scholarly journals Stark trade-offs and elegant solutions in arthropod visual systems

2021 ◽  
Vol 224 (4) ◽  
pp. jeb215541
Author(s):  
Michael Meece ◽  
Shubham Rathore ◽  
Elke K. Buschbeck
Keyword(s):  
Color Vision ◽  
Polarized Light ◽  
Low Light ◽  
Spectral Content ◽  
Light Levels ◽  
Visual Systems ◽  
Trade Offs ◽  
Detection Of Objects ◽  
Physical Limitations ◽  
The Subject

ABSTRACTVision is one of the most important senses for humans and animals alike. Diverse elegant specializations have evolved among insects and other arthropods in response to specific visual challenges and ecological needs. These specializations are the subject of this Review, and they are best understood in light of the physical limitations of vision. For example, to achieve high spatial resolution, fine sampling in different directions is necessary, as demonstrated by the well-studied large eyes of dragonflies. However, it has recently been shown that a comparatively tiny robber fly (Holcocephala) has similarly high visual resolution in the frontal visual field, despite their eyes being a fraction of the size of those of dragonflies. Other visual specializations in arthropods include the ability to discern colors, which relies on parallel inputs that are tuned to spectral content. Color vision is important for detection of objects such as mates, flowers and oviposition sites, and is particularly well developed in butterflies, stomatopods and jumping spiders. Analogous to color vision, the visual systems of many arthropods are specialized for the detection of polarized light, which in addition to communication with conspecifics, can be used for orientation and navigation. For vision in low light, optical superposition compound eyes perform particularly well. Other modifications to maximize photon capture involve large lenses, stout photoreceptors and, as has been suggested for nocturnal bees, the neural pooling of information. Extreme adaptations even allow insects to see colors at very low light levels or to navigate using the Milky Way.

scholarly journals Diverse Cell Types, Circuits, and Mechanisms for Color Vision in the Vertebrate Retina

2019 ◽  
Vol 99 (3) ◽  
pp. 1527-1573 ◽  
Author(s):  
Wallace B. Thoreson ◽  
Dennis M. Dacey
Keyword(s):  
Color Vision ◽  
Ganglion Cells ◽  
Color Perception ◽  
Visible Spectrum ◽  
Cell Types ◽  
Photon Flux ◽  
Low Light ◽  
Vertebrate Retina ◽  
Light Levels ◽  
Synaptic Interactions

Synaptic interactions to extract information about wavelength, and thus color, begin in the vertebrate retina with three classes of light-sensitive cells: rod photoreceptors at low light levels, multiple types of cone photoreceptors that vary in spectral sensitivity, and intrinsically photosensitive ganglion cells that contain the photopigment melanopsin. When isolated from its neighbors, a photoreceptor confounds photon flux with wavelength and so by itself provides no information about color. The retina has evolved elaborate color opponent circuitry for extracting wavelength information by comparing the activities of different photoreceptor types broadly tuned to different parts of the visible spectrum. We review studies concerning the circuit mechanisms mediating opponent interactions in a range of species, from tetrachromatic fish with diverse color opponent cell types to common dichromatic mammals where cone opponency is restricted to a subset of specialized circuits. Distinct among mammals, primates have reinvented trichromatic color vision using novel strategies to incorporate evolution of an additional photopigment gene into the foveal structure and circuitry that supports high-resolution vision. Color vision is absent at scotopic light levels when only rods are active, but rods interact with cone signals to influence color perception at mesopic light levels. Recent evidence suggests melanopsin-mediated signals, which have been identified as a substrate for setting circadian rhythms, may also influence color perception. We consider circuits that may mediate these interactions. While cone opponency is a relatively simple neural computation, it has been implemented in vertebrates by diverse neural mechanisms that are not yet fully understood.

scholarly journals The color of night: Surface color categorization by color defective observers under dim illuminations

2008 ◽  
Vol 25 (3) ◽  
pp. 475-480 ◽  
Author(s):  
JOEL POKORNY ◽  
MARGARET LUTZE ◽  
DINGCAI CAO ◽  
ANDREW J. ZELE
Keyword(s):  
Color Vision ◽  
Surface Color ◽  
Low Light ◽  
Light Levels ◽  
Color Categories ◽  
Wide Range ◽  
Basic Color ◽  
Color Vision Deficiencies ◽  
Orange Color ◽  
Color Scales

People with normal trichromatic color vision experience variegated hue percepts under dim illuminations where only rod photoreceptors mediate vision. Here, hue perceptions were determined for persons with congenital color vision deficiencies over a wide range of light levels, including very low light levels where rods alone mediate vision. Deuteranomalous trichromats, deuteranopes and protanopes served as observers. The appearances of 24 paper color samples from the OSA Uniform Color Scales were gauged under successively dimmer illuminations from 10 to 0.0003 Lux (1.0 to −3.5 log Lux). Triads of samples were chosen representing each of eight basic color categories; “red,” “pink,” “orange,” “yellow,” “green,” “blue,” “purple,” and “gray.” Samples within each triad varied in lightness. Observers sorted samples into groups that they could categorize with specific color names. Above −0.5 log Lux, the dichromatic and anomalous trichromatic observers sorted the samples into the original representative color groups, with some exceptions. At light levels where rods alone mediate vision, the color names assigned by the deuteranomalous trichromats were similar to the color names used by color normals; higher scotopic reflectance samples were classified as blue-green-grey and lower reflectance samples as red-orange. Color names reported by the dichromats at the dimmest light levels had extensive overlap in their sample scotopic lightness distributions. Dichromats did not assign scotopic color names based on the sample scotopic lightness, as did deuteranomalous trichromats and colour-normals. We reasoned that the reduction in color gamut that a dichromat experiences at photopic light levels leads to a limited association of rod color perception with objects differing in scotopic reflectance.

scholarly journals Wide-field motion tuning in nocturnal hawkmoths

2009 ◽  
Vol 277 (1683) ◽  
pp. 853-860 ◽  
Author(s):  
Jamie C. Theobald ◽  
Eric J. Warrant ◽  
David C. O'Carroll
Keyword(s):  
Manduca Sexta ◽  
Light Sensitivity ◽  
Wide Field ◽  
Visually Guided ◽  
Temporal Acuity ◽  
Low Light ◽  
Light Levels ◽  
Trade Offs ◽  
Spatial Frequencies ◽  
Deilephila Elpenor

Nocturnal hawkmoths are known for impressive visually guided behaviours in dim light, such as hovering while feeding from nectar-bearing flowers. This requires tight visual feedback to estimate and counter relative motion. Discrimination of low velocities, as required for stable hovering flight, is fundamentally limited by spatial resolution, yet in the evolution of eyes for nocturnal vision, maintenance of high spatial acuity compromises absolute sensitivity. To investigate these trade-offs, we compared responses of wide-field motion-sensitive neurons in three species of hawkmoth: Manduca sexta (a crepuscular hoverer), Deilephila elpenor (a fully nocturnal hoverer) and Acherontia atropos (a fully nocturnal hawkmoth that does not hover as it feeds uniquely from honey in bees' nests). We show that despite smaller eyes, the motion pathway of D. elpenor is tuned to higher spatial frequencies and lower temporal frequencies than A. atropos , consistent with D. elpenor 's need to detect low velocities for hovering. Acherontia atropos , however, presumably evolved low-light sensitivity without sacrificing temporal acuity. Manduca sexta , active at higher light levels, is tuned to the highest spatial frequencies of the three and temporal frequencies comparable with A. atropos . This yields similar tuning to low velocities as in D. elpenor , but with the advantage of shorter neural delays in processing motion.

Video microscopy in cell biology

1987 ◽  
Vol 45 ◽  
pp. 632-632
Author(s):  
Shinya Inoué
Keyword(s):  
Cell Biology ◽  
Random Noise ◽  
Polarized Light ◽  
Image Features ◽  
Depth Of Field ◽  
Video Enhancement ◽  
Low Light ◽  
Stereo Display ◽  
Light Levels ◽  
Laser Disk

The application of video improves the image quality and extends the applicability of the light microscope to an unprecedented degree. Rectified, Plan Apochromatic high N.A. objectives can be used at full condenser N.A. in polarized light, D.I.C., single sideband edge enhanced, brightfield, or fluorescence, etc., microscopy to yield exceptionally well-corrected images with high resolution and shallow depth of field. Contrast and image features barely visible through the ocular are clearly displayed after analog and digital video enhancement. Stationary image blemishes and random noise due to low light levels can both be removed, and either recorded- or current-dynamic images can be projected for pseudocolor, monochrome, and stereo display. Serial optical sections recorded on laser disk recorders can be played back at different through-focusing speeds, or as through-focal stereo pairs, to reveal extraordinarily fine cellular details. Several examples of such applications in cell biology will be demonstrated at the meetings.

Species variability in growth response to light across climatic regions in northwestern British Columbia

1998 ◽  
Vol 28 (6) ◽  
pp. 871-886 ◽  
Author(s):  
Elaine F Wright ◽  
K Dave Coates ◽  
Charles D Canham ◽  
Paula Bartemucci
Keyword(s):  
British Columbia ◽  
Shade Tolerance ◽  
Growth Response ◽  
High Light ◽  
Low Light ◽  
Climatic Regions ◽  
Light Levels ◽  
Tolerant Species ◽  
Trade Offs ◽  
Shade Tolerant Species

We characterize variation in radial and height growth of saplings of 11 tree species across a range of light levels in boreal, sub-boreal, subalpine, and temperate forests of northwestern British Columbia. Shade-tolerant species had the greatest response to an increase in light at low-light levels but had low asymptotic growth at high light. Shade-intolerant species had weaker responses to increases at low light but had the highest growth rates at high light. The effects of climate on intraspecific variation in sapling response to light were also related to shade tolerance: across different climatic regions, the most shade-tolerant species varied in their response to low-light but not high light, while shade-intolerant species varied only in their high-light growth. Species with intermediate shade tolerance varied both their amplitude of growth at high light and the slope of the growth response at low light. Despite the interspecific trade-offs between high- and low-light growth, there was a striking degree of overlap in the light response curves for the component species in virtually all of the climatic regions. Successional dynamics in these forests appear to be more strongly governed by interspecific variation in sapling survival than growth.

Electronic aids to night vision

1971 ◽  
Vol 269 (1196) ◽  
pp. 233-263 ◽  
Keyword(s):  
Image Intensifier ◽  
Night Vision ◽  
Low Light ◽  
Significant Component ◽  
Image Detector ◽  
Statistical Fluctuations ◽  
Light Levels ◽  
Different Types ◽  
Physical Limitations ◽  
Remote Viewing

The human eye is a very sensitive and versatile image detector, but has a number of physical limitations. The most important of these at very low light levels is the restriction in sensitivity resulting from the statistical fluctuations in the numbers of detected photons. It is shown how electronic image intensifies can provide a fundamental improvement in this situation by capturing a larger fraction of the available photons and using these more efficiently. The important parameters of such instruments are discussed, together with the principles of operation of their most significant component: the image intensifier tube. This is followed by a more detailed discussion of the possible performance of night vision equipments based on different types of tube, both for direct and remote viewing applications.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

1997 ◽  
Vol 75 (9) ◽  
pp. 1424-1435 ◽  
Author(s):  
D. Mailly ◽  
J. P. Kimmins
Keyword(s):  
Leaf Morphology ◽  
Biomass Accumulation ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Low Light ◽  
Growing Seasons ◽  
Light Levels ◽  
Light Gradient ◽  
Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

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