Early exposure to UV radiation causes telomere shortening and poorer condition later in life

Determining the contribution of elevated ultraviolet–B radiation (UVBR; 280 — 315 nm) to amphibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life history stages might affect post–metamorphic stages via long–term carryover effects. We acutely exposed tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a multi–factorial experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners. Higher doses of UVBR exposure in larvae yielded improved rates of metamorphosis. However, exposure at a high irradiance resulted in frogs metamorphosing smaller in size and in poorer condition than frogs exposed to low and medium irradiance UVBR as larvae. We also demonstrate some of the first empirical evidence of UVBR-induced telomere shortening in vivo, which is one possible mechanism for life–history trade–offs impacting condition post-metamorphosis. These findings contribute to our understanding of how acute UVBR exposure regimes in early life affect later life–history stages, which has implications for how this stressor may shape population dynamics.

A Simple Conservation Tool to Aid Restoration of Amphibians following High-Severity Wildfires: Use of PVC Pipes by Green Tree Frogs (Hyla cinerea) in Central Texas, USA

Amphibians are the most threatened vertebrate class based on the IUCN Red List. Their decline has been linked to anthropogenic activities, with wildfires being among the most conspicuous agents of habitat alterations affecting native amphibians. In 2011, the most destructive wildfire in Texas history occurred in the Lost Pines ecoregion of central Texas, USA, burning 39% of the 34,400 ha forest and drastically decreasing available habitats for many native wildlife species, including the green tree frog (Hyla cinerea). We investigated use of PVC pipes as artificial refuges for green tree frogs in different habitats within this post-fire pine forest. We monitored green tree frog use of small (diameter 38.1-mm, 1.5 inch) and large (diameter 50.8-mm, 2 inch) pipes located adjacent to, and 5 m from, ponds in burned and unburned areas over a 5-month period. We caught 227 frogs, 101 (24 adults and 77 juveniles) in burned and 126 (61 adults, 63 juveniles, and 2 unknown) in unburned areas. A relationship between pipe use by adults and/or juveniles and pipe location in burned versus unburned areas was found, but pipe use by adults and/or juveniles and pipe size were independent. Pipe use by adults and/or juveniles and pipe size were also independent. Juveniles were more frequently observed in pipes located adjacent to ponds. Our results confirmed that PVC pipes merit consideration as a simple, inexpensive, conservation tool to aid in restoration of green tree frog populations after high-severity wildfires. Such artificial refuges may be particularly important for survival of juveniles in severely altered post-fire habitats.

First extraction of eDNA from tree hole water to detect tree frogs: a simple field method piloted in Madagascar

Environmental DNA (eDNA) is becoming an increasingly used tool for monitoring cryptic species within terrestrial and aquatic systems. We present the first method for extracting water from tree holes for eDNA studies of tree-dwelling frogs, and the first use of eDNA for amphibian monitoring in Madagascar. This pilot study expands on a previously developed method and aims to provide a simple field protocol for DNA extraction from very small water samples, using a relatively inexpensive kit compared to other collection methods. We collected 20 ml of water from tree holes in Ambohitantely Special Reserve in Madagascar, with the aim to survey for the Critically Endangered tree frog Anodonthyla vallani, and we developed species specific cytochrome c oxidase 1 primers for this species. While our two samples did not detect A. vallani, we successfully extracted up to 16.6 ng/µl of eDNA from the samples and using 16S rRNA primers barcoded the tree frog Plethodontohyla mihanika in one of the samples. Despite just two samples being collected, we highlight the future potential of eDNA from tree holes for investigating cryptic habitat specialist amphibians given we extracted frog eDNA from just 20 ml of water. The method provides a rapid, simple, and cost-effective method which can assist cryptic species monitoring in challenging and time-consuming field conditions and should be developed further for frog surveying in Madagascar and beyond. The newly developed primers can be used for further work using this eDNA method to survey threatened Anodonthyla frog species.

Two new frog species from the Litoria rubella species group from eastern Australia

The bleating tree frog (Litoria dentata) is one of the more prominent pelodryadid frogs of eastern Australia by virtue of its extremely loud, piercing, male advertisement call. A member of the Litoria rubella species group, L. dentata has a broad latitudinal distribution and is widespread from coastal and subcoastal lowlands through to montane areas. A recent mitochondrial DNA analysis showed a deep phylogeographic break between populations of L. dentata on the mid-north coast of New South Wales. Here we extended the mitochondrial survey with more geographically comprehensive sampling and tested the systematic implications of our findings with nuclear genome wide single-nucleotide polymorphism, morphological and male advertisement call datasets. While similar in appearance and in male advertisement call, our integrative analysis demonstrates the presence of three species which replace each other in a north-south series. We redescribe Litoria dentata, which is restricted to coastal north-eastern New South Wales, and formally describe Litoria balatus sp. nov., from south-eastern Queensland, and Litoria quiritatus sp. nov., from the mid-coast of New South Wales to north-eastern Victoria.

Thermal Acclimation to the Highest Natural Ambient Temperature Compromises Physiological Performance in Tadpoles of a Stream-Breeding Savanna Tree Frog

Amphibians may be more vulnerable to climate-driven habitat modification because of their complex life cycle dependence on land and water. Considering the current rate of global warming, it is critical to identify the vulnerability of a species by assessing its potential to acclimate to warming temperatures. In many species, thermal acclimation provides a reversible physiological adjustment in response to temperature changes, conferring resilience in a changing climate. Here, we investigate the effects of temperature acclimation on the physiological performance of tadpoles of a stream-breeding savanna tree frog (Bokermannohyla ibitiguara) in relation to the thermal conditions naturally experienced in their microhabitat (range: 18.8–24.6°C). We quantified performance measures such as routine and maximum metabolic rate at different test (15, 20, 25, 30, and 34°C) and acclimation temperatures (18 and 25°C). We also measured heart rate before and after autonomic blockade with atropine and sotalol at the respective acclimation temperatures. Further, we determined the critical thermal maximum and warming tolerance (critical thermal maximum minus maximum microhabitat temperature), which were not affected by acclimation. Mass-specific routine and mass-specific maximum metabolic rate, as well as heart rate, increased with increasing test temperatures; however, acclimation elevated mass-specific routine metabolic rate while not affecting mass-specific maximum metabolic rate. Heart rate before and after the pharmacological blockade was also unaffected by acclimation. Aerobic scope in animals acclimated to 25°C was substantially reduced, suggesting that physiological performance at the highest temperatures experienced in their natural habitat is compromised. In conclusion, the data suggest that the tadpoles of B. ibitiguara, living in a thermally stable environment, have a limited capacity to physiologically adjust to the highest temperatures found in their micro-habitat, making the species more vulnerable to future climate change.

A non-bactericidal cathelicidin provides prophylactic efficacy against bacterial infection by driving phagocyte influx

The roles of bactericidal cathelicidins against bacterial infection have been extensively studied. However, the anti-bacterial property and mechanism of action of non-bactericidal cathelicidins are rarely known. Herein, a novel naturally occurring cathelicidin (PopuCATH) from tree frog (Polypedates puerensis) didn’t show any direct anti-bacterial activity in vitro. Intriguingly, intraperitoneal injection of PopuCATH before bacterial inoculation significantly reduced the bacterial load in tree frogs and mice, and reduced the inflammatory response induced by bacterial inoculation in mice. PopuCATH pretreatment also increased the survival rates of septic mice induced by a lethal dose of bacterial inoculation or cecal ligation and puncture (CLP). Intraperitoneal injection of PopuCATH significantly drove the leukocyte influx in both frogs and mice. In mice, PopuCATH rapidly drove neutrophil, monocyte/macrophage influx in mouse abdominal cavity and peripheral blood with a negligible impact on T and B lymphocytes, and neutrophils, monocytes/macrophages, but not T and B lymphocytes, were required for the preventive efficacy of PopuCATH. PopuCATH did not directly act as chemoattractant for phagocytes, but PopuCATH obviously drove phagocyte migration when it was cultured with macrophages. PopuCATH significantly elicited chemokine/cytokine production in macrophages through activating p38/ERK mitogen-activated protein kinases (MAPKs) and NF-κB p65. PopuCATH markedly enhanced neutrophil phagocytosis via promoting the release of neutrophil extracellular traps (NETs). Additionally, PopuCATH showed low side effects both in vitro and in vivo. Collectively, PopuCATH acts as a host-based immune defense regulator that provides prophylactic efficacy against bacterial infection without direct antimicrobial effects. Our findings reveal a non-bactericidal cathelicidin which possesses unique anti-bacterial action, and highlight the potential of PopuCATH to prevent bacterial infection.