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At least 595 records · Page 33Linked to original sources
PubMed1996

Ventilatory and metabolic responses of a bat, Phyllostomus discolor, to hypoxia and CO2: implications for the allometry of respiratory control.

The ventilatory and metabolic responses of lesser spear-nosed bats to hypoxia and hypercapnia were measured to determine whether these corresponded to preliminary allometries and a positive relationship between hypoxic ventilatory threshold and P50. Ventilatory responses of lesser spear-nosed bats to 3, 5 and 7% CO2 differed significantly from ventilation on air and each other. The magnitude of their ventilatory response to CO2 is consistent with the prediction of a smaller ventilatory response to hypercapnia in small compared to large mammals [% delta V varies MB0.130; Williams et al. (1994)]. Among 12, 10 and 8% O2 treatments only the ventilatory response to 8% O2 differed significantly from ventilation on air or the other treatments. Metabolic rate was significantly reduced at both 10 and 8% O2. The hypoxic ventilatory response of these bats does not support the prediction of a greater response in small compared to large mammals [% delta V veries MB0.273; Boggs and Tenney (1984)]. Their metabolic response is consistent with the hypoxic hypometabolism typical of small mammals, though not of comparable magnitude. The response, expressed as percent change in convection requirement (V/VO2), is also less than that observed in other small mammals. This relative insensitivity to hypoxia may be associated with this bat's unusually high affinity hemoglobin (P50 = 27.5 torr).

Anaerobiosis↗
PubMed2002

Postnatal growth, age estimation and development of foraging behaviour in the fulvous fruit bat Rousettus leschenaulti.

This study documents the postnatal growth, age estimation and development of the foraging behaviour of the fulvous fruit bat Rousettus 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.

Animals↗
PubMed2001

Accumulation of organochlorine pesticides and polychlorinated biphenyls in sediments, aquatic organisms, birds, bird eggs and bat collected from south India.

Concentrations of polychlorinated biphenyls (PCBs), DDT and its metabolites (DDTs), HCH isomers (HCHs), chlordane compounds (CHLs) and hexachlorobenzene (HCB) were determined in sediment, soil, whole body homogenates of resident and migratory birds and their prey items (including fish, green mussel, snail, earthworm, crabs, prawn, lizard and frogs), bird eggs and bats collected from southern India during 1995 and 1998. Accumulation pattern of organochlorines (OCs) in biota was, in general, in the order, HCHs > DDTs > PCBs > CHLs = HCB. Magnitude of OC concentrations increased in the order of sediments < green mussel < earthworm < from < lizard < fish < bird egg < bats < birds tissues. Biomagnification features of OCs were examined in resident and migrant birds to evaluate the exposure levels of these chemicals in wintering grounds of migrant birds. Accumulation of DDTs in migratory birds during wintering in India may be of concern due to the great biomagnification potential of DDTs. Eggs of some resident species contained noticeable concentrations of OCs. Concentrations of OCs in three species of bats analyzed in this study were lower than that found in passerine birds. In addition to OCs, butyltin compounds were also detected at low concentrations in bats.

Animals↗
PubMed2006

Echolocation calls of Poey's flower bat (Phyllonycteris poeyi) unlike those of other phyllostomids.

Unlike any other foraging phyllostomid bat studied to date, Poey's flower bats (Phyllonycteris poeyi-Phyllostomidae) emit relatively long (up to 7.2 ms), intense, single-harmonic echolocation calls. These calls are readily detectable at distances of at least 15 m. Furthermore, the echolocation calls contain only the first harmonic, which is usually filtered out in the vocal tract of phyllostomids. The foraging echolocation calls of P. poeyi are more like search-phase echolocation calls of sympatric aerial-feeding bats (Molossidae, Vespertilionidae, Mormoopidae). Intense, long, narrowband, single-harmonic echolocation calls focus acoustic energy maximizing range and favoring detection, which may be particularly important for cruising bats, like P. poeyi, when flying in the open. Flying in enclosed spaces, P. poeyi emit short, low-intensity, frequency-modulated, multiharmonic echolocation calls typical of other phyllostomids. This is the first report of a phyllostomid species emitting long, intense, single-harmonic echolocation calls with most energy in the first harmonic.

Animals↗
PubMed2000

Biological monitoring of standardized exposure to ethylbenzene: evaluation of a biological tolerance (BAT) value.

The results of standardized 8 h lasting exposures of n = 18 volunteers to ethylbenzene (EthBz) at levels of 25 and 100% of the maximum allowable concentrations at the workplace (MAK) value of 100 ppm as well as the results of field studies are considered to evaluate a biological tolerance (BAT) value for EthBz. On the basis of the relationship between the external and internal exposure a BAT value of 1.5 mg/l has been set for the EthBz concentration in blood as the most sensitive and specific parameter of exposure to this aromatic hydrocarbon. The interpretation of EthBz blood values has to take into account the short half-life of t1/2 = 0.5 +/- 0.08 h in the first hour after the end of exposure in which this aromatic hydrocarbon is eliminated from the blood. The additional determination of the EthBz metabolites mandelic acid (MA) and phenylglyoxylic acid (PGA), respectively, excreted in post shift urine as well as in urine samples at the beginning of the next shift shows good correlations with the external exposure. The biological half-life of MA was calculated to t1/2 = 5.3 +/- 1.1 h. Because the time of sampling can vary the relationship between the levels of MA to PGA the total concentration of the excreted metabolites depends less on this influence and is therefore better suited for monitoring exposed persons. On the basis of the standardized experiments a BAT value has been proposed of 2 g MA plus PGA corrected per gram creatinine. Both BAT values are adjusted to data which result from earlier standardized exposures during 30 min to EthBz under physical activity of 50 watt on a bicycle ergometer.

Aged↗
PubMed1998

Audiovocal behavior of Doppler-shift compensation in the horseshoe bat survives bilateral lesion of the paralemniscal tegmental area.

The role of the paralemniscal tegmental area of the horseshoe bat, Rhinolophus rouxi, in the control of vocalization and Doppler-shift compensation was investigated using electrical and pharmacological stimulation and lesioning techniques. The paralemniscal tegmental area is situated in the dorsolateral tegmentum ventral to the inferior colliculus and rostral and medial to the dorsal and intermediate nuclei of the lateral lemniscus. Vocalizations indistinguishable from spontaneously uttered calls can be elicited with both electrical and pharmacological stimulation methods, demonstrating that the stimulation of neural elements within the area and not fibers passing through the area are responsible for the stimulated call emission. The audiovocal feedback system for Doppler-shift compensation was also investigated. Doppler-shift compensation adjusts the frequency of the emitted calls according to the increases in the frequency of the echoes that are normally encountered in flying bats. Bats compensate for Doppler shifts not only under natural conditions but also when echoes are played back to the bat following spontaneous vocalizations or vocalizations induced by electrical or pharmacological stimulation of the investigated brain area. Unilateral electrolytic lesions of the paralemniscal tegmental area did not impair the ability to evoke vocalizations with electrical stimulation of the unlesioned side. The calls had exactly the same structure and frequency composition as those emitted prior to lesioning. Unilateral lesions also did not impair Doppler-shift compensation performance. After bilateral lesioning of the paralemniscal area, vocalizations could not be evoked with electrical stimulation. However, normal calls were emitted spontaneously and Doppler-shift compensation during spontaneous call emission was unaltered compared with the intact condition. The paralemniscal tegmental area is therefore not an audiovocal feedback system required for Doppler-shift compensation, but rather a brain area whose stimulation and activation is sufficient but not necessary for call emission. It is also not directly involved in the control of spectral parameters of vocalization but contributes to the control of the occurrence of vocal output.

Acoustic Stimulation↗
PubMed2001

Food chain aspects of chlordane poisoning in birds and bats.

We have observed recurring chlordane poisonings of large numbers of common grackles (Quiscalus quiscula), European starlings (Sturnus vulgaris), and American robins (Turdus migratorius) at suburban roosts in New Jersey during the month of July. This paper describes aspects of the food chain uptake of chlordane that account for the periodicity of these poisonings. Chlordane concentrations ranged from < 0.02 to 20.3 microg/g wet weight in 11 soil samples collected from residential lawns and a golf course near one roost. Of the 10 species of insects and soil invertebrates collected from the area, two scarab beetles, the oriental beetle (Anomala orientalis) and Japanese beetle (Popilla japonica), had the highest concentrations of chlordane-related compounds (15.1 and 5.9 microg/g wet weight, respectively). Concentrations in the other eight species ranged from < 0.04 to 1.3 microg/g. Oriental and Japanese beetles collected from a rural location had concentrations of 0.03 and < 0.02 microg/g, respectively. Emergence of adult beetles peaked in mid- to late July, when bird mortality also peaked. Fecal pellets collected near the roost (n = 24) contained the remains of 1-5 beetles each (mean = 2), and scarab beetles accounted for 40% of the total number of insect parts in the stomach contents of common grackles (n = 8). Unlike soil samples, in which cis- and trans-chlordane predominated, beetles contained large amounts of the more toxic metabolites heptachlor epoxide and oxychlordane. Total chlordane-related compounds ranged from < 0.05 to 18.4 microg/g in Japanese beetles collected from 16 sites in New Jersey and 2 sites in Ohio. The highest concentrations were found in beetles from suburban areas and golf courses. We also analyzed brain tissue from insectivorous bats (15 big brown bats, Eptesicus fuscus, and 5 little brown bats, Myotis lucifugus) that were submitted to the New Jersey Rabies Laboratory in late June/July 1998 and 1999 but found to be rabies-negative. We suggest that high concentrations in three of the bats caused debility or abnormal behavior that may have precipitated submission for rabies testing.

Animals↗
PubMed2003

Fine control of call frequency by horseshoe bats.

The auditory system of horseshoe bats is narrowly tuned to the sound of their own echoes. During flight these bats continuously adjust the frequency of their echolocation calls to compensate for Doppler-effects in the returning echo. Horseshoe bats can accurately compensate for changes in echo frequency up to 5 kHz, but they do so through a sequence of small, temporally-independent, step changes in call frequency. The relationship between an echo's frequency and its subsequent impact on the frequency of the very next call is fundamental to how Doppler-shift compensation behavior works. We analyzed how horseshoe bats control call frequency by measuring the changes occurring between many successive pairs of calls during Doppler-shift compensation and relating the magnitude of these changes to the frequency of each intervening echo. The results indicate that Doppler-shift compensation is mediated by a pair of (echo)frequency-specific sigmoidal functions characterized by a threshold, a slope, and an upper limit to the maximum change in frequency that may occur between successive calls. The exact values of these parameters necessarily reflect properties of the underlying neural circuitry of Doppler-shift compensation and the motor control of vocalization, and provide insight into how neural feedback can accommodate the need for speed without sacrificing stability.

Animals↗
PubMed2004

Object classification by echolocation in nectar feeding bats: size-independent generalization of shape.

The nectar-feeding bat Glossophaga can be trained to discriminate two hollow forms, a hollow hemisphere and a paraboloid with the same diameter and depth, in total darkness. During training a saturation level of about 85-90% correct choices or more can be reached within 50-100 visits. To investigate generalization abilities, the bats were tested with pairs of the same shape but of different size. Although no reward was offered, they preferred the hollow sphere (30 mm and 50 mm diameter, but not 18 mm) over the corresponding paraboloids. Thus, the bats were able to generalize some features of the rewarded form and detect them in forms of the same shape but different size. This transposition is remarkable, since the bats could not use absolute spectral characters, but had to pay attention to size-independent features common to hollow hemispheres. Possible cues are the variation of echoes in dependence of different angles of calling direction (constant in spheres, changing with position in paraboloids) and/or the "timbre" of the echoes, i.e. their spectral pattern independent of their absolute pitch

Animals↗
PubMed2006

The transfer function of a target limits the jitter detection threshold with signals of echolocating FM-bats.

The delay jitter discrimination threshold in bats is a disputed subject. Some investigators have obtained results indicating that bats are able to discriminate alternations in delay down to 10 ns, which appears incredible for purely physical reasons. Using actual bat echolocation sequences recorded during an easy detection task to measure simulated delay jitter, it is shown here that jitter detection thresholds in the order of some tens of nanoseconds are actually physically realizable. However, if the transfer function of the target simulating apparatus is not perfect, the lowest thresholds are in the order of hundreds of nanoseconds and variable between individual bats. This phenomenon is shown to arise as a consequence of the variation in signal parameters from call to call. When the transfer function from a real jitter experiment was artificially applied to the echoes, the jitter detection thresholds again were several hundred nanoseconds. This is the first study to point out a limiting role of the transfer function of a system faced with variations in echolocation signal parameters, something that should be considered in evaluating all sonar systems with variable signal structure.

Acoustic Stimulation↗
PubMed2000

The role of echolocation in the hunting of terrestrial prey--new evidence for an underestimated strategy in the gleaning bat, Megaderma lyra.

The observation that gleaning bats detect prey by its noises, together with difficulties in recording their faint sonar calls, have led some authors to conclude that gleaning bats may not use echolocation in certain hunting situations. In particular, it is conjectured that echolocation plays no role in the classification and tracking of prey. In the present study, we show that the gleaning bat, Megaderma lyra, is able to find silent and motionless prey on the ground. The significance of sonar for catching a variety of terrestrial prey is established in a standardized situation. Sonar calls were found to be emitted during all stages, i.e. approach, hovering above the prey, and return to the roost, of every hunting flight. The harmonic pattern of the calls differed significantly between these stages, calls with three or more prominent components prevailing during hovering. Bats identified prey and rejected dummies while hovering above them. During this stage, increased call rates and reduced call durations were found. Echolocation activity during, and the duration of, the hovering phase depended on prey type, in particular on prey movement. The prey-dependent shifts in sonar activity, the broadband call structure with an emphasis on higher harmonics, and a systematic shift of the calls' peak frequencies during hovering, are discussed as adaptations to identifying prey by sonar.

Animals↗
PubMed1997

Bat-deafness in day-flying moths (Lepidoptera, Notodontidae, Dioptinae).

Assuming that bat-detection is the primary function of moth ears, the ears of moths that are no longer exposed to bats should be deaf to echolocation call frequencies. To test this, we compared the auditory threshold curves of 7 species of Venezuelan day-flying moths (Notodontidae: Dioptinae) to those of 12 sympatric species of nocturnal moths (Notodontidae: Dudusinae, Noctuidae and Arctiidae). Whereas 2 dioptines (Josia turgida, Zunacetha annulata) revealed normal ears, 2 (J. radians, J. gopala) had reduced hearing at bat-specific frequencies (20-80 kHz) and the remaining 3 (Thirmida discinota, Polypoetes circumfumata and Xenorma cytheris) revealed pronounced to complete levels of high-frequency deafness. Although the bat-deaf ears of dioptines could function in other purposes (e.g., social communication), the poor sensitivities of these species even at their best frequencies suggest that these moths represent a state of advanced auditory degeneration brought about by their diurnal life history. The phylogeny of the Notodontidae further suggests that this deafness is a derived (apomorphic) condition and not a retention of a primitive (pleisiomorphic), insensitive state.

Acoustic Stimulation↗
PubMed2000

Energy, water balance and the roost microenvironment in three Australian cave-dwelling bats (Microchiroptera).

The ghost bat, Macroderma gigas, and the orange leaf-nosed bat, Rhinonycteris aurantius, occupy similar ranges across northern Australia and are often found in the same roost caves. Both species are considered rare and vulnerable to further population decline. A third small species, the large bent-wing bat, Miniopterus schreibersii, has a similar body mass to R. aurantius, but has one of the largest ranges of any Australian mammal. In the present study we examine the effect and sensitivity of the animals' roosting microclimates on their energy and water balance. M. schreibersii exhibits a basal metabolic rate about 40% greater than other bats of similar body mass, whereas the other two species are close to predicted levels. R. aurantius shows a decrease in body temperatures below thermoneutrality. R. aurantius has levels of pulmocutaneous water loss among the highest seen for a mammal, and calculations based on nasal tip temperatures suggest that most of this loss is across the skin. Calculated ambient temperatures at which metabolic water production is equal to pulmocutaneous water loss in dry air are -14.7 degrees C for R. aurantius, 9.8 degrees C for M. schreibersii and -0.3 degrees C for M. gigas. Exposing the animals to relative humidities of between 80% and 90% shifted these calculated temperatures to 5.6 degrees C, 25.2 degrees C, and 2.9 degrees C, respectively. For each species the ratio of metabolic water production to evaporative water loss has been treated as a joint function of humidity and ambient temperature. The resulting surface plot shows that under known roosting conditions in caves R. aurantius and M. schreibersii remain in positive water balance, whereas M. gigas does not.

Animals↗
PubMed1999

Field metabolic rates and water uptake in the blossom-bat Syconycteris australis (Megachiroptera).

Blossom-bats, Syconycteris australis (18 g) are known to be highly active throughout the night. Since this species frequently enters torpor, we postulated that their use of heterothermy may be related to a high energy expenditure in the field. To test this hypothesis we measured field metabolic rates (FMR) of S. australis at a subtropical site using the doubly labelled water (DLW) method. We also measured DLW turnover in captive animals held at constant ambient temperature (Ta) with ad libitum food to estimate whether Ta and food availability affect energy expenditure under natural conditions. The FMR of S. australis was 8.55 ml CO2 g-1 h-1 or 76.87 kJ day-1 which is 7.04 times the basal metabolic rate (BMR) and one of the highest values reported for endotherms to date. Mass-specific energy expenditure by bats in the laboratory was about two-thirds of that of bats in the field, but some of this difference was explained by the greater body mass in captive bats. This suggests that foraging times in the field and laboratory were similar, and daily energy expenditure was not strongly affected by Ta or ad libitum food. Water uptake in the field was significantly higher than in the laboratory, most likely because nectar contained more water than the laboratory diet. Our study shows that S. australis has a FMR that is about double that predicted for its size although its BMR is lower than predicted. This supports the view that caution must be used in making assumptions from measurements of BMR in the laboratory about energy and other biological requirements in free-ranging animals.

Animals↗
PubMed1997

The distribution of GABA and glycine immunostaining in the cochlear nucleus of the mustached bat (Pteronotus parnellii).

The distribution of neuronal elements immunoreactive for gamma-aminobutyric acid (GABA) and glycine in the cochlear nucleus of the mustached bat Pteronotus parnellii has been studied by means of the postembedding technique on serial semithin sections. Our goal has been to identify similarities and differences in the organization of putatively inhibitory circuits between a highly specialized echolocating bat and previously studied non-echolocating mammals. The results reveal a basically conserved pattern of putatively GABAergic and glycinergic elements in the bat cochlear nucleus, and subtle but distinct modifications in certain inhibitory circuits. As in other mammals, immunoreactive cells possibly representing local interneurons are most abundant in the dorsal cochlear nucleus. These include single-GABA-immunoreactive cells and double-labeled cells in the superficial layers and single-glycine-labeled cells in the deep layers. Coincident with the phylogenetic trend toward a reduced lamination of the dorsal cochlear nucleus in bats, there is a clear reduction in the numbers of local interneurons of the superficial layer. In contrast, the tuberculoventral system of the deep layer appears hypertrophied. As in other mammals, the ventral cochlear nucleus contains a few large single-glycine-immunoreactive cells and scattered double-labeled cells. Immunoreactive puncta are abundant throughout the cochlear nucleus complex with no trends indicating a differential strength of inhibitory inputs to regions representing the various harmonics of the echolocating signal.

Animals↗
PubMed2003

Effects of habitat disruption on the activity of nectarivorous bats (Chiroptera: Phyllostomidae) in a dry tropical forest: implications for the reproductive success of the neotropical tree Ceiba grandiflora.

In the tropical dry forest of the central Pacific coast of Mexico the pollination and reproductive success of the bombacaceous tree Ceiba grandiflora was negatively affected by habitat disruption. Two of the three bat species that function as effective pollinators for this species ( Glossophaga soricina and Musonycteris harrisoni) visited flowers found in trees in disturbed habitats significantly less than trees found in undisturbed habitats. A similar pattern was observed for the effective bat pollinator, Leptonycteris curasoae; however the difference was not significant. The three nectarivorous bats that functioned as effective pollinators of C. grandiflora also visited flowers to exclusively feed on pollen by biting or pulling off an anther (see Fig. S1 of Electronic Supplementary Material). The number of pollen grains deposited on stigmas from flowers in undisturbed areas was significantly greater than from flowers in disturbed habitats. The greater visitation rate and the greater number of pollen grains deposited on flowers from trees in undisturbed forest resulted in a significantly greater fruit set for trees in these areas. Our study demonstrates the negative effect that habitat disruption has on bat pollinators in tropical dry forest ecosystems and documents the negative consequences for the plants they pollinate.

Animals↗
PubMed2004

Causal mechanisms underlying host specificity in bat ectoparasites.

In parasites, host specificity may result either from restricted dispersal capacity or from fixed coevolutionary host-parasite adaptations. Knowledge of those proximal mechanisms leading to particular host specificity is fundamental to understand host-parasite interactions and potential coevolution of parasites and hosts. The relative importance of these two mechanisms was quantified through infection and cross-infection experiments using mites and bats as a model. Monospecific pools of parasitic mites (Spinturnix myoti and S. andegavinus) were subjected either to individual bats belonging to their traditional, native bat host species, or to another substitute host species within the same bat genus (Myotis). The two parasite species reacted differently to these treatments. S. myoti exhibited a clear preference for, and had a higher fitness on, its native host, Myotis myotis. In contrast, S. andegavinus showed no host choice, although its fitness was higher on its native host M. daubentoni. The causal mechanisms mediating host specificity can apparently differ within closely related host-parasite systems.

Animals↗
PubMed1979

Bat-associated histoplasmosis in Maryland bridge workers.

An epidemic of acute prolonged febrile respiratory disease affecting nine of 19 workers on a Maryland State bridge maintenance crew was diagnosed as histoplasmosis by serologic testing in all and by isolation of the organism in one. In our investigation, it was revealed that work on a particular bridge was associated with disease. Culture of bat guano from the site two months later revealed H. capsulatum. Four previously uninfected epidemiologic investigators also became ill with histoplasmosis following collection of soil and bat guano. This outbreak reveals that bats and bat guano are a source of histoplasmosis, suggests that only brief exposure is necessary for acute infection and reemphasizes that histoplasmosis is not confined to the midwestern states.

Animals↗