RAGHURAM H
@americancollege.edu.in
Assistant Professor in Zoology
The American College, Madurai
EDUCATION
M.Sc. (Integrated Biology), Ph.D. (Biology)
RESEARCH INTERESTS
Behavioural Ecology, Animal Behaviour, Bioacoustics
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Sahayanathan Gracy Jenifer, Ganapathy Marimuthu, and Hanumanthan Raghuram
Wiley
Chitinases are capable of hydrolyzing insoluble chitin into its oligo and monomeric parts and have received increased consideration because of their wide scope of biotechnological applications. The commercial application of microbial chitinase is appealing due to the relative ease of enormous production and to meet the current world demands. This study aimed at isolation and characterization of chitin degrading bacteria from the gut of Indian tropical insectivorous black‐bearded tomb bat, Taphozous melanopogon. The isolated bacterial strains were characterized through biochemical analysis and nucleic acid‐based approaches by 16S ribosomal RNA amplification and sequencing. The BLAST (Basic Local Alignment Search Tool) and phylogenetic analysis showed that the bacterial strain exhibited a close resemblance with Escherichia fergusonii. The chitinolytic activity of the E. fergusonii AMC01 was identified using supplemented colloidal chitin with agar medium. Compiling all, these findings would facilitate in constructing a database and presumably promote the use of E. fergusonii AMC01 as an efficient strain for the chitinase production.
A. F. P. Allwin Mabes Raj, K. Emmanuvel Rajan, and H. Raghuram
Current Science Association
Valliyappan Mahandran, Hanumanthan Raghuram, and Parthasarathy Thiruchenthil Nathan
Springer Science and Business Media LLC
Geophagy has been reported in many mammals and birds. However, in pteropodid bats, this behaviour has not been reported. Here, we document geophagy behaviour by the pteropodid bat, Cynopterus sphinx, during foraging in the fruiting trees of Madhuca latifolia (Sapotaceae). These bats removed single fruits from the foraging tree and carried it to the feeding roost for consumption. At around 1900 h, we observed three individuals of C. sphinx gleaning over the ground surface by circling flights. The bats landed with their wings spread apart and started licking the soil with head movements. Their ventral body surface rested completely on the ground while consuming the soil. A total of 91 feeding bouts of soil consumption were recorded within 1 h; however, thereafter, this behaviour was not observed. In order to understand the function of geophagy, we quantitatively analysed the composition of minerals in the soil, as well as in the M. latifolia fruits (partially ripe) along with its secondary metabolites from the study site. Our results revealed that the partially ripe fruits contained high levels of secondary metabolites (alkaloids, tannins, coumarins and saponins). The soil contained higher levels of Mg, Ca, Fe, Na and K minerals than the fruits. These findings suggest that bats may gain essential minerals that are low in their fruit diet by consuming soil. In addition, the observed minerals that play a role in detoxification of the secondary metabolites present in the partially ripe fruits that might be detrimental to the consuming bats. Frugivory, nectarivory and folivory are well understood in C. sphinx; however, geophagy behaviour has not been reported in this species so far. This may represent an ‘adaptive behavioural plasticity’ in the foraging behaviour of the observed C. sphinx population.
Subramanian Mariappan, Wieslaw Bogdanowicz, Hanumanthan Raghuram, Ganapathy Marimuthu, and Koilmani Emmanuvel Rajan
Springer Science and Business Media LLC
We conducted a set of playback experiments aimed at understanding whether distress-call structure in the greater short-nosed fruit bat Cynopterus sphinx is specific in encoding information relating to stress that attracts conspecifics. We tested the specificity by playing their distress call and its modified version at a foraging site for free-ranging bats, as well as under captive conditions involving either a small group or individuals. In a separate playback experiment, bats showed a significantly greater response when the natural call as opposed to a modified call was played back to captive as well as free-ranging bats at the foraging site. Under captive conditions, bats showed less of a response to the playback of distress calls when in a group than when alone. We subsequently found that tyrosine hydroxylase (TH) and its transcription factor—nuclear receptor related factor 1 (Nurr-1); and the dopamine transporter (DAT) and its receptor (D1DR) were elevated significantly in the amygdala of bats both emitting and responding to a distress call, but not in the case of bats responding to the modified call. These results suggest that distress-call structure encodes information on the state of stress that is capable of being conveyed to conspecifics.
Hanumanthan Raghuram, Rittik Deb, Diptarup Nandi, and Rohini Balakrishnan
The Royal Society
Males that produce conspicuous mate attraction signals are often at high risk of predation from eavesdropping predators. Females of such species typically search for signalling males and their higher motility may also place them at risk. The relative predation risk faced by males and females in the context of mate-finding using long-distance signals has rarely been investigated. In this study, we show, using a combination of diet analysis and behavioural experiments, that katydid females, who do not produce acoustic signals, are at higher risk of predation from a major bat predator, Megaderma spasma , than calling males. Female katydids were represented in much higher numbers than males in the culled remains beneath roosts of M. spasma . Playback experiments using katydid calls revealed that male calls were approached in only about one-third of the trials overall, whereas tethered, flying katydids were always approached and attacked. Our results question the idea that necessary costs of mate-finding, including risk of predation, are higher in signalling males than in searching females.
Ambigapathy Ganesh, Hanumanthan Raghuram, Parthasarathy T. Nathan, Ganapathy Marimuthu, and Koilmani Emmanuvel Rajan
Springer Science and Business Media LLC
Individuals in distress emit audible vocalizations to either warn or inform conspecifics. The Indian short-nosed fruit bat, Cynopterus sphinx, emits distress calls soon after becoming entangled in mist nets, which appear to attract conspecifics. Phase I of these distress calls is longer and louder, and includes a secondary peak, compared to phase II. Activity-dependent expression of egr-1 was examined in free-ranging C. sphinx following the emissions and responses to a distress call. We found that the level of expression of egr-1 was higher in bats that emitted a distress call, in adults that responded, and in pups than in silent bats. Up-regulated cDNA was amplified to identify the target gene (TOE1) of the protein Egr-1. The observed expression pattern Toe1 was similar to that of egr-1. These findings suggest that the neuronal activity related to recognition of a distress call and an auditory feedback mechanism induces the expression of Egr-1. Co-expression of egr-1 with Toe1 may play a role in initial triggering of the genetic mechanism that could be involved in the consolidation or stabilization of distress call memories.
Parthasarathy Thiruchenthil Nathan, Thangavel Karuppudurai, Hanumanthan Raghuram, and Ganapathy Marimuthu
Museum and Institute of Zoology at the Polish Academy of Sciences
The sympatrically occurring Indian short-nosed fruit bat Cynopterus sphinx and Indian flying fox Pteropus giganteus visit Madhuca latifolia (Sapotaceae), which offers fleshy corollas (≈ 300 mg) to pollinating bats. The flowers are white, tiny and in dense fascicles. The foraging activities of the two bat species were segregated in space and time. Cynopterus sphinx fed on resources at lower heights in the trees than P. giganteus and its peak foraging activity occurred at 19:30 h, before that of P. giganteus. Foraging activities involved short searching flights followed by landing and removal of the corolla by mouth. Cynopterus sphinx detached single corollas from fascicles and carried them to nearby feeding roosts, where it sucked the juice and spat out the fibrous remains. Pteropus giganteus landed on top of the trees and fed on the corollas in situ; its peak activity occurred at 20:30 h. This species glided and crawled between the branches and held the branches with claws and forearms when removing fleshy corollas with its mouth. Both C. sphinx and P. giganteus consumed fleshy corollas with attached stamens and left the gynoecium intact. Bagging experiments showed that fruit-set in bat-visited flowers was significantly higher (P < 0.001) than in self-pollinated flowers.
Hanumanthan Raghuram, Chinnathambi Thangadurai, Nagappan Gopukumar, Kulam Nathar, and Kandula Sripathi
Springer Science and Business Media LLC
Hanumanthan Raghuram and Ganapathy Marimuthu
Museum and Institute of Zoology at the Polish Academy of Sciences
Vadamalai Elangovan, Elangovan Yuvana Satya Priya, Hanumanth Raghuram, and Ganapathy Marimuthu
Elsevier BV
Hanumanthan Raghuram and Granapathy Marimuthu
Wiley
We studied development of prey capture, under captive conditions, on five newly weaned Indian false vampire bats Megaderma lyra. We tested the hypothesis that the young bats are able to improve the ability of hunting by trial and error. An additional hypothesis was that their rate of prey consumption and method of handling prey improve with age. We separated the juveniles from their mothers and observed them individually at different ages. At 58 d of age, M. lyra roosted 2 m above floor level, flew down only towards moving frogs, landed >1 m away from them and returned to roosts without showing attempt to capture. At day 60, bats roosted at 50-cm heights, landed approx. 1 m away from frogs and moved towards them. Although bats intercepted frogs, their attempts to capture were still unsuccessful. At day 62, bats landed <1 m from frogs, made similar attempts and most of them were successful. Bats carried frogs, roosted at heights of 100 cm and started consuming. Numbers of jumps made by frogs and attempts made by bats during successful captures decreased with increase in age of bats. Furthermore, the distance between landing sites of bats and places where frogs stayed during landings decreased with advancement of age. Until 75 d of age, M. lyra devoured frogs with legs-first on significantly more occasions. After 75 d, most of the consumptions started with heads of frogs, similar to adults. Duration of feeding on single frogs was significantly longer compared with that of mothers until young were 75-d old. The study revealed that juveniles were inefficient on localization, rate of consumption, and handling prey at earlier ages (e.g. 60 d). They became efficient on these behavioural components at later age, i.e. after 75 d. Thus, the results were in accordance with both the hypotheses. Bats did not respond to stationary frogs.
John M. Ratcliffe, Hanumanthan Raghuram, Ganapathy Marimuthu, James H. Fullard, and M. Brock Fenton
Springer Science and Business Media LLC
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.
V. Elangovan, H. Raghuram, E. Yuvana Satya Priya, and G. Marimuthu
Oxford University Press (OUP)
Abstract We studied development of wings of Leschenault's rousette, Rousettus leschenaulti. Wingspan and wing area grows linearly until 45 days of age. Young bats begin to flutter at 45 days, manage sustained flight at 60 days, and achieve independent foraging flight at 75 days. Aspect ratio varies until 15 days, and adult proportions are attained at 2 months. Wing loading decreases linearly until 50 days and thereafter increases slowly, possibly because of completion of growth of wing area. Wingspan growth fits a logistic model, whereas wing area growth fits a Gompertz model. Minimum predicted flight power (Pmp) and maximum range power (Pmr) begin to increase linearly after remaining relatively constant for 30 days. At 150 days both are nearly equal to 65% of the power requirements of postpartum females. The predicted minimum power speed (Vmp), maximum range speed (Vmr), and minimum theoretical radius of a banked turn (rmin) decrease for 40 days, thereafter increase linearly, and at 150 days all are close to 90% of the respective values of the postpartum females.
Kandula Sripathi, Hanumanthan Raghuram, Raman Rajasekar, Thangavel Karuppudurai, and Suba Gnana Abraham
Museum and Institute of Zoology at the Polish Academy of Sciences
We used the Jolly-Seber method to analyze mark-recapture data and estimate both survival and population size in the Indian false vampire bat Megaderma lyra in Madurai (South India). Population size of bats from 2001 to 2003 varied from 379 to 476, and showed fluctuation in numbers for both sexes. The mean (plusmn;SE) survival rate of females (1.26 ± 0.33) exceeded that of males (1.02 ± 0.16) although the differences were not statistically significant. We observed a gradual decline in reproduction as indicated by the number of pups born in each year. This was consistent with a declining trend in population size from 1995 to 2003. We hypothesize a few reasons for this fall in population size, including habitat destruction and human poaching of bats.
Vadamalai Elangovan, Elangovan Yuvana Satya Priya, Hanumanthan Raghuram, and Ganapathy Marimuthu
Museum and Institute of Zoology at the Polish Academy of Sciences
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.
V. Elangovan, H. Raghuram, E. Yuvana Satya Priya, and G. Marimuthu
Springer Science and Business Media LLC
This study documents the postnatal growth, age estimation and development of the foraging behaviour of the fulvous fruit batRousettus leschenaulti under captive conditions. At birth, the young were naked and pink with closed eyes and folded pinnae. By day four of age, their eyes had opened and the pups began to move. The mean length of forearm in 5-day-old pups was 24.9 mm and body mass was 10.8 g, equivalent to 32.3% and 14.2% of the values from postpartum females. The length of forearm and body mass increased linearly until 45 and 50 days, respectively, and thereafter maintained an apparent stability. The epiphyseal gap of the fourth metacarpal-phalangeal joint increased until 15 days, then decreased linearly until 75 days and thereafter closed. Age was estimated quantitatively, based on linear changes observed in the length of the forearm and epiphyseal gap. Pups began to roost separately, but adjacent to their mothers when 30 days old and flew clumsily when they were about 40 days old. After attaining clumsy flight, the young bats made independent foraging attempts feebly by biting and licking small fruit pieces. Young bats were engaged in suckling as well as ingesting fruits when they were about 50 days old. Between 55 and 65 days, they flew well and fed on fruits. At the age of 75 days, the young bats were completely weaned and at two months, their foraging behaviour was similar to that of their mothers. There was no significant difference in the growth pattern of the young maintained in captivity compared with those under natural conditions.