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1.
The role of arctic zooplankton in biogeochemical cycles: respiration and excretion of ammonia and phosphate during summer 总被引:1,自引:0,他引:1
M. Alcaraz R. Almeda A. Calbet E. Saiz C. M. Duarte S. Lasternas S. Agustí R. Santiago J. Movilla A. Alonso 《Polar Biology》2010,33(12):1719-1731
The study of the structural and functional properties of key components of polar marine ecosystems has received increased
attention in order to better understand the ecological consequences of future sea temperature rise and seasonal ice retraction.
Owing to this purpose, during the ATOS-Arctic cruise, held in July 2007 in the framework of the 2007–2008 International Polar
Year, we studied the respiratory carbon demand of mesozooplankton as well as their contribution to the regeneration of inorganic
nitrogen and phosphorus (NH4-N and PO4-P) via excretion. The studied area comprised several stations along a latitudinal gradient in the East Greenland current, plus a
network of stations NW of the Svalbard islands. The specific respiratory carbon losses and phosphorus (PO4-P) excretion rates were similar or slightly higher than some reports for Arctic mesozooplankton, but the nitrogen (NH4-N) excretion rates were higher by a factor of 3 when compared with previous data sets. The mesozooplankton respiratory losses
were equivalent to 23% of primary production, and at turn zooplankton contributed by excretion to more than 50% of the N and
P required by phytoplankton. Although C:N, C:P and N:P metabolic atomic quotients almost coincided with the average Redfield’s
stoichiometric ratios, the low C:N values when compared to previous reports suggested a predominance of protein-related metabolic
substrates. The potential consequences of changes observed in the C:N, N:P and C:P metabolic ratios of mesozooplankton for
Arctic marine ecosystems are discussed. 相似文献
2.
Rory P. Wilson Hannah J. Williams Mark D. Holton Agustina di Virgilio Luca Brger Jonathan R. Potts Richard Gunner Alex Arkwright Andreas Fahlman Nigel C. Bennett Abdulaziz Alagaili Nik C. Cole Carlos M. Duarte David M. Scantlebury 《Ecology and evolution》2020,10(10):4291-4302
- Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
- Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
- We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
- We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
- Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.
3.
Michael H Woo John R Vance Ana R Otero Marcos Christian Bailly Mary-Ann Bjornsti 《The Journal of biological chemistry》2002,277(6):3813-3822
DNA topoisomerase I (Top1p) catalyzes topological changes in DNA and is the cellular target of the antitumor agent camptothecin (CPT). Non-CPT drugs that target Top1p, such as indolocarbazoles, are under clinical development. However, whether the cytotoxicity of indolocarbazoles derives from Top1p poisoning remains unclear. To further investigate indolocarbazole mechanism, rebeccamycin R-3 activity was examined in vitro and in yeast. Using a series of Top1p mutants, where substitution of residues around the active site tyrosine has well-defined effects on enzyme catalysis, we show that catalytically active, CPT-resistant enzymes remain sensitive to R-3. This indolocarbazole did not inhibit yeast Top1p activity, yet was effective in stabilizing Top1p-DNA complexes. Similar results were obtained with human Top1p, when Ser or His were substituted for Asn-722. The mutations altered enzyme function and sensitivity to CPT, yet R-3 poisoning of Top1p was unaffected. Moreover, top1delta, rad52delta yeast cells expressing human Top1p, but not catalytically inactive Top1Y723Fp, were sensitive to R-3. These data support hTop1p as the cellular target of R-3 and indicate that distinct drug-enzyme interactions at the active site are required for efficient poisoning by R-3 or CPT. Furthermore, resistance to one poison may potentiate cell sensitivity to structurally distinct compounds that also target Top1p. 相似文献
4.
Sophie Arnaud-Haond Marianna Migliaccio Elena Diaz-Almela Sara Teixeira Mirjiam Susanne van de Vliet Filipe Alberto Gabriele Procaccini Carlos M. Duarte Ester A. Serrão 《Journal of Biogeography》2007,34(6):963-976
Aim The seagrass, Posidonia oceanica is a clonal angiosperm endemic to the Mediterranean Sea. Previous studies have suggested that clonal growth is far greater than sexual recruitment and thus leads to low clonal diversity within meadows. However, recently developed microsatellite markers indicate that there are many different genotypes, and therefore many distinct clones present. The low resolution of markers used in the past limited our ability to estimate clonality and assess the individual level. New high‐resolution dinucleotide microsatellites now allow genetically distinct individuals to be identified, enabling more reliable estimation of population genetic parameters across the Mediterranean Basin. We investigated the biogeography and dispersal of P. oceanica at various spatial scales in order to assess the influence of different evolutionary factors shaping the distribution of genetic diversity in this species. Location The Mediterranean. Methods We used seven hypervariable microsatellite markers, in addition to the five previously existing markers, to describe the spatial distribution of genetic variability in 34 meadows spread throughout the Mediterranean, on the basis of an average of 35.6 (± 6.3) ramets sampled. Results At the scale of the Mediterranean Sea as a whole, a strong east–west cleavage was detected (amova) . These results are in line with those obtained using previous markers. The new results showed the presence of a putative secondary contact zone at the Siculo‐Tunisian Strait, which exhibited high allelic richness and shared alleles absent from the eastern and western basins. F statistics (pairwise θ ranges between 0.09 and 0.71) revealed high genetic structure between meadows, both at a small scale (about 2 to 200 km) and at a medium scale within the eastern and western basins, independent of geographical distance. At the intrameadow scale, significant spatial autocorrelation in six out of 15 locations revealed that dispersal can be restricted to the scale of a few metres. Main conclusions A stochastic pattern of effective migration due to low population size, turnover and seed survival is the most likely explanation for this pattern of highly restricted gene flow, despite the importance of an a priori seed dispersal potential. The east–west cleavage probably represents the outline of vicariance caused by the last Pleistocene ice age and maintained to this day by low gene flow. These results emphasize the diversity of evolutionary processes shaping the genetic structure at different spatial scales. 相似文献
5.
Summary The maximum density achievable by aquatic organisms is an inverse linear function of their body size. As a consequence, the maximum achievable biomass is independent of body size, and is 2 orders of magnitude higher than the biomass in natural populations. The minimum interorganismic terorganismic distance, calculated from the maximum density to allow comparison between aquatic and terrestrial organisms, scales as the 1/3 power of body size in both habitats. The similarities in the interorganismic distance of terrestrial and aquatic plant and animal communities suggest a fundamental regularity in the way organisms use the space. 相似文献
6.
To produce many small or few large eggs: a size-independent reproductive tactic of fish 总被引:2,自引:2,他引:0
Summary We demonstrate here the existence of a range of size-independent reproductive tactics in teleostean fish involving the allocation of a size-dependent reproductive effort between fecundity and egg size. Despite considerable evidence that larger eggs and the larvae hatching from them are more likely to survive than smaller ones, we found no evidence of evolutionary trends towards greater egg sizes. Fish with pelagic eggs tend to spawn many, and therefore small, eggs, whereas demersal spawners tend to produce large, and therefore few, eggs. Maximizing egg number should increase the number of eggs hatching in suitable locations in the patchy pelagic environment and, hence, increase the reproductive success of pelagic spawners. On the other hand, the reproductive success of demersal spawners, which reduce the variance in growing conditions experienced by the off spring, should be more dependent on the survival of the individual larvae, which increases as egg size increases. 相似文献
7.
8.
The present study was carried out to evaluate the suitability of the unstable white-zeste system in Drosophila melanogaster by testing 4 organophosphorus insecticides for potential genotoxic activity: dimethoate, fenitrothion, malathion, and methyl parathion. In view of the high sensitivity to insecticides of the unstable zeste strain used in this assay and the negative results obtained in this work, the white-zeste system does not appear to be sufficiently accurate for the evaluation of the mutagenic potential of specifically toxic chemicals, like insecticides. 相似文献
9.
To extend the data on the mutagenic effects of intercalating agents in Drosophila melanogaster, chloroquine and quinacrine were tested for the induction of genetic damage in D. melanogaster males. Sex-linked recessive lethals and sex-chromosome loss induction were studied following treatment of adult males using a feeding technique. Our results show that both intercalating compounds increase significantly the frequency of sex-linked recessive lethals, but are unable to induce sex-chromosome loss in male germ cells under the conditions of testing. 相似文献
10.
Effect of Phospholipase Digestion and Lysophosphatidylcholine on Dopamine Receptor Binding 总被引:4,自引:4,他引:0
[3H]Spiperone specific binding by microsomal membranes isolated from sheep caudate nucleus is decreased by trypsin and phospholipase A2 (Vipera russeli), but is insensitive to neuraminidase. The inhibitory effect of phospholipase A2 is correlated with phospholipid hydrolysis. After 15 min of phospholipase (5 micrograms/mg protein) treatment, a maximal effect is observed; the maximal lipid hydrolysis is about 56% and produces 82% reduction in [3H]spiperone binding. Equilibrium binding studies in nontreated and treated membranes showed a reduction in Bmax from a value of 388 +/- 9.2 fmol/mg protein before phospholipase treatment to a value of 52 +/- 7.8 fmol/mg protein after treatment, but no change in affinity (KD = 0.24 +/- 0.042 nM) was observed. Albumin washing of treated membranes removes 47% of lysophosphatidylcholine produced by phospholipid hydrolysis without recovering [3H]spiperone binding activity. However, the presence of 2.5% albumin during phospholipase A2 action (1.5 micrograms/mg protein) prevents the inhibitory effect of phospholipase on [3H]spiperone binding to the membranes, although 28% of the total membrane phospholipid is hydrolysed. Lysophosphatidylcholine, a product of phospholipid hydrolysis, mimics the phospholipase A2 effect on receptor activity, but the [3H]spiperone binding inhibition can be reversed by washing with 2.5% defatted serum albumin. Addition of microsomal lipids to microsomal membranes pretreated with phospholipase does not restore [3H]spiperone stereospecific binding. It is concluded that the phospholipase-mediated inhibition of [3H]spiperone binding activity results not only from hydrolysis of membrane phospholipids, but also from an alteration of the lipid environment by the end products of phospholipid hydrolysis. 相似文献