scholarly journals The remarkable visual capacities of nocturnal insects: vision at the limits with small eyes and tiny brains

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160063 ◽  
Author(s):  
Eric J. Warrant
Keyword(s):  
Temporal Summation ◽  
Optic Lobe ◽  
Night Vision ◽  
Visual Signals ◽  
Compound Eyes ◽  
Begging The Question ◽  
Light Levels ◽  
Dim Light ◽  
Control Flight ◽  
Light Capture

Nocturnal insects have evolved remarkable visual capacities, despite small eyes and tiny brains. They can see colour, control flight and land, react to faint movements in their environment, navigate using dim celestial cues and find their way home after a long and tortuous foraging trip using learned visual landmarks. These impressive visual abilities occur at light levels when only a trickle of photons are being absorbed by each photoreceptor, begging the question of how the visual system nonetheless generates the reliable signals needed to steer behaviour. In this review, I attempt to provide an answer to this question. Part of the answer lies in their compound eyes, which maximize light capture. Part lies in the slow responses and high gains of their photoreceptors, which improve the reliability of visual signals. And a very large part lies in the spatial and temporal summation of these signals in the optic lobe, a strategy that substantially enhances contrast sensitivity in dim light and allows nocturnal insects to see a brighter world, albeit a slower and coarser one. What is abundantly clear, however, is that during their evolution insects have overcome several serious potential visual limitations, endowing them with truly extraordinary night vision. This article is part of the themed issue ‘Vision in dim light’.

Neural Image Enhancement Allows Honeybees to See at Night

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 37-37 ◽  
Author(s):  
E J Warrant ◽  
T Porombka ◽  
W H Kirchner
Keyword(s):  
Spatial Resolution ◽  
Life Style ◽  
Theoretical Calculations ◽  
Optical Design ◽  
Neural Mechanisms ◽  
Visual Performance ◽  
Compound Eyes ◽  
Nocturnal Activity ◽  
Dim Light ◽  
Light Capture

The optical design of most insect apposition compound eyes should restrict activity to daylight because at night the tiny lenses of the isolated ommatidia cannot collect sufficient light. However, several bee species have adopted nocturnal activity, taking advantage of the benefits of night foraging. By measuring behavioural visual performance in honeybees, we show that insects can possess better spatial resolution in dim light than the optics and physiology of their apposition eyes suggest, implying the presence of higher neural mechanisms which enhance vision at night. Theoretical calculations reveal that honeybees improve light capture at night by neurally summing photons in space and time. Even though summation compromises both spatial and temporal resolution, the improved photon capture enhances vision sufficiently for bees to discriminate coarse images in moonlight. This explains how bees and many other insects can adopt a nocturnal life style despite having an eye design typical of a day-active insect.

scholarly journals Characterization of a reduced-eye mutant of the grasshopper, Melanoplus sanguinipes

Development ◽  
1984 ◽  
Vol 83 (1) ◽  
pp. 189-211
Author(s):  
D. J. Emery ◽  
K. A. Bell ◽  
W. Chapco ◽  
J. D. Steeves
Keyword(s):  
Compound Eye ◽  
Optic Lobe ◽  
Compound Eyes ◽  
Movement Detector ◽  
Melanoplus Sanguinipes ◽  
Optic Chiasma ◽  
Morphological Alterations ◽  
Tactile Stimuli ◽  
Normal Manner ◽  
Contralateral Movement

A reduced-eye (re) mutant grasshopper of Melanoplus sanguinipes has been characterized by small flat compound eyes lacking facets, no lateral ocelli and only a remnant of the median ocellus. The re grasshoppers walk, jump, fly and feed in a normal manner, but do not respond to visual and auditory stimuli, suggesting they may be blind and deaf. Extracellular recordings from the ventral nerve cord of re mutants verified the lack of neural activity in response to visual and auditory inputs, yet the mutants detected mechanical and tactile stimuli. Electroretinograms implied that a visual deficit may be within the photoreceptors of the compound eye. Histological examination of the compound eyes and ocelli indicated that the cells of the mutant compound eye incompletely differentiate. The optic lamina underlying the retina is missing, as is the outer optic chiasma. The medulla and lobula of the mutant optic lobe are present, however, the neuropil of the medulla lacks the characteristic axonal projection patterns of wild-type grasshoppers. The re grasshopper also lacks all ocellar nerves. Ocellar nerves are normally formed from processes of second order ocellar neurons (SONs), suggesting that if the mutant SONs are present within the protocerebrum, their morphology is drastically altered. Comparison of embryos and juvenile nymphs supports the suggestion that the alterations in the re visual system are the result of abnormal differentiation during development. Even though there is clear evidence of morphological alterations in second and third order optic lobe interneurons, one higher order visual interneuron of the midbrain, the descending contralateral movement detector (DCMD), has the same morphology as the DCMD in a wildtype brain. In this instance, the complete deprivation of the primary sensory input does not appear to alter cellular development.

scholarly journals ANALYSIS OF APPLICATION OF CONTEMPORARY NIGHT VISION GOGGLES ON THE BASIS OF ELECTRONIC-OPTICAL CONVERTER BY THE HELICOPTER CREWS. PROSPECTIVE HELICOPTER OPTOELECTRONIC SYSTEMS OF AERIAL RECONNAISSANCE/SURVEILLANCE

2020 ◽  
pp. 50-55
Author(s):  
O. Kuzmich ◽  
V. Kuznetsov ◽  
M. Andrushko
Keyword(s):  
Search And Rescue ◽  
Night Vision ◽  
Target Acquisition ◽  
Optoelectronic System ◽  
Night Time ◽  
Low Light ◽  
Spectral Bands ◽  
Light Levels ◽  
Aerial Reconnaissance ◽  
Optoelectronic Systems

The paper studies the matters of using of night vision goggles by the helicopter crews of the State Aviation of Ukraine. The analysis of the perspective systems that can replace night vision goggles based on electronic-optical converter and provide round-the-clock and all-weather flights, landing of the helicopter on unprepared and unlit areas in poor visibility was treated. Currently, the practice of using combat and transport helicopters involves their wider use in the night-time conditions (air warfare, delivery of goods, search-and-rescue operations). Due to low light levels, until recently, most night-time target acquisition tasks have been related with the necessities of providing the artificial target illumination, but in certain instances such illumination deteriorates visibility through an lighttight, phosphorescent atmospheric shells or it just can‟t be carried out. The need for a large number of channels included in the optoelectronic system, caused by the variety of tasks that are solved by it, as well as the imperfection of each individual channel. This forces them to be combined to improve the efficiency of the optoelectronic systems themselves, so that the disadvantages of one channel are offset by the advantages of another. In fact, it is only possible way to ensure the fulfilment of combat task by combining channels operating in different spectral bands in one scheme and by combining detection devices. It can be stated that, despite the undisputed advantages of optoelectronic systems as compared to night-vision goggles, in case of the selecting for installing on a helicopter of optoelectronic systems, it should take into account the much higher cost of optoelectronic systems compared with night-vision goggles. Therefore, the rationale for installing optoelectronic systems must be determined based on the scope of the executing tasks, which are to be conducted by a specific helicopter.

scholarly journals Light intensity regulates flower visitation in Neotropical nocturnal bees

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rodolfo Liporoni ◽  
Guaraci Duran Cordeiro ◽  
Paulo Inácio Prado ◽  
Clemens Schlindwein ◽  
Eric James Warrant ◽  
...  
Keyword(s):  
Light Intensity ◽  
Strong Dependence ◽  
Foraging Activity ◽  
Know How ◽  
Minimum Light ◽  
Light Levels ◽  
Flower Visitation ◽  
Five Factors ◽  
Main Variable ◽  
Dim Light

Abstract The foraging activity of diurnal bees often relies on flower availability, light intensity and temperature. We do not know how nocturnal bees, which fly at night and twilight, cope with these factors, especially as light levels vary considerably from night to day and from night to night due to moon phase and cloud cover. Given that bee apposition compound eyes function at their limits in dim light, we expect a strong dependence of foraging activity on light intensity in nocturnal bees. Besides being limited by minimum light levels to forage, nocturnal bees should also avoid foraging at brighter intensities, which bring increased competition with other bees. We investigated how five factors (light intensity, flower availability, temperature, humidity, and wind) affect flower visitation by Neotropical nocturnal bees in cambuci (Campomanesia phaea, Myrtaceae). We counted visits per minute over 30 nights in 33 cambuci trees. Light intensity was the main variable explaining flower visitation of nocturnal bees, which peaked at intermediate light levels occurring 25 min before sunrise. The minimum light intensity threshold to visit flowers was 0.00024 cd/m2. Our results highlight the dependence of these nocturnal insects on adequate light levels to explore resources.

scholarly journals Species and sex differences in eye morphometry and visual responsivity of two crepuscular sweat bee species (Megalopta spp., Hymenoptera: Halictidae)

2020 ◽  
Vol 130 (3) ◽  
pp. 533-544
Author(s):  
Beryl M Jones ◽  
Brett M Seymoure ◽  
Troy J Comi ◽  
Ellis R Loew
Keyword(s):  
Sympatric Species ◽  
Visual Sensitivity ◽  
Ecological Niches ◽  
Physiological Mechanisms ◽  
Light Levels ◽  
Morphological Adaptations ◽  
Dim Light ◽  
Future Work ◽  
Facet Size ◽  
Light Foraging

Abstract Visually dependent dim-light foraging has evolved repeatedly, broadening the ecological niches of some species. Many dim-light foraging lineages evolved from diurnal ancestors, requiring immense visual sensitivity increases to compensate for light levels a billion times dimmer than daylight. Some taxa, such as bees, are anatomically constrained by apposition compound eyes, which function well in daylight but not in starlight. Even with this constraint, the bee genus Megalopta has incredibly sensitive eyes, foraging in light levels up to nine orders of magnitude dimmer than diurnal relatives. Despite many behavioural studies, variation in visual sensitivity and eye morphometry has not been investigated within and across Megalopta species. Here we quantify external eye morphology (corneal area and facet size) for sympatric species of Megalopta, M. genalis and M. amoena, which forage during twilight. We use electroretinograms to show that males, despite being smaller than females, have equivalent visual sensitivity and increased retinal responsivity. Although males have relatively larger eyes compared with females, corneal area and facet size were not correlated with retinal responsivity, suggesting that males have additional non-morphological adaptations to increase retinal responsiveness. These findings provide the foundation for future work into the neural and physiological mechanisms that interface with morphology to influence visual sensitivity, with implications for understanding niche exploitation.

Alternatives to superposition images in clear-zone compound eyes

1971 ◽  
Vol 179 (1055) ◽  
pp. 97-124 ◽  
Keyword(s):  
Scattered Light ◽  
Retinula Cell ◽  
Compound Eyes ◽  
Clear Zone ◽  
Light Effect ◽  
Angular Sensitivity ◽  
Dim Light ◽  
Optical Pathway ◽  
Receptor Layer

The clear zone between the cones and the receptor layer in dark -adapted eyes of insects that are active in dim light has formerly been explained as a space to allow formation of a superposition image. Although erect images have been seen in Ephestia (Lepidoptera) and Hydrophilus (Coleoptera), new experiments show that they are accompanied by scattered light and that the angular sensitivity of individual receptors must be wide in the dark-adapted state. Alternatives to the superposition theory are examined, and it is concluded that in eyes with crystalline cones the clear zone (in general, in the numerous shapes and sizes of eyes of nocturnally active insects) enables light entering by many facets to sum upon individual receptors on the far side of the clear zone. In addition to the scattered light effect, light is carried across the clear zone in crystalline tracts or retinula cell columns, which provide a separate optical pathway for each ommatidium also in the light-adapted state.

scholarly journals Functional preservation and variation in the cone opsin genes of nocturnal tarsiers

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160075 ◽  
Author(s):  
Gillian L. Moritz ◽  
Perry S. Ong ◽  
George H. Perry ◽  
Nathaniel J. Dominy
Keyword(s):  
Colour Vision ◽  
Purifying Selection ◽  
Opsin Gene ◽  
Long Wavelength ◽  
Cone Opsin ◽  
Light Levels ◽  
Tarsius Bancanus ◽  
Dim Light ◽  
Two Stages ◽  
Functional Preservation

The short-wavelength sensitive (S-) opsin gene OPN1SW is pseudogenized in some nocturnal primates and retained in others, enabling dichromatic colour vision. Debate on the functional significance of this variation has focused on dark conditions, yet many nocturnal species initiate activity under dim (mesopic) light levels that can support colour vision. Tarsiers are nocturnal, twilight-active primates and exemplary visual predators; they also express different colour vision phenotypes, raising the possibility of discrete adaptations to mesopic conditions. To explore this premise, we conducted a field study in two stages. First, to estimate the level of functional constraint on colour vision, we sequenced OPN1SW in 12 wild-caught Philippine tarsiers ( Tarsius syrichta ). Second, to explore whether the dichromatic visual systems of Philippine and Bornean ( Tarsius bancanus ) tarsiers—which express alternate versions of the medium/long-wavelength sensitive (M/L-) opsin gene OPN1MW / OPN1LW —confer differential advantages specific to their respective habitats, we used twilight and moonlight conditions to model the visual contrasts of invertebrate prey. We detected a signature of purifying selection for OPN1SW , indicating that colour vision confers an adaptive advantage to tarsiers. However, this advantage extends to a relatively small proportion of prey–background contrasts, and mostly brown arthropod prey amid leaf litter. We also found that the colour vision of T. bancanus is advantageous for discriminating prey under twilight that is enriched in shorter (bluer) wavelengths, a plausible idiosyncrasy of understorey habitats in Borneo. This article is part of the themed issue ‘Vision in dim light’.

Nocturnal and diurnal foraging behaviour of brown bears (Ursus arctos) on a salmon stream in coastal British Columbia

2002 ◽  
Vol 80 (8) ◽  
pp. 1317-1322 ◽  
Author(s):  
D R Klinka ◽  
T E Reimchen
Keyword(s):  
British Columbia ◽  
Ursus Arctos ◽  
Night Vision ◽  
Black Bears ◽  
Spawning Migration ◽  
Brown Bears ◽  
Light Levels ◽  
Nocturnal Foraging ◽  
Consumption Rates ◽  
Coastal British Columbia

Brown bears (Ursus arctos) have been reported to be primarily diurnal throughout their range in North America. Recent studies of black bears during salmon migration indicate high levels of nocturnal foraging with high capture efficiencies during darkness. We investigated the extent of nocturnal foraging by brown bears during a salmon spawning migration at Knight Inlet in coastal British Columbia, using night-vision goggles. Adult brown bears were observed foraging equally during daylight and darkness, while adult females with cubs, as well as subadults, were most prevalent during daylight and twilight but uncommon during darkness. We observed a marginal trend of increased capture efficiency with reduced light levels (day, 20%; night, 36%) that was probably due to the reduced evasive behaviour of the salmon. Capture rates averaged 3.9 fish/h and differed among photic regimes (daylight, 2.1 fish/h; twilight, 4.3 fish/h; darkness, 8.3 fish/h). These results indicate that brown bears are highly successful during nocturnal foraging and exploit this period during spawning migration to maximize their consumption rates of an ephemeral resource.

scholarly journals Convergent Phenotypic Evolution of Rhodopsin for Dim-Light Sensing across Deep-Diving Vertebrates

2021 ◽  
Author(s):  
Yu Xia ◽  
Yimeng Cui ◽  
Aishan Wang ◽  
Fangnan Liu ◽  
Hai Chi ◽  
...  
Keyword(s):  
Release Rate ◽  
Light Level ◽  
Emperor Penguin ◽  
Light Sensing ◽  
Deep Diving ◽  
Light Levels ◽  
Critical Residue ◽  
Retinal Chromophore ◽  
Dim Light ◽  
Changing Light

Abstract Rhodopsin comprises an opsin attached to a retinal chromophore and is the only visual pigment conferring dim-light vision in vertebrates. On activation by photons, the retinal group becomes detached from the opsin, which is then inactive until it is recharged. Of all vertebrate species, those that dive face unique visual challenges, experiencing rapid decreases in light level and hunting in near darkness. Here, we combine sequence analyses with functional assays to show that the rhodopsin pigments of four divergent lineages of deep-diving vertebrates have undergone convergent increases in their retinal release rate. We compare gene sequences and detect parallel amino acids between penguins and diving mammals and perform mutagenesis to show that a single critical residue fully explains the observed increases in retinal release rate in both the emperor penguin and beaked whale. At the same time, we find that other shared sites have no significant effect on retinal release, implying that convergence does not always signify adaptive significance. We propose that accelerated retinal release confers rapid rhodopsin recharging, enabling the visual systems of diving species to adjust quickly to changing light levels as they descend through the water column. This contrasts with nocturnal species, where adaptation to darkness has been attributed to slower retinal release rates.

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