The role of the underwater polarized light pattern, in sun compass navigation of the grass shrimp, Palaemonetes vulgaris

1991 ◽  
Vol 169 (4) ◽  
pp. 479-491 ◽  
Author(s):  
Sydnee M. Goddard ◽  
Richard B. Forward
Keyword(s):  
Grass Shrimp ◽  
Polarized Light ◽  
Sun Compass ◽  
Light Pattern ◽  
Compass Navigation

scholarly journals Honeybee navigation: critically examining the role of the polarization compass

2014 ◽  
Vol 369 (1636) ◽  
pp. 20130037 ◽  
Author(s):  
C. Evangelista ◽  
P. Kraft ◽  
M. Dacke ◽  
T. Labhart ◽  
M. V. Srinivasan
Keyword(s):  
Food Source ◽  
Polarized Light ◽  
Vertical Direction ◽  
The Sun ◽  
Principal Diagonal ◽  
Light Pattern ◽  
Polarization Compass ◽  
Observation Hive ◽  
The Right

Although it is widely accepted that honeybees use the polarized-light pattern of the sky as a compass for navigation, there is little direct evidence that this information is actually sensed during flight. Here, we ask whether flying bees can obtain compass cues derived purely from polarized light, and communicate this information to their nest-mates through the ‘waggle dance’. Bees, from an observation hive with vertically oriented honeycombs, were trained to fly to a food source at the end of a tunnel, which provided overhead illumination that was polarized either parallel to the axis of the tunnel, or perpendicular to it. When the illumination was transversely polarized, bees danced in a predominantly vertical direction with waggles occurring equally frequently in the upward or the downward direction. They were thus using the polarized-light information to signal the two possible directions in which they could have flown in natural outdoor flight: either directly towards the sun, or directly away from it. When the illumination was axially polarized, the bees danced in a predominantly horizontal direction with waggles directed either to the left or the right, indicating that they could have flown in an azimuthal direction that was 90° to the right or to the left of the sun, respectively. When the first half of the tunnel provided axial illumination and the second half transverse illumination, bees danced along all of the four principal diagonal directions, which represent four equally likely locations of the food source based on the polarized-light information that they had acquired during their journey. We conclude that flying bees are capable of obtaining and signalling compass information that is derived purely from polarized light. Furthermore, they deal with the directional ambiguity that is inherent in polarized light by signalling all of the possible locations of the food source in their dances, thus maximizing the chances of recruitment to it.

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 Exciton-to-trion conversion as a control mechanism for valley polarization in room-temperature monolayer WS2

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Joris J. Carmiggelt ◽  
Michael Borst ◽  
Toeno van der Sar
Keyword(s):  
Room Temperature ◽  
Polarized Light ◽  
Optical Excitation ◽  
Equation Model ◽  
Chemical Doping ◽  
Transition Metal Dichalcogenide ◽  
Net Charge ◽  
Circularly Polarized Light ◽  
Valley Polarization

Abstract Transition metal dichalcogenide (TMD) monolayers are two-dimensional semiconductors with two valleys in their band structure that can be selectively addressed using circularly polarized light. Their photoluminescence spectrum is characterized by neutral and charged excitons (trions) that form a chemical equilibrium governed by the net charge density. Here, we use chemical doping to drive the conversion of excitons into trions in $$\text {WS}_{2}$$ WS 2 monolayers at room temperature, and study the resulting valley polarization via photoluminescence measurements under valley-selective optical excitation. We show that the doping causes the emission to become dominated by trions with a strong valley polarization associated with rapid non-radiative recombination. Simultaneously, the doping results in strongly quenched but highly valley-polarized exciton emission due to the enhanced conversion into trions. A rate equation model explains the observed valley polarization in terms of the doping-controlled exciton-trion equilibrium. Our results shed light on the important role of exciton-trion conversion on valley polarization in monolayer TMDs.

Anatomical basis of sun compass navigation II: The neuronal composition of the central complex of the monarch butterfly

2012 ◽  
Vol 521 (2) ◽  
pp. 267-298 ◽  
Author(s):  
Stanley Heinze ◽  
Jeremy Florman ◽  
Surainder Asokaraj ◽  
Basil el Jundi ◽  
Steven M. Reppert
Keyword(s):  
Monarch Butterfly ◽  
Central Complex ◽  
Sun Compass ◽  
Anatomical Basis ◽  
Compass Navigation
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