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[Ecological and epidemiologic aspects of the attacks by vampire bats and paralytic rabies in Argentina and analysis of the proposals carried out for their control].

The authors describe the ecology of attacks by vampire bats and the epidemiology of rabies (paralytic rabies) transmitted by these bats in Argentina, based on data obtained from an epidemiological vigilance programme conducted between 1984 and 1993. It was found that rabies spread rapidly among vampire bats, causing high mortality (over 50%); subsequently, the population recovered slowly due to the low reproductive rate. This explains the features of paralytic rabies, such as high mortality among affected populations, brief duration and subsequent recurrence. Paralytic rabies occurs throughout the year without evidence of seasonal occurrence and with no relationship to rainfall. This is because vampire bats remain active within their habitat, neither hibernating nor migrating. The problem created by vampire bats depends on the ecosystem of their habitat. In the livestock ecosystem, the bats are synanthropic and their population is abundant. They feed almost exclusively on livestock and attacks on human beings are sporadic. In this ecosystem, paralytic rabies is a serious economic problem because of its frequency and readiness to spread (41 separate outbreaks were recorded in addition to an epidemic). On the contrary, in the scarcely populated livestock ecosystem, the vampire but population is much smaller; they feed on various species of animals, and attacks on human beings are more common, but paralytic rabies occurs only sporadically (one isolated outbreak). For overall control of paralytic rabies, the authors recommend reduction of the vampire bat population to a safe level, in order to break the chain of rabies transmission and diminish attacks by bats.

Animals↗

Vomeronasal organ in bats and primates: extremes of structural variability and its phylogenetic implications.

The mere appearance of a tubular, epithelially-covered, bilateral structure, no matter how minuscule, on the anteroventral nasal septum of tetrapods, is generally called the vomeronasal organ (of Jacobson). However, considering the functionality of this chemosensory structure, the presence of a non-cilated (microvillar) neuroepithelium (and not just any odd type of epithelium) encased in a variously shaped vomeronasal cartilage, along with vomeronasal nerve bundles and above all an accessory olfactory bulb connected to the limbic vomeronasal amygdala, are the absolute essential neurostructural characteristics and anatomic requirement for a functional VNO and the accessory olfactory system in any tetrapod. The distribution of the vomeronasal organ is reported here in two mammalian orders: Chiroptera and Primates. An impressive data pool on the vomeronasal organ of bats is now available, pointing to the fact that at this time bats may be the only group in which this organ system is extremely variable, ranging from total absence (even in the embryo) to spectacular development with numerous intervening stages in different chiropteran species. Of the eighteen bat families, only one family of New World leaf-nosed bats, family Phyllostomidae, exhibits functional vomeronasal organs. The vespertilionid bat Miniopterus, and the mormoopid bat Pteronotus, present exceptions to this rule. Among Primates, very few species have been rigorously studied. As a result, developmental variability of the vomeronasal organ is almost unknown; either the vomeronasal organ is well developed (such as in New World monkeys) or absent (as in Old World monkeys and great apes) in the adult. The concept whether adult humans or embryonic and fetal forms are endowed with this so-called sixth sense, is a controversial one and is under intense study in our laboratory and by others. The general phylogenetic implications based on our cladistic analysis of bats are that the vomeronasal organ complex has evolved several times. Among the prosimians and platyrrhine primates, the organ is well developed, although to a varying degree. Among catarrhine primates, its loss has occurred only once, as it is generally absent in the adult forms.

Age Factors↗

Echolocation by young bats on their initial and subsequent flights.

This study documents developmental changes in the vocal reaction of bats to obstacles and describes the pulse patterns of young bats on their 1st and subsequent flights. The pulse repetition rate of young bats showed an increase just before the bats approached obstacles. This pattern differs from that of older bats. The distance at which the change in pulse repetition rate occurs is roughly twice as far from the obstacle in adults as it is in young bats. Even on their 1st flights young bats (25-29 days old) seemed to perform better than chance. This capability seems to be resistant to environmental manipulation during the preweaning period.

Age Factors↗

Social calls coordinate foraging in greater spear-nosed bats

The function of social calls emitted by foraging bats has received little study. Here we use observations of free-ranging greater spear-nosed bats, Phyllostomus hastatus, and field playbacks to determine whether audible, broad-band 'screech' calls attract mates, warn conspecifics or influence access to food. Five lines of evidence suggest that screech calls enable adult females from the same roosting group to fly together from the day roost to feeding sites. (1) Seasonal differences in diet influenced the rate of screech calling recorded outside the cave roost, as well as how often bats departed together. Bats called more often and flew in larger groups when feeding on a concentrated resource, balsa, Ochroma lagopus, flowers, in winter than on more dispersed Cecropia peltata fruit in spring. (2) Observations of bats flying outside the cave, in flyways and at feeding sites indicated that screech calls occurred more often when bats flew in groups than alone. (3) Females from the same roosting group were netted at the same feeding site, sometimes simultaneously, several kilometres from the cave. (4) Calling colour-marked adult females outside the cave were joined by a female group member, both on initial departures and on second foraging trips, more often than non-calling bats. (5) Playbacks attracted conspecifics at roost and feeding sites. Screech calls appear to function as contact calls that recruit and coordinate foraging among group members. We postulate that females benefit from foraging with unrelated roost-mates because they can defend feeding sites more effectively. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

Molecular typing of Histoplasma capsulatum isolated from infected bats, captured in Mexico.

The present paper represents data on the genetic polymorphism of 13 Histoplasma capsulatum isolates recovered from infected bats randomly captured in the Mexican states of Morelos, Puebla, and Oaxaca. The polymorphic DNA patterns were analyzed by two-primer RAPD-PCR (random amplified polymorphic DNA-polymerase chain reaction) method. To amplify the fungal genome by PCR, the following primer arrangements were used: 5'-AACGCGCAAC-3' and 5'-AAGAGCCCGT-3'; 5'-AACGCGCAAC-3' and 5'-GTTTCCGCCC-3'; or 5'-AACGCGCAAC-3' and 5'-GCGATCCCCA-3'. A common polymorphic DNA pattern of H. capsulatum was revealed in different assays. This pattern is shared by 7 H. capsulatum isolates recovered from different specimens of nonmigratory bats (Artibeus hirsutus) captured in a cave in Morelos, by 5 isolates recovered from infected migratory bats (Leptonycteris nivalis) captured in Morelos and Puebla, and by 1 isolate from another migratory bat (L. curasoae) captured in Oaxaca. This polymorphic DNA pattern of H. capsulatum could represent fungal markers for the geographic areas studied, and considering its distribution in three different states of the Mexican Republic, the role of bats as responsible for H. capsulatum spreading in nature, in relation to their movements and migrations besides their shelter habits, is suggested. Analyses of DNA patterns of H. capsulatum isolated from infected bats, from clinical cases, and from blackbird excreta, have shown a major relatedness between bats and clinical isolates, in contrast to those isolates from bird excreta.

Animals↗

Observations on serum 25-hydroxyvitamin D and calcium concentrations from wild-caught and captive neotropical bats, Artibeus jamaicensis.

Most bats of the suborder Microchiroptera are nocturnal, actively avoid sunlight, and eat mineral-poor diets. In those bats previously studied with respect to mineral metabolism, extensive bone remodeling occurs, and it has been suggested that calcium has been an important constraint on reproduction. There have been no previous studies of vitamin D or its metabolites in microchiropteran bats with respect to calcium metabolism. Reported is the utilization of current advances for the determination of serum levels of the vitamin D metabolite 25-hyroxyvitamin D (25-OH-D) in a neotropical bat, Artibeus jamaicensis. Serum from wild-caught animals contained low levels of 25-OH-D (5.6 +/- 3.0 ng/ml, n = 8). Bats maintained on a vitamin-D-supplemented diet had higher serum 25-OH-D levels and when the diet containing vitamin D was discontinued, mean serum 25-OH-D levels declined significantly after 6 months. Serum calcium concentrations in wild-caught bats (8.5 +/- 0.4 mg%) showed very little variation and were not significantly different in any of the vitamin-D-supplemented animals. A pairwise correlation analysis between 25-OH-D and serum calcium levels revealed no linear correlation. The results indicate either that 25-OH-D does not appear to play a key role or that low levels of 25-OH-D may be adequate in regulating serum calcium levels in this bat.

25-Hydroxyvitamin D 2↗

Integration time for short broad band clicks in echolocating FM-bats (Eptesicus fuscus).

Vespertilionid FM-bats (four Eptesicus fuscus and one Vespertilio murinus) were trained in an electronic phantom target simulator to detect synthetic echoes consisting of either one or two clicks. The threshold sound pressure for single clicks was around 47 dB peSPL for all five bats corresponding to a threshold energy of -95 dB re 1 Pa2*s. By varying the interclick interval, delta T, for double clicks it was shown that the threshold intensity was around -3 dB relative to the threshold for single clicks at delta T up to 2.4 ms, indicating perfect power summation of both clicks. A threshold shift of -13.5 dB for a 1 ms train of 20 clicks (0.05 ms interclick interval) confirmed that the bats integrated the power of the stimuli. At delta T longer than around 2.5 ms the threshold for double clicks was the same as for single clicks. Thus, the bats performed like perfect energy detectors with an integration time of approximately 2.4 ms. This integration time is an order of magnitude shorter than that reported for bats listening passively for pure tones. In our setup the bats emitted sonar signals with durations of 2-3 ms. Hence, the results may indicate that while echolocating the bats integration time is adapted to the duration of the sonar emissions.

Animals↗

Sound strategy: acoustic aposematism in the bat-tiger moth arms race.

The night sky is the venue for an ancient arms race. Insectivorous bats with their ultrasonic sonar exert an enormous selective pressure on nocturnal insects. In response insects have evolved the ability to hear bat cries, to evade their hunting maneuvers, and some, the tiger moths (Arctiidae), to utter an ultrasonic reply. We here determine what it is that tiger moths "say" to bats. We chose four species of arctiid moths, Cycnia tenera, Euchaetes egle, Utetheisa ornatrix, and Apantesis nais, that naturally differ in their levels of unpalatability and their ability to produce sound. Moths were tethered and offered to free-flying naive big brown bats, Eptesicus fuscus. The ability of the bats to capture each species was compared to their ability to capture noctuid, geometrid, and wax moth controls over a learning period of 7 days. We repeated the experiment using the single arctiid species E. egle that through diet manipulation and simple surgery could be rendered palatable or unpalatable and sound producing or mute. We again compared the capture rates of these categories of E. egle to control moths. Using both novel learning approaches we have found that the bats only respond to the sounds of arctiids when they are paired with defensive chemistry. The sounds are in essence a warning to the bats that the moth is unpalatable-an aposematic signal.

Animals↗

DDT and the decline of free-tailed bats (Tadarida brasiliensis) at Carlsbad Cavern, New Mexico.

DDT is believed to have caused the population of Brazilian free-tailed bats (Tadarida brasiliensis mexicana) at Carlsbad Cavern to decline severely after 1936. Nevertheless, previous data supporting this hypothesis are limited to a single study from 1974, which indicated that 20% of young free-tails from the cavern may have died of DDE poisoning during their first southward migration. In this study I compared organochlorine residues among samples of free-tails collected in Carlsbad Cavern in 1930, 1956, 1965, 1973, and 1988. Samples of skin cut from dry museum specimens were chemically analyzed, except for the 1973 data, which were derived from analyses of whole bats minus gastrointestinal tracts. Accumulated residue levels of DDT compounds in bats from 1965 and 1956 exceeded those in 1973 bats by approximately 4.8 times and approximately 2.7 times, respectively. This suggests that lethal effects of DDT compounds were substantially greater in the 1950s and 1960s than in the 1970s. Residues in 1988 bats resembled those for 1973 bats. It is concluded that DDT played a major role in this severe population decline. These results can be applied by management personnel in evaluating the present and future status of this population regarding persisting organochlorine insecticides as well as other agricultural chemicals now in use. The case of the Carlsbad colony is discussed relative to the general issue of other bat population declines.

Animals↗

Object recognition by echolocation: a nectar-feeding bat exploiting the flowers of a rain forest vine.

In the bat-pollinated vine Mucuna holtonii only the first visit to a flower is rewarded with a substantial amount of nectar, which is released when a bat lands on the flower and triggers an explosion mechanism. During later visits the bats receive only small amounts of nectar. Nevertheless, the inflorescences as a whole remain attractive, since further buds successively open during the night. Nectar-feeding bats Glossophaga commissarisi selectively visit unexploded, "virgin" flowers. They can discriminate buds, virgin and exploded flowers using echolocation. In field experiments bats exploited virgin flowers, the vexillum of which had been replaced by a same-sized triple mirror or by an artificial vexillum. Such flowers were frequently inspected, but not as often exploited as natural flowers. In two-alternative-forced-choice experiments the bats learned to discriminate between replicas of the vexillum and triple mirrors. The recognition distance was between 15 and 50 cm. Echoes of the three flowering stages differ in their spectral composition, which changes in dependence of the sound incidence angle in a characteristic way. We conclude that glossophagine bats are able to recognize small motionless structures like flowers and to accurately adjust their landing manoeuvres by using their echolocation system alone.

Animals↗

Can two streams of auditory information be processed simultaneously? Evidence from the gleaning bat Antrozous pallidus.

A tenet of auditory scene analysis is that we can fully process only one stream of auditory information at a time. We tested this assumption in a gleaning bat, the pallid bat (Antrozous pallidus) because this bat uses echolocation for general orientation, and relies heavily on prey-generated sounds to detect and locate its prey. It may therefore encounter situations in which the echolocation and passive listening streams temporally overlap. Pallid bats were trained to a dual task in which they had to negotiate a wire array, using echolocation, and land on one of 15 speakers emitting a brief noise burst in order to obtain a food reward. They were forced to process both streams within a narrow 300 to 500 ms time window by having the noise burst triggered by the bats' initial echolocation pulses as it approached the wire array. Relative to single task controls, echolocation and passive sound localization performance was slightly, but significantly, degraded. The bats also increased echolocation interpulse intervals during the dual task, as though attempting to reduce temporal overlap between the signals. These results suggest that the bats, like humans, have difficulty in processing more than one stream of information at a time.

Acoustic Stimulation↗

Reproductive energetics of the nectar-feeding bat Glossophaga soricina (Phyllostomidae).

Pregnancy and lactation are energetically demanding periods for female mammals. Unique amongst mammals, bats have to allocate considerable amounts of energy into their offspring because juveniles cannot be weaned until they are capable of flying at almost adult size. Similar to other bat species, female nectar-feeding bats should increase their energy intake after parturition to meet the energy demands of offspring growth. However, previous studies have shown that nectar-feeding bats differ from other similar-sized bats in having a much higher metabolic rate. Therefore, I examined how nectarivorous bats respond to the energetic challenge of reproduction. In this study, the daily energy intake of pregnant and lactating Glossophaga soricina was measured during a 6-week period prior to and a 10-week period after parturition. Body mass of G. soricina increased linearly until parturition. Within the same time period, daily flight time decreased and daily energy intake remained constant. Probably, the reduced flight activity of pregnant bats compensated for the increased power requirements of flight, thus resulting in an almost constant daily energy turnover. During 35 days after parturition, neither flight time, body mass nor daily energy intake of lactating females changed significantly. On average, the daily energy intake of pregnant, lactating or non-reproducing G. soricina was not significantly different. Possibly, for unknown reasons, female G. soricina maintain a daily energy intake of a constant high level during and beyond reproduction.

Animals↗

Thermal physiology of pregnant and lactating female and male long-eared bats, Nyctophilus geoffroyi and N. gouldi.

During roosting in summer, reproductive female bats appear to use torpor less frequently and at higher body temperatures (Tb) than male bats, ostensibly to maximise offspring growth. To test whether field observations result from differences in thermal physiology or behavioural thermoregulation during roosting, we measured the thermoregulatory response and energetics of captive pregnant and lactating female and male long-eared bats (Nyctophilus geoffroyi 8.9 g and N. gouldi 11.5 g) during overnight exposure to a constant ambient temperature (Ta) of 15 degrees C. Bats were captured 1-1.5 h after sunset and measurements began at 21:22+/-0:36 h. All N. geoffroyi entered torpor commencing at 23:47+/-01:01 h. For N. gouldi, 10/10 males, 9/10 pregnant females and 7/8 lactating females entered torpor commencing at 01:10+/-01:40 h. The minimum Tb of torpid bats was 15.6+/-1.1 degrees C and torpid metabolic rate (TMR) was reduced to 0.05+/-0.02 ml O2 g(-1) h(-1). Sex or reproductive condition of either species did not affect the timing of entry into torpor (F=1.5, df=2, 19, P=0.24), minimum TMR (F=0.21, df=4, 40, P=0.93) or minimum Tb (F=0.76, df=5, 41, P=0.58). Moreover, sex or reproductive condition did not affect the allometric relationship between minimum resting metabolic rate and body mass (F=1.1, df=4, 37, P=0.37). Our study shows that under identical thermal conditions, thermal physiology of pregnant and lactating female and male bats are indistinguishable. This suggests that the observed reluctance by reproductive females to enter torpor in the field is predominantly because of ecological rather than physiological differences, which reflect the fact that females roost gregariously whereas male bats typically roost solitarily.

Acclimatization↗

Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera).

Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats showed a large variation in body temperature (Tb) (33 to 37 degrees C) over a wide range of ambient temperatures (Tas) and a relatively low basal metabolic rate (1.29 ml O2 g-1 h-1). Bats entered torpor frequently in the laboratory at Tas between 14 and 25 degrees C. Entry into torpor always occurred when lights were switched on in the morning, independent of Ta. MRs during torpor were reduced to about 20-40% of normothermic bats and Tbs were regulated at a minimum of 23.1 +/- 1.4 degrees C. The duration of torpor bouts increased with decreasing Ta in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum Tb and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the Tb was also about 5 degrees C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected by Ta and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor.

Adaptation, Physiological↗

A view of the world through the bat's ear: the formation of acoustic images in echolocation.

Echolocating bats perceive objects as acoustic images derived from echoes of the ultrasonic sounds they emit. They can detect, track, identify, and intercept flying insects using sonar. Many species, such as the big brown bat, Eptesicus fuscus, emit frequency-modulated sonar sounds and perceive the distance to targets, or target range, from the delay of echoes. For Eptesicus, a point-target's image has a sharpness along the range axis that is determined by the acuity of echo-delay perception, which is about 10 ns under favorable conditions. The image as a whole has a fine range structure that corresponds to the cross-correlation function between emissions and echoes. A complex target- which has reflecting points, called "glints", located at slightly different distances and reflects echoes containing overlapping components with slightly different delays--is perceived in terms of its range profile. The separation of the glints along the range dimension is encoded by the shape of the echo spectrum created by interference between overlapping echo components. However, Eptesicus transforms the echo spectrum back into an estimate of the original delay separation of echo components. The bat thus converts spectral cues into elements of an image expressed in terms of range. The absolute range of the nearest glint is encoded by the arrival time of the earliest echo component, and the spectrally encoded range separation of additional glints is referred to this time-encoded reference range for the image as a whole. Each individual glint is represented by a cross-correlation function for its own echo component, the nearest of which is computed directly from arrival-time measurements while further ones are computed by transformation of the echo spectrum. The bat then sums the cross-correlation functions for multiple glints to form the entire image of the complex target. Range and shape are two distinct features of targets that are separately encoded by the bat's auditory system, but the bat perceives unitary images that require fusion of these features to create a synthetic psychological dimension of range. The bat's use of cross-correlation-like images reveals neural computations that achieve fusion of stimulus features and offers an example of high-level operations involved in the formation of perceptual "wholes".

Animals↗

Exercise-training reduces BAT thermogenesis in rats.

In the energy balance equation, physical activity represents one component of energy expenditure. From various studies it appears that exercise-training does not affect clearly thermogenesis which depends on brown adipose tissue (BAT) activity. In the present work we examine how exercise-training can influence food intake and body weight regulation in relation to BAT thermogenesis. The proton conductance of the uncoupling protein of BAT was examined in male adult Wistar trained 2 h/day for 20 days and compared to that of sedentary (2 h of fasting instead of exercise) or control animals. All animals were provided with separate sources of the 3 macronutrients (protein, fat and carbohydrate) containing an identical percentage of vitamins, salt mixture and cellulose powder. At the end of training, rats were placed at 5 degrees C during 10 days, then during 4 days at 28 degrees C. This condition has been demonstrated to favour and amplify BAT responsiveness to moderate modifications of stimulation. The body weight of trained rats became significantly lower than that of the control and sedentary rats and this difference persisted all throughout the experiment. When placed at 5 degrees C, all rats increased their total ingestion: control rats enhanced fat intake, while sedentary and trained rats enhanced carbohydrate ingestion. When placed at 28 degrees C, all rats had identical total energy and that of the 3 items intakes. BAT proton conductance was about 40% lower in the trained compared with the sedentary plus the control rats. This indicated a lower BAT thermogenic activity in the trained animals. It could be concluded that exercise-training in rats induces negative energy balance; the reduced BAT activity could restrain weight loss and overeating.

Adipose Tissue, Brown↗

Toxicity and tissue distribution of pentachlorophenol and permethrin in pipistrelle bats experimentally exposed to treated timber.

The dependence of bats in Britain on houses as roosts may result in them being exposed to pesticides used in remedial timber treatments. Pentachlorophenol (PCP) and permethrin are used as a fungicide and an insecticide for timber treatment, respectively. The present study investigated toxicity and distribution in body tissues of these two pesticides in pipistrelle bats. Four groups of nine to ten bats were kept in separate outdoor flight enclosures and were provided with roost boxes treated with either PCP only, permethrin, PCP/permethrin mixture or solvent only (control). At the start of the experiment, mean (+/-SE) PCP and permethrin concentrations on the surface of wooden blocks that had been treated in the same way as roost boxes were 69.32+/-6.76 mg g(-1) (n=6) and 3.3+/-1.6 mg g(-1) (n=3), respectively. All bats exposed to PCP and PCP/permethrin treated boxes died within 24 and 120 h, respectively; nine out of the ten controls survived the 32 day experimental period (P<0.001; both groups compared with control). Bats exposed to permethrin treated boxes survived as well as controls. Mean (+/-SE) carcass PCP concentration (excluding deposits on fur) of bats exposed to PCP and PCP/permethrin treated boxes was 13.11+/-2.52 microg g(-1)BW (n=20). PCP burdens on fur were positively correlated with total weight of PCP in the carcass (P<0.001). PCP was present in fat depots, liver, kidney and the remainder of the body which, despite containing low PCP concentrations, was the main PCP reservoir (66.4+/-5.0% of carcass PCP load; n=20). Total PCP in the carcass was significantly correlated with lipid weight (P<0.005). Permethrin was not detectable in body washes and tissues of bats exposed to PCP/permethrin mixture or permethrin.

Journal Article↗

A comparative study of bile acid CoA:amino acid:N-acyltransferase (BAT) from four mammalian species.

1. Bile acid CoA:amino acid:N-acyltransferase (BAT) was partially purified from dog, human, pig and rat livers. The interspecies variation in substrate specificity and kinetics were determined for glycine and taurine. 2. BAT activity from dog liver formed bile acid conjugates with taurine exclusively, whereas BAT activity from each of the other species formed conjugates with both taurine and glycine. 3. Biliary composition of glycine and taurine bile acid conjugates could partly be accounted for by substrate affinity (Km) and turnover number (Vmax) of BAT activity. 4. A monospecific anti-human BAT polyclonal antibody reacted on Western blot analysis with a 40 kDa band in a 100,000 g supernatant fraction from rat liver. 5. Immunoabsorption chromatography using an anti-human BAT antibody-Sepharose affinity column showed that both the immunoreactive protein band and BAT activity were removed from the 100,000 g supernatant fraction from human and rat livers.

Acetyltransferases↗