Over the last few days six members of our team (Dave Newell, Harry Hines, Laura Grogan, Mariel Familiar Lopez, Thais Sasso Lopes and Liam Bolitho) attended the combined meeting of the Australian Society of Herpetologists and the Society for Research on Amphibians and Reptiles in New Zealand, held at Kindilan Camp, Redland Bay, Queensland, Australia.
It was a great conference with an impressive selection of research presented in two parallel sessions over 2.5 days. Below are the abstracts from our team members.
Batrachochytrium dendrobatidis presence within species: a review on ecological scales and influential variables
Sasso Lopes, Thais, Grogan, Laura and McCallum, Hamish
Environmental Futures Research Institute, Griffith University, Nathan, 4111, QLD, Australia.
Since the identification of the infectious agent Batrachochytrium dendrobatidis (Bd) 20 years ago, numerous studies have helped to build solid documentation on the impact of amphibian chytridiomycosis, the worst disease ever recorded to affect biodiversity. Bd presence in frogs has been investigated over a broad range of ecological scales. Studies have extended from differences in infection load within individuals, disease prevalence among habitats at the population level, as well as presence of Bd across the landscape level. These studies have examined both environmental and intrinsic species-specific factors to explain the variable occurrence of Bd within species. The scale of interest has a profound influence on our understanding of which processes underpin the disease dynamics and on the scope of our conclusions and predictions. To evaluate the breadth of studies performed to date we quantitatively reviewed the Bd literature, and classified studies with regard to the spatial scale explored, methodological design and overall findings. We systematized which variables were most strongly associated with heterogeneity of disease occurrence. Among the 80 peer-reviewed papers published between 2004 and 2018 that fitted our criteria, air temperature and rainfall or humidity were commonly investigated environmental parameters. Variables such as life stage, distance to urban areas or zooplankton composition were seldom investigated, but were shown to influence Bd prevalence among different populations of the same species. Chytridiomycosis remains a dire threat to amphibians worldwide, and an intricacy of factors influences its occurrence and consequently its effects. Our review emphasises that understanding the complexity of Bd impact requires an integration of studies tackling Bd-host interaction at multiple scales and perspectives.
Temporal variation of the skin bacterial community and Batrachochytrium dendrobatidis infection in the frog Philoria loveridgei
Familiar López, Mariel (1), Rebollar, Eria A. (2), Harris, Reid N. (3), Vredenburg, Vance T. (4) and Hero, Jean-Marc (5)
(1) School of Environment and Science, Griffith University, Gold Coast, QLD 4222; (2) Centre for Genomic Sciences, UNAM, Cuernavaca, Morelos 62210; (3) Department of Biology, James Madison University, Harrisonburg, VA 22807; (4) Department of Biology, San Francisco State University, San Francisco, CA 94132; (5) School of Science and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4556.
Microbial symbiotic communities are ubiquitous in animals and plants as some can play
an important role in disease resistance of host, hence the focus of much current research.
Globally, amphibian population declines and extinctions have occurred due to chytridiomycosis, a skin disease caused by the pathogen Batrachochytrium dendrobatidis (Bd). Currently amphibian skin bacteria are increasingly recognized as important symbiont communities with a relevant role in the defense against pathogens, as some bacteria can inhibit the growth of Bd. This study aims to document the Bd infection status of wild populations of a terrestrial cryptic frog (Philoria loveridgei), and to determine whether infection status is correlated with changes in the skin microbial communities. Skin samples of P. loveridgei were collected along an altitudinal range within the species distribution in subtropical rainforests in southeast Australia. Sampling was conducted in two years during two breeding seasons with the first classified as a “La Niña” year. We used Taqman real-time PCR to determine Bd infection status and 16S amplicon sequencing techniques to describe the skin community structure. We found Bd-positive frogs only in the second sampling year with low infection intensities, and no correlation between Bd infection status and altitude, frog sex or size. Skin bacterial diversity was significantly higher in P. loveridgei frogs sampled in the 1st year than in the 2nd year. In addition, 7.4% of the total OTUs were significantly more abundant in the 1st year compared to the 2nd year. We identified 67 bacterial OTUs with a significant positive correlation between infection intensity and an OTU’s relative abundance. Forty-five percent of these OTUs belonged to the family Enterobacteriaceae. Overall, temporal variation was strongly associated with changes in Bd infection status and bacterial community structure of wild populations of P. loveridgei.
Bioacoustic monitoring reveals the calling activity of an endangered mountain-top frog (Philoria kundagungan) in response to environmental conditions
Bolitho, Liam and Newell, David
Forest Research Centre, Southern Cross University, NSW, Australia.
Globally, amphibians have declined at an unprecedented rate in recent decades with more than 30% of amphibian species listed as threatened by the International Union for Conservation of Nature. The Mountain Frog, Philoria kundagungan, is an endangered amphibian species endemic to the upland rainforests of northern New South Wales and southeast Queensland, Australia. This species is considered to be at risk from future climate change however, the population trajectory of P. kundagungan is poorly known and surveys have been hampered by their cryptic calling behaviour and subterranean habits. Environmental conditions are strong drivers of amphibian calling behaviour but are often poorly understood aspects of amphibian ecology. With detailed knowledge of the calling phenology of this species, surveys can be appropriately timed thus increasing detection probabilities. The influence of environmental variables on P. kundagungan calling activity was investigated at six sites across the species’ geographic and altitudinal range. Audio recording equipment (Wildlife Acoustics, Songmeter II) was deployed at each site and programmed to record sound every hour for ten minutes between July 2016 and March 2018. Soil temperature along with a range of meteorological conditions were recorded every hour at each site. Kaleidoscope 4.5.4 (Wildlife Acoustics, Inc.), an automatic call recognition programme was used to automatically detect P. kundagungan calls in sound files. Kaleidoscope detected a total of 2,031,848 P. kundagungan calls in 8760 hours of sound recordings. The true positive rate for the presence of P. kundagungan calls in 5000 randomly selected recordings was >98%. The results of this study indicate that, P. kundagungan calling activity is driven primarily by soil temperature and time of day. This study will allow future targeted surveys of this visually cryptic species to be conducted under conditions that induce calling activity and further understand the implications climate change may have on this endangered mountain-top frog.
Chytridiomycosis causes catastrophic organism-wide metabolic dysregulation including profound failure of cellular energy pathways
Grogan, Laura F. (1), Skerratt, L.F. (2), Berger, L. (2), Cashins, S.D. (2), Trengove, R.D. (3, 4) and Gummer, J.P.A. (3, 4)
(1) Griffith Wildlife Disease Ecology Group, Environmental Futures Research Institute, School of Environment, Griffith University, Nathan, Queensland 4111, Australia; (2) One Health Research Group, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland 4811, Australia; (3) Separation Science and Metabolomics Laboratory, Murdoch University, Perth, Western Australia 6150, Australia; (4) Metabolomics Australia, Murdoch University Node, Murdoch University, Perth, Western Australia 6150, Australia.
Chytridiomycosis is among several recently emerged fungal diseases of wildlife that have
caused decline or extinction of naïve populations. Despite recent advances in understanding
pathogenesis, host response to infection remains poorly understood. Here we modelled a total of 162 metabolites across skin and liver tissues of 61 frogs from four populations (three long exposed and one naïve to the fungus) of the Australian Alpine Tree Frog (Litoria verreauxii alpina) throughout a longitudinal exposure experiment involving both infected and negative control individuals. We found that chytridiomycosis dramatically altered the organism-wide metabolism of clinically diseased frogs. Chytridiomycosis caused catastrophic failure of normal homeostatic mechanisms (interruption of biosynthetic and degradation metabolic pathways), and pronounced dysregulation of cellular energy metabolism. Key intermediates of the tricarboxylic acid cycle were markedly depleted, including in particular α-ketoglutarate and glutamate that together constitute a key nutrient pathway for immune processes. This study was the first to apply a non-targeted metabolomics approach to a fungal wildlife disease and specifically to dissect the host-pathogen interface of Bd-infected frogs. The patterns of metabolite accumulation we have identified reveal whole-body metabolic dysfunction induced by a fungal skin infection, and these findings have broad relevance for other fungal diseases.
Automated recording systems and sound recognition software in the conservation management of the critically endangered Kroombit Tinkerfrog
Ecological Assessment Unit, Queensland Parks and Wildlife Service, Department of
Environment and Science, PO Box 15187, City East, Queensland, Australia 4002,
The Kroombit Tinkerfrog, Taudactylus pleione, is a critically endangered species restricted to 12 montane rainforest patches totalling 596ha in Kroombit Tops National Park in central Queensland, Australia. Most of these rainforest patches are difficult to access as they occur in steep, narrow gullies, mostly below the eastern escarpment. Despite many years of targeted research, eggs and tadpoles have not been observed and females and juveniles very rarely. As Kroombit Tinkerfrogs are small (maximum length ~30 mm), cryptically patterned and inhabit rock piles and leaf litter, detectability is dependent upon the male advertisement call. Males tend to call more or less continuously for extended periods. The call is relatively loud and simple in structure. Combined, these factors suggested the use of automated recording systems and call recognition software may efficiently and significantly enhance knowledge of the seasonal and daily patterns of calling and thus refine survey and monitoring methods and target conditions under which breeding likely occurs. Automated recordings systems (Song Meters and more recently BARs) were used to capture ~800 K one minute field recordings (e.g., 1 min every 30 min throughout the day) from up to nine sites over seven seasons. The sound recognition software SoundID was used to batch analyse these recordings. Accuracy of the analyses was assessed through random and targeted validation. The results have confirmed the local extinction of the species from three sites and provided detailed calling phenology from extant sites. Whilst more detailed analyses are pending, it is clear that in the case of Kroombit Tinkerfrog the combination of automated recording systems and sound recognition software has greatly enhanced knowledge of calling phenology, detectability and assessment of site occupancy, and will be a significant tool in the conservation management of this species.