似文献
9.
In recent years, marine scientists have become increasingly alarmed over the decline of live coral cover throughout the Caribbean
and tropical western Atlantic region. The Holocene and Pleistocene fossil record of coral reefs from this region potentially
provides a wealth of long-term ecologic information with which to assess the historical record of changes in shallow water
coral reef communities. Before fossil data can be applied to the modern reef system, critical problems involving fossil preservation
must be addressed. Moreover, it must be demonstrated that the classic reef coral zonation patterns described in the early
days of coral reef ecology, and upon which “healthy” versus “unhealthy” reefs are determined, are themselves representative
of reefs that existed prior to any human influence. To address these issues, we have conducted systematic censuses of life
and death assemblages on modern “healthy” patch reefs in the Florida reef tract that conform to the classic Caribbean model
of reef coral zonation, and a patch reef in the Bahamas that is currently undergoing a transition in coral dominance that
is part of a greater Caribbean-wide phenomenon. Results were compared to censuses of ancient reef assemblages preserved in
Pleistocene limestones in close proximity to each modern reef. We have determined that the Pleistocene fossil record of coral
reefs may be used to calibrate an ecological baseline with which to compare modern reef assemblages, and suggest that the
current and rapid decline of Acropora cervicornis observed on a Bahamian patch reef may be a unique event that contrasts with the long-term persistence of this taxon during
Pleistocene and Holocene time.
Accepted: 19 May 1998 相似文献
10.
Keith Johnson 《Journal of biological physics》2012,38(1):85-95
Water nanoclusters are shown from first-principles calculations to possess unique terahertz-frequency vibrational modes in
the 1–6 THz range, corresponding to O–O–O “bending,” “squashing,” and “twisting” “surface” distortions of the clusters. The
cluster molecular-orbital LUMOs are huge Rydberg-like “S,” “P,” “D,” and “F” orbitals that accept an extra electron via optical
excitation, ionization, or electron donation from interacting biomolecules. Dynamic Jahn–Teller coupling of these “hydrated-electron”
orbitals to the THz vibrations promotes such water clusters as vibronically active “structured water” essential to biomolecular
function such as protein folding. In biological microtubules, confined water-cluster THz vibrations may induce their “quantum
coherence” communicated by Jahn–Teller phonons via coupling of the THz electromagnetic field to the water clusters’ large
electric dipole moments. 相似文献
11.
Tsutom Hiura 《Trees - Structure and Function》1998,12(5):274-280
Relationships between leaf or shoot size, number, and arrangement in response to light were investigated to test the hypothesis
that these characteristics are linked. In order to test this hypothesis, the divergence in allometry and shoot dynamics in
saplings of Japanese beech (Fagus crenata) obtained from four populations and having different leaf sizes were examined in a nursery under both full sun and shade
conditions. Trees with different leaf sizes also showed large differences in canopy structure, particularly when shade-grown
saplings were compared. The final leaf mass distributions of the large-leaf populations were conical or “bottom - heavy”,
while those of the small-leaf populations were planar or “top - heavy”. The slope of the allometric relations between leaf
mass and shoot and branch mass in small-leaved populations were steeper than those in large-leaf populations. The four populations
were classified into two growth types: populations producing a few large leaf and shoot modules corresponded to “stem growth
type”, and those producing many small leaf and shoot modules corresponded to “leaf growth type”. These kinds of intra-specific
variation in architecture and growth of F. crenata trees may influence the structure and dynamics of forests in accordance with differences in competitive ability or sensitivity
to disturbances such as windstorm.
Received: 18 March 1997 / Accepted: 21 October 1997 相似文献
12.
F. J. Gallego C. Benito 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):393-399
Aluminium (Al) tolerance in roots of two cultivars (“Ailés” and “JNK”) and two inbred lines (“Riodeva” and “Pool”) of rye
was studied using intact roots immersed in a nutrient solution at a controlled pH and temperature. Both the cultivars and
the inbred lines analysed showed high Al tolerance, this character being under multigenic control. The inbred line “Riodeva”
was sensitive (non-telerant) at a concentration of 150 μM, whereas the “Ailes” cultivar showed the highest level of Al tolerance
at this concentration. The segregation of aluminium-tolerance genes and several isozyme loci in different F1s, F2s and backcrosses between plants of “Ailés” and “Riodeva” were also studied. The segregation ratios obtained for aluminium
tolerance in the F2s analysed were 3 : 1 and 15 : 1 (tolerant : non-tolerant) while in backcrosses they were 1 : 1 and 3 : 1. These results indicated
that Al tolerance is controlled by, at least, two major dominant and independent loci in rye (Alt1 and Alt3). Linkage analyses carried out between Al-tolerance genes and several isozyme loci revealed that the Alt1 locus was linked to the aconitase-1 (Aco1), nicotinamide adenine dinucleotide dehydrogenase-2 (Ndh2), esterase-6 (Est6) and esterase-8 (Est8) loci, located on chromosome arm 6RL. The order obtained was Alt1-Aco1-Ndh2-Est6-Est8. The Alt3 locus was not linked to the Lap1, Aco1 and Ndh2 loci, located on chromosome arms, 6RS, 6RL and 6RL respectively. Therefore, the Alt3 locus is probably on a different chromosome.
Received: 18 March 1997 / Accepted: 21 March 1997 相似文献
13.
Mammalian prenatal neocortical development is dominated by the synchronized formation of the laminae and migration of neurons.
Postnatal development likewise contains “sensitive periods” during which functions such as ocular dominance emerge. Here we
introduce a novel neuroinformatics approach to identify and study these periods of active development. Although many aspects
of the approach can be used in other studies, some specific techniques were chosen because of a legacy dataset of human histological
data (Conel in The postnatal development of the human cerebral cortex, vol 1–8. Harvard University Press, Cambridge, 1939–1967). Our method calculates normalized change vectors from the raw histological data, and then employs k-means cluster analysis of the change vectors to explore the population dynamics of neurons from 37 neocortical areas across
eight postnatal developmental stages from birth to 72 months in 54 subjects. We show that the cortical “address” (Brodmann
area/sub-area and layer) provides the necessary resolution to segregate neuron population changes into seven correlated “k-clusters” in k-means cluster analysis. The members in each k-cluster share a single change interval where the relative share of the cortex by the members undergoes its maximum change.
The maximum change occurs in a different change interval for each k-cluster. Each k-cluster has at least one totally connected maximal “clique” which appears to correspond to cortical function. 相似文献
14.
The molecular biology of barophilic bacteria 总被引:4,自引:1,他引:3
Many microorganisms from the deep-sea display high-pressure-adapted — also described as barophilic or piezophilic — growth
characteristics. Phylogenetic studies have revealed that a large proportion of the barophilic bacteria currently in culture
collections belong to a distinct subgroup of the genus Shewanella, referred to as the “barophile branch.“ Many of the basic properties of barophiles that enable their survival at extremes
of pressure remain to be elucidated. However, several genes whose expression is regulated by pressure, or which appear to
be critical to baroadaptation, have been uncovered. One such operon, whose presence appears to be restricted to the “barophile
branch,” has been identifed in DNA samples obtained from sediments recovered in the deepest ocean trench. In the case of another
set of pressure-regulated genes, regulatory elements required for pressure signaling have been uncovered. The nature and regulation
of these genes is discussed.
Received: February 19, 1997 / Accepted: March 3, 1997 相似文献
15.
Karin Riemann-Zürneck 《Polar Biology》2000,23(9):604-608
In 1993, a small, inconspicuous sea anemone, Oractis bursifera sp. nov., was collected during cruise ARK IX/4 of RV “Polarstern” from 3000 m depth in the central Arctic deep sea (Amundsen
Basin). Histological sections revealed a unique morphological trait in the form of ten sac-like invaginations of the oral
disc lined with an unusual, presumably glandular, epithelium. Another remarkable observation relates to its sexual status:
testicular follicles are present in the eight macromesenteries, with one of these mesenteries also harbouring a single, large,
apparently mature oocyte. Whether these peculiarities are related to each other and may thus be part of a reproductive pattern
in extreme habitats such as the Arctic deep sea is discussed. The peculiar characters of the new species confirm the extraordinary
position of the genus Oractis McMurrich, 1893, and warrant the establishment of the new family Oractiidae within the endomyarian sea anemones.
Accepted: 6 March 2000 相似文献
16.
C. A. Abella X. P. Cristina A. Martinez I. Pibernat X. Vila 《Archives of microbiology》1998,169(5):452-459
Two new phototrophic consortia, “Chlorochromatium lunatum” and “Pelochromatium selenoides”, were observed and collected in the hypolimnion of several dimictic lakes in Wisconsin and Michigan (USA). The two consortia
had the same morphology but different pigment composition. The cells of the photosynthetic components of the consortia were
half-moon-shaped. This morphology was used to differentiate them from the previously described motile phototrophic consortia
“Chlorochromatium aggregatum” and “Pelochromatium roseum”. These phototrophic cells did not resemble any described unicellular green sulfur bacteria. The predominant pigments detected
were bacteriochlorophyll d and chlorobactene for the green-colored “Clc. lunatum”, and bacteriochlorophyll e and isorenieratene for the brown-colored “Plc. selenoides”. Their pigment compositions and the presence of chlorosomes attached to the inner face of the cytoplasmic membrane in both
kinds of photosynthetic cells confirmed this new half-moon-shaped morphotype as a green sulfur bacterium. Both consortia were
found thriving in lakes with low concentrations of sulfide (< 60 μM), below the layers of “Clc. aggregatum” and “Plc. roseum”. The green consortia were observed in lakes where the oxic-anoxic interface was located at shallow depths (2–7 m), while
the brown consortia were found at greater depths (8–16 m). The two newly described consortia were never detected together
at the same depth in any lake.
Received: 30 April 1997 / Accepted: 17 January 1998 相似文献
17.
Fruit ethylene production genotypes for Md-ACS1 and Md-ACO1 were determined for 60 apple cultivars and 35 advanced breeding
selections. Two alleles for each gene are commonly found in cultivated apple. Earlier studies showed that genotypes homozygous
for the ACS1-2 allele produce less ethylene and have firmer fruit than ACS1-1/2 and ACS1-1/1 genotypes. ACO1 plays a minor
role compared to ACS1, with homozygous ACO1-1 having lower ethylene production. In this study, ACS1-2 and ACO1-1 homozygotes
had firmer fruit at harvest and after 60 days of 0–1°C cold storage compared to other genotypes. These genotypes, ACS1-2/2
and ACO1-1/1, were observed for the following 8 of 95 cultivars/selections: “Delblush”, “Fuji”, “Pacific Beauty”, “Sabina”
and four breeding selections. Cultivars/selections that were homozygous ACS1-2 but not ACO1-1 were: “Ambrosia”, “Aurora Golden
Gala”, “CrimsonCrisp”, “Gala”, “GoldRush”, “Huaguan”, “Pacific Rose, “Pacific Queen”, “Pinova”, “Sansa”, “Sonja”, “Sundance”,
“Zestar”, and 17 breeding selections. Cultivars with the heterozygous ACS1-1/2 genotype were “Arlet”, “Braeburn”, “Cameo”,
“Delicious”, “Delorgue”, “Empire”, “Enterprise”, “Ginger Gold”, “Golden Delicious”, “Granny Smith”, “Honeycrisp”, “Orin”,
“Pink Lady”, “Silken”, “Suncrisp”, “Sundowner”, “Sunrise” and 11 breeding selections. No cultivars were detected homozygous
for both ACS1-1 and ACO1-1, or for both ACS1-2 and ACO1-2. This study is the first large-scale allelic genotyping of both
ethylene synthesis genes for a comprehensive set of apple breeding parents used in an ongoing breeding project. The data reported
here are important for informative selection of parent combinations and marker-assisted selection of progeny for breeding
low ethylene-producing apple cultivars for better storability and improved consumer acceptance. 相似文献
18.
Four callus lines from immature embryos of a self-crossed maize (Zea mays L.) hybrid cultivar were selected for “high” (two lines) and “low” (two lines) polyamine (PA) levels. Each selected line
was exposed to culture media containing no (control) or 1% (0.171 m) NaCl and the relative growth rates were compared after subculture. Low-PA lines appeared to be tolerant to salt stress,
while high-PA lines were sensitive. Analysis of PA at the end of the subculture showed that treated calli of sensitive lines
had increased their putrescine content in comparison with their control, while putrescine remained constant in tolerant lines.
Callus lines were analysed by RAPD (random amplification of polymorphic DNA) markers. One polymorphism (550-bp band) was found,
demonstrating a genetic difference between the lines.
Received: 18 January 1997 / Revision received: 14 April 1997 / Accepted 15 July 1997 相似文献
19.
The phototrophic consortium “Chlorochromatium aggregatum” was enriched from sediment samples of a eutrophic freshwater lake and was maintained at high numbers in anoxic sulfide-reduced
medium. Growth of intact consortia was observed only in the light and in the presence of 2-oxoglutarate as an organic carbon
source. Consortia of “C. aggregatum” reached maximum growth rates at light intensities ≥ 5 μmol quanta m–2 s–1. Of ten compounds tested, sulfide, thiosulfate, 2-oxoglutarate, and citrate served as a chemoattractant for “C. aggregatum”. When incubated in the presence of sulfide and in the light, epibionts reduced the fluorochrome 5-cyano-2,3-di-4-tolyl-tetrazolium
chloride (CTC). Reduction of CTC was not observed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) or in the dark, indicating that sulfide serves as an electron donor for the phototrophic epibiont.
Motile consortia accumulated scotophobically in microcuvettes at a wavelength of 740 nm. Since this wavelength corresponds
to the position of the absorption maximum of bacteriochlorophylls c or d, the photosynthetic pigments are most likely the photoreceptors of the scotophobic response. It is concluded that, within
the consortia, a rapid interspecies signal transfer occurs between the nonmotile, green-colored epibiont and the motile, colorless
central bacterium.
Received: 27 May 1997 / Accepted: 5 September 1997 相似文献
20.
Chains of coupled oscillators of simple “rotator” type have been used to model the central pattern generator (CPG) for locomotion
in lamprey, among numerous applications in biology and elsewhere. In this paper, motivated by experiments on lamprey CPG with
brainstem attached, we investigate a simple oscillator model with internal structure which captures both excitable and bursting
dynamics. This model, and that for the coupling functions, is inspired by the Hodgkin–Huxley equations and two-variable simplifications
thereof. We analyse pairs of coupled oscillators with both excitatory and inhibitory coupling. We also study traveling wave
patterns arising from chains of oscillators, including simulations of “body shapes” generated by a double chain of oscillators
providing input to a kinematic musculature model of lamprey..
Received: 25 November 1996 / Revised version: 9 December 1997 相似文献