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At least 1,531 records · Page 85Linked to original sources
PubMed2001

Frequency discrimination threshold at search call frequencies in the echolocating bat, Eptesicus fuscus.

While searching for prey in open spaces, Epteisicus fuscus emits long-duration, downward frequency-modulated calls which cover a frequency band of about 28-22 kHz. In the ascending auditory pathways of E. fuscus, neurons tuned to these search call frequencies are characterised by a remarkably high frequency selectivity and very sensitive absolute thresholds. We investigated whether this narrow tuning is reflected in an exceptional psychoacoustic frequency discrimination ability. The average frequency difference limen of E. fuscus at search call frequencies determined in a two-alternative, forced-choice experiment amounted to about 420 Hz, corresponding to a Weber ratio of 0.017. This value is similar to those found in non-echolocating mammals, and an order of magnitude larger than the frequency difference limens of bats emitting constant-frequency call components. We discuss these differences in frequency difference limen, and relate them to different echolocation strategies.

Acoustics↗
PubMed2003

Metabolic responses induced by fasting in the common vampire bat Desmodus rotundus.

This study explored the effects of fasting on body fuel mobilization in the common vampire bat (Desmodus rotundus) fed a high-protein diet (bovine blood). An uncommon fragility during food deprivation has been reported for this species to the point of untimely deaths after only 2-3 nights of fasting. The immediate biochemical responses to fasting, however, have not been established. Thus, blood glucose, plasma FFA, glycogen, protein, and fat concentrations in the liver and muscles were determined in fed and 24-, 48- and 72 h-fasted individuals. The results indicate that D. rotundus is unable to maintain adequate levels of blood glucose during fasting, probably due to low tissue stores of energy fuels or difficulty in mobilizing them. Other factors may play an important role in this species abundance, such as the previously reported behavior of reciprocal blood regurgitation.

Animals↗
PubMed2006

Variation in body composition of female big brown bats (Eptesicus fuscus) during lactation.

Most small mammals support the nutritional requirements of milk production by increasing food intake. However, when nutrient intake is low, maternal body reserves may be mobilized to maintain adequate milk output. We examined patterns of body composition, including dry matter, fat, protein, and mineral content in big brown bats, Eptesicus fuscus, during lactation. Concentrations of fat and phosphorus were markedly lower in lactating mothers during week three of lactation than during the first two weeks, but these constituents rebounded to previous levels in the fourth and fifth week. Rapid recovery from fat depletion suggests that females are able to adjust to changes in demands for energy. The decrease in phosphorus during mid-lactation suggests bone demineralization, but an interspecific comparison of adult concentrations of minerals prevalent in bone suggests that mineral concentrations may never reach critically low levels in reproductively active females.

Animals↗
PubMed2000

Intraspecific scaling of flight power in the bat Glossophaga soricina (Phyllostomidae).

Aerodynamic theory predicts that power output during flight should vary with body mass by an exponent of 1.56 when wing morphology remains constant (within an individual), and by an exponent of 1.19 when wing morphology changes with body mass (within a species or between species). I tested these predictions by estimating the power input during horizontal flight in three pregnant and two subadult Glossophaga soricina using a multivariate regression model. This analysis yielded power input during resting and flight as well as the energetic equivalent of change in body mass. A comparison of the estimated flight power for pregnant G. soricina, with published data on flight power of nonpregnant adults, revealed that energy turnover in flight is highest for pregnant G. soricina. Flight power of a 13-g pregnant G. soricina was even higher than that of a 16-g non-pregnant Glossophaga longirostris. A least-squares regression analysis yielded the following equations for the intraspecific scaling of flight power with body mass: power input during horizontal flight (Pf) = 24099 body mass (bm; kg)2.15 (r2 = 0.97) for the intra-individual allometry (pregnancy) and Pf = 113 bm(kg)0.95 (r2 = 0.99) for the inter-individual allometry (ontogeny). Both mass exponents are not significantly different from the predicted values for the scaling relationship of flight power within an individual (1.56) and within a species (1.19). This is the first measurement of power input during flight for subadult and pregnant bats.

Adaptation, Physiological↗
PubMed2001

The metabolism of New Guinean pteropodid bats.

Rate of metabolism and body temperature were measured in eight species of pteropodid bats that live in Papua New Guinea. These data and those from 13 other species available in the literature are examined to determine the factors with which the energetics of pteropodids are correlated. Lowland populations of species that weigh < 35 g generally have low basal rates and often become torpid, whereas their highland populations had standard or high basal rates and were precise thermoregulators, as were all adult pteropodids that weighed more than 60 g. In large pteropodids belonging to the genera Dobsonia and Pteropus, females are smaller and consequently have lower total basal rates than males. Compared to species found on continents and large islands, species limited in distribution to small islands have lower basal rates, both because of a smaller mass and a reduction of metabolism independent of body mass. These trends are most marked in females that belong to small-island species, adjustments that may facilitate reproduction and survival on small oceanic islands with a limited resource base. Minimal thermal conductances are usually low in species that roost exposed in trees, whereas large species that roost in caves have either standard or high conductances.

Animals↗
PubMed1997

Milk composition and lactational output in the greater spear-nosed bat, phyllostomus hastatus.

Growth rates of mammalian young are closely linked to the ability of the mother to provide nutrients; thus, milk composition and yield provide a direct measure of maternal investment during lactation in many mammals. We studied changes in milk composition and output throughout lactation in a free-ranging population of the omnivorous bat, Phyllostomus hastatus. Fat and dry matter of milk increased from 9 to 21% and from 21 to 35% of wet mass, respectively, throughout lactation. Energy increased from 6 to 9 kJ.g-1 wet mass, primarily due to the increase in fat concentration. Total sugar levels decreased slightly but non-significantly. Mean sugar level was 4.0% of wet mass. Protein concentration increased from 6 to 11% of wet mass at peak lactation and then decreased as pups approached weaning age. Total milk energy output until pups began to forage was 3609 kJ. Milk levels of Mg, Fe, Ca, K, and Na averaged 0.55 %/- 0.26, 0.23 +/- 0.2, 8.75 +/- 4.17, 5.42 +/- 2.11, and 9.87 +/- 4.3 mg.g-1 dry matter, respectively. Of the minerals studied, calcium appears to be most limiting in this species. The high degree of variability in foraging time, milk composition and milk yield between individuals at the same stage of lactation could potentially yield high variance in reproductive success among females of this polygynous species.

Animals↗
PubMed1998

Changes in the classification of carcinogenic chemicals in the work area. Section III of the German List of MAK and BAT Values.

Carcinogenic chemicals in the work area are currently classified into three categories in section III of the German List of MAK and BAT Values (list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification is based on qualitative criteria and reflects essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. It is proposed that these categories - IIIA1, IIIA2, IIIB - be retained as Categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by nongenotoxic mechanisms and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in Category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose-response relationships and toxicokinetics, and for which risk at low doses can be assessed are classified in Category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for Category 4 (1,4-dioxane) and Category 5 (styrene) are presented.

Animals↗
PubMed1998

Changes in the classification of carcinogenic chemicals in the work area. (Section III of the German List of MAK and BAT values).

Carcinogenic chemicals in the work area were previously classified into three categories in section III of the German List of MAK and BAT values (the list of values on maximum workplace concentrations and biological tolerance for occupational exposures). This classification was based on qualitative criteria and reflected essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. In the new classification scheme the former sections IIIA1, IIIA2, and IIIB are retained as categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to the risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by non-genotoxic mechanisms, and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose/response relationships and toxicokinetics and for which risk at low doses can be assessed are classified in category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for category 4 (1,4-dioxane) and category 5 (styrene) are presented.

Animals↗
PubMed2004

Characterization of Oita virus 296/1972 of Rhabdoviridae isolated from a horseshoe bat bearing characteristics of both lyssavirus and vesiculovirus.

Oita virus 296/1972 was isolated from the blood of a wild horseshoe bat, Rhinolophus cornutus (Temminck) in 1972. We investigated the pathogenicity of this virus in mice in relation to its histological, immunohistochemical and ultrastructural characteristics and the entire sequence of nucleoprotein gene. This virus caused lethal encephalitis in mice through intracerebral route. This susceptibility of mice was until 3 weeks of age. Immunohistochemical analysis using the convalescent sera obtained from survived adult mice after intracerebral inoculation revealed that many neurons were positive in the cytoplasm, besides no cross reactivity with normal and rabies virus-infected mouse brain tissues to this anti-sera. Ultrastructural analysis disclosed many bullet-shaped and enveloped virions in neurons. These morphological characteristics of the virions are consistent of that of viruses in the family Rhabdoviridae. Budding from endoplasmic membrane suggests that this virus has a similarity with lyssaviruses. Molecular analysis of cDNA coding a tentative nucleoprotein sequence revealed homology with those of viruses in the family Rhabdoviridae. Distance matrix analysis of this gene sequence with those of other rhabdoviruses isolated from mammals disclosed the discrete position of this virus in the phylogenic tree of rhabdoviridae infecting mammals and we renamed this virus as Oita rhabdovirus.

Age Factors↗
PubMed2000

The tympanic membrane: highly developed smooth muscle arrays in the annulus fibrosus of mustached bats.

The annulus fibrosus tympanicus is the thickened peripheral rim of the pars tensa of the tympanic membrane. It is an area into which the connective tissue matrix of the membrane extends to attach to the tympanic bone (ring). Light microscopy, SEM, TEM and confocal microscopy were used to study the area in mustached bats Pteronotus p. parnellii, P. p. portoricensis and P. quadridens. In cross sections of the annulus morphologically distinct apical and basal or myovascular zones could be recognized. The apical zone had a collagenous matrix that was continuous with the pars tensa. The myovascular zone contained an extensive network of thin walled endothelial tubes and a well-developed array of radially arranged smooth muscle cells that filled the interval between the vessels. The muscle tissue occupied the interval between the densely collagenous "apical zone" and the bony tympanic ring and was closely associated with bundles of unmyelinated nerve fibers. The structure and arrangement of the tissue suggests a highly developed specialization for the tonic control of tension of the pars tensa and a system that potentially regulates sound transmission to the middle and inner ear.

Animals↗
PubMed1993

Morphological study by scanning electron microscopy of the lingual papillae in the common European bat (Pipistrellus pipistrellus).

There are many accounts of the tongues of mammals observed with scanning electron microscopy (SEM), but apparently only one article about the tongue of the Chiroptera. In the present study the tongue surface (after removing extracellular material) of the European common bat (Pipistrellus pipstrellus) was examined. The tongue is covered with papillae and has an elevation between its medial and posterior half. There are three types of papillae: filiform, fungiform and circumvallate, and the filiform can be classified as strictly filiform, conical and crown-like. The shapes and disposition of these papillae are related to function, which is principally to retain captured food during flight. At higher magnification the surface of the filiform papillae has many pores and microridges, which may serve for the production and distribution of mucus over the papillary surface.

Animals↗
PubMed1981

Localization of brain stem motoneurons innervating the laryngeal muscles in the rufous horseshoe bat, Rhinolophus rouxi.

The motoneurons innervating the laryngeal muscles were localized in the rufous horseshoe bat, Rhinolophus rouxi, using the HRP method. HRP was applied to the cricothyroid muscle and to the cut end of the recurrent laryngeal nerve. Labeled motoneurons were found in two completely separated regions of the nucleus ambiguus. The motoneurons innervating the cricothyroid muscle via the superior laryngeal nerve (SLN) are located within the ventrolateral portion of the nucleus reaching the caudal pole of the motor nucleus of the facial nerve. The motoneurons innervating the other intrinsic laryngeal muscles via the recurrent laryngeal nerve (RLN) are situated in the caudal half of the nucleus ambiguus. The innervation is strictly homolateral.

Animals↗
PubMed1984

Auditory space representation in the superior colliculus of the big brown bat, Eptesicus fuscus.

The auditory response areas of 123 superior collicular (SC) units of Eptesicus fuscus were studied under free-field acoustic stimulus conditions. A stimulus was delivered from a loudspeaker placed 14 cm in front of a bat. The best frequency of a unit was determined by changing the stimulus frequency until the minimum threshold was measured. A best frequency stimulus was then delivered as the loud-speaker was moved across the auditory space to determine the response center of the auditory response area of each unit. The response center was defined as the direction at which the unit had its lowest minimum threshold. The stimulus intensity was then raised 2-20 dB above the lowest minimum threshold of the unit and the response area for each stimulus intensity was determined. The response area of a unit expands with stimulus intensity, but the expansion is not even in all directions. The size of the response area of a unit does not correlate with its minimum threshold, best frequency, or recording depth. Response centers of 7 units were located directly in front of the animal, but most response centers were located in a limited portion of the contralateral auditory space. Although each unit has a response center which is the point of maximal sensitivity, the point-to-point representation of the auditory space is not systematically organized. We suggest that an animal with highly mobile external pinnae may not need an orderly auditory space map in its neural tissue for accurate sound localization.

Acoustic Stimulation↗
PubMed1987

Auditory spatial response areas of single neurons and space representation in the cerebellum of echo locating bats.

Using free-field acoustic stimulation conditions, we studied the auditory spatial response areas of 242 cerebellar neurons of Eptesicus fuscus. A best frequency stimulus was delivered from a loudspeaker which was moved across the frontal auditory space in order to determine the response center of each cerebellar neuron. At the response center, the neuron had its lowest minimum threshold. The stimulus was then raised 5-15 dB above the lowest minimum threshold of each neuron and the spatial response area for each stimulus intensity was measured. The spatial response area of each neuron expanded asymmetrically with the stimulus intensity. The size of the spatial response area was not correlated with the minimum threshold, best frequency or recording depth of the neuron. The distribution of the best frequencies of single neurons was not correlated with their recording depths or minimum thresholds. The response centers of all cerebellar neurons were located within a small area of the central portion of the frontal auditory space suggesting that the cerebellum could play an effective role in orienting the bat toward the echo source within the frontal gaze during insect capture.

Acoustic Stimulation↗
PubMed1987

Auditory space representation in the inferior colliculus of the FM bat, Eptesicus fuscus.

The auditory spatial response areas of 333 inferior collicular (IC) neurons of Eptesicus fuscus were studied under free-field acoustic stimulus conditions. A stimulus was delivered from a loudspeaker placed 14 cm in front of a bat and the best frequency of an encountered neuron was determined. Then a best frequency (BF) stimulus was delivered as the loudspeaker was moved across the frontal auditory space to determine the response center of the neuron. At the response center, the neuron had the lowest minimum threshold. The stimulus was then raised 3-15 dB above the lowest minimum threshold of the neuron and the spatial response area for each stimulus intensity was measured. The response center and spatial response area of a neuron measured with a one-octave downward-sweep FM stimulus were similar to those measured with the pure tone pulse. The spatial response area of a neuron expanded asymmetrically with the stimulus intensity. High BF neurons generally had smaller spatial response areas than low BF neurons had. All 333 response centers were located in the contralateral auditory space. Response centers of low BF neurons tended to be located laterally while those of high BF neurons were located medially. Although each neuron had a point of lowest minimum threshold in the contralateral auditory space, the point-to-point representation of the auditory space was not systematically organized. This representation was not correlated with the recording sites of the neurons in the mediolateral, posteroanterior and dorsoventral axes of the IC.

Acoustic Stimulation↗
PubMed1987

Anatomical study of neural projections to the superior colliculus of the big brown bat, Eptesicus fuscus.

Auditory inputs to the intermediate and deep layers of the superior colliculus of the bat, Eptesicus fuscus, were studied by iontophoretic injection of horseradish peroxidase (HRP) into the superior colliculus. HRP was injected into the recording sites of superior collicular neurons that responded to acoustic stimuli (4 ms duration, 0.5 ms rise-decay times). The results showed that the superior colliculus received its auditory projections mainly from the inferior colliculus bilaterally, but with ipsilateral projections prevailing. A few projections came from the dorsal nucleus of the lateral lemniscus. HRP-labeled neurons were also found in 11 other brain structures.

Acoustic Stimulation↗
PubMed1988

Functional zones in the auditory cortex of the echolocating bat, Myotis lucifugus.

Neurophysiological mapping experiments in the auditory cortex of the frequency-modulated bat, Myotis lucifugus, reveal 3 functional subregions: a tonotopic zone located dorsally, a delay-sensitive zone more ventrally, and an intermediate zone of major overlap. The unique finding of an overlapping cortical region representing both spectral and time-delay information of echoes is intriguing in view of a recent behavioral study suggesting the convergence of such echo cues in auditory perception. (Simmons et al., Soc. Neurosci. Abstr., 13 [1987] 870).

Acoustic Stimulation↗
PubMed1988

Auditory spatial sensitivity of inferior collicular neurons of echolocating bats.

The sensitivity of 94 inferior collicular (IC) neurons of Eptesicus fuscus and Myotis lucifugus to spatial location of the acoustic stimulus were studied under free-field stimulus conditions. The best frequency (BF) and minimum threshold (MT) of each neuron were determined with sound delivered in front of the bat. Then the variation in discharge rate of the neuron was measured with a BF sound broadcast from a moving loudspeaker at different angular positions along the horizontal, vertical or diagonal plane of the frontal auditory space. A wide range of stimulus intensities above the MT of the neuron was used. Neurons were classified into 3 classes on the basis of their spatial sensitivity: (1) omnisensitive neurons (15%) were broadly tuned to sound delivered in the frontal auditory space and their responses did not show any correlation with sound location; (2) stimulus intensity-dependent neurons (28%) varied their discharge rates with sound location and intensity so that the peak of their spatial response profiles also varied with stimulus intensity; and (3) stimulus intensity-independent neurons (57%) varied their discharge rates only with sound location over a wide range of stimulus intensities so that their peak discharge always appeared at the same or a small range of angle. In most cases, the medial limbs of the spatial sensitivity curve for these neurons were extremely sharp and congruent. By moving the loudspeaker along the horizontal, vertical and diagonal planes, it was possible to approximate the boundary of the spatial response area of a neuron. Most IC neurons responded to sound delivered within 20 degrees ipsilateral, 60 degrees contralateral, 45 degrees up and 40 degrees down of the frontal auditory space, confirming previous similar studies. In general, an increasing stimulus repetition rate appeared to sharpen the spatial sensitivity curve of a neuron. Conversely, an increasing moving velocity of the stimulus decreased its response. The possible role of these 3 classes of neurons in echolocation and neural mechanisms underlying the spatial sensitivity of these neurons is discussed.

Acoustic Stimulation↗