Resource overlap between co-occurring copepods: effects of predation and environmental fluctuation

1976 ◽  
Vol 54 (6) ◽  
pp. 933-940 ◽  
Author(s):  
Edward J. Maly
Keyword(s):  
High Altitude ◽  
Laboratory Experiments ◽  
Population Characteristics ◽  
Congeneric Species ◽  
Season Length ◽  
Environmental Fluctuation ◽  
Temporal Differences ◽  
Resource Overlap ◽  
Primary Determinant ◽  
Competition For Resources

Two high-altitude copepods, Diaptomus shoshone and D. coloradensis, exhibit temporal differences in development and abundance, and they are of different size. Studies of adult sizes attained and of diets reveal that competition for resources between the two species is slight; however, laboratory experiments demonstrate that D. shoshone, the larger of the two species, preys extensively upon D. coloradensis. The population characteristics of the two species can be attributed both to avoidance of predation by the smaller species and to high variation in season length. Results are discussed in relation to theory, indicating that competition is a primary determinant of degree of resource overlap between congeneric species.

scholarly journals A global quantification of “normal” sleep schedules using smartphone data

2016 ◽  
Vol 2 (5) ◽  
pp. e1501705 ◽  
Author(s):  
Olivia J. Walch ◽  
Amy Cochran ◽  
Daniel B. Forger
Keyword(s):  
Laboratory Experiments ◽  
Population Level ◽  
Light Level ◽  
Sleep Scheduling ◽  
Sleep Habits ◽  
Wake Time ◽  
Sleep Timing ◽  
The World ◽  
Primary Determinant ◽  
Normal Sleep

The influence of the circadian clock on sleep scheduling has been studied extensively in the laboratory; however, the effects of society on sleep remain largely unquantified. We show how a smartphone app that we have developed, ENTRAIN, accurately collects data on sleep habits around the world. Through mathematical modeling and statistics, we find that social pressures weaken and/or conceal biological drives in the evening, leading individuals to delay their bedtime and shorten their sleep. A country’s average bedtime, but not average wake time, predicts sleep duration. We further show that mathematical models based on controlled laboratory experiments predict qualitative trends in sunrise, sunset, and light level; however, these effects are attenuated in the real world around bedtime. Additionally, we find that women schedule more sleep than men and that users reporting that they are typically exposed to outdoor light go to sleep earlier and sleep more than those reporting indoor light. Finally, we find that age is the primary determinant of sleep timing, and that age plays an important role in the variability of population-level sleep habits. This work better defines and personalizes “normal” sleep, produces hypotheses for future testing in the laboratory, and suggests important ways to counteract the global sleep crisis.

Interspecific copulation in and co-occurrence of similar-sized freshwater centropagid copepods

1984 ◽  
Vol 35 (2) ◽  
pp. 153 ◽  
Author(s):  
EJ Maly
Keyword(s):  
Laboratory Experiments ◽  
Calanoid Copepod ◽  
Average Length ◽  
Mating Behaviour ◽  
Copepod Species ◽  
Spatial Differences ◽  
Interspecific Copulation ◽  
Competition For Resources

Laboratory experiments were performed in which males of a given centropagid calanoid copepod species were placed with females of another species. Five interspecific pairings were tested, and in four of these, males attempted copulation or copulated with the partner of a different species. Metasome lengths of copepods in all populations used for experiments were determined: males attempted copulation with females whose average length was 0.88-1.09 times the normal size of the female for that species. These results imply that co-occurrence of similar-sized calanoids may be rare because of mating behaviour, temporal or spatial differences in mating, rather than because of competition for resources. A survey of reported co-occurrences of centropagid copepods in the genera Boeckella and Calamoecia found in Australia supports this contention.

Quasi-cycles in crappie populations are forced by interactions among population characteristics and environment

2001 ◽  
Vol 58 (3) ◽  
pp. 594-601 ◽  
Author(s):  
Micheal S Allen ◽  
Leandro E Miranda
Keyword(s):  
Time Series ◽  
Environmental Conditions ◽  
Empirical Data ◽  
Population Model ◽  
Population Characteristics ◽  
Environmental Fluctuation ◽  
Density Dependent ◽  
Stock Recruitment ◽  
Variable Recruitment ◽  
Random Fluctuations

Crappie (Pomoxis spp.) populations have been characterized as cyclic, with strong year-classes recurring at 2- to 4-year intervals. We evaluated the potential for cyclic trends in crappie populations using a population model that included a density-dependent stock recruitment function and random environmental variation. Slow, medium, and fast growth were simulated over 100 years. The model predicted highly variable recruitment that was strongly influenced by environmental fluctuation at low and intermediate stock densities. At high stock density, recruitment was low, even if environmental conditions were favorable. Significant quasi-cycles occurred, but they were not sustained throughout the time series due to random environmental fluctuation. Quasi-cycles occurred because intermediate stock density and favorable environmental conditions occasionally combined to produce a very strong year-class that greatly increased stock density in the following 1–3 years and produced low recruitment, even if environmental conditions were favorable. Empirical data from 32 years of sampling age-0 crappies at Ross Barnett Reservoir showed trends similar to the simulated fluctuations. We conclude that crappie populations likely do not exhibit true cycles but may show quasi-cycles as a result of the interaction between random fluctuations in environment and density-dependent mechanisms. The frequency of such quasi-cycles may be enhanced by rapid growth and high exploitation.

scholarly journals Constant timing of medusa release in bivalve-inhabiting hydrozoans of the genus Eugymnanthea (Hydrozoa: Leptomedusae: Eirenidae)

2008 ◽  
Vol 88 (8) ◽  
pp. 1607-1609 ◽  
Author(s):  
Shin Kubota
Keyword(s):  
Light Intensity ◽  
Water Temperature ◽  
Breeding Season ◽  
Laboratory Experiments ◽  
Mytilus Galloprovincialis ◽  
Congeneric Species ◽  
Natural Conditions ◽  
Night Time

At the end of the breeding season in autumn, under natural conditions, mature medusae of Eugymnanthea japonica are released from its host Mytilus galloprovincialis at night-time. In laboratory experiments, mature medusae of the congeneric species E. inquilina are also released at night-time in autumn. At that time of the year, sunset is earlier and the water temperature is lower than in summer, when, under natural conditions, medusa release of E. japonica takes place at sunset instead. The release thus takes place at the same hours of the day in summer as well as in autumn. The circadial timing of medusa release of E. japonica is likely constant throughout the whole period in the breeding season and not correlated with the decrease of light intensity at sunset.

scholarly journals Professor Bengt Saltin Symposium – Environmental challenges to human performance

2017 ◽  
Vol 42 (1) ◽  
pp. 104-107
Author(s):  
Philip N. Ainslie
Keyword(s):  
High Altitude ◽  
Laboratory Experiments ◽  
Human Performance ◽  
Exercise Physiology ◽  
Muscle Metabolism ◽  
Short Review ◽  
Important Work ◽  
The North ◽  
The Andes ◽  
High Altitude Natives

This short review is from a presentation made at the Bengt Saltin Symposium, October 15–17, at the 2015 Canadian Society for Exercise Physiology conference, Hamilton, Canada. The review provides context of the important work of the late Dr. Saltin’s contributions to environmental physiology. In addition to well-controlled laboratory experiments to better understand the influence of hypoxia or temperature, or both, Dr. Saltin also led several field expeditions to the North Greenland, Kenya, Himalayas, and the Andes, where he studied several aspects of human adaptation to environment. The 1998 Danish High-Altitude Expedition to the Andes, in particular, resulted in many major contributions to the field of altitude physiology including, but not limited to, mechanisms of reductions in maximal oxygen uptake, the lactate paradox, acclimatization, muscle metabolism, gas exchange, cerebrovascular physiology, etc. Of note, many of these related studies were conducted in both Danish sojourners to altitude and Bolivian altitude natives of Aymara ancestry, thus providing some of the most mechanistic comparisons with high altitude natives to date. A framework of these physiological contributions in terrestrial extremes is provided in this review.

scholarly journals No anomalous supersaturation in ultracold cirrus laboratory experiments

2019 ◽  
Author(s):  
Benjamin W. Clouser ◽  
Kara D. Lamb ◽  
Laszlo Sarkozy ◽  
Alexandra Nisenoff ◽  
Jan Habig ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Altitude ◽  
Laboratory Experiments ◽  
Cirrus Clouds ◽  
Final Value ◽  
Radiative Impact

Abstract. High-altitude cirrus clouds are climatically important: their formation freeze-dries air ascending to the stratosphere to its final value, and their radiative impact is disproportionately large. However, their formation and growth are not fully understood, and multiple in-situ aircraft campaigns have observed frequent and persistent apparent water vapor supersaturations of 5 %–25 % in ultracold cirrus (T 

scholarly journals Seasonal persistence and population characteristics of Escherichia coli and enterococci in deep backshore sand of two freshwater beaches

2006 ◽  
Vol 4 (3) ◽  
pp. 313-320 ◽  
Author(s):  
Muruleedhara N. Byappanahalli ◽  
Richard L. Whitman ◽  
Dawn A. Shively ◽  
W. T. Evert Ting ◽  
Charles C. Tseng ◽  
...  
Keyword(s):  
Water Table ◽  
Laboratory Experiments ◽  
Lake Michigan ◽  
Population Characteristics ◽  
Human Pathogens ◽  
Indicator Organisms ◽  
E Coli ◽  
Pollution Events

We studied the shoreward and seasonal distribution of E. coli and enterococci in sand (at the water table) at two southern Lake Michigan beaches—Dunbar and West Beach (in Indiana). Deep, backshore sand (∼20 m inland) was regularly sampled for 15 months during 2002–2003. E. coli counts were not significantly different in samples taken at 5-m intervals from 0–40 m inland (P=0.25). Neither E. coli nor enterococci mean counts showed any correlation or differences between the two beaches studied. In laboratory experiments, E. coli readily grew in sand supplemented with lake plankton, suggesting that in situ E. coli growth may occur when temperature and natural organic sources are adequate. Of the 114 sand enterococci isolates tested, positive species identification was obtained for only 52 (46%), with E. faecium representing the most dominant species (92%). Genetic characterization by ribotyping revealed no distinct genotypic pattern (s) for E. coli, suggesting that the sand population was rather a mixture of numerous strains (genotypes). These findings indicate that E. coli and enterococci can occur and persist for extended periods in backshore sand at the groundwater table. Although this study was limited to two beaches of southern Lake Michigan, similar findings can be expected at other temperate freshwater beaches. The long-term persistence of these bacteria, perhaps independent of pollution events, complicates their use as indicator organisms. Further, backshore sand at the water table may act as a reservoir for these bacteria and potentially for human pathogens.

Population characteristics of southern sea garfish (Hyporhamphus melanochir, Hemiramphidae) in South Australia

2008 ◽  
Vol 59 (5) ◽  
pp. 429 ◽  
Author(s):  
A. J. Fowler ◽  
M. A. Steer ◽  
W. B. Jackson ◽  
M. T. Lloyd
Keyword(s):  
Large Scale ◽  
Annual Variation ◽  
South Australia ◽  
Population Characteristics ◽  
Season Length ◽  
Age Classes ◽  
Gulf Region ◽  
Commercial Catch ◽  
Important Species ◽  
Fishery Exploitation

Population dynamics, demography and spatial distribution of an important species of ‘halfbeak’, the southern sea garfish (Hyporhamphus melanochir), were studied in South Australia, which accounts for most of the national catch. Commercial catch and effort data were used to indicate spatial and temporal abundance. Catch sampling provided fish measurements and estimates of age, sex and reproductive maturity. Catches were from throughout South Australia’s gulf region, but three areas separated by hundreds of kilometres produced the highest catches. These relatively protected areas support extensive beds of intertidal and subtidal seagrasses. Statewide commercial fishery catches demonstrated considerable inter-annual variation of 240–320 t year–1. Catches were dominated by 1+ and 2+ fish, with few individuals from the 3+ to 5+ age classes. Females dominated the sex ratios, were the largest individuals, and the largest from each age class. No running ripe fish were sampled. Seasonal variation in the catch and in the lack of spawning fish suggested that adults might move from fishing areas during the spawning season. Length/weight and length/age relationships did not differ between areas separated by hundreds of kilometres, suggesting large-scale movement. Possible population truncation related to fishery exploitation has prompted a stock rebuilding program for the South Australian stock.

Contrast of Filament Bright Rims

1994 ◽  
Vol 144 ◽  
pp. 365-367
Author(s):  
E. V. Kononovich ◽  
O. B. Smirnova ◽  
P. Heinzel ◽  
P. Kotrč
Keyword(s):  
High Altitude ◽  
Line Profile ◽  
Line Center ◽  
Magnetic Structures ◽  
The Mean

AbstractThe Hα filtergrams obtained at Tjan-Shan High Altitude Observatory near Alma-Ata (Moscow University Station) were measured in order to specify the bright rims contrast at different points along the line profile (0.0; ± 0.25; ± 0.5; ± 0.75 and ± 1.0 Å). The mean contrast value in the line center is about 25 percent. The bright rims interpretation as the bases of magnetic structures supporting the filaments is suggested.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

1999 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Kh.I. Ibadinov
Keyword(s):  
Laboratory Experiments ◽  
Cometary Nucleus ◽  
Sublimation Rate ◽  
Cometary Nuclei ◽  
Short Period Comet ◽  
Short Period ◽  
Brightness Decrease ◽  
Crust Thickness ◽  
Ice Sublimation ◽  
Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

Sign in / Sign up

Export Citation Format

Share Document