A normal feature of the facial anatomy of many species of bat is the presence of bony discontinui... more A normal feature of the facial anatomy of many species of bat is the presence of bony discontinuities or clefts, which bear a remarkable similarity to orofacial clefts that occur in humans as a congenital pathology. These clefts occur in two forms: a midline cleft between the two premaxillae (analogous to the rare midline craniofacial clefts in humans) and bilateral paramedian clefts between the premaxilla and the maxillae (analogous to the typical cleft lip and palate in humans). Here, we describe the distribution of orofacial clefting across major bat clades, exploring the relationship of the different patterns of clefting to feeding mode, development of the vomeronasal organ, development of the nasolacrimal duct and mode of emission of the echolocation call in different bat groups. We also present the results of detailed radiographic and soft tissue dissections of representative examples of the two types of cleft. The midline cleft has arisen independently multiple times in bat phylogeny, whereas the paramedian cleft has arisen once and is a synapomorphy uniting the Rhinolophidae and Hipposideridae. In all cases examined, the bony cleft is filled in by a robust fibrous membrane, continuous with the periosteum of the margins of the cleft. In the paramedian clefts, this membrane splits to enclose the premaxilla but forms a loose fold laterally between the premaxilla and maxilla, allowing the premaxilla and nose‐leaf to pivot dorsoventrally in the sagittal plane under the action of facial muscles attached to the nasal cartilages. It is possible that this is a specific adaptation for echolocation and/or aerial insectivory. Given the shared embryological location of orofacial clefts in bats and humans, it is likely that aspects of the developmental control networks that produce cleft lip and palate in humans may also be implicated in the formation of these clefts as a normal feature in some bats. A better understanding of craniofacial development in bats with and without clefts may therefore suggest avenues for research into abnormal craniofacial development in humans.
Developmental and Comparative Immunology, Jun 1, 2021
Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in North America, h... more Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in North America, has decimated bat populations within a decade. The fungus impacts bats during hibernation when physiological functions, including immune responses, are down-regulated. Studies have shown that Pd is native to Europe, where it is not associated with mass mortalities. Moreover, genomic and proteomic studies indicated that European bats may have evolved an effective immune defence, which is lacking in North American bats. However, it is still unclear which defence strategy enables European bats to cope with the pathogen. Here, we analysed selected physiological and immunological parameters in torpid, Pd infected European greater mouse-eared bats (Myotis myotis) showing three different levels of infection (asymptomatic, mild and severe symptoms). From a subset of the studied bats we tracked skin temperatures during one month of hibernation. Contrasting North American bats, arousal patterns remained unaffected by Pd infections in M. myotis. In general, heavier M. myotis aroused more often from hibernation and showed less severe disease symptoms than lean individuals; most likely because heavy bats were capable of reducing the Pd load more effectively than lean individuals. In the blood of severely infected bats, we found higher gene expression levels of an inflammatory cytokine (IL-1β), but lower levels of an acute phase protein (haptoglobin), reactive oxygen metabolites (ROMs) and plasma non-enzymatic antioxidant capacity (OXY) compared to conspecifics with lower levels of infection. We conclude that M. myotis, and possibly also other European bat species, tolerate Pd infections during torpor by using selected acute phase response parameters at baseline levels, yet without arousing from torpor and without synthesizing additional immune molecules.
The reliability of species identification is of primary importance as much of biodiversity studie... more The reliability of species identification is of primary importance as much of biodiversity studies, ecology, legislation, and conservation are based on this taxonomic level. Species identification problems can obscure the conservation status, especially for rare and endangered species, which are of special concern for conservation. This problem is especially significant for some taxonomic groups such as chiropterans, as many monitoring programs are run during the hibernation season when animals should not be disturbed, hence not handled. In the present study, we used
Extra‐organismal DNA (eoDNA) from material left behind by organisms (noninvasive DNA, e.g., feces... more Extra‐organismal DNA (eoDNA) from material left behind by organisms (noninvasive DNA, e.g., feces, hair) or from environmental samples (eDNA, e.g., water, soil) is a valuable source of genetic information. However, the relatively low quality and quantity of eoDNA, which can be further degraded by environmental factors, results in reduced amplification and sequencing success. This is often compensated for through cost‐ and time‐intensive replications of genotyping/sequencing procedures. Therefore, system‐ and site‐specific quantifications of environmental degradation are needed to maximize sampling efficiency (e.g., fewer replicates, shorter sampling durations), and to improve species detection and abundance estimates. Using 10 environmentally diverse bat roosts as a case study, we developed a robust modeling pipeline to quantify the environmental factors degrading eoDNA, predict eoDNA quality, and estimate sampling‐site‐specific ideal exposure duration. Maximum humidity was the strongest eoDNA‐degrading factor, followed by exposure duration and then maximum temperature. We also found a positive effect when hottest days occurred later. The strength of this effect fell between the strength of the effects of exposure duration and maximum temperature. With those predictors and information on sampling period (before or after offspring were born), we reliably predicted mean eoDNA quality per sampling visit at new sites with a mean squared error of 0.0349. Site‐specific simulations revealed that reducing exposure duration to 2–8 days could substantially improve eoDNA quality for future sampling. Our pipeline identified high humidity and temperature as strong drivers of eoDNA degradation even in the absence of rain and direct sunlight. Furthermore, we outline the pipeline's utility for other systems and study goals, such as estimating sample age, improving eDNA‐based species detection, and increasing the accuracy of abundance estimates.
Emerging infectious diseases may become serious threats to wildlife, a prominent example being th... more Emerging infectious diseases may become serious threats to wildlife, a prominent example being the white-nose disease (WND). In case of WND, the cold-loving fungus Pseudogymnoascus destructans colonizes bats during hibernation, invades the skin and has already lead to the death of millions of bats in North America. P. destructans most likely originated from Europe, where it also causes lesions but without associated mortalities. However, it is still unclear how European bats cope with the fungus. Hence, it is important to have tools that precisely characterise disease progression. Because hibernation is a physiological state during which bats are vulnerable to disturbance, in-situ assessments of the clinical status should be carried out minimal-invasively to avoid detrimental impacts on bats. However, currently available disease assessment methods require handling/touching bats and are therefore invasive: i) UV-light trans-illumination of wing membranes to detect lesions and ii) a qPCR-based quantification of fungal material from wing membrane swabs. Since P. destructans (‘Pd') becomes visible on all furless skin with distinct distribution patterns, we investigated the use of visible symptoms to assess levels of infections without handling/touching bats. We introduce a technique which we termed ‘Visual Pd-score’ (a visual classification scheme), which can be applied without disturbing the animals. To assess its reliability, we used P. destructans infected greater mouse-eared bats (Myotis myotis) to compare the novel method with the two existing golden-standard techniques. Our results show that infection levels obtained from all three techniques are correlated. Importantly, the information carried by the Visual Pd-score is most similar to a composite index combining the information from the qPCR-based and UV-light quantification methods. We conclude that the Visual Pd-score represents a promising index to better characterise disease severity as it is simultaneously representative for fungal colonization and wing damage. We discuss advantages and disadvantages of the applied techniques and conclude that the Visual Pd-score is particularly useful for routine hibernacula counts or large-scale P. destructans-surveillance. In combination with the lesion detection technique the new method is also applicable to immunological studies where both fungal colonization and associated damage have to be investigated, while qPCRs from swabs of all body parts are especially useful if it is necessary to detect cryptic infections, e.g. during the early hibernation period.
White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascus destructans, repres... more White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascus destructans, represents one of the greatest threats for North-American hibernating bats. Research on molecular data has significantly advanced our knowledge on various aspects of the disease, yet more studies are needed regarding patterns of P. destructans genetic diversity distribution. In the present study, we investigate three sites within the native range of the fungus in detail: two natural hibernacula (karst caves) in Bulgaria, South-Eastern Europe, and one artificial hibernaculum (disused cellar) in Germany, Northern Europe, that we intensively surveyed between 2014 and 2019. Using 18 microsatellite and two mating type markers, we describe how P. destructans genetic diversity is distributed between and within sites, the latter including differentiation across years and seasons of sampling; across sampling locations within the site; and between bats and hibernaculum walls. We found significant geneti...
ABSTRACTEmerging infectious diseases pose a remarkable threat to wildlife, and their incidence wi... more ABSTRACTEmerging infectious diseases pose a remarkable threat to wildlife, and their incidence will likely be further exacerbated due to climate change. Therefore, developing new, preferably minimally invasive yet effective monitoring systems is crucial for conservation. We investigated whether the occurrence of white-nose disease (WND), a fungal disease of hibernating bats, can be predicted using local climatic conditions and host community composition at hibernation sites. In addition, we used our model to predict the current worldwide potential global distribution of white-nose disease, revealing areas that may be under risk if the pathogen is introduced, and further applied our model to a climate change scenario to illuminate how the potential global distribution of the disease may shift in the future. To achieve this, we fitted a logistic regression model using open-source climate data (mean annual surface temperature (MAST), annual precipitation) and hibernation site census da...
The development of methods for individual identification in wild species and the refinement of Ca... more The development of methods for individual identification in wild species and the refinement of Capture-Mark-Recapture (CMR) models during the past decades has greatly improved the assessment of population demographic rates to answer ecological and conservation questions. In particular, multi-state models, with their flexibility for the analysis of complex study systems, have become popular in the ecological community. We have addressed here the issue of mark loss and the often associated recycling of remarked individuals, which remains to be further explored in the context of the increasing use of these models. To explore this knowledge gap we used a wide range of simulation scenarios reflecting frequently encountered real case studies inspired from the survival rates of 700 vertebrates' species. We estimated the effects of mark loss and recycled individuals on parameter estimates using a multi-state, Arnason-Schwartz (AS), modelling framework. We explored parameter bias through...
A normal feature of the facial anatomy of many species of bat is the presence of bony discontinui... more A normal feature of the facial anatomy of many species of bat is the presence of bony discontinuities or clefts, which bear a remarkable similarity to orofacial clefts that occur in humans as a congenital pathology. These clefts occur in two forms: a midline cleft between the two premaxillae (analogous to the rare midline craniofacial clefts in humans) and bilateral paramedian clefts between the premaxilla and the maxillae (analogous to the typical cleft lip and palate in humans). Here, we describe the distribution of orofacial clefting across major bat clades, exploring the relationship of the different patterns of clefting to feeding mode, development of the vomeronasal organ, development of the nasolacrimal duct and mode of emission of the echolocation call in different bat groups. We also present the results of detailed radiographic and soft tissue dissections of representative examples of the two types of cleft. The midline cleft has arisen independently multiple times in bat phylogeny, whereas the paramedian cleft has arisen once and is a synapomorphy uniting the Rhinolophidae and Hipposideridae. In all cases examined, the bony cleft is filled in by a robust fibrous membrane, continuous with the periosteum of the margins of the cleft. In the paramedian clefts, this membrane splits to enclose the premaxilla but forms a loose fold laterally between the premaxilla and maxilla, allowing the premaxilla and nose‐leaf to pivot dorsoventrally in the sagittal plane under the action of facial muscles attached to the nasal cartilages. It is possible that this is a specific adaptation for echolocation and/or aerial insectivory. Given the shared embryological location of orofacial clefts in bats and humans, it is likely that aspects of the developmental control networks that produce cleft lip and palate in humans may also be implicated in the formation of these clefts as a normal feature in some bats. A better understanding of craniofacial development in bats with and without clefts may therefore suggest avenues for research into abnormal craniofacial development in humans.
Developmental and Comparative Immunology, Jun 1, 2021
Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in North America, h... more Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in North America, has decimated bat populations within a decade. The fungus impacts bats during hibernation when physiological functions, including immune responses, are down-regulated. Studies have shown that Pd is native to Europe, where it is not associated with mass mortalities. Moreover, genomic and proteomic studies indicated that European bats may have evolved an effective immune defence, which is lacking in North American bats. However, it is still unclear which defence strategy enables European bats to cope with the pathogen. Here, we analysed selected physiological and immunological parameters in torpid, Pd infected European greater mouse-eared bats (Myotis myotis) showing three different levels of infection (asymptomatic, mild and severe symptoms). From a subset of the studied bats we tracked skin temperatures during one month of hibernation. Contrasting North American bats, arousal patterns remained unaffected by Pd infections in M. myotis. In general, heavier M. myotis aroused more often from hibernation and showed less severe disease symptoms than lean individuals; most likely because heavy bats were capable of reducing the Pd load more effectively than lean individuals. In the blood of severely infected bats, we found higher gene expression levels of an inflammatory cytokine (IL-1β), but lower levels of an acute phase protein (haptoglobin), reactive oxygen metabolites (ROMs) and plasma non-enzymatic antioxidant capacity (OXY) compared to conspecifics with lower levels of infection. We conclude that M. myotis, and possibly also other European bat species, tolerate Pd infections during torpor by using selected acute phase response parameters at baseline levels, yet without arousing from torpor and without synthesizing additional immune molecules.
The reliability of species identification is of primary importance as much of biodiversity studie... more The reliability of species identification is of primary importance as much of biodiversity studies, ecology, legislation, and conservation are based on this taxonomic level. Species identification problems can obscure the conservation status, especially for rare and endangered species, which are of special concern for conservation. This problem is especially significant for some taxonomic groups such as chiropterans, as many monitoring programs are run during the hibernation season when animals should not be disturbed, hence not handled. In the present study, we used
Extra‐organismal DNA (eoDNA) from material left behind by organisms (noninvasive DNA, e.g., feces... more Extra‐organismal DNA (eoDNA) from material left behind by organisms (noninvasive DNA, e.g., feces, hair) or from environmental samples (eDNA, e.g., water, soil) is a valuable source of genetic information. However, the relatively low quality and quantity of eoDNA, which can be further degraded by environmental factors, results in reduced amplification and sequencing success. This is often compensated for through cost‐ and time‐intensive replications of genotyping/sequencing procedures. Therefore, system‐ and site‐specific quantifications of environmental degradation are needed to maximize sampling efficiency (e.g., fewer replicates, shorter sampling durations), and to improve species detection and abundance estimates. Using 10 environmentally diverse bat roosts as a case study, we developed a robust modeling pipeline to quantify the environmental factors degrading eoDNA, predict eoDNA quality, and estimate sampling‐site‐specific ideal exposure duration. Maximum humidity was the strongest eoDNA‐degrading factor, followed by exposure duration and then maximum temperature. We also found a positive effect when hottest days occurred later. The strength of this effect fell between the strength of the effects of exposure duration and maximum temperature. With those predictors and information on sampling period (before or after offspring were born), we reliably predicted mean eoDNA quality per sampling visit at new sites with a mean squared error of 0.0349. Site‐specific simulations revealed that reducing exposure duration to 2–8 days could substantially improve eoDNA quality for future sampling. Our pipeline identified high humidity and temperature as strong drivers of eoDNA degradation even in the absence of rain and direct sunlight. Furthermore, we outline the pipeline's utility for other systems and study goals, such as estimating sample age, improving eDNA‐based species detection, and increasing the accuracy of abundance estimates.
Emerging infectious diseases may become serious threats to wildlife, a prominent example being th... more Emerging infectious diseases may become serious threats to wildlife, a prominent example being the white-nose disease (WND). In case of WND, the cold-loving fungus Pseudogymnoascus destructans colonizes bats during hibernation, invades the skin and has already lead to the death of millions of bats in North America. P. destructans most likely originated from Europe, where it also causes lesions but without associated mortalities. However, it is still unclear how European bats cope with the fungus. Hence, it is important to have tools that precisely characterise disease progression. Because hibernation is a physiological state during which bats are vulnerable to disturbance, in-situ assessments of the clinical status should be carried out minimal-invasively to avoid detrimental impacts on bats. However, currently available disease assessment methods require handling/touching bats and are therefore invasive: i) UV-light trans-illumination of wing membranes to detect lesions and ii) a qPCR-based quantification of fungal material from wing membrane swabs. Since P. destructans (‘Pd') becomes visible on all furless skin with distinct distribution patterns, we investigated the use of visible symptoms to assess levels of infections without handling/touching bats. We introduce a technique which we termed ‘Visual Pd-score’ (a visual classification scheme), which can be applied without disturbing the animals. To assess its reliability, we used P. destructans infected greater mouse-eared bats (Myotis myotis) to compare the novel method with the two existing golden-standard techniques. Our results show that infection levels obtained from all three techniques are correlated. Importantly, the information carried by the Visual Pd-score is most similar to a composite index combining the information from the qPCR-based and UV-light quantification methods. We conclude that the Visual Pd-score represents a promising index to better characterise disease severity as it is simultaneously representative for fungal colonization and wing damage. We discuss advantages and disadvantages of the applied techniques and conclude that the Visual Pd-score is particularly useful for routine hibernacula counts or large-scale P. destructans-surveillance. In combination with the lesion detection technique the new method is also applicable to immunological studies where both fungal colonization and associated damage have to be investigated, while qPCRs from swabs of all body parts are especially useful if it is necessary to detect cryptic infections, e.g. during the early hibernation period.
White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascus destructans, repres... more White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascus destructans, represents one of the greatest threats for North-American hibernating bats. Research on molecular data has significantly advanced our knowledge on various aspects of the disease, yet more studies are needed regarding patterns of P. destructans genetic diversity distribution. In the present study, we investigate three sites within the native range of the fungus in detail: two natural hibernacula (karst caves) in Bulgaria, South-Eastern Europe, and one artificial hibernaculum (disused cellar) in Germany, Northern Europe, that we intensively surveyed between 2014 and 2019. Using 18 microsatellite and two mating type markers, we describe how P. destructans genetic diversity is distributed between and within sites, the latter including differentiation across years and seasons of sampling; across sampling locations within the site; and between bats and hibernaculum walls. We found significant geneti...
ABSTRACTEmerging infectious diseases pose a remarkable threat to wildlife, and their incidence wi... more ABSTRACTEmerging infectious diseases pose a remarkable threat to wildlife, and their incidence will likely be further exacerbated due to climate change. Therefore, developing new, preferably minimally invasive yet effective monitoring systems is crucial for conservation. We investigated whether the occurrence of white-nose disease (WND), a fungal disease of hibernating bats, can be predicted using local climatic conditions and host community composition at hibernation sites. In addition, we used our model to predict the current worldwide potential global distribution of white-nose disease, revealing areas that may be under risk if the pathogen is introduced, and further applied our model to a climate change scenario to illuminate how the potential global distribution of the disease may shift in the future. To achieve this, we fitted a logistic regression model using open-source climate data (mean annual surface temperature (MAST), annual precipitation) and hibernation site census da...
The development of methods for individual identification in wild species and the refinement of Ca... more The development of methods for individual identification in wild species and the refinement of Capture-Mark-Recapture (CMR) models during the past decades has greatly improved the assessment of population demographic rates to answer ecological and conservation questions. In particular, multi-state models, with their flexibility for the analysis of complex study systems, have become popular in the ecological community. We have addressed here the issue of mark loss and the often associated recycling of remarked individuals, which remains to be further explored in the context of the increasing use of these models. To explore this knowledge gap we used a wide range of simulation scenarios reflecting frequently encountered real case studies inspired from the survival rates of 700 vertebrates' species. We estimated the effects of mark loss and recycled individuals on parameter estimates using a multi-state, Arnason-Schwartz (AS), modelling framework. We explored parameter bias through...
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