scholarly journals Behavioural and physiological mechanisms of polarized light sensitivity in birds

2011 ◽  
Vol 366 (1565) ◽  
pp. 763-771 ◽  
Author(s):  
Rachel Muheim
Keyword(s):  
Physiological Mechanism ◽  
Polarized Light ◽  
Light Sensitivity ◽  
Convincing Evidence ◽  
Polarization Pattern ◽  
Compass Orientation ◽  
Receptor System ◽  
Sun Compass ◽  
Skylight Polarization ◽  
Compass Calibration

Polarized light (PL) sensitivity is relatively well studied in a large number of invertebrates and some fish species, but in most other vertebrate classes, including birds, the behavioural and physiological mechanism of PL sensitivity remains one of the big mysteries in sensory biology. Many organisms use the skylight polarization pattern as part of a sun compass for orientation, navigation and in spatial orientation tasks. In birds, the available evidence for an involvement of the skylight polarization pattern in sun-compass orientation is very weak. Instead, cue-conflict and cue-calibration experiments have shown that the skylight polarization pattern near the horizon at sunrise and sunset provides birds with a seasonally and latitudinally independent compass calibration reference. Despite convincing evidence that birds use PL cues for orientation, direct experimental evidence for PL sensitivity is still lacking. Avian double cones have been proposed as putative PL receptors, but detailed anatomical and physiological evidence will be needed to conclusively describe the avian PL receptor. Intriguing parallels between the functional and physiological properties of PL reception and light-dependent magnetoreception could point to a common receptor system.

scholarly journals Matched-filter coding of sky polarization results in an internal sun compass in the brain of the desert locust

2020 ◽  
Vol 117 (41) ◽  
pp. 25810-25817
Author(s):  
Frederick Zittrell ◽  
Keram Pfeiffer ◽  
Uwe Homberg
Keyword(s):  
Spatial Orientation ◽  
Matched Filter ◽  
Polarized Light ◽  
Central Complex ◽  
Insect Brain ◽  
The Sun ◽  
Polarization Pattern ◽  
Sun Compass ◽  
Small Spot ◽  
Polarization Compass

Many animals use celestial cues for spatial orientation. These include the sun and, in insects, the polarization pattern of the sky, which depends on the position of the sun. The central complex in the insect brain plays a key role in spatial orientation. In desert locusts, the angle of polarized light in the zenith above the animal and the direction of a simulated sun are represented in a compass-like fashion in the central complex, but how both compasses fit together for a unified representation of external space remained unclear. To address this question, we analyzed the sensitivity of intracellularly recorded central-complex neurons to the angle of polarized light presented from up to 33 positions in the animal’s dorsal visual field and injected Neurobiotin tracer for cell identification. Neurons were polarization sensitive in large parts of the virtual sky that in some cells extended to the horizon in all directions. Neurons, moreover, were tuned to spatial patterns of polarization angles that matched the sky polarization pattern of particular sun positions. The horizontal components of these calculated solar positions were topographically encoded in the protocerebral bridge of the central complex covering 360° of space. This whole-sky polarization compass does not support the earlier reported polarization compass based on stimulation from a small spot above the animal but coincides well with the previously demonstrated direct sun compass based on unpolarized light stimulation. Therefore, direct sunlight and whole-sky polarization complement each other for robust head direction coding in the locust central complex.

Navigation and Compass Orientation by Insects According to the Polarization Pattern of the Sky

1988 ◽  
Vol 43 (5-6) ◽  
pp. 467-469 ◽  
Author(s):  
K. Kirschfeld
Keyword(s):  
Polarized Light ◽  
Recent Theory ◽  
Polarization Pattern ◽  
Natural Conditions ◽  
Compass Orientation ◽  
Small Patch ◽  
Foraging Site

A recent theory attempts to explain how bees take their compass orientation from the pattern of polarized light in the sky (S. Rossel and R . Wehner, Nature 323, 128-131 (1986)). According to this theory, orientation can be erroneous and lead to the wrong course of a recruited bee in search of the foraging site whenever only a small patch of the blue sky is visible to the bee. It is shown that orientation under natural conditions is not erroneous, if the compass reference is variable in time but equally defined for both, scout bees and recruits.

Conditional Perception Under Stimulus Ambiguity: Polarization- and Azimuth-Sensitive Neurons in the Locust Brain Are Inhibited by Low Degrees of Polarization

2011 ◽  
Vol 105 (1) ◽  
pp. 28-35 ◽  
Author(s):  
Keram Pfeiffer ◽  
Mario Negrello ◽  
Uwe Homberg
Keyword(s):  
Polarized Light ◽  
The Sun ◽  
Intracellular Recordings ◽  
Polarization Pattern ◽  
Direct Sunlight ◽  
Compass Orientation ◽  
Stimulus Ambiguity ◽  
Low Degrees ◽  
The Brain ◽  
Intensity Contrast

Sensory perception often relies on the integration and matching of multisensory inputs. In the brain of desert locusts, identified neurons that signal the sun's direction relative to the animal's head integrate information about the polarization pattern of the sky with information on the color and intensity contrast of the sky. The cloudless blue sky exhibits a gradient from unpolarized sunlight to strongly polarized light at 90° from the sun. Therefore the percentage of polarized light in the sky is highest at dusk and dawn and lowest when the sun is in the zenith. We investigated the effect of different degrees of polarization on neurons of the anterior optic tubercle of the desert locust through intracellular recordings. Whereas dorsal presentation of strongly polarized light largely excited the neurons, weakly polarized light, i.e., a blend of polarized light of many orientations, led to inhibition. The data suggest that the polarization input to these neurons is inhibited within a radius of 50° around the sun, thereby avoiding conflicting input from the polarization and direct sunlight channels. These properties can be regarded as sensory filters to avoid ambiguous signaling during sky compass orientation.

Sun-compass orientation in the characidCheirodon pulcher

1992 ◽  
Vol 35 (3) ◽  
pp. 321-325 ◽  
Author(s):  
Luis E. Levin ◽  
Pedro Belmonte ◽  
Olga González
Keyword(s):  
Compass Orientation ◽  
Sun Compass

Advancing an Ecosystem Approach in the Gulf of Maine

2012 ◽  
Keyword(s):  
New England ◽  
Gulf Of Maine ◽  
Environmental Gradients ◽  
Polarized Light ◽  
Ecosystem Approach ◽  
Water Bloom ◽  
Sun Compass ◽  
Fine Sediments ◽  
Wide Range ◽  
Crangon Septemspinosa

<i>Abstract</i> .—Because of partial recirculation and steep bottom slopes, the Gulf of Maine (GoM) contains steep environmental gradients in both space and time. I focus, in particular, on optical properties associated with both resources and risks. The GoM estuary-shelf systems differ from those whose fine sediments are trapped behind barrier bars; in the GoM, nepheloid layers prevail over a wide range of depths, and onshore-offshore turbidity gradients at a given water depth are also steep. Turbidity reduces predation risk. Three crustacean species that are major fish forages respond to the strong environmental gradients in resources and risks by migrating seasonally both horizontally and vertically. Northern shrimp (also known as pink shrimp) <i>Pandalus borealis</i> , sevenspine bay shrimp <i>Crangon septemspinosa</i> , and the most common mysid shrimp in the GoM, <i>Neomysis americana</i> , share both stalked eyes that appear capable of detecting polarized light and statocysts. This pair of features likely confers sun-compass navigational ability, facilitating use of multiple habitats. All three species converge on a shallow-water bloom at depths <100 m of the western GoM shelf in December–March, well before the basin-wide, climatological spring bloom in April. In addition to reaching abundant food resources, I propose that they are also using optical protection, quantified as the integral of the beam attenuation coefficient from the surface to the depth that they occupy during daylight. Spring immigration into, and fall emigration from, estuaries appear to be common in GoM sevenspine bay shrimp and <i>N. americana</i> , out of phase with their populations south of New England and with turbidity differences a likely cause. Migration studies that include measurements of turbidity are needed, however, to test the strength of the effect of optical protection on habitat use by all three species. Simultaneous sampling of estuaries and the adjacent shelf, together with trace-element tracer studies, would be very useful to resolve timing and extent of mass migrations, which likely are sensitive to turbidity change resulting from climate change. These migrations present special challenges to ecosystem-based management by using so many different habitats.

scholarly journals How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment

2014 ◽  
Vol 470 (2166) ◽  
pp. 20130787 ◽  
Author(s):  
Balázs Bernáth ◽  
Alexandra Farkas ◽  
Dénes Száz ◽  
Miklós Blahó ◽  
Ádám Egri ◽  
...  
Keyword(s):  
North Atlantic ◽  
Eleventh Century ◽  
Field Tests ◽  
Baffin Island ◽  
Sun Compass ◽  
The North ◽  
Skylight Polarization ◽  
Before And After ◽  
Birefringent Crystals ◽  
New Interpretation

Vikings routinely crossed the North Atlantic without a magnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagas mentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a ‘twilight board’, which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about ±4° when the artificially occluded Sun had elevation angles between +10° and −8° relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago.

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