Ganapathy Marimuthu

Social entrainment of the circadian rhythm in the flight activity of the microchiropteran bat Hipposideros speoris

Summary1.We investigated the problem of how members of the microchiropteran bat species Hipposideros speoris that live in a true cave clock their flight activity rhythms in the absence of time cues.2.The bats become restless well in advance of sunset and then fly towards the cavemouth to sample light.3.We investigated whether each bat roosting 40 m from the cave entrance must sample outside light levels for itself in order to emerge at the appropriate time. Three captive bats were tested and each began activity when the conspecifics left the cave in the evenings.4.In another series of experiments a solitary bat was held captive in a solitary cave for 50 days and its circadian rhythm was recorded. In the absence of other conspecifics the circadian rhythm ‘free ran’ with a period shorter than 24 h.5.We concluded from the results of our studies that there exists a clear-cut case for social synchronization of the circadian rhythms of this cave-dwelling bat.

The use of acoustical cues for prey detection by the Indian False Vampire Bat,Megaderma lyra

Summary1.The response of the echolocating bat,Megaderma lyra, was tested to different kinds of prey in an outdoor cage. The bats caught larger flying insects (moths, beetles, grasshoppers, and cockroaches) on the wing and also picked up arthropods (solifugid spiders, beetles and cockroaches) and small vertebrates (mice, fishes, frogs and geckoes) from the ground. After touching the prey with the muzzle, the bats were able to differentiate between species. Scorpions and toads were not taken byM. lyra.2.In lighted and in dark conditions,M. lyra detected and caught prey only when it moved. Dead frogs briskly pulled over the floor were also detected and caught, whereas stationary dead frogs were disregarded by the bats (Table 1).3.When dead frogs were pulled over the watered surface of a glass plate to eliminate noises by motion, the motion no longer alarmed the bats. From the results of these experiments it was concluded thatM. lyra detects prey on the ground by listening to the noise of the moving target only, and not by echolocation (Table 1 C, Fig. 1). Furthermore,M. lyra were not attracted by frog calls.4.M. lyra differentiated between palatable frogs and non-palatable toads only after touching the prey with the muzzle.5.Experiments with freshly killed frogs coated with toad secretions or covered with toad skins indicate thatM. lyra differentiates between frogs and toads by chemical means. There was no evidence that these prey were differentiated by means of echolocation.

Hunting in unfamiliar space: echolocation in the Indian false vampire bat, Megaderma lyra, when gleaning prey

The literature suggests that in familiar laboratory settings, Indian false vampire bats (Megaderma lyra, family Megadermatidae) locate terrestrial prey with and without emitting echolocation calls in the dark and cease echolocating when simulated moonlit conditions presumably allow the use of vision. More recent laboratory-based research suggests that M. lyra uses echolocation throughout attacks but at emission rates much lower than those of other gleaning bats. We present data from wild-caught bats hunting for and capturing prey in unfamiliar conditions mimicking natural situations. By varying light level and substrate complexity we demonstrated that hunting M. lyra always emit echolocation calls and that emission patterns are the same regardless of light/substrate condition and similar to those of other wild-caught gleaning bats. Therefore, echoic information appears necessary for this species when hunting in unfamiliar situations, while, in the context of past research, echolocation may be supplanted by vision, spatial memory or both in familiar spaces.

Ontogenesis of tonotopy in inferior colliculus of a hipposiderid bat reveals postnatal shift in frequency-place code

SummaryThe postnatal development of midbrain tonotopy was investigated in the inferior colliculus (IC) of the south Indian CF-FM batHipposideros speoris. The developmental progress of the three-dimensional frequency representation was determined by systematic stereotaxic recordings of multiunit clusters from the 1st up to the 7th postnatal week. Additional developmental measures included the tuning characteristics of single units (Figs. 3f; 4f; 5f), the analysis of the vocalised pulse repertoire (Figs. 3e, 4e, 5e), and morphometric reconstructions of the brains of all experimental animals (Fig. 1).The maturation of auditory processing could be divided into two distinct, possibly overlapping developmental periods: First, up to the 5th week, the orderly tonotopy in the IC developed, beginning with the low frequency representation and progressively adding the high frequency representation. With regard to the topology of isofrequency sheets within the IC, maturation progresses from dorsolateral to ventromedial (Figs. 3c, 4c). At the end of this phase the entire IC becomes specialised for narrowly tuned and sensitive frequency processing. This includes the establishment of the ‘auditory fovea’, i.e. the extensive spatial representation of a narrow band of behaviorally relevant frequencies in the ventromedial part of the IC. In the 5th postnatal week the auditory fovea is concerned with frequencies from 100–118 kHz (Fig. 4c, d). During subsequent development, the frequency tuning of the auditory fovea increases by 20–25 kHz and finally attains the adult range of ca. 125–140 kHz. During this process, neither the bandwidth of the auditory fovea (15–20 kHz) nor the absolute sensitivity of its units (ca. 50 dB SPL) were changed. Further maturation occurred at the single unit level : the sharpness of frequency tuning increased from the 5th to the 7th postnatal weeks (Q-10-dB-values up to 30–60), and upper thresholds emerged (Figs. 4f, 5f).Although in the adult the frequency of the auditory fovea matches that of the vocalised pulses, none of the juvenile bats tested from the 5th to the 7th weeks showed such a frequency match between vocalisation and audition (Figs. 4e, 5e).The results show that postnatal maturation of audition in hipposiderid bats cannot be described by a model based on a single developmental parameter.

Nectar feeding and pollen carrying from Ceiba pentandra by pteropodid bats

Abstract We studied nectar-feeding behavior of 3 pteropodid bats under natural conditions. Cynopterus sphinx and Pteropus giganteus visited Ceiba pentandra trees throughout the night, whereas Rousettus leschenaulti visited only during early evening. Peak visits occurred at 2300 h for C. sphinx and 2000–2100 h for P. giganteus, coinciding with maximum nectar production and sugar concentration of floral resources. C. sphinx foraged at 6–10 m, R. leschenaulti at 10–18 m and P. giganteus at 15–20 m heights in the trees. Chemiluminescent-tagged C. sphinx foraged on nectar mostly in single trees until midnight and switched to 2–4 nearby trees later. We observed coats of pollen of C. pentandra on the abdomens, wings, and heads in 40% of C. sphinx captured in mist nets. Pollen loads on the abdomen were greater on males than on females. Our observations on R. leschenaulti and P. giganteus also showed adherence of pollen grains on their bodies. Presence of pollen grains on the bodies of these bats strongly suggests that they pollinate C. pentandra.

Seasonal Variation in the Diet of the Indian Pygmy Bat, Pipistrellus mimus, in Southern India

We evaluated seasonal dietary variation of the Indian pygmy bat, Pipistrellus mimus , from southern India, by collecting biweekly fecal samples from beneath a maternity roost for 1 year and comparing these samples with insects collected using a light trap on the same dates. Our analyses indicate that P. mimus fed on coleopterans (26.3% volume), dipterans (20.4%), homopterans (17.5%), lepidopterans (13.6%), formicids (10.5%), hemipterans (5.7%), and isopterans (5.1%) and thus are generalized feeders. One unidentified scarabaeid species made up much of the coleopteran material and was abundant in the diet of P. mimus from late April through late August. Formicid alates were consumed throughout the year but were especially important from late July through September. Isopteran alates were important in September and October. Relative proportions of insects that were eaten differed significantly from insects captured in a light trap. In other studies, investigators interpreted such differences as evidence of selection; however, we argue that most insect traps do not provide reliable data on availability and that bats may feed in other areas than where the insects are captured. Our results indicate that >20 fecal pellets are needed in any one sample to determine important dietary items eaten by this species, although this sampling protocol likely overlooks minor food items.

Effect of moonlight on the foraging behaviour of a megachiropteran bat Cynopterus sphinx

We studied the influence of moonlight upon the foraging activity pattern of the fruit bat Cynopterus sphinx. We observed the bats when foraging on the fruits of Calophyllum inophyllum and on the leaves of Mimusops elengi and Cassia fistula for 31, 27 and 28 days, respectively at the botanical garden in the Madurai Kamaraj University campus. The number of feeding bouts was recorded every hour between 18:00 and 05:00. A feeding bout involves a bat landing on the tree and collecting a part (or whole) of the fruit or a leaf. The total number of feeding bouts was negatively correlated with per cent moonlight each night. The number of feeding bouts decreased during the waxing phases of the moon. During the period of new moon the mean number of feeding bouts was significantly higher compared to the periods of other phases. During the first quarter and the last quarter phases, feeding occurred more during the dark part of the night, especially when the bats foraged upon M. elengi and C. fistula. While cloud cover enhanced the foraging activity, lightning and thunder suppressed it. Our study indicates that moonlight influences the foraging activity of C. sphinx.

TEMPORAL PATTERNS OF RESOURCE USE BY THE SHORT-NOSED FRUIT BAT, CYNOPTERUS SPHINX (MEGACHIROPTERA: PTEROPODIDAE)

Abstract The short-nosed fruit bat, Cynopterus sphinx (Megachiroptera: Pteropodidae), is a common plant-visiting bat that is widely distributed throughout the Indomalayan region. We quantified foraging behavior of C. sphinx as individuals fed on fruits of Annona squamosa, leaves of Cassia fistula and Mimusops elengi, and fruits and leaves of Coccinia indica. After making several circling flights and engaging in brief hovering bouts, bats typically land directly on a single fruit and remove all or part of it with the mouth. In contrast, individuals remove leaves from trees during flight, without landing or hovering. C. sphinx typically transports fruits and leaves to feeding roosts where it extracts soluble contents and expels fibrous spats beneath day and feeding roosts. This bat consumes mostly fruits upon emergence from day roosts and feeds on leaves later in the night. These temporal differences in nightly foraging behavior may reflect the higher water and carbohydrate (energy) contents of fruits, compared with leaves, and help sustain flight activity throughout the night.

Postnatal development in the Indian short-nosed fruit bat Cynopterus sphinx: growth rate and age estimation

We studied the patterns of postnatal growth and changes in length of forearm, body mass and total epiphyseal gap in the captive free-flying short-nosed fruit bat Cynopterus sphinx. At birth young were altricial. By day five, their eyes had opened, and the pinnae become unfolded between sixth and ninth day of age. At the age of three days, the mean forearm length and body mass were equivalent to 42.2% and 18.2%, respectively of the values of postpartum females. The length of forearm increased linearly until 36 days and attained 94.1% of mean forearm length of postpartum females at the age of 219 days. Body mass of pups increased linearly until 60 days and attained 72.7% of mean mass of postpartum females at the age of 219 days. The length of total epiphyseal gap of fourth metacarpal-phalangeal joint increased until 15 days of age and subsequently decreased linearly, and closed at about 60 days of age. The age predicting equation based on the length of forearm is valid when its dimensions are between 29.4 mm and 52.4 mm (3–36 days of age). Similar equation but based on the length of total epiphyseal gap is valid when its dimensions range from 47.0 µm to 6.0 µm (15–60 days of age). Growth patterns of forearm length and body mass were best described by the logistic and Gompertz nonlinear growth models, respectively. There was no significant difference in the growth patterns of body mass and length of total epiphyseal gap with reference to lengths of forearm of captive and wild-grown pups.

Association of Per3 length polymorphism with bipolar I disorder and schizophrenia

Background Sleep–wake disturbances have frequently been reported in bipolar disorder and schizophrenia, and are considered to be caused by an underlying circadian rhythm disorder. The study presented here was designed to investigate the existence of Per3 polymorphism in bipolar disorder type I (BD-I) and schizophrenic patients in South India. Methods Blood samples were collected from 311 BD-I patients, 293 schizophrenia patients, and 346 age- and sex-matched normal controls. Per3 genotyping was performed on DNA by polymerase chain reaction using specific primers. Results An increased prevalence of five repeat homozygotes was seen in BD-I patients as compared with healthy controls (odds ratio =1.72 [95% confidence interval: 1.08–2.76, P=0.02]). In BD-I patients, the frequency of the five repeat allele was higher (allele frequency =0.41), and that of the four repeat allele lower (allele frequency =0.36) (χ2=4.634; P<0.03) than in the control group. No significant association was observed in the allele frequencies of four and five repeat alleles in schizophrenia patients when compared with controls. Conclusion The occurrence of the five repeat allele of Per3 may be a risk factor for BD-I onset in this ethnic group.