Measurement of the light intensity of the axis at the center of gravity of a focused light beam

1972 ◽  
Vol 15 (6) ◽  
pp. 696-699 ◽  
Author(s):  
�. I. Gel'fer ◽  
V. B. Kravtsov ◽  
S. E. Finkel'shtein
Keyword(s):  
Light Intensity ◽  
Light Beam ◽  
Center Of Gravity

scholarly journals The Eyes and the Photonegative Behaviour of Nephtys (Annelida, Polychaeta)

1956 ◽  
Vol 33 (3) ◽  
pp. 461-477
Author(s):  
R. B. CLARK
Keyword(s):  
Light Intensity ◽  
Light Beam ◽  
Linear Function ◽  
Posterior Part ◽  
Dorsal Surface ◽  
Epidermal Cells ◽  
Small Species ◽  
Accessory Cells ◽  
Vacuolated Cells ◽  
The Brain

1. The photoreceptors found in the Nephtyidae are: (a) Two pairs of vacuolated cells lying in pigment cups, with accessory cells, embedded in the posterior part of the supra-oesophageal ganglion. (b) One or two cells, which may or may not be vacuolated, on either side, lying a little anterior to the ganglion. (c) Undifferentiated epidermal cells surrounded by pigment granules may be photosensitive. 2. There are both morphological and behavioural grounds for concluding that the prostomial eyes of Nephtys are homologous with the eyes of Nereis, and that they are involved in the same types of behaviour. 3. The frequency with which Nephtys swims is, within limits, a linear function of the light intensity. Although the ganglionic eyes are directional receptors the worm does not orientate itself in a light beam; presumably the light reaching them is too diffuse. In the very small species N. cornuta, the eyes are close to the surface of the brain and the worm does orientate itself in a light beam. 4. Swimming is an essential prelude to burrowing, and the brighter the light the more frequently the worm swims and the sooner it is buried. Activity in light can be inhibited by stimulating receptors on the dorsal surface of the animal by contact.

Directional Differences in the Colour Sensitivity of Daphnia Magna

1974 ◽  
Vol 61 (1) ◽  
pp. 261-267
Author(s):  
STEPHEN YOUNG
Keyword(s):  
Eye Movements ◽  
Light Intensity ◽  
Light Beam ◽  
Compound Eye ◽  
Action Spectrum ◽  
Stimulus Light ◽  
Free Swimming ◽  
Action Spectra ◽  
Light Receptor ◽  
Flashing Light

1. The Daphnia compound eye movements can be driven by a flashing light. 2. The action spectrum for the threshold light intensity required to evoke this response depends on the orientation of the stimulus light beam with respect to the animal. 3. If the light falls on the eye through the top of the animal's head the action spectrum peaks at the low wavelength end of the spectrum, while if it falls on the eye through the side of the head the peak is in the yellow-green. 4. Eye movements cannot be evoked by illuminating any part of the animal except the compound eye so neither of these action spectra is due to a light receptor other than the compound eye. 5. Some anomalous action spectra in the literature on the behaviour of free-swimming Daphnia are accounted for.

The Varieties of Activity Detectors

2018 ◽  
pp. 217-220
Author(s):  
John R. B. Lighton
Keyword(s):  
Light Intensity ◽  
Far Infrared ◽  
Magnetic Activity ◽  
Center Of Gravity ◽  
Activity Level ◽  
Mechanical Activity ◽  
Activity Detection ◽  
Gravity Sensor ◽  
Flow Through ◽  
Metabolic Data

Metabolic measurements are sensitive to the activity level of the animal being measured. This chapter describes the various technologies available for recording the activity level of a study organism in synchrony with metabolic data, usually obtained using a flow-through system. These technologies include optical activity detection, in which information is extracted from fluctuations in light intensity; video activity detection; magnetic activity detection; capacitive activity detection; passive far-infrared activity detection; mechanical activity detection, often using a center of gravity sensor below a cage or chamber; and microwave reflectance activity detection.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

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