Hema Somanathan

Hema Somanathan
Indian Institute of Science Education and Research Thiruvananthapuram · School of Biology

PhD

About

57
Publications
17,308
Reads
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990
Citations
Additional affiliations
September 2009 - present
Indian Institute of Science Education and Research
Position
  • Professor (Assistant)

Publications

Publications (57)
Article
Full-text available
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. 10⁻² 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 i...
Article
Several interesting facets of bee behaviour have fascinated the human mind since historical times. Prominent amongst them is their interaction with flowers, symbolising the mutualistic nature of this relationship. In their search for flowers, bees are known to fly far from a central place—the nest or the hive—and employ multiple sensory systems, in...
Article
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 th...
Article
Full-text available
Touch-sensitive movement in stigmas of angiosperm flowers is a phenomenon observable in a timescale of seconds or minutes. Despite its early documentation in a small fraction of angiosperm species, touch-sensitive stigmas (TSS) have been little studied. In this review, we examine its occurrence in the angiosperm phylogeny and investigate associatio...
Article
Full-text available
Artificial lighting at nights (ALAN) affects behaviour in many animals, especially nocturnal species. However, its effect on frugivorous bats remains less explored, especially in the family Pteropodidae. Since they rely predominantly on vision and light-based cues, ALAN at roost sites could have consequences on their behaviour, activity, and the ec...
Article
Full-text available
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...
Article
Full-text available
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 b...
Article
Lunar eclipses are known to influence flight activity of tropical bats at foraging sites. However, little is known about the onset and offset of flight activity from the roost during lunar eclipses compared to other full moon nights. Emergence from and return to the roost were observed during a total lunar eclipse at a colony of the fruit bat Rouse...
Article
Full-text available
Animal personalities and behavioural syndromes have overarching implications for in�dividual survival, fitness and cooperative task participation. In social spiders, person�ality in boldness and aggression, and their association into behavioural syndromes, are thought to play a role in individual participation and task specialisation in collective...
Article
Full-text available
Animal architecture is diverse in form and structure, and extraordinarily intricate, often facilitated by the collective behaviour of several individuals. Social spider webs are one such example of animal architecture, robustly supporting the collective colony weight and intercepting prey for the entire colony. Thus, these webs are interesting, yet...
Article
Full-text available
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....
Article
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Predatory social wasps (Vespidae) are opportunistic, invasive and generalist foragers which employ distinct foraging strategies to meet the nutritional needs of adults and larvae. They are agile, visual predators that can hunt on the fly, scavenge on carcasses and collect tree sap, honeydew, nectar and sugars from rotting fruits. Their diverse fora...
Article
Full-text available
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 ro...
Article
Full-text available
Bees exemplify flights under bright sunlight. A few species across bee families have evolved nocturnality, displaying remarkable adaptations to overcome limitations of their daylight-suited apposition eyes. Phase inversion to nocturnality in a minority of bees that co-exist with diurnal bees provides a unique opportunity to study ecological benefit...
Article
Innate colour preferences in insects were long considered to be a non-flexible representation of a floral 'search image' guiding insects 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 pomon...
Article
Full-text available
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 viscoela...
Article
Dispersal is inherent to all living organisms. Sit-and-wait predators such as social spiders, with their sedentary lifestyles, present an intriguing and underexplored case to examine the proximate and ultimate reasons for dispersal. Though a reduction in dispersal tendencies must accompany the evolution of sociality in spiders, a fraction of the co...
Article
Full-text available
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 b...
Preprint
Full-text available
Spider silk possesses unique mechanical properties like large extensibility, high tensile strength, super-contractility, etc. Understanding these mechanical responses require 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 viscoelas...
Preprint
Full-text available
Spider silk possesses unique mechanical properties like large extensibility, high tensile strength, super-contractility, etc. Understanding these mechanical responses require 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 viscoelas...
Article
This article comments on: Jennifer L. Ison, Elizabeth S. L. Tuan, Matthew H. Koski, Jack S. Whalen and Laura F. Galloway. 2019. The role of pollinator preference in the maintenance of pollen colour variation. Annals of Botany 123(6): 951–960.
Article
Full-text available
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...
Article
Full-text available
In addition to sugars, nectar contains multiple nutrient compounds in varying concentrations, yet little is known of their effect on the reward properties of nectar and the resulting implications for insect behaviour. We examined the pre-ingestive responses of honeybees to sucrose solutions containing a mix of pollen compounds, the amino acids prol...
Article
Full-text available
Predators living in social groups often show consistent interindividual differences in prey capture behavior that may be linked to personality. Though personality predisposes individuals for certain behaviors, responses can also be influenced by context. Studies examining personality-dependent participation in prey capture have largely employed onl...
Article
Full-text available
Spontaneous colour preferences have been extensively studied in flower-visiting insects and such preferences exhibited by inexperienced flower-visiting insects are proposed to be adaptive by guiding them to the most rewarding flowers. Thus, spontaneous preferences are hypothesised to reflect the floral reward properties of the habitats in which the...
Article
Full-text available
Recent studies increasingly show that personality types in animals can vary with time. Personality types including boldness and aggression have been recently reported as important determinants of collective task performance, task specialisation and task proficiency in social spiders. These studies were performed in subadult and adult spiders and ov...
Article
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Myristica fatua is a dioecious specialist species restricted to the endangered, freshwater Myristica swamp forests in the Western Ghats, India. Earlier studies have alluded to pollination by deception in members of the Myristica genus, and thus we examined the pollination ecology comprising floral biology, flower production, flower visitors, and re...
Article
Ecologists are often required to accurately estimate the number of individuals residing in groups of variable sizes inside opaque shelters. Here, we have used X-rays as a non-destructive solution to this problem in social spiders which reside within collectively built opaque, silken, nest-like retreats. Social spiders are model systems for understa...
Article
Full-text available
Dispersal is important for the exploitation of new habitat and for outbreeding. A precondition for sociality in spiders is reduced dispersal propensity leading to largely inbred societies. Despite this, social spiders have been observed to disperse from natal colonies and form new or satellite colonies. Proximate factors shaping dispersal, inter-in...
Article
Full-text available
Dispersal is important for the exploitation of new habitat and for outbreeding. A precondition for sociality in spiders is reduced dispersal propensity leading to largely inbred societies. Despite this, social spiders have been observed to disperse from natal colonies and form new or satellite colonies. Proximate factors shaping dispersal, inter-in...
Article
Full-text available
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...
Article
Full-text available
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...
Data
Field experiments estimating the reaction of perching male X. tenuiscapa to stones thrown of known sizes. (XLSX)
Data
Mate location behaviour and associated morphological adaptations reported in male carpenter bees. (DOCX)
Article
Full-text available
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 fam-ilies with crassulacean acid metabolism (CAM),and 71% di...
Article
Full-text available
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 specialised habitats. In patchy, freshwater My...
Article
Batesian mimics typically dupe visual predators by resembling noxious or deadly model species. Ants are unpalatable and dangerous to many arthropod taxa, and are popular invertebrate models in mimicry studies. Ant mimicry by spiders, especially jumping spiders, has been studied and researchers have examined whether visual predators can distinguish...
Article
Full-text available
Behavioural differences between individuals that are consistent over time or across context are termed behavioural types or personalities. Social spiders are an emerging model for studying animal personality in social systems and our study was motivated by the lack of work examining the persistence of personality in the long-term and under changed...
Article
Full-text available
Communication of any sort is complex and communication between plants and animals is particularly so. Plant-pollinator mutualisms are amongst the most celebrated partnerships that have received a great deal of attention for many centuries. At the outset, most pollination studies focused on phenotypic matches and invoked co-evolution to explain plan...
Article
Full-text available
Communication of any sort is complex and communication between plants and animals is particularly so. Plant–pollinator mutualisms are amongst the most celebrated partnerships that have received a great deal of attention for many centuries. At the outset, most pollination studies focused on phenotypic matches and invoked co-evolution to explain plan...
Article
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 stu...
Article
Little is known about the role of crabs as seed dispersers and predators. Recently, there has been interest in understanding their influence on plant recruitment in coastal forests. Secondary seed removal by crabs in a swamp-specialist tree, Myristica fatua, was investigated in the rare and patchy freshwater Myristica swamps in the Western Ghats in...
Article
Full-text available
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...
Article
Full-text available
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...
Article
Honeybees, like humans and most other vertebrates, are colour-blind in dim light. Bees are primarily day-active and have apposition compound eyes, the typical eye design of diurnal insects. Most bees are trichromats with photoreceptors sensitive in the UV, blue and green [1]. While their diurnal colour vision was established almost 100 years ago, h...
Article
Full-text available
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...
Article
Full-text available
Les écureuils, particulièrement ceux des régions tempérées, font des provisions de graines dans des caches terrestres soit éparpillées ou dans un garde-manger. Les caches dans les arbres sont rares. Nous démontrons ici pour la première fois que l'écureuil géant de l'Inde (Ratufa indica) cache ses provisions de graines dans des nids dans les arbres,...
Article
Fruit set is pollen-limited in the self-incompatible tree Heterophragma quadriloculare (Bignoniaceae), pollinated by long-distance flying carpenter bees, and in the self-compatible shrub Lasiosiphon eriocephalus (Thymdeaceae), pollinated by weak-flying, sedentary beetles. We studied a single H. quadriloculare population over high and low flowering...
Article
We provide the first data on nocturnal pollination by bees. Heterophragma quadriloculare is a self–incompatible hermaphroditic tree solely pollinated at night by the carpenter bee Xylocopa (Mesotrichia) tenuiscapa Westwood, whose pollinating flights were lunar insensitive and unaffected by low nighttime temperatures (2–l4 ° C). The number of carpen...
Article
The population structure of three dioecious species, Diospyros montana, Diospyros sylvatica and Garcinia talbotii was studied in a seasonal cloud forest in the Western Ghats of India. In an undisturbed, natural population of D. montana, female fecundity was not significantly influenced by distance to neighbours or by flower numbers on neighbours. I...

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