Comparison of the reactions of fish to a trawl gear, at high and low light intensities

1989 ◽  
Vol 7 (3) ◽  
pp. 249-266 ◽  
Author(s):  
C.W. Glass ◽  
C.S. Wardle
Keyword(s):  
Low Light ◽  
Light Intensities

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

COMBINATION AND DISPROPORTIONATION OF ETHYL RADICALS: INFLUENCE OF THE REACTION H+C2H5 = C2H6

1955 ◽  
Vol 33 (5) ◽  
pp. 821-829 ◽  
Author(s):  
Moyra J. Smith ◽  
Patricia M. Beatty ◽  
J. A. Pinder ◽  
D. J. Le Roy
Keyword(s):  
Light Intensity ◽  
Excellent Agreement ◽  
Mercury Concentration ◽  
Rate Constants ◽  
Room Temperature ◽  
Low Light ◽  
Ethylene Concentration ◽  
Light Intensities ◽  
Ethyl Radicals ◽  
Hydrogenation Of Ethylene

The mercury (3P1) photosensitized hydrogenation of ethylene has been studied at room temperature as a function of ethylene concentration, mercury concentration, and light intensity. In addition to combination and disproportionation, ethyl radicals have been shown to take part in the reaction[Formula: see text]The conditions favoring this reaction have been established and anomalous values previously found for the ratio of ethane to butane have been explained. The value obtained for the ratio of the rate constants for the disproportionation and combination of ethyl radicals, 0.15 ±.01, is in excellent agreement with the values obtained by other methods. Hexane formation is of some importance at low light intensities and high ethylene concentrations, and is adequately accounted for by the reactions[Formula: see text]

scholarly journals THE EFFECTS OF ILLUMINATION ON THE EARLY DEVELOPMENT OF AMPHIBIANS (AMPHIBIA: ANURA AND CAUDATA)

2018 ◽  
Vol 15 (30) ◽  
pp. 152-159
Author(s):  
A. B. RUCHIN
Keyword(s):  
Survival Rate ◽  
Early Development ◽  
Rana Arvalis ◽  
Low Light ◽  
Amphibian Species ◽  
Triturus Cristatus ◽  
Lissotriton Vulgaris ◽  
Light Intensities ◽  
Tailless Amphibians

The effects of illumination on the early development of four amphibian species — Lissotriton vulgaris (Linnaeus, 1758), Triturus cristatus (Laurenti, 1768), Rana arvalis (Nilsson, 1842), and R. temporaria (Linnaeus, 1758) — have been studied. In general, the rate of their early development is rather independent of illumination. The eggs of tailless amphibians develop almost similarly under any illumination conditions, whereas the eggs of tailed amphibians better develop at an illumination of 700 lx. Illumination mainly influences the survival rate of embryos and prolarvae, which increases at low light intensities and decreases in the dark. Possible mechanisms and causes underlying the observed facts are discussed.

scholarly journals Hybrid tea-roses under controlled light conditions. 2. Flowering of seedlings as dependent on the level of irradiance.

1978 ◽  
Vol 26 (1) ◽  
pp. 128-132
Author(s):  
D.P. de Vries ◽  
L. Smeets
Keyword(s):  
Selection Procedure ◽  
Light Conditions ◽  
Low Light ◽  
Light Requirement ◽  
Experimental Conditions ◽  
Light Intensities

Under the experimental conditions described in the preceding abstract, mortality increased with decreasing light intensities. The percentage of flowering seedlings increased and that of aborting ones decreased with irradiance. For the populations studied, no genotype-environment interactions for the percentages of flowering seedlings occurred. A selection procedure for roses with a low light requirement for flowering is considered. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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