The role of olfaction and vision in the foraging behaviour of an echolocating megachiropteran fruit bat,Rousettus leschenaulti (Pteropodidae)

Many mammals use multimodal sensory information to find their food in complex environments. We studied the roles of olfactory and visual cues in the foraging behaviour of Rousettus leschenaulti, a tongue-clicking megachiropteran bat. We conducted experiments by offering a whole fruit, mashed fruit without shape and an artificial fruit to R. leschenaulti in dim light as well as in total darkness. R. leschenaulti responded to whole guava fruit and mashed guava fruit even in total darkness, whereas, artificial fruit similar to real fruit in size, shape and structure was ignored even when illuminated. These results reveal that odour may act as the primary cue for R. leschenaulti in finding fruit.     

Target-detection by the echolocating bat,Eptesicus fuscus

Summary The long-range echo-detection capabilities of echolocating bats (Eptesicus fuscus) were studied in a two-choice psychophysical procedure.E. fuscus can detect 4.8 mm diameter spheres at a distance of 2.9 m, and 19.1 mm diameter spheres at a distance of 5.1 m. The threshold of echo-detection corresponds to the distance at which a target returns an echo amplitude in the region of 0 dB SPL. The results demonstrate that the maximum effective range of bat sonar is greater than previously indicated by obstacleavoidance and target-interception tasks.     

Calibrated earphones for the echolocating bat,Rhinolophus ferrumequinum

Summary A method to construct and calibrate earphones (physiologically) suitable for small bats and probably other small mammals is described. Particular emphasis was placed on getting a flat frequency response curve between 75kHz and 110kHz, the most important range forRhinolophus ferrumequinum. Below 60kHz the slope declined by about 30dB down to the audible frequency range. The maximal output without harmonic distortion (30dB down) was 80–90dB SPL, but up to 115dB SPL could be attained when accepting harmonics.Supported by the grants: Stiftung Volkswagenwerk, 111858; Deutsche Forschungsgemeinschaft, Schl 117/4; Schn 138/6     

Kinetics of spermatogenesis in megachiropteran bat, Rousettus leschenaulti (Desmarset): seminiferous epithelial cycle, frequency of stages, spermatogonial renewal and germ cell degeneration.

The paper describes in detail the cytomorphology of different types of germ cells, the 10 typical cellular associations or stages of the cycle of seminiferous epithelium (CSE), frequency of appearance of these stages, pattern of spermatogonial stem cell renewal and per cent degeneration of various germ cells in R. leschenaulti. Of the 14 steps of spermiogenesis (stained with PAS-haematoxylin) the first 10 were associated with the stages I-X, whereas, the remaining were found in association with one of the first six stages. The frequency of appearance of the various stages ranged from 3.84% (stage V) to 19.84% (stage I). These observations indicate that stage V is of shortest duration and stage I is of the longest duration in the bat. Five types of spermatogonia (A1, A2, A3, In and B) were identified based on their shape, size and nuclear morphology. Type A spermatogonia are oval with a large nucleus containing 1 or 2 nucleoli. The chromatin showed progressive condensation from A1 to A3 so that the latter appeared darkest among all the A type spermatogonia. The In type derived from A3 are smaller but appear darker than A3 due to heterochromatin crusts along the inner border of the nucleus. The B type spermatogonia derived from In are round and possess single nucleolus. The B type spermatogonia divided mitotically before entering meiosis or the actual production of the primary spermatocytes. The various spermatogonia divided mitotically at fixed stages of the cycle giving rise to their next generations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Haematology and iron status of the Egyptian fruit bat, Rousettus aegyptiacus

1. Haematological values and iron status of wild and captive fruit bats (Rousettus aegyptiacus) were determined. 2. Plasma iron concentrations were 175 micrograms/dl in wild males, and 286-316 micrograms/dl in captive bats. 3. Total splenic stores were small (around 100 micrograms) in relation to hepatic stores (3 mg) and total haem iron (2.6 mg). 4. Haemoglobin levels, red cell counts and haematocrits were unusually high and mean corpuscular volumes low. 5. Lactating wild bats showed no deficits in iron status or in haematological values. 6. It is concluded that the ascorbic acid content of fruit, together with the bats' high food requirement, has ensured an ample iron supply in this vegetarian species.     

Effect of aging on the photic entrainment in the frugivorous bat, Rousettus leschenaulti

Aging disrupted the photic entrainment in old (∼15 years) frugivorous Rousettus leschenaulti bats as natural light - dark (LD) cycles in the field or artificial LD cycles of 12 h of light at 2000 lux and 12 h of complete darkness failed to entrain them (Vanlalnghaka & Joshi 2005; Vanlalnghaka et al. 2005). The results were attributed to the age-related decline in photic sensitivity and/or the period of zeitgeber (T) deviating too much from the free-running period (τ) of bats. In the present study, the old bats were subjected to LD cycles in which the intensity of the photophase was raised to 6000 lux and Ts of 23.2 h and 24.9 h were exactly that of τ in the scotophase of LD cycles and in constant darkness, respectively. These LD cycles also failed to entrain the old bats which unambiguously demonstrates that aging in R. leschenaulti disrupted the integrity of the photic entrainment mechanism.     

Ultrastructure of the pineal gland of the tropical bat Rousettus leschenaulti

The ultrastructure of the pineal organ was studied in the tropical megachiropteran Rousettus leschenaulti. The pineal lies deep beneath the hemispheres adjacent to the third ventricle and is traversed by the habenular commissure anteriorly. Its parenchyma consists of a uniform population of light and occasional dark pinealocytes which appear to differ only in the degree of cytoplasmic staining. Pinealocytes are characterized by well developed Golgi bodies associated with numerous small vesicles, many mitochondria and polyribosomes, and frequent subsurface cisternae. Lipid droplets and elements of smooth endoplasmic reticulum are scant. Cisternae of granular endoplasmic reticulum are occasionally dilated. A distinct feature is the abundance of clear vesicles in the pinealocyte pericapillary terminals, which also frequently contain granular vesicles and a very large vacuole. The pineal is further characterized by the presence of a small number of glial cells and myelinated nerve fibers. A broad perivascular space investing numerous capillaries contains glial-cell and pinealocyte processes, collagen fibrils and abundant unmyelinated nerve fibers. Tortuous extensions of the perivascular space enter the pineal parenchyma where they come in close proximity to branched intercellular channels or canaliculi characterized by specialized junctions and microvilli. Differences between the pineal of the non-hibernating megachiropteran Rousettus and that of the hibernating microchiropteran bats, and structural similarities to the pineal of tropical rodents are discussed.     

Lipid composition of the spinal cord in the fruit bat Rousettus aegyptiacus

Spinal cords were removed from ten Egyptian fruit bats Rousettus aegyptiacus and the lipids analysed. The major phosphatides were choline glycerophosphatide (32.3%), ethanolamine glycerophosphatide (29.3%), serine glycerophosphatide (15.2%) and phosphatidylinositol (8.4%). Sphingomyelin accounted for 13.8% of the phospholipid. Glycosphingolipids amounted to 43.2 mol/100 mol lipid phosphorus, plasmalogens 32.5 mol/100 mol P and cholesterol 159.5 mol/100 mol P. The fatty acid composition of whole cord, sphingomyelin and non-hydroxy cerebroside were determined. The results were compared with data from other species.     

Characterization of microsatellite loci in fulvous fruit bat Rousettus leschenaulti

Rousettus leschenaulti is an abundant species in many countries of South‐East Asia, including south China. We isolated seven microsatellite loci in R. leschenaulti from genomic DNA enriched for CA repeats with the enriched library method. A total of 56 samples from a population in the Guangxi Province of China were tested with these microsatellite markers. The polymorphism ranged from seven to 16 alleles, and the observed heterozygosity was 84–94%. It is the first time microsatellite markers were characterized from R. leschenaulti, and these markers can be an important tool for analysing population structure and genotypic diversity.     

Electromotility of outer hair cells from the cochlea of the echolocating bat,Carollia perspicillata

Isolated outer hair cells (OHCs) and explants ot the organ of Corti were obtained from the cochlea of the echolocating bat, Carollia perspicillata, whose hearing range extends up to about 100 kHz. The OHCs were about 10–30 m long and produced resting potentials between-30 to -69 mV. During stimulation with a sinusoidal extracellular voltage field (voltage gradient of 2 mV/m) cyclic length changes were observed in isolated OHCs. The displacements were most prominent at the level of the cell nucleus and the cuticular plate. In the organ of Corti explants, the extracellular electric field induced a radial movement of the cuticular plate which was observed using video subtraction and photodiode techniques. Maximum displacements of about 0.3–0.8 m were elicited by stimulus frequencies below 100 Hz. The displacement amplitude decreased towards the noise level of about 10–30 nm for stimulus frequencies between 100–500 Hz, both in apical and basal explants. This compares well with data from the guinea pig, where OHC motility induced by extracellular electrical stimulation exhibits a low pass characteristic with a corner frequency below 1 kHz. The data indicate that fast OHC movements presumably are quite small at ultrasonic frequencies and it remains to be solved how they participate in amplifying and sharpening cochlear responses in vivo.Abbreviations BM basilar membrane - FFT fast Fourier Transfer - IHC inner hair cell - OHC outer hair cell     

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat,Rhinolophus rouxi

Summary Doppler shift compensation behaviour in horseshoe bats, Rhinolophus rouxi, was used to test the interference of pure tones and narrow band noise with compensation performance. The distortions in Doppler shift compensation to sinusoidally frequency shifted echoes (modulation frequency: 0.1 Hz, maximum frequency shift: 3 kHz) consisted of a reduced compensation amplitude and/or a shift of the emitted frequency to lower frequencies (Fig. 1).Pure tones at frequencies between 200 and 900 Hz above the bat's resting frequency (RF) disturbed the Doppler shift compensation, with a maximum of intererence between 400 and 550 Hz (Fig. 2). Minimum duration of pure tones for interference was 20 ms and durations above 40 ms were most effective (Fig. 3). Interfering pure tones arriving later than about 10 ms after the onset of the echolocation call showed markedly reduced interference (Fig. 4). Doppler shift compensation was affected by pure tones at the optimum interfering frequency with sound pressure levels down to –48 dB rel the intensity level of the emitted call (Figs. 5, 6).Narrow bandwidth noise (bandwidth from ± 100 Hz to ± 800 Hz) disturbed Doppler shift compensation at carrier frequencies between –250 Hz below and 800 Hz above RF with a maximum of interference between 250 and 500 Hz above resting frequency (Fig. 7). The duration and delay of the noise had similar influences on interference with Doppler shift compensation as did pure tones (Figs. 8, 9). Intensity dependence for noise interference was more variable than for pure tones (-32 dB to -45 dB rel emitted sound pressure level, Fig. 10).The temporal and spectral gating in Doppler shift compensation behaviour is discussed as an effective mechanism for clutter rejection by improving the processing of frequency and amplitude transients in the echoes of horseshoe bats.Abbreviations CF constant frequency - FM frequency modulation - RF resting frequency - SPL sound pressure level     

Spectral selectivity of FM-FM neurons in the auditory cortex of the echolocating bat,Myotis lucifugus

1. Spectral sensitivity was examined in delay-sensitive neurons in the auditory cortex of the awake FM bat, Myotis lucifugus. FM stimuli sweeping 60 kHz downward in 4 ms were used as simulated pulse-echo pairs to measure delay-dependent responses. At each neuron's best delay, the pulse and/or echo were divided into 4 FM quarters (Ist, IInd, IIIrd, and IVth), each sweeping 15 kHz in 1 ms, and quarters essential for delay sensitivity were determined for both pulse and echo. 2. For the pulse, the IVth quarter was essential for delay sensitivity in the majority of neurons. For the echo, the essential quarter for most neurons was the IInd, IIIrd, or IVth. 3. Different quarters of the pulse and echo were essential for delay sensitivity in 68% of the neurons examined. 4. This study provides neurophysiological evidence linking both spectral and temporal processing in delay-sensitive neurons of Myotis. Since spectral cues can provide target-shape information, sensitivity to both spectral and temporal parameters in single neurons may endow these neurons in FM bats with the potential for target analysis other than echo-ranging.