32 results on '"Somanathan, H"'
Search Results
2. Migration in honey bees
- Author
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Vijayan, S. and Somanathan, H.
- Published
- 2023
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Catalog
3. Visual associative learning and olfactory preferences of the greater banded hornet, Vespa tropica
- Author
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Balamurali, G. S., Reshnuraj, R. S., Johnson, J., Kodandaramaiah, U., and Somanathan, H.
- Published
- 2021
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4. A matter of taste: the adverse effect of pollen compounds on the pre-ingestive gustatory experience of sugar solutions for honeybees
- Author
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Nicholls, E., Krishna, S., Wright, O., Stabler, D., Krefft, A., Somanathan, H., and Hempel de Ibarra, N.
- Published
- 2019
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5. Correction to: Visual associative learning and olfactory preferences of the greater banded hornet, Vespa tropica
- Author
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Balamurali, G. S., Reshnuraj, R. S., Johnson, J., Kodandaramaiah, U., and Somanathan, H.
- Published
- 2021
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6. Migration in honey bees
- Author
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Vijayan, S., primary and Somanathan, H., additional
- Published
- 2022
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- View/download PDF
7. Cold case: The disappearance of Egypt bee virus, a fourth distinct master strain of deformed wing virus linked to honeybee mortality in 1970’s Egypt
- Author
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de Miranda, JR, Brettell, LE, Chejanovsky, N, Childers, AK, Dalmon, A, Deboutte, W, de Graaf, DC, Doublet, V, Gebremedhn, H, Genersch, E, Gisder, S, Granberg, F, Haddad, NJ, Kaden, R, Manley, R, Matthijnssens, J, Meeus, I, Migdadi, H, Milbrath, MO, Mondet, F, Remnant, EJ, Roberts, JMK, Ryabov, EV, Sela, N, Smagghe, G, Somanathan, H, Wilfert, L, Wright, ON, Martin, SJ, and Ball, BV more...
- Subjects
600 Technik, Medizin, angewandte Wissenschaften::630 Landwirtschaft::630 Landwirtschaft und verwandte Bereiche ,Varroidae ,Honeybee ,Short Report ,Western blot ,Infectious and parasitic diseases ,RC109-216 ,Deformed wing virus ,RECOMBINANTS ,Zoologi ,SEQUENCE ,qx_565 ,Virology ,Genetics ,Animals ,RNA Viruses ,Genetik ,PARASITE ,Bioinformatic ,Science & Technology ,qx_4 ,screening ,DNA Viruses ,Biology and Life Sciences ,RNA sequencing ,Bees ,READ ALIGNMENT ,PICORNA-LIKE VIRUS ,Infectious Diseases ,qx_20 ,VARROA-DESTRUCTOR ,APIS-MELLIFERA ,Varroa destructor ,Master strain ,Bioinformatic screening ,RNA ,Egypt ,Apis mellifera ,Zoology ,Life Sciences & Biomedicine ,Egypt bee virus - Abstract
In 1977, a sample of diseased adult honeybees (Apis mellifera) from Egypt was found to contain large amounts of a previously unknown virus, Egypt bee virus, which was subsequently shown to be serologically related to deformed wing virus (DWV). By sequencing the original isolate, we demonstrate that Egypt bee virus is in fact a fourth unique, major variant of DWV (DWV-D): more closely related to DWV-C than to either DWV-A or DWV-B. DWV-A and DWV-B are the most common DWV variants worldwide due to their close relationship and transmission by Varroa destructor. However, we could not find any trace of DWV-D in several hundred RNA sequencing libraries from a worldwide selection of honeybee, varroa and bumblebee samples. This means that DWV-D has either become extinct, been replaced by other DWV variants better adapted to varroa-mediated transmission, or persists only in a narrow geographic or host range, isolated from common bee and beekeeping trade routes. Supplementary Information The online version contains supplementary material available at 10.1186/s12985-022-01740-2. more...
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- 2022
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8. Does neighborhood floral display matter? Fruit set in carpenter bee-pollinated Heterophragma quadriloculare and beetle-pollinated Lasiosiphon eriocephalus
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Somanathan, H., Borges, R. M., and Srinivasa Chakravarthy
- Subjects
Ecology, Evolution, Behavior and Systematics
9. Why diversity matters for understanding the visual ecology and behaviour of bees.
- Author
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Somanathan H
- Subjects
- Animals, Bees physiology, Ecosystem, Biodiversity, Visual Perception, Behavior, Animal physiology
- Abstract
Two bee species, the European honeybee and the buff-tailed bumblebee, are well-developed models of visual behaviour and ecology. How representative of bees across phylogeny and geography are these two species? Bee sensory systems likely differ between temperate and tropical species due to differences in the intensity or the types of selection pressures. Differences in temperate and tropical floral diversity, abundance and seasonality can influence sensory adaptations and behaviours. Niche partitioning in the speciose tropics along the microhabitat and temporal axes is increasingly reported to involve special visual adaptations in bees. Inclusive approaches encompassing other bee species and building on lessons from the 'model' bees will inform how ecology shapes bee senses, and, in turn, the structure of plant-bee mutualisms., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.) more...
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- 2024
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10. Dim-light colour vision in the facultatively nocturnal Asian giant honeybee, Apis dorsata .
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Vijayan S, Balamurali GS, Johnson J, Kelber A, Warrant EJ, and Somanathan H
- Subjects
- Bees, Animals, Species Specificity, Light, Adaptation, Physiological, Color Vision
- Abstract
We discovered nocturnal colour vision in the Asian giant honeybee Apis dorsata- a facultatively nocturnal species - at mesopic light intensities, down to half-moon light levels (approx. 10
ipt>-2 cd m -2 ). The visual threshold of nocturnality aligns with their reported nocturnal activity down to the same light levels. Nocturnal colour vision in A. dorsata is interesting because, despite being primarily diurnal, its colour vision capabilities extend into dim light, while the 'model' European honeybee Apis mellifera is reported to be colour-blind at twilight. By employing behavioural experiments with naturally nesting A. dorsata colonies, we show discrimination of the trained colour from other stimuli during the day, and significantly, even at night. Nocturnal colour vision in bees has so far only been reported in the obligately nocturnal carpenter bee Xylocopa tranquebarica. The discovery of colour vision in these two bee species, despite differences in the extent of their nocturnality and the limitations of their apposition compound eye optics, opens avenues for future studies on visual adaptations for dim-light colour vision, their role in pollination of flowers at night, and the effect of light pollution on nocturnal activity in A. dorsata, a ubiquitous pollinator in natural, agricultural and urban habitats in the Asian tropics and sub-tropics. more...- Published
- 2023
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11. Home ranges, directionality and the influence of moon phases on the movement ecology of Indian flying fox males in southern India.
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Murugavel B, Kandula S, Somanathan H, and Kelber A
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- Male, Animals, Humans, Moon, India, Homing Behavior, Chiroptera
- Abstract
Flying foxes of the genus Pteropus are amongst the largest fruit bats and potential long-range pollinators and seed dispersers in the paleotropics. Pteropus giganteus (currently P. medius) is the only flying fox that is distributed throughout the Indian mainland, including in urban and rural areas. Using GPS telemetry, we mapped the home ranges and examined flight patterns in P. giganteus males across moon phases in a semi-urban landscape in southern India. Home range differed between the tracked males (n=4), likely due to differences in their experience in the landscape. We found that nightly time spent outside the roost, distance commuted and the number of sites visited by tracked individuals did not differ significantly between moon phases. In 61% of total tracked nights across bats, the first foraging site was within 45˚ of the emergence direction. At the colony-level, scan-based observations showed emergence flights were mostly in the northeast (27%), west (22%) and southwest (19%) directions that could potentially be related to the distribution of foraging resources. The movement ecology of fruit bats in relation to the pollination and seed dispersal services they provide requires to be investigated in future studies. This article has an associated First Person interview with the first author of the paper., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.) more...
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- 2023
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12. Retinal Ganglion Cell Topography and Spatial Resolution in Three Indian Pteropodid Bats.
- Author
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Murugavel B, Mitkus M, Somanathan H, and Kelber A
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- Animals, Ecosystem, Retina, Visual Acuity, Retinal Ganglion Cells, Chiroptera
- Abstract
Pteropodidae is the only phytophagous bat family that predominantly depends on visual and olfactory cues for orientation and foraging. During daytime, pteropodids of different species roost in sites with varying light exposure. Pteropodids have larger eyes relative to body size than insectivorous bats. Retinal topography has been studied in less than 10% of the approximately 200 pteropodid species, a behavioural estimation of spatial resolution is available only for Pteropus giganteus, and little is known about the relationship between their roost site preference and visual ecology. We present retinal ganglion cell topographic maps and anatomical estimates of spatial resolution in three southern Indian pteropodid species with different roosting preferences. Ganglion cell densities are between 1,000 and 2,000 cells/mm2 in the central retina and lower in the dorsal and ventral periphery. All three species have a temporal area in the retina with peak ganglion cell densities of 4,600-6,600 cells/mm2. As a result, the foliage-roosting Cynopterus sphinx and the cave-roosting Rousettus leschenaultii have similar anatomical resolution (2.7 and 2.8 cycles/degree, respectively). The anatomical estimate for the larger tree-roosting P. giganteus (4.0 cycles/degree) is higher than the spatial resolution determined earlier in behavioural tests. Like other pteropodids and unlike other vertebrates, all three species have choroidal papillae. Based on 15 pteropodid species studied to date, we find no relationship between roost type and eye size or visual acuity. For a general understanding of the sensory ecology of pteropodids that perform key ecosystem services in the tropics, it will be essential to study additional species., (© 2022 S. Karger AG, Basel.) more...
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- 2023
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13. An update on polyethylene and biodegradable plastic mulch films and their impact on the environment.
- Author
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Somanathan H, Sathasivam R, Sivaram S, Mariappan Kumaresan S, Muthuraman MS, and Park SU
- Subjects
- Agriculture methods, Fossil Fuels, Polyethylene, Soil, Soil Microbiology, Biodegradable Plastics
- Abstract
Many ways are being developed in the realm of agriculture to increase crop yield while inflicting minimal damage to the soil and environment. One among them is the application of agricultural, biodegradable mulch (BDM) films. Organic substances or synthetic materials are used for making mulches. Also, bio-based polymers derived from bacteria, microorganisms, or fossil fuels are used to make BDM films. BDM films are used in crop production because of their high agronomical advantages which lead to sustainable agriculture. These films are placed on the soil's surface, around the plants. Mulches help in conserving the moisture, control the temperature of the soil, control the growth of the weed, and help in the utilization of soil nutrients thus, overall enhancing the crop yield. The usage of plastic mulch in agriculture has expanded substantially all around the world, over the past ten years, this is because polyethylene films are cheaper, easily produced, highly flexible, and durable. However, the improper disposal of used plastic films has resulted in soil pollution and environmental contamination. Traditional mulches are replaced by BDM, which is a more environmentally friendly alternative. After being used, degradable mulch films could be tilled into the soil and are expected to disintegrate over time. This review focuses on the BDMs, their history, plastic mulches, how BDMs became an alternative source for plastic mulches, their composition, and also addresses their significance. In addition, we discuss the environmental impact of films, including how it alters the climate, soil, temperature, and weed management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.) more...
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- 2022
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14. Colour vision in nocturnal insects.
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Warrant E and Somanathan H
- Subjects
- Animals, Bees, Color Perception physiology, Ecosystem, Flowers, Insecta, Pollination, Color Vision, Lizards
- Abstract
The ability to see colour at night is known only from a handful of animals. First discovered in the elephant hawk moth Deilephila elpenor , nocturnal colour vision is now known from two other species of hawk moths, a single species of carpenter bee, a nocturnal gecko and two species of anurans. The reason for this rarity-particularly in vertebrates-is the immense challenge of achieving a sufficient visual signal-to-noise ratio to support colour discrimination in dim light. Although no less challenging for nocturnal insects, unique optical and neural adaptations permit reliable colour vision and colour constancy even in starlight. Using the well-studied Deilephila elpenor , we describe the visual light environment at night, the visual challenges that this environment imposes and the adaptations that have evolved to overcome them. We also explain the advantages of colour vision for nocturnal insects and its usefulness in discriminating night-opening flowers. Colour vision is probably widespread in nocturnal insects, particularly pollinators, where it is likely crucial for nocturnal pollination. This relatively poorly understood but vital ecosystem service is threatened from increasingly abundant and spectrally abnormal sources of anthropogenic light pollution, which can disrupt colour vision and thus the discrimination and pollination of flowers. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'. more...
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- 2022
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15. Defensive shimmering responses in Apis dorsata are triggered by dark stimuli moving against a bright background.
- Author
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Vijayan S, Warrant EJ, and Somanathan H
- Subjects
- Animals, Bees, Nesting Behavior, Predatory Behavior
- Abstract
Giant honeybees, including the open-nesting Asian giant honeybee Apis dorsata, display a spectacular collective defence behaviour - known as 'shimmering' - against predators, which is characterised by travelling waves generated by individual bees flipping their abdomens in a coordinated and sequential manner across the bee curtain. We examined whether shimmering is visually mediated by presenting moving stimuli of varying sizes and contrasts to the background (dark or light) in bright and dim ambient light conditions. Shimmering was strongest under bright ambient light, and its strength declined under dim light in this facultatively nocturnal bee. Apis dorsata shimmered only when presented with the darkest stimulus against a light background, but not when this condition was reversed (light stimulus against dark background). This response did not attenuate with repeated exposure to the stimuli, suggesting that shimmering behaviour does not undergo habituation. We suggest that this is an effective anti-predator strategy in open-nesting A. dorsata colonies which are exposed to high ambient light, as flying predators are more easily detected when they appear as dark moving objects against a bright sky. Moreover, the stimulus detection threshold (smallest visual angular size) is much smaller in this anti-predatory context (1.6-3.4 deg) than in the context of foraging (5.7 deg), indicating that ecological context affects the visual detection threshold., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.) more...
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- 2022
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16. Spatial resolution and sensitivity of the eyes of the stingless bee, Tetragonula iridipennis.
- Author
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Jezeera MA, Tichit P, Balamurali GS, Baird E, Kelber A, and Somanathan H
- Subjects
- Animals, Australia, Bees, Body Size, Vision, Ocular
- Abstract
Stingless bees are important pollinators in the tropics. The tremendous variation in body size makes them an excellent group to study how miniaturization affects vision and visual behaviours. Using direct measurements and micro-CT, we reconstructed the eye structure, estimated anatomical spatial resolution and optical sensitivity of the stingless bee Tetragonula iridipennis. T. iridipennis is similar in size to the Australian stingless bee Tetragonula carbonaria and is smaller than honeybees. It has correspondingly small eyes (area = 0.56 mm
2 ), few ommatidia (2451 ± 127), large inter-facet (3.0 ± 0.6°) and acceptance angles (2.8°). Theoretical estimates suggest that T. iridipennis has poorer spatial resolution (0.17 cycles degree-1 ) than honeybees, bumblebees, and T. carbonaria. Its optical sensitivity (0.08 µm2 sr), though higher than expected, is within the range of diurnal bees. This may provide them with greater contrast sensitivity, which is likely more relevant than the absolute sensitivity in this diurnal bee. Behaviourally determined detection thresholds for single targets using y-maze experiments were 11.5° for targets that provide chromatic contrast alone and 9.1° for targets providing chromatic and achromatic contrast. Further studies into microhabitat preferences and behaviour are required to understand how miniaturization influences its visual ecology., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.) more...- Published
- 2022
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17. Visual detection thresholds in the Asian honeybee, Apis cerana.
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Meena A, Kumar AMV, Balamurali GS, and Somanathan H
- Subjects
- Animals, Bees physiology, Visual Perception physiology
- Abstract
To understand how insect pollinators find flowers against complex backgrounds in diverse natural habitats, it is required to accurately estimate the thresholds for target detection. Detection thresholds for single targets vary between bee species and have been estimated in the Western honeybee, a species of bumblebee and in a stingless bee species. We estimated the angular range of detection for coloured targets in the Asian honeybee Apis cerana. Using a Y-maze experimental set up, we show that targets that provided both chromatic and green receptor contrast were detected at a minimum visual angle of 7.7°, while targets with only chromatic contrast were detected at a minimum angle of 13.2°. Our results thus provide a robust foundation for future studies on the visual ecology of bees in a comparative interspecific framework. more...
- Published
- 2021
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18. Light, flight and the night: effect of ambient light and moon phase on flight activity of pteropodid bats.
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Murugavel B, Kelber A, and Somanathan H
- Subjects
- Animals, Moon, Photoperiod, Species Specificity, Behavior, Animal physiology, Caves, Chiroptera physiology, Ecosystem, Flight, Animal physiology
- Abstract
Fruit-feeding pteropodid bats roost under varying light conditions. Some roost in trees with high exposure to daylight (> 1000 lx), while others roost in dark caves (< 0.1 lx). To understand the effect of ambient light intensity and moon phase on flight activity, we examined flight times across five lunar cycles in three pteropodid species whose roosts differ in daylight exposure. We found significant interspecific differences in flight emergence and termination times. All species initiated flights after sunset but Rousettus leschenaultii, which typically roosts in caves, delayed emergence (40 ± 11 min) more than the two tree-roosting species Pteropus giganteus (16 ± 6 min) and Cynopterus sphinx (19 ± 7 min). R. leschenaultii terminated flights earlier (30 ± 7 min before sunrise) than P. giganteus (11 ± 11 min) and C. sphinx (16 ± 10 min). All individuals from P. giganteus and C. sphinx roosts emerged within less than an hour, while emergence times were more spread out in the R. leschenaultii colony. Peak emergence times differed across moon phases in the cave-roosting R. leschenaultii but not in the other species. Flight activity in R. leschenaultii is restricted to comparatively lower light levels than the tree-roosting species. The observed interspecific differences suggest that bat species, sharing same landscapes may respond differently to light pollution. more...
- Published
- 2021
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19. Complex multi-modal sensory integration and context specificity in colour preferences of a pierid butterfly.
- Author
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Balamurali GS, Rose S, Somanathan H, and Kodandaramaiah U
- Subjects
- Animals, Color, Female, Flowers, Learning, Male, Odorants, Butterflies
- Abstract
Innate colour preferences in insects were long considered to be a non-flexible representation of a floral 'search image' guiding them to flowers during initial foraging trips. However, these colour preferences have recently been shown to be modulated by multi-sensory integration of information. Using experiments on the butterfly Catopsilia pomona (common emigrant), we demonstrate that cross-modal integration of information not only affects colour preferences but also colour learning, and in a sex-specific manner . We show that spontaneous colour preference in this species is sexually dimorphic, with males preferring both blue and yellow while females prefer yellow. With minimal training (two training sessions), both males and females learned to associate blue with reward, but females did not learn green. This suggests that the aversion to green, in the context of foraging, is stronger in females than in males, probably because green is used as a cue to find oviposition sites in butterflies. However, females learned green after extensive training (five training sessions). Intriguingly, when a floral odour was present along with green during training, female colour preference during the subsequent choice tests resembled their innate preference (preference for yellow). Our results show that multi-sensory integration of information can influence preference, sensory bias, learning and memory in butterflies, thus modulating their behaviour in a context-specific manner., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2020. Published by The Company of Biologists Ltd.) more...
- Published
- 2020
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20. Strain softening and stiffening responses of spider silk fibers probed using a Micro-Extension Rheometer.
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Dubey S, Joshi CH, Veer S, Uma D, Somanathan H, Majumdar S, and Pullarkat PA
- Subjects
- Animals, Elastic Modulus, Kinetics, Rheology, Spiders, Tensile Strength, Viscosity, Silk chemistry
- Abstract
Spider silk possesses unique mechanical properties like large extensibility, high tensile strength, super-contractility, etc. Understanding these mechanical responses requires characterization of the rheological properties of silk beyond the simple force-extension relations which are widely reported. Here we study the linear and non-linear viscoelastic properties of dragline silk obtained from social spider Stegodyphus sarasinorum using a Micro-Extension Rheometer that we have developed. Unlike continuous extension data, our technique allows for the probing of the viscoelastic response by applying small perturbations about sequentially increasing steady-state strain values. In addition, we extend our analysis to obtain the characteristic stress relaxation times and the frequency responses of the viscous and elastic moduli. Using these methods, we show that in a small strain regime (0-4%) dragline silk of social spiders shows a strain softening response followed by a strain stiffening response at higher strains (>4%). The stress relaxation time, on the other hand, increases monotonically with increasing strain for the entire range. We also show that the silk stiffens while ageing within the typical lifetime of a web. Our results demand the inclusion of the kinetics of domain unfolding and refolding in the existing models to account for the relaxation time behavior. more...
- Published
- 2020
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21. Spatial Vision and Visually Guided Behavior in Apidae.
- Author
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Kelber A and Somanathan H
- Abstract
The family Apidae, which is amongst the largest bee families, are important pollinators globally and have been well studied for their visual adaptations and visually guided behaviors. This review is a synthesis of what is known about their eyes and visual capabilities. There are many species-specific differences, however, the relationship between body size, eye size, resolution, and sensitivity shows common patterns. Salient differences between castes and sexes are evident in important visually guided behaviors such as nest defense and mate search. We highlight that Apis mellifera and Bombus terrestris are popular bee models employed in the majority of studies that have contributed immensely to our understanding vision in bees. However, other species, specifically the tropical and many non-social Apidae, merit further investigation for a better understanding of the influence of ecological conditions on the evolution of bee vision. more...
- Published
- 2019
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22. How are pollinators guided by colourful floral structures? A commentary on: 'The role of pollinator preference in the maintenance of pollen colour variation'.
- Author
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Hempel de Ibarra N and Somanathan H
- Subjects
- Color, Pollen, Pollination
- Published
- 2019
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23. Foraging strategies and physiological adaptations in large carpenter bees.
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Somanathan H, Saryan P, and Balamurali GS
- Subjects
- Animals, Adaptation, Physiological physiology, Bees physiology, Feeding Behavior physiology
- Abstract
Large carpenter bees are charismatic and ubiquitous flower visitors in the tropics and sub-tropics. Unlike honeybees and bumblebees that have been popular subjects of extensive studies on their neuroethology, behaviour and ecology, carpenter bees have received little attention. This review integrates what is known about their foraging behaviour as well as sensory, physiological and cognitive adaptations and is motivated by their versatility as flower visitors and pollinators. This is evident from their extremely generalist foraging and adeptness at handling diverse flower types as legitimate pollinators and as illegitimate nectar robbers. They purportedly use traplining to forage between isolated patches and are long-distance flyers over several kilometres suggesting well-developed spatial learning, route memory and navigational capabilities. They have a broad range of temperature tolerance and thermoregulatory capabilities which are likely employed in their forays into crepuscular and nocturnal time periods. Such temporal extensions into dim-light periods invoke a suite of visual adaptations in their apposition optics. Thus, we propose that carpenter bees are an excellent though understudied group for exploring the complex nature of plant-pollinator mutualisms from ecological and mechanistic perspectives. more...
- Published
- 2019
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24. A comparative analysis of colour preferences in temperate and tropical social bees.
- Author
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Balamurali GS, Nicholls E, Somanathan H, and Hempel de Ibarra N
- Subjects
- Animals, Learning, Species Specificity, Tropical Climate, Ultraviolet Rays, Bees physiology, Choice Behavior physiology, Color, Flowers physiology
- Abstract
The spontaneous occurrence of colour preferences without learning has been demonstrated in several insect species; however, the underlying mechanisms are still not understood. Here, we use a comparative approach to investigate spontaneous and learned colour preferences in foraging bees of two tropical and one temperate species. We hypothesised that tropical bees utilise different sets of plants and therefore might differ in their spontaneous colour preferences. We tested colour-naive bees and foragers from colonies that had been enclosed in large flight cages for a long time. Bees were shortly trained with triplets of neutral, UV-grey stimuli placed randomly at eight locations on a black training disk to induce foraging motivation. During unrewarded tests, the bees' responses to eight colours were video-recorded. Bees explored all colours and displayed an overall preference for colours dominated by long or short wavelengths, rather than a single colour stimulus. Naive Apis cerana and Bombus terrestris showed similar choices. Both inspected long-wavelength stimuli more than short-wavelength stimuli, whilst responses of the tropical stingless bee Tetragonula iridipennis differed, suggesting that resource partitioning could be a determinant of spontaneous colour preferences. Reward on an unsaturated yellow colour shifted the bees' preference curves as predicted, which is in line with previous findings that brief colour experience overrides the expression of spontaneous preferences. We conclude that rather than determining foraging behaviour in inflexible ways, spontaneous colour preferences vary depending on experimental settings and reflect potential biases in mechanisms of learning and decision-making in pollinating insects. more...
- Published
- 2018
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25. Visual Adaptations for Mate Detection in the Male Carpenter Bee Xylocopa tenuiscapa.
- Author
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Somanathan H, Borges RM, Warrant EJ, and Kelber A
- Subjects
- Animals, Female, Male, Sex Characteristics, Adaptation, Physiological, Bees physiology, Eye anatomy & histology, Sexual Behavior, Animal, Vision, Ocular
- Abstract
Sexual dimorphism in eye structure is attributed to sexual selection in animals that employ vision for locating mates. In many male insects, large eyes and eye regions of higher acuity are believed to facilitate the location of females. Here, we compare various features of male and female eyes in three sympatric carpenter bee species, which include two diurnal species (Xylocopa tenuiscapa and X. leucothorax) as well as a nocturnal species (X. tranquebarica). In X. tenuiscapa, males have larger eyes than females, while in the nocturnal X. tranquebarica, males have slightly smaller eyes and in X. leucothorax, the eyes are of similar size in both sexes. X. tenuiscapa males detect females by perching near nest sites (resource defence) or along fly-ways and other open areas with good visibility. Males of the other two species search for females by patrolling. We postulate that the larger eyes of male X. tenuiscapa are beneficial to their mode of mate detection since perching males may benefit from a larger visual area of high resolution detecting moving stimuli across the sky, and which may be germane to the more social and gregarious nesting behaviour of this species, compared to the other solitary bees. We tested the performance of the eyes of male X. tenuiscapa behaviourally and find that a perching male can detect a flying female at a distance of 20 m, which darkens the visual field of a single ommatidium by just 2%. This, together with the bee's high spatial resolution permits detection of moving stimuli at least as well or even better than achieved by honey bee drones., Competing Interests: The authors have declared that no competing interests exist. more...
- Published
- 2017
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26. Patterns and Processes in Nocturnal and Crepuscular Pollination Services.
- Author
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Borges RM, Somanathan H, and Kelber A
- Subjects
- Adaptation, Physiological, Animals, Climate, Ecosystem, Flight, Animal, Insecta classification, Magnoliopsida classification, Photoperiod, Plant Nectar physiology, Time Factors, Circadian Rhythm, Flowers physiology, Insecta physiology, Magnoliopsida physiology, Pollen physiology, Pollination
- Abstract
Night, dawn, and dusk have abiotic features that differ from the day. Illumination, wind speeds, turbulence, and temperatures are lower while humidity may be higher at night. Nocturnal pollination occurred in 30% of angiosperm families across 68% of orders, 97% of families with C3, two-thirds of families with crassulacean acid metabolism (CAM), and 71% dicot families with C4 photosynthesis. Despite its widespread occurence, nocturnal pollination occurs in more families with xerophytic adaptations than helophytes or mesophytes, suggesting that nocturnal flowering is primarily an adaptation to water stress since flowering is a water-intensive process. We propose the arid or water stress hypothesis for nocturnal flowering suggesting that plants facing water stress in a habitat (e.g., deserts) or a habitat stratum (e.g., upper canopy for epiphytes) gain a selective advantage by nocturnal flowering by reducing water loss through evapotranspiration, leading to larger flowers that provide more nectar or other resources, to support pollinators with higher rewards. Contrary to the wide taxonomic occurrence of nocturnal flowering, few animal taxa serve as nocturnal pollinators. We discuss the sensory and physiological abilities that enable pollinator movement, navigation, and detection of flowers within the nocturnal temporal niche and present a unified framework for investigation of nocturnal flowering and pollination. more...
- Published
- 2016
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27. Spatiotemporal strategies that facilitate recruitment in a habitat specialist tree species.
- Author
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Krishna S and Somanathan H
- Abstract
Our understanding of processes underlying plant recruitment emerges from species and habitats that are widely distributed at regional and global scales. However, the applicability of dispersal-recruitment models and the role of dispersal limitation versus microsite limitation have not been examined for specialized habitats. In patchy, freshwater Myristica swamp forests (Western Ghats, India), we examine the roles of primary seed dispersal, secondary seed removal and microsite suitability for the establishment of a swamp specialist tree, Myristica fatua We estimated primary seed shadows, performed secondary removal experiments and enumerated recruits in swamp sites. Steady-state fruiting was observed with the extended production (>7 months) of small numbers of fruits. Frugivores dropped most of the large and heavy seeds under parent crowns, while a few seeds were transported over short distances by hornbills. Seed placement experiments indicated that removal, germination and establishment were similar within swamp microsites, while seeds failed to survive in matrix habitats surrounding the swamp. Crabs, which were major secondary removers of M. fatua, did not alter the initial seed dispersal patterns substantially, which led to the retention of seeds within the swamp. Distribution of saplings and adults from previous seasons also suggest that dispersal-recruitment dynamics in the swamp specialist M. fatua did not strictly follow predictions of Janzen-Connell model while abiotic effects were significant. Large seeds, steady-state fruiting and small crop sizes may be significant selective forces facilitating escape from density and distance-dependent effects in space and time in specialist plant species such as M. fatua., (Published by Oxford University Press on behalf of the Annals of Botany Company.) more...
- Published
- 2016
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28. Motion cues improve the performance of harnessed bees in a colour learning task.
- Author
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Balamurali GS, Somanathan H, and Hempel de Ibarra N
- Subjects
- Animals, Conditioning, Classical physiology, Female, Lasers, Photic Stimulation, Time Factors, Bees physiology, Color, Cues, Learning physiology, Motion
- Abstract
The proboscis extension conditioning (PER) is a successful behavioural paradigm for studying sensory and learning mechanisms in bees. Whilst mainly used with olfactory and tactile stimuli, more recently reliable PER conditioning has been achieved with visual stimuli such as colours and looming stripes. However, the results reported in different studies vary quite strongly, and it remains controversially discussed how to best condition visual PER. It is particularly striking that visual PER leads to more limited performance as compared to visual conditioning of free-flying bees. It could be that visual PER learning is affected by the lack of movement and that the presence of visual motion cues could compensate for it. We tested whether bees would show differences in learning performances when conditioned either with a colour and motion stimulus in combination or with colour alone. Colour acquisition was improved in the presence of the motion stimulus. The result is consistent with the idea that visual learning might be tightly linked to movement in bees, given that they use vision predominantly during flight. Our results further confirm recent findings that successful visual PER conditioning in bees is achievable without obligatorily removing the antennae. more...
- Published
- 2015
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29. Resolution and sensitivity of the eyes of the Asian honeybees Apis florea, Apis cerana and Apis dorsata.
- Author
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Somanathan H, Warrant EJ, Borges RM, Wallén R, and Kelber A
- Subjects
- Adaptation, Physiological, Animals, Bees anatomy & histology, Body Size, Compound Eye, Arthropod anatomy & histology, Species Specificity, Visual Acuity, Bees physiology, Compound Eye, Arthropod physiology, Vision, Ocular physiology
- Abstract
Bees of the genus Apis are important foragers of nectar and pollen resources. Although the European honeybee, Apis mellifera, has been well studied with respect to its sensory abilities, learning behaviour and role as pollinators, much less is known about the other Apis species. We studied the anatomical spatial resolution and absolute sensitivity of the eyes of three sympatric species of Asian honeybees, Apis cerana, Apis florea and Apis dorsata and compared them with the eyes of A. mellifera. Of these four species, the giant honeybee A. dorsata (which forages during moonlit nights) has the lowest spatial resolution and the most sensitive eyes, followed by A. mellifera, A. cerana and the dwarf honeybee, A. florea (which has the smallest acceptance angles and the least sensitive eyes). Moreover, unlike the strictly diurnal A. cerana and A. florea, A. dorsata possess large ocelli, a feature that it shares with all dim-light bees. However, the eyes of the facultatively nocturnal A. dorsata are much less sensitive than those of known obligately nocturnal bees such as Megalopta genalis in Panama and Xylocopa tranquebarica in India. The differences in sensitivity between the eyes of A. dorsata and other strictly diurnal Apis species cannot alone explain why the former is able to fly, orient and forage at half-moon light levels. We assume that additional neuronal adaptations, as has been proposed for A. mellifera, M. genalis and X. tranquebarica, might exist in A. dorsata. more...
- Published
- 2009
- Full Text
- View/download PDF
30. Visual ecology of Indian carpenter bees II: adaptations of eyes and ocelli to nocturnal and diurnal lifestyles.
- Author
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Somanathan H, Kelber A, Borges RM, Wallén R, and Warrant EJ
- Subjects
- Animals, Flight, Animal, Bees anatomy & histology, Circadian Rhythm, Eye anatomy & histology, Vision, Ocular
- Abstract
Most bees are diurnal, with behaviour that is largely visually mediated, but several groups have made evolutionary shifts to nocturnality, despite having apposition compound eyes unsuited to vision in dim light. We compared the anatomy and optics of the apposition eyes and the ocelli of the nocturnal carpenter bee, Xylocopa tranquebarica, with two sympatric species, the strictly diurnal X. leucothorax and the occasionally crepuscular X. tenuiscapa. The ocelli of the nocturnal X. tranquebarica are unusually large (diameter ca. 1 mm) and poorly focussed. Moreover, their apposition eyes show specific visual adaptations for vision in dim light, including large size, large facets and very wide rhabdoms, which together make these eyes 9 times more sensitive than those of X. tenuiscapa and 27 times more sensitive than those of X. leucothorax. These differences in optical sensitivity are surprisingly small considering that X. tranquebarica can fly on moonless nights when background luminance is as low as 10(-5) cd m(-2), implying that this bee must employ additional visual strategies to forage and find its way back to the nest. These strategies may include photoreceptors with longer integration times and higher contrast gains as well as higher neural summation mechanisms for increasing visual reliability in dim light. more...
- Published
- 2009
- Full Text
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31. Nocturnal bees learn landmark colours in starlight.
- Author
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Somanathan H, Borges RM, Warrant EJ, and Kelber A
- Subjects
- Animals, Homing Behavior, Light, Bees physiology, Color Vision, Discrimination Learning, Night Vision
- Published
- 2008
- Full Text
- View/download PDF
32. Visual ecology of Indian carpenter bees I: light intensities and flight activity.
- Author
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Somanathan H, Borges RM, Warrant EJ, and Kelber A
- Subjects
- Adaptation, Physiological, Animals, Bees radiation effects, Circadian Rhythm physiology, Circadian Rhythm radiation effects, Compound Eye, Arthropod radiation effects, Darkness, Light, Motor Activity radiation effects, Sensory Thresholds physiology, Sensory Thresholds radiation effects, Species Specificity, Vision, Ocular radiation effects, Bees physiology, Compound Eye, Arthropod physiology, Flight, Animal physiology, Motor Activity physiology, Vision, Ocular physiology
- Abstract
Bees are mostly active during the daytime, but nocturnality has been reported in some bee families. We studied temporal flight activity in three species of carpenter bees (genus Xylocopa) in relation to light intensities. X. leucothorax is diurnal, X. tenuiscapa is largely diurnal being only occasionally crepuscular, while X. tranquebarica is truly nocturnal. Occasional forays into dim light by X. tenuiscapa are likely to be due to the availability of richly rewarding Heterophragma quadriloculare (Bignoniaceae) flowers, which open at night. X. tranquebarica can fly even during the moonless parts of nights when light intensities were lower than 10(-5) cd m(-2), which makes this species the only truly nocturnal bee known so far. Other known dim-light species fly during crepuscular or moonlit periods. We compare eye and body sizes with other known diurnal and dim-light bees. We conclude that while extremely large ocellar diameters, large eye size:body size ratio, large number of ommatidia and large ommatidial diameters are all adaptations to dim-light foraging, these alone do not sufficiently explain the flights of X. tranquebarica in extremely dim light. We hypothesise that additional adaptations must confer extreme nocturnality in X. tranquebarica. more...
- Published
- 2008
- Full Text
- View/download PDF
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