A laboratory study of preferential predation by the newt Notophthalmus v. viridescens

1980 ◽  
Vol 58 (9) ◽  
pp. 1712-1717 ◽  
Author(s):  
Etienne N. Attar ◽  
Edward J. Maly
Keyword(s):  
Relative Density ◽  
Laboratory Study ◽  
Prey Density ◽  
Activity Patterns ◽  
Relative Proportion ◽  
Experimental Results ◽  
Turbid Water ◽  
Total Abundance ◽  
Hunting Behavior ◽  
Reduced Temperature

Experiments were performed to determine if the newt Notophthalmus v. viridescens preferred the amphipod Hyalella over the cladoceran Daphnia under laboratory conditions and how temperature, relative proportion of prey, and total abundance of prey affects prey preference. Experiments demonstrate that Hyalella is the preferred prey at high prey densities but that Daphnia is preferred at low prey densities. Relative density of prey does not affect the preference for Hyalella at high prey density, but reduced temperature eliminates the preference for Hyalella at these high densities. Turbid water reduces the feeding rate.The experimental results can be attributed to hunting behavior of the newt and to size and activity patterns of the prey. The results suggest that the newt is an opportunistic feeder and that prey movement affects numbers of prey eaten.

The physiology of Venezillo arizonicus (Isopoda, Armadillidae): metabolism and thermal tolerance

Crustaceana ◽  
2021 ◽  
Vol 94 (2) ◽  
pp. 159-175
Author(s):  
Zechariah C. Harris ◽  
Jonathan C. Wright
Keyword(s):  
Metabolic Rate ◽  
Thermal Tolerance ◽  
Metabolic Regulation ◽  
Activity Patterns ◽  
Lethal Temperature ◽  
Habitat Productivity ◽  
Catabolic Rate ◽  
Thermal Maximum ◽  
Desert Habitat ◽  
Reduced Temperature

Abstract Venezillo arizonicus (Mulaik & Mulaik, 1942) is the only oniscidean isopod native to the Southwest Desert Province of North America. In accordance with its desert habitat, we hypothesized that V. arizonicus would have a higher upper lethal temperature than mesic oniscideans. If oniscidean thermal tolerance is limited by an oxygen consumption-uptake mismatch (physiological hypoxia), as indicated by recent work with other land isopods, we further hypothesized that V. arizonicus would possess highly efficient pleopodal lungs, as defined by its capacity for metabolic regulation in reduced . Other adaptations to counter oxygen limitation at high temperatures could include reduced temperature sensitivity of metabolism (low ) and an overall reduction in metabolic rate. Thermal tolerance was measured using the progressive method of Cowles & Bogert and the catabolic rate of animals () was measured as a function of temperature and . The critical thermal maximum (CTmax) of winter-acclimatized animals was 43.0 ± 0.85°C, 1.6-2.6°C higher than published values for summer-acclimatized mesic oniscideans. The catabolic rate at 25°C was 1.50 ± 0.203 μl min−1 g−1, markedly lower than values determined for mesic Oniscidea (4-6 μl min−1 g−1) and was unaffected by hypoxia as low as 2% O2 (ca. 2 kPa). Catabolism was, however, quite sensitive to temperature, showing a mean of 2.58 over 25-42°C. The efficient pleopodal lungs and low metabolic rate of V. arizonicus will both tend to mitigate physiological hypoxia, consistent with the species’ high CTmax. A low catabolic rate may also be an adaptation to low habitat productivity and seasonally constrained activity patterns.

scholarly journals STABILITY OF HIGH DENSITY CUBES IN RUBBLE MOUND BREAKWATERS

2020 ◽  
pp. 4
Author(s):  
Yalcin Yuksel ◽  
Marcel van Gent ◽  
Esin Cevik ◽  
H. Alper Kaya ◽  
Irem Gumuscu ◽  
...  
Keyword(s):  
Relative Density ◽  
Slope Angle ◽  
High Density ◽  
Experimental Results ◽  
Normal Density ◽  
Stability Number ◽  
Damage Initiation ◽  
Rubble Mound ◽  
The Stability ◽  
Rubble Mound Breakwaters

The stability number for rubble mound breakwaters is a function of several parameters and depends on unit shape, placing method, slope angle, relative density, etc. In this study two different densities for cubes in breakwater armour layers were tested to determine the influence of the density on the stability. The experimental results show that the stability of high density blocks were found to be more stable and the damage initiation for high density blocks started at higher stability numbers compared to normal density cubes.

scholarly journals Tectal pathways of regenerating goldfish optic axons after nasal or temporal half retinal removal

Development ◽  
1988 ◽  
Vol 102 (3) ◽  
pp. 479-488
Author(s):  
M.F. Humphrey ◽  
C.A.O. Stuermer
Keyword(s):  
Optic Nerve ◽  
Relative Density ◽  
Relative Proportion ◽  
Axonal Growth ◽  
Nerve Section ◽  
Optic Axons

The tectal pathways of regenerating goldfish optic axons are abnormal but not random. The relative proportion of temporal axons is highest in rostral tectum (65%) drops in midtectum (31%) and is very low in caudal tectum (4%). By contrast, nasal axons proceed into caudal tectum and are therefore relatively evenly distributed throughout the tectum. In this study, we have tested whether temporal axons are confined to rostral tectum by the presence of nasal axons in caudal tectum or whether they have a preference for rostral tectum regardless of other axons. We similarly tested whether nasal axons would grow preferentially into caudal tectum in the absence of temporal axons. At the time of optic nerve section either the nasal or temporal half retina was removed. Either 35 or 70 days after nerve section, the regenerating optic axons were labelled with HRP and both their pathways and distribution determined in DAB-reacted tectal wholemounts. In the absence of nasal axons, the relative density of temporal axons in rostral, mid and caudal tectum was 70%, 28% and 2%, respectively. The corresponding values for nasal axons, in the absence of temporal axons, were 30%, 40% and 30%, respectively. Thus, the overall distribution of nasal and temporal axons in the half retinal regenerates was similar to that of whole retinal regenerates, demonstrating that the retinotopic preferences of the axons were not dependent upon interaxonal interactions. Thus, nasal and temporal axons obviously discriminate between rostral and caudal tectum despite pathway disorganization and the absence of axons from the opposite hemiretina. This is consistent with axonal growth being under the influence of positional markers in tectum.

Occupancy, detectability, and density of crab-eating fox (Cerdocyon thous) in two protected areas of restinga habitats in Brazil

2019 ◽  
Vol 97 (10) ◽  
pp. 952-959
Author(s):  
Priscila Stéfani Monteiro-Alves ◽  
Débora Molino Helmer ◽  
Atilla Colombo Ferreguetti ◽  
Juliane Pereira-Ribeiro ◽  
Carlos Frederico Duarte Rocha ◽  
...  
Keyword(s):  
Protected Areas ◽  
Activity Patterns ◽  
Camera Traps ◽  
Total Abundance ◽  
Nocturnal Activity ◽  
Starting Point ◽  
Cerdocyon Thous ◽  
Future Work ◽  
Mammal Communities ◽  
Management And Conservation

Crab-eating foxes (Cerdocyon thous (Linnaeus, 1766)) are frequently recorded in lists of mammal communities. However, studies quantifying aspects of the ecology of the species are uncommon in the literature. Thus, we aimed to quantify the density, activity, habitat use, and potential threats of C. thous in two protected areas (PAs) in the State of Espírito Santo, Brazil. We used data derived from camera traps and sand plots to model occupancy, detectability, activity; we also used random encounter models (REMs) to model density and abundance. We also estimated the activity of the species. Density of C. thous was 0.82 individuals/km2 with a total abundance of 119 individuals. We concluded that in the PAs studied, C. thous had bimodal, twilight–nocturnal activity patterns and was associated with water sources. Although the species in the area has a relatively high density compared with that from other areas in Brazil, it could be locally threatened by the highway that crosses the two PAs, promoting roadkill events, and by domestic dogs (Canis familiaris Linnaeus, 1758) recorded in these areas. Results presented herein can be a starting point to support future work in the region and to make predictions regarding the management and conservation of C. thous, a widely distributed species.

Hunting Behavior, Prey Selection, and Energetics of Snail Kites in Guyana: Consumer Choice by a Specialist

The Auk ◽  
1983 ◽  
Vol 100 (1) ◽  
pp. 84-92 ◽  
Author(s):  
Steven R. Beissinger
Keyword(s):  
Consumer Choice ◽  
Prey Selection ◽  
Activity Patterns ◽  
Caloric Intake ◽  
Handling Time ◽  
Time Of Day ◽  
Rice Fields ◽  
Hunting Behavior ◽  
Time Activity ◽  
Prey Handling

Abstract The hunting behavior, snail size selection, and time-activity patterns of non-breeding Snail Kites (Rostrhamus sociabilis sociabilis) were studied in Guyana rice fields. Kites spent 62% of the photoperiod perching, 19% foraging, 13% in maintenance activities, and 6% flying. As the day progressed, the percentage of daylight hours spent perching increased significantly, while foraging decreased significantly. Kites successfully captured and ingested Pomacea snails in 78% of the foraging bouts observed. The mode of hunting was evenly split between coursing (50.7%) and still-hunting (49.3%). Searching and returning times were related to time of day, as significantly more coursing hunts and still-hunts occurred in mornings and late afternoons, respectively. Prey handling time was the most time-consuming component of a foraging bout. Time spent searching for prey, returning, or handling prey was not related to snail size. The size distribution of captured snails differed significantly from that of available snails; kites selected more medium snails and fewer small snails and took large snails in equal frequency to that at which large snails were available. Kites captured the same-sized snails when coursing as when still-hunting. As rice grew, kite utilization of rice fields declined, and the frequency of still-hunting decreased while course-hunting attempts increased. The daily caloric intake of kites was estimated to be 104.2 kcal, the daily energy expenditure 85.7 kcal. Results are discussed in relation to consumer choices of specialists. The most important decision a foraging Snail Kite may make is what patch to search in and how long to search before abandoning patches.

THE EFFECT OF MOLECULAR ORIENTATION TO SOLID–SOLID AND MELTING TRANSITIONS

2009 ◽  
Vol 23 (09) ◽  
pp. 1207-1220
Author(s):  
MUSTAFA YAZICI ◽  
ŞÜKRÜ ÖZGAN
Keyword(s):  
Molecular Orientation ◽  
Orientational Order ◽  
Experimental Results ◽  
Plastic Crystals ◽  
Entropy Changes ◽  
Melting Transitions ◽  
D 20 ◽  
Solid Liquid ◽  
Reduced Temperature ◽  
Theoretical Results

The thermodynamics of solid–solid and solid–liquid transitions are investigated with an account of the number of molecular orientation. The variations of the positional and orientational orders with the reduced temperature are studied. It is found out that orientational order parameter is very sensitive to the number of allowed orientation. The reduced transition temperatures, volume changes and entropy changes of the phase transitions and theoretical phase diagrams are obtained. The entropy changes of melting transitions for different numbers of allowed orientation of the present model are compared with the theoretical results and some experimental data. The quantitative predictions of the model are compared with experimental results for plastic crystals and agreement between predictions of the model and the experimental results are approximately good. Also, different numbers of allowed orientation D correspond to different experimental results HI , HBr , H 2 S for D = 2; HBr , CCl 4, HI for D = 4; C 2 H 12 for D = 6; CH 4, PH 3 for D = 20.

scholarly journals Effect of TiB content on the properties of Al-TiB composites

2018 ◽  
Vol 50 (2) ◽  
pp. 237-244 ◽  
Author(s):  
Shen Yang ◽  
Zuoxing Guo ◽  
Maosheng Xia
Keyword(s):  
Wear Resistance ◽  
Relative Density ◽  
Titanium Boride ◽  
Experimental Results ◽  
Al Matrix

In this study, titanium boride (TiB) was used to make Al-TiB composites. The contents of TiB added into Al matrix were 1 wt.%, 5 wt.% and 10 wt.%, respectively. The composites were pressed at a pressure of 382 MPa and sintered at 600?C for 4 hours. The microstructures and properties of density, hardness and wear were investigated. Experimental results indicated that, the composite with 5 wt.% TiB owned the highest relative density and hardness among the three parameters. In addition, TiB particles dramatically improved the wear resistance of the Al matrix and the more TiB content the better of the wear resistance. That is, the composite with 10 wt.% TiB owned the best wear resistance.

Laboratory Study of Cylindrical Sedimentation Traps

1979 ◽  
Vol 36 (10) ◽  
pp. 1288-1291 ◽  
Author(s):  
Y. L. Lau
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Key Words ◽  
Laboratory Study ◽  
Fluid Motion ◽  
Bottom Layer ◽  
Experimental Results ◽  
Dimensionless Variables ◽  
Different Diameters ◽  
Neutrally Buoyant

Observations of the motion of fluid particles in cylindrical sedimentation traps showed that with an increase of the aspect ratio, there is also an increase in the Reynolds number below which neutrally buoyant droplets that were placed near the floor of the trap would remain in the bottom layer. The dependence of the fluid motion on these two dimensionless variables was demonstrated using traps of different diameters. For single cylindrical traps, the experimental results can be used to obtain estimates of the Reynolds number below which resuspension of settled material would not be expected to occur. Key words: sedimentation trap, aspect ratio, Reynolds number, limnological instrument

Influence of gravel density in the behaviour of soft soils improved with stone columns

2015 ◽  
Vol 52 (12) ◽  
pp. 1968-1980 ◽  
Author(s):  
Marina Miranda ◽  
Almudena Da Costa ◽  
Jorge Castro ◽  
César Sagaseta
Keyword(s):  
Relative Density ◽  
Soil Column ◽  
Experimental Results ◽  
Stone Columns ◽  
Small Scale ◽  
Replacement Ratio ◽  
Soft Soils ◽  
Stress Concentration Ratio ◽  
Area Replacement Ratio ◽  
Horizontal Slice

Stone columns are frequently employed to improve the bearing capacity of soft soils, to reduce settlements, and to increase the speed of consolidation. Their behaviour depends on several factors, such as the density of the aggregate that forms the column and the area replacement ratio. This paper presents a study of the influence of the density of the gravel forming the columns on the deformation and stresses around end-bearing stone columns installed in soft soils. For this purpose, the behaviour of a horizontal slice of a unit cell has been analyzed by small-scale laboratory tests performed in a Rowe–Barden cell. Tests have been performed with a gravel relative density of Dr = 30% and with two area replacement ratios. Their results have been analyzed along with those from similar tests performed with a gravel density of Dr = 100%. The study is focused on the soil–column stress concentration ratio and the reduction of settlements. Finally, the experimental results are compared with numerical simulations. The results show that a reduction of settlements around 10% occurs when the relative density of the gravel increases from Dr = 30% to 100%. Numerical analyses reproduce well the behaviour of stone columns and are in good agreement with the experimental results.

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