Fruit Bats Research Articles

Electron Microscopic Studies of the Adrenal Gland during Seasonal Cycle of Fruit Eating Bat Pteropus Giganteus giganteus

The fine structure of the adrenal gland is testified in many mammals; whereas, very diminutive information is available on the fine structure of the bat’s adrenal gland. The present work is constrained to the ultrastructural studies of the adrenal gland of Pteropus giganteus giganteus. The adrenal gland of the male bat has two distinct perceptible zonations viz., cortex and medulla. The cortex is divided into three illustrious zones namely, zona glomerulosa, zona fasciculata and zona reticularis. The differences in the zonation under the electron microscope becomes more acute when the studied bat is sexually active. Histoarchitectural study of the adrenal gland designate prominent structures and striking differences in the adrenocortical zone during the sexually active period than the sexually quiescent period. The zona fasciculata is well developed during the sexually active period than that of the sexually quiescent period. Likewise, zona fasciculata is well developed as compared to zona glomerulosa and zona reticularis of the adrenal cortex in both active and quiescent stages. Light microscopic studies on adrenal gland are confirmed by the ultrastructural studies.

Generating bat primary and immortalised cell-lines from wing biopsies.

Bats are becoming recognised as new model species to study naturally evolved mammalian extended healthspan and disease tolerance. However, this research is limited by the lack of bat specific cellular resources. Here we describe an optimised protocol to develop both primary and immortalised fibroblast cell-lines from wing biopsy punches from the Egyptian fruit bat, Rousettus aegyptiacus. We show that the immortalised cell lines and primary cells show similar characteristics in their proliferative capacity and response to oxidative stress. They also exhibited a similar response in their NF-κB immune response to TLR agonists including SARS-CoV2. As wing punches can be acquired non-lethally, these methods can be used to develop primary and immortalised cells, from potentially any bat species, including those of conservation concern that cannot be sacrificed. This can expand the scope of bat species that can be studied in the future, and the development of key cellular resources required to functionally validate the regulators of bats' unique longevity.

Old world fruit bats (Pteropodidae, Chiroptera) from the pleistocene of Vietnam

Isolated teeth of a lesser short-nosed fruit bat Cynopterus brachyotis (Müller, 1838), a fulvous fruit bat Rousettus leschenaultii (Desmarest, 1820), and a dawn bat Eonycteris spelaea (Dobson, 1871) are described from the Middle Pleistocene Tham Hai cave locality in northern Vietnam (Lang Son Province). These are the first fossil findings of the Old World fruit bats in Vietnam. The Middle Pleistocene association of Pteropodidae from the Tham Hai locality may largely reflect the composition of species that roosted in local caves.

Reproductive cycle of the Egyptian Fruit Bat, Rousettus aegyptiacus (Chiroptera: Petropodidae) in northern Egypt

The reproductive patterns of both sexes of the Egyptian Fruit Bat, Rousettus aegyptiacus, were studied in a population inhabiting a roost within Giza Governorate, northern Egypt. Bat specimens were collected over a period of 13 months extending from June 2017 to June 2018, inclusive. The reproductive cycle of males consisted of four consecutive phases, namely the active phase in autumn and the early winter months (October to January), the regressing phase in late winter and early spring months (February to April), the regressed phase in late spring and summer (May to August), and the recrudescence phase in early autumn (September). No active sperms were observed in smears of the cauda epididymis during the regressed phase (June–August) and males were considered to be sexually inactive during this phase. Varying percentages of reproductively active females (pregnant, lactating, pregnant and lactating) were collected in all months, with peaks in summer (June–July) and late autumn and early winter (November–January).

Stochastic analysis of Ebola infection in small zoonotic niches.

The size of fruit bat colonies ranges from dozens to hundreds of thousands of individuals, depending on the species. While a deterministic modelling approach is appropriate for large colonies, the role of population fluctuations can be all-important for small colonies. From this perspective, we analyse the infection dynamics in small zoonotic niches due to filoviruses, e.g. Ebola. To this end, we perform stochastic numerical simulations and analytical calculations. The inherent stochasticity in ecological processes may play a significant role in driving small populations towards extinction. Here, we reveal that fluctuations can either lead to virus eradication or to sustain infection compared with the deterministic dynamics, depending on the size of the zoonotic niche. Altogether, our findings reveal non-trivial stochastic effects, which can shed light on the infection dynamics in small- and medium-sized bat colonies and help design preventive measures for zoonotic diseases.

Ecological and Reproductive Cycles Drive Henipavirus Seroprevalence in the African Straw-Coloured Fruit Bat (Eidolon helvum).

Bats are known to host zoonotic viruses, including henipaviruses that cause high fatality rates in humans (Nipah virus and Hendra virus). However, the determinants of zoonotic spillover are generally unknown, as the ecological and demographic drivers of viral circulation in bats are difficult to ascertain without longitudinal data. Here we analyse serological data collected from African straw-coloured fruit bats (Eidolon helvum) in Ghana over the course of 2 years and across four sites, comprising three wild roosts and one captive colony. We focus on antibody affinity to five henipavirus antigens: Ghanaian bat henipavirus (GhV), Nipah virus (NiV), Hendra virus (HeV), Mojiang virus (MojV) and Cedar virus (CedV). In the wild roosts, we detected seasonal variations in henipavirus antibody binding, possibly associated with bat life-history cycles and migration patterns. In the captive colony, we identified increases in antibody affinity levels among pregnant bats, suggesting possible shifts in the immune system during pregnancy. These bats then pass maternal antibodies to their pups, which wane before antibody affinity levels rise later in life following initial infections and/or reactivation of latent infections. These results improve our understanding of the links between bat ecology and viral circulation, including for GhV, a locally-circulating African henipavirus.

Increased Susceptibility of Rousettus aegyptiacus Bats to Respiratory SARS-CoV-2 Challenge Despite Its Distinct Tropism for Gut Epithelia in Bats

Increasing evidence suggests bats are the ancestral hosts of the majority of coronaviruses. In general, coronaviruses primarily target the gastrointestinal system, while some strains, especially Betacoronaviruses with the most relevant representatives SARS-CoV, MERS-CoV, and SARS-CoV-2, also cause severe respiratory disease in humans and other mammals. We previously reported the susceptibility of Rousettus aegyptiacus (Egyptian fruit bats) to intranasal SARS-CoV-2 infection. Here, we compared their permissiveness to an oral infection versus respiratory challenge (intranasal or orotracheal) by assessing virus shedding, host immune responses, tissue-specific pathology, and physiological parameters. While respiratory challenge with a moderate infection dose of 1 × 104 TCID50 caused a systemic infection with oral and nasal shedding of replication-competent virus, the oral challenge only induced nasal shedding of low levels of viral RNA. Even after a challenge with a higher infection dose of 1 × 106 TCID50, no replication-competent virus was detectable in any of the samples of the orally challenged bats. We postulate that SARS-CoV-2 is inactivated by HCl and digested by pepsin in the stomach of R. aegyptiacus, thereby decreasing the efficiency of an oral infection. Therefore, fecal shedding of RNA seems to depend on systemic dissemination upon respiratory infection. These findings may influence our general understanding of the pathophysiology of coronavirus infections in bats.

Viral interactions with host factors (TIM-1, TAM -receptors, Glut-1) are related to the disruption of glucose and ascorbate transport and homeostasis, causing the haemorrhagic manifestations of viral haemorrhagic fevers.

The haemorrhagic features of viral haemorrhagic fevers may be caused by common patterns of metabolic disturbances of the glucose and ascorbate homeostasis. Haemorrhages and vasculature disfunctions are a clinical feature not only of viral haemorrhagic fevers, but also in scurvy, diabetes and thrombotic microangiopathic haemolytic anaemia. Interestingly, the expression of glucose and ascorbate transporter Glut-1 on the erythrocyte membrane is associated with the inability to synthesize ascorbate and is restricted to that very species that are susceptible to filoviruses (primates, humans and fruit bats). Glut-1 may play a pivotal role in haemorrhagic fever pathogenesis. TIM-1 and TAM receptors have been recognized to enhance entry of Ebola, Lassa and Dengue viruses and viral interferences with TIM-1 could disturb its function, disturbing the expression of Glut-1. In those species not able to synthesize ascorbate and expressing Glut-1 on erythrocytes virus could interact with Glut-1 or other functionally related protein, and the influx of glucose into the cells would be severely impaired. As a consequence, transient hyperglycemia and a marked oxidative stress coupled with the high levels of glucose in plasma would be established, and then promote the activation of NF–κB transcription, exacerbating a pro-inflammatory response mediated by cytokines and chemokines: The inability to synthesize ascorbate is an Achilles Heel when trying to counteract the oxidative stress.

Cancer Prevalence across Vertebrates.

Cancer is pervasive across multicellular species, but what explains the differences in cancer prevalence across species? Using 16,049 necropsy records for 292 species spanning three clades of tetrapods (amphibians, sauropsids, and mammals), we found that neoplasia and malignancy prevalence increases with adult mass (contrary to Peto's paradox) and somatic mutation rate but decreases with gestation time. The relationship between adult mass and malignancy prevalence was only apparent when we controlled for gestation time. Evolution of cancer susceptibility appears to have undergone sudden shifts followed by stabilizing selection. Outliers for neoplasia prevalence include the common porpoise (<1.3%), the Rodrigues fruit bat (<1.6%), the black-footed penguin (<0.4%), ferrets (63%), and opossums (35%). Discovering why some species have particularly high or low levels of cancer may lead to a better understanding of cancer syndromes and novel strategies for the management and prevention of cancer. Significance: Evolution has discovered mechanisms for suppressing cancer in a wide variety of species. By analyzing veterinary necropsy records, we can identify species with exceptionally high or low cancer prevalence. Discovering the mechanisms of cancer susceptibility and resistance may help improve cancer prevention and explain cancer syndromes.

Structural Analysis of Virus Regulatory N6-Methyladenosine (m6A) Machinery of the Black Flying Fox (Pteropus alecto) and the Egyptian Fruit Bat (Rousettus aegyptiacus) Shows Evolutionary Conservation Amongst Mammals

Background: N6-methyladenosine (m6A) is an abundant RNA epitranscriptomic modification in eukaryotes. The m6A machinery includes cellular writer, eraser and reader proteins that regulate m6A. Pteropus alecto (P. alecto) (the Australian black flying fox) and Rousettus aegyptiacus (R. aegyptiacus) (the Egyptian fruit bat) are bats associated with several viral zoonoses yet neglected in the field of m6A epigenetics studies. Objectives: This study utilises various bioinformatics and in silico tools to genetically identify, characterise and annotate the m6A machinery in P. alecto and R. aegyptiacus. Methods: A range of bioinformatic tools were deployed to comprehensively characterise all known m6A-associated proteins of P. alecto and R. aegyptiacus. Results: Phylogenetically, the m6A fat mass and obesity-associated protein (FTO) eraser placed the order Chiroptera (an order including all bat species) in a separate clade. Additionally, it showed the lowest identity matrices in P. alecto and R. aegyptiacus when compared to other mammals (74.1% and 72.8%) and Homo sapiens (84.0% and 76.1%), respectively. When compared to humans, genetic loci-based analysis of P. alecto and R. aegyptiacus showed syntenic conservation in multiple flanking genes of 8 out the 10 m6A-associated genes. Furthermore, amino acid alignment and protein tertiary structure of the two bats’ m6A machinery demonstrated conservation in the writers but not in erasers and readers, compared to humans. Conclusions: These studies provide foundational annotation and genetic characterisation of m6A machinery in two important species of bats which can be exploited to study bat–virus interactions at the interface of epitranscriptomics.

Why do bats fly into cave doors? Inattentional blindness in echolocating animals.

Echolocating bats can navigate complex 3D environments by integrating prior knowledge of spatial layouts and real-time sensory cues. This study demonstrates that inattentional blindness to sensory information undermines successful navigation in Egyptian fruit bats, Rousettus aegyptiacus , a species that has access to vision and echolocation to traverse natural environments. Bats flew over repeated trials to a perch at a fixed location in the light, allowing them to navigate using both vision and echolocation. The experiment was then repeated in the dark to exclude the bat's use of vision. The perch was subsequently displaced by either 15 or 30 cm in one of six different directions (up, down, left, right, front, back). Echolocation behavior was recorded using a 25-channel microphone array, while flight paths were tracked using 13 motion capture cameras. The directional aim of echolocation clicks served as a metric for the bat's spatial attention to locations in their environment. In the light, bats modified their flight paths to successfully land on a perch that was moved 15 cm but surprisingly, often failed to land on it when displaced by 30 cm. In the dark, bats often failed to land on the perch after it was moved by only 15 cm. Landing failures suggest that learned spatial priors invoked inattentional blindness to changes in the environment, which interfered with successful navigation. In both the light and dark, when bats failed to land on the perch at its new location, they directed their attention toward the original perch position. Performance differences in the light and dark suggest that the bat's attentional spotlight may be narrower when it relies on echolocation than vision. To our knowledge, these findings provide the first evidence of inattentional blindness in a flying echolocating animal, demonstrating that spatial priors can dominate sensory processing during navigation.

Anthropogenic disturbances alter the trophic niche structure and ecological relationships of understory bat communities in the Ecuadorian Andean Chocó

Human disturbances have reduced the three basic niche dimensions for the survival of some mammalian species (space, time, and resources). Anthropic activities cause the extinction of ecological functionalities faster than species extinctions. In this study, we identified four types of habitats in the Ecuadorian Andean Chocó: primary forest (PF), secondary forest in natural regeneration (SF1), secondary forest in assisted regeneration (SF2), and pastures for cattle (P). The main objective was to determine the responses in the trophic niche and the ecological relationships of understory phyllostomid bat communities. We captured bats with mist nets and obtained fecal samples from 21 species. These were analyzed to quantify seeds, pollen, insects, and vertebrates consumed by each individual, with counts organized by species and habitat type. We conducted an ecological relationship analysis to understand the structure of bat–fruit networks and their dietary preferences. We calculated niche breadth and niche overlap to understand the trophic niche composition of each species. We applied null models to evaluate if there is evidence of trophic niche partitioning among these species. Despite a relatively small sample size, the results obtained are nevertheless interesting. While niche breadth was not useful for detecting the effects of human disturbances, niche overlap was significantly higher in disturbed habitats (SF1, SF2 and P), where ecological relationships were weaker. Most of the species were related to the consumption of seeds from the genus Piper. These results indicate that bat communities and their ecosystem services may be highly endangered due to anthropogenic disturbances. Network interactions in bats are highly variable in geographic space and time, and little is known about the community structure of bat–seed interactions. Studying mutualistic networks in bats and seeds is crucial because of their role in ecosystem support, supply, and regulation services that depend on them.

Thermomechanical properties of bat and human red blood cells—Implications for hibernation

Hibernation is a widespread and highly efficient mechanism to save energy in mammals. However, one major challenge of hibernation is maintaining blood circulation at low body temperatures, which strongly depends on the viscoelastic properties of red blood cells (RBCs). Here, we examined at physiologically relevant timescales the thermomechanical properties of hundreds of thousands of individual RBCs from the hibernating common noctule bat (Nyctalus noctula), the nonhibernating Egyptian fruit bat (Rousettus aegyptiacus), and humans (Homo sapiens). We exposed RBCs to temperatures encountered during normothermia and hibernation and found a significant increase in elasticity and viscosity with decreasing temperatures. Our data demonstrate that temperature adjustment of RBCs is mainly driven by membrane properties and not the cytosol while viscous dissipation in the membrane of both bat species exceeds the one in humans by a factor of 15. Finally, our results show that RBCs from both bat species reveal a transition to a more viscous-like state when temperature decreases. This process on a minute timescale has an effect size that is comparable with fluctuations in RBC viscoelasticity over the course of the year, implying that environmental factors, such as diets, have a lower impact on the capability of RBCs to respond to different temperatures than general physical properties of the cell membrane. In summary, our findings suggest membrane viscoelasticity as a promising target for identifying mechanisms that could be manipulated to ensure blood circulation at low body temperatures in humans, which may be one first step toward safe synthetic torpor in medicine and space flight.

Cerebellar activity predicts vocalization in fruit bats

Echolocating bats exhibit remarkable auditory behaviors, enabled by adaptations both within and outside their auditory system. Yet research on echolocating bats has focused mostly on brain areas that belong to the classic ascending auditory pathway. This study provides direct evidence linking the cerebellum, an evolutionarily ancient and non-classic auditory structure, to vocalization and hearing. We report that in the fruit-eating bat Carollia perspicillata, external sounds can evoke cerebellar responses with latencies below 20ms. Such fast responses are indicative of early inputs to the bat cerebellum. After establishing fruit-eating bats as a good model to study cerebellar auditory responses, we searched for a neural correlate of vocal production within the cerebellum. We investigated spike trains and field potentials occurring before and after vocalization and found that the type of sound produced (echolocation pulses or communication calls) can be decoded from pre-vocal and post-vocal neural signals, with prediction accuracies that reach above 85%. The latter provides a direct correlate of vocalization in an ancient motor-coordination structure that lies outside of the classic ascending auditory pathway. Taken together, our findings provide evidence of specializations for vocalization and hearing in the cerebellum of an auditory specialist.

Using serosurveys to optimize surveillance for zoonotic pathogens.

Zoonotic pathogens pose a significant risk to human health, with spillover into human populations contributing to chronic disease, sporadic epidemics, and occasional pandemics. Despite the widely recognized burden of zoonotic spillover, our ability to identify which animal populations serve as primary reservoirs for these pathogens remains incomplete. This challenge is compounded when prevalence reaches detectable levels only at specific times of year. In these cases, statistical models designed to predict the timing of peak prevalence could guide field sampling for active infections. Thus, we develop a general model that leverages routinely collected serosurveillance data to optimize sampling for elusive pathogens by predicting time windows of peak prevalence. Using simulated data sets, we show that our methodology reliably identifies times when pathogen prevalence is expected to peak. Then, we demonstrate an implementation of our method using publicly available data from two putative Ebolavirus reservoirs, straw-colored fruit bats (Eidolon helvum) and hammer-headed bats (Hypsignathus monstrosus). We envision our method being used to guide the planning of field sampling to maximize the probability of detecting active infections, and in cases when longitudinal data is available, our method can also yield predictions for the times of year that are most likely to produce future spillover events. The generality and simplicity of our methodology make it broadly applicable to a wide range of putative reservoir species where seasonal patterns of birth lead to predictable, but potentially short-lived, pulses of pathogen prevalence.

Elevated vitamin D levels in diurnally-active female fruit bats

Animal species have evolved to enhance their survival by focusing their temporal activity on specific parts of the diurnal-nocturnal cycle. Various factors, including inter-specific competition and anti-predator behavior, as well as anthropogenic effects like light pollution, have prompted some species to expand or shift their temporal niches. Our study focuses on the temporal niche shift of the Egyptian fruit bat (Rousettus aegyptiacus) to diurnal activity in Israel.Through an extensive citizen-science study, we assessed the distribution of these bats’ diurnal activity across Israel. We also documented the sex and age of bats from a colony known for its diurnal activity and collected blood samples from them for metabolic analysis.Our findings indicate that the shift toward daytime activity predominantly takes place in urban settings and is mostly exhibited by females. We found a significant physiological effect of this temporal shift, namely: diurnal bats’ vitamin D levels were significantly higher, and their parathyroid hormone (PTH) levels were significantly lower than those of nocturnal bats.We suggest that the reproductive metabolic demands of female bats might be a key factor driving this shift to diurnal activity. We hypothesize that the increase in vitamin D, derived from sunlight hours, might play a crucial role in regulating calcium homeostasis, thus contributing to the bats’ physiological needs during the reproduction season.

Knowledge of Healthcare Workers Towards NIPAH Virus: A Cross-Sectional Study

Purpose: To evaluate the healthcare workers’ (HCWs) knowledge towards Nipah virus and identify the associated variables with good knowledge. Methods: A cross-sectional design was conducted in Najran, Kingdom of Saudi Arabia (KSA) to evaluate the knowledge of HCWs towards Nipah virus. A validated questionnaire was employed to collect the data of HCWs. It consisted of two parts: Socio-demographic characteristics of the participants and questions related to the knowledge towards Nipah virus. Percentages and median (Q1, Q3) were used to present the data and were compared by Mann–Whitney and Kruskal Wallis. The associated variables with good knowledge were identified by logistic regression. Results: The study included 247 participants. The median (Q1, Q3) knowledge score was 45% (10%, 60%), reflecting poor knowledge. About 62% of the HCWs stated that the symptoms of Nipah virus infection could be acute respiratory distress, convulsions, and coma. Only 36.8% reported no available vaccine to prevent Nipah virus infection, and more than 50% identified the virus’s main reservoir (fruit bat) as the possibility of transmission from animal to human. Roughly 57% of them reported that the virus can be transmitted among people through droplets. Less than 40% stated the Nipah virus can cause AIDS. The significantly associated variable with good knowledge was only nationality. Conclusion: The present study showed a poor knowledge of HCWs. Good knowledge was associated with nationality. Therefore, the implementation of education and training programmes are highly recommended throughout conducting prospective and interventional studies.

Characterization of a mammalian orthoreovirus isolated from the large flying fox, Pteropus vampyrus, in Indonesia.

Fruit bats serve as an important reservoir for many zoonotic pathogens, including Nipah virus, Hendra virus, Marburg virus and Lyssavirus. To gain a deeper insight into the virological characteristics, pathogenicity and zoonotic potential of bat-borne viruses, recovery of infectious viruses from field samples is important. Here, we report the isolation and characterization of a mammalian orthoreovirus (MRV) from a large flying fox (Pteropus vampyrus) in Indonesia, which is the first detection of MRV in Southeast Asia. MRV was recovered from faecal samples of three different P. vampyrus in Central Java. Nucleotide sequence analysis revealed that the genome of the three MRV isolates shared more than 99% nucleotide sequence identity. We tentatively named one isolated strain as MRV12-52 for further analysis and characterization. Among 10 genome segments, MRV12-52 S1 and S4, which encode the cell-attachment protein and outer capsid protein, had 93.6 and 95.1% nucleotide sequence identities with known MRV strains, respectively. Meanwhile, the remaining genome segments of MRV12-52 were divergent with 72.9-80.7 % nucleotide sequence identities. Based on the nucleotide sequence of the S1 segment, MRV12-52 was grouped into serotype 2, and phylogenetic analysis demonstrated evidence of past reassortment events. In vitro characterization of MRV12-52 showed that the virus efficiently replicated in BHK-21, HEK293T and A549 cells. In addition, experimental infection of laboratory mice with MRV12-52 caused severe pneumonia with 75% mortality. This study highlights the presence of pathogenic MRV in Indonesia, which could serve as a potential animal and public health concern.

Bats generate lower affinity but higher diversity antibody responses than those of mice, but pathogen-binding capacity increases if protein is restricted in their diet.

Bats are reservoirs of many zoonotic viruses that are fatal in humans but do not cause disease in bats. Moreover, bats generate low neutralizing antibody titers in response to experimental viral infection, although more robust antibody responses have been observed in wild-caught bats during times of food stress. Here, we compared the antibody titers and B cell receptor (BCR) diversity of Jamaican fruit bats (Artibeus jamaicensis; JFBs) and BALB/c mice generated in response to T-dependent and T-independent antigens. We then manipulated the diet of JFBs and challenged them with H18N11 influenza A-like virus or a replication incompetent Nipah virus VSV (Nipah-riVSV). Under standard housing conditions, JFBs generated a lower avidity antibody response and possessed more BCR mRNA diversity compared to BALB/c mice. However, withholding protein from JFBs improved serum neutralization in response to Nipah-riVSV and improved serum antibody titers specific to H18 but reduced BCR mRNA diversity.

Discovery and biological confirmation of a highly divergent Tacaribe virus in metatranscriptomic data from neotropical bats.

Clade B New World arenaviruses (NWA) include rodent-borne lethal hemorrhagic fever viruses, whereas Tacaribe virus (TCRV) stands out because of its detection in bats and its presumably low zoonotic potential. However, the bat association of TCRV was put into question by lethal experimental neotropical fruit bat infections and rare TCRV detection in bats. Scarce genomic data include near-identical viruses from Caribbean bats and ticks from the US sampled 50 years later. The prototype TCRV isolate used for experimental risk assessments has an extensive passage history in suckling mouse brains. Exploring the true genetic diversity, geographic distribution, and host range of bat-borne NWA is pivotal to assess their zoonotic potential and transmission cycles. We analyzed metatranscriptomic data for evidence of NWA identifying a highly divergent TCRV in bats and confirmed virus detection in original biological materials, supporting the association of TCRV with neotropical bats and warranting investigation of strain-associated TCRV pathogenicity.