Chytridiomycosis, the disease caused by Batrachochytrium dendrobatidis, is considered to be a disease exclusively of amphibians. However, B. dendrobatidis may also be capable of persisting in the ...environment, and non-amphibian vectors or hosts may contribute to disease transmission. Reptiles living in close proximity to amphibians and sharing similar ecological traits could serve as vectors or reservoir hosts for B. dendrobatidis, harbouring the organism on their skin without succumbing to disease. We surveyed for the presence of B. dendrobatidis DNA among 211 lizards and 8 snakes at 8 sites at varying elevations in Panama where the syntopic amphibians were at pre-epizootic, epizootic or post-epizootic stages of chytridiomycosis. Detection of B. dendrobatidis DNA was done using qPCR analysis. Evidence of the amphibian pathogen was present at varying intensities in 29 of 79 examined Anolis humilis lizards (32%) and 9 of 101 A. lionotus lizards (9%), and in one individual each of the snakes Pliocercus euryzonus, Imantodes cenchoa, and Nothopsis rugosus. In general, B. dendrobatidis DNA prevalence among reptiles was positively correlated with the infection prevalence among co-occurring anuran amphibians at any particular site (r = 0.88, p = 0.004). These reptiles, therefore, may likely be vectors or reservoir hosts for B. dendrobatidis and could serve as disease transmission agents. Although there is no evidence of B. dendrobatidis disease-induced declines in reptiles, cases of coincidence of reptile and amphibian declines suggest this potentiality. Our study is the first to provide evidence of non-amphibian carriers for B. dendrobatidis in a natural Neotropical environment.
Globally, competition and disease from introduced Red-eared Slider (Trachemys scripta elegans) is a threat to co-existing native turtles. Red-eared Slider has been introduced throughout south coastal ...British Columbia (BC), mainly as pet turtle releases. Urban centres receive the most individuals, particularly in the Lower Mainland area outlying Vancouver, on southern Vancouver Island, and on the Sunshine Coast. The range of Red-eared Sliders in BC overlaps that of the Threatened Pacific Coast population of Western Painted Turtle (Chrysemys picta bellii). Herein we report on a survey for both species, noting presence, assessed population sizes, and nesting activity. Across 19 sites in the south coast occupied by both turtle species, we found the median abundance of Red-eared Sliders to be 2.5 times larger than that of Western Painted Turtles (Mann–Whitney U = 104, n1 = n2 = 19, Z-Score = −2.2188, P = 0.02642, two-tailed). There had been no evidence of Red-eared Sliders successfully hatching in the wild in BC until our study. We observed complete development, with 19 neonates from three different nesting sites between 2015 and 2017. Thus, Red-eared Slider is indeed established and able to breed in BC and thus competition and disease introduction from the species likely contributes to the decline of the Pacific Coast population of Western Painted Turtle, particularly at sites with low painted turtle numbers. The scale and mechanisms of impact requires further investigation.
The pathogenic chytrid fungus,
Batrachochytrium dendrobatidis
, has been implicated as the main driver of many enigmatic amphibian declines in neotropical sites at high elevation.
Batrachochytrium ...dendrobatidis
is thought to be a waterborne pathogen limited by temperature, and the extent to which it persists and causes disease in amphibians at lower elevations in the neotropics is not known. It also is unclear by what mechanism(s)
B. dendrobatidis
has emerged as a pathogenic organism. To test whether
B. dendrobatidis
is limited by elevation in Panamá, we sought to determine the prevalence and intensity of
B. dendrobatidis
in relation to anuran abundance and diversity using quantitative PCR (qPCR) analyses. Sites were situated at varying elevations, from 45 to 1215 m, and were at varying stages of epizootic amphibian decline, including pre-epizootic, mid-epizootic, 2 years post-epizootic, and 10 years post-epizootic.
Batrachochytrium dendrobatidis
was found in all sites regardless of elevation or stage of epizootic decline. Levels of prevalence and infection intensity were comparable across all sites except at the mid-epizootic site, where both prevalence and intensity were significantly higher than at other sites. Symptoms of chytridiomycosis and corresponding declines in amphibian populations were variably seen at all elevations along a post-epizootic gradient. Because it is inherently difficult to prove a negative proposition, it can neither be proven that
B. dendrobatidis
is truly not present where it is not detected nor proven that it is only recently arrived where it is detected. Thus, there will always be doubts about whether
B. dendrobatidis
is enzootic or invasive. In any case, our results, coupled with current knowledge, suggest most clearly that the disease, chytridiomycosis, may be novel and invasive, and that the pathogen,
B. dendrobatidis
either is, or is becoming, globally ubiquitous.
Chytridiomycosis is a globally emerging disease of amphibians and the leading cause of population declines and extirpations at species-diverse montane sites in Central America. We continued long-term ...monitoring efforts for the presence of the fungal pathogen
Batrachochytrium dendrobatidis
(
Bd
) and for amphibian populations at two sites in western Panama, and we began monitoring at three new sites to the east. Population declines associated with chytridiomycosis emergence were detected at Altos de Campana National Park. We also detected
Bd
in three species east of the Panama Canal at Soberanía National Park, and prevalence data suggests that
Bd
may be enzootic in the lowlands of the park. However, no infected frogs were found further east at Tortí (prevalence <7.5% with 95% confidence). Our results suggest that Panama’s diverse and not fully described amphibian communities east of the canal are at risk. Precise predictions of future disease emergence events are not possible until factors underlying disease emergence, such as dispersal, are understood. However, if the fungal pathogen spreads in a pattern consistent with previous disease events in Panama, then detection of
Bd
at Tortí and other areas east of the Panama Canal is imminent. Therefore, development of new management strategies and increased precautions for tourism, recreation, and biology are urgently needed.
The pathogenic chytrid fungus, Batrachochytrium dendrobatidis , causes population decline and extinction of numerous species of tropical, principally montane, amphibians. Is B. dendrobatidis an ...enzootic pathogen emerging as a disease, or rather a novel invasive pathogen infecting naïve amphibians? Are only high-elevation amphibians susceptible to the pathogen? If the chytrid is enzootic, then it may be in the environment before or after epidemic decline and may infect both montane and lowland amphibians as well as other organisms. To determine distribution of the pathogen and corresponding anuran abundance, I established eight research sites of varying elevations and stages of epidemic infection from west to east, ranging from 45 m to 1215 m elevation throughout Panama west of the Canal. Differential infection susceptibility among anurans was addressed in relation to three ecological factors: anuran body size, season and habitat. Prevalence and infection intensity of the chytrid were determined at all sites and for all factors using sensitive DNA-based RT-qPCR amplification. Amphibian populations at all elevations and stages of decline showed at least some degree of chytrid infection, and the chytrid was found on reptiles. In addition to presence of the pathogen, effects of the disease chytridiomycosis were variably seen at all elevations. Habitat and season did not seem to have a strong effect on infection prevalence and/or intensity, but frogs did appear to show greater infection at smaller anuran body sizes. All of the above results are suggestive of an enzootic pathogen and perhaps only the current epidemic of chytridiomycosis disease is novel. Since the infection can remain in frog communities at any elevation, habitat and season, can persist for long periods of time (up to 11 years), and can survive on non-amphibian hosts, the eventual reintroduction of captive-bred amphibians as a plausible management plan for conservation should be carefully examined.
Biogenic carbonates are important archives for reconstructing the marine sulfur cycle. However, uncertainties exist about the exact location of carbonate associated sulfate (CAS) and a possible ...biological control on sulfate incorporation. The behavior of CAS in biogenic carbonates during diagenetic alteration is even more poorly constrained. To investigate the mechanisms of sulfur incorporation and the effects of alteration on sulfur in biogenic carbonates, modern marine bivalve shells of Arctica islandica species were hydrothermally altered at 100 °C and 175 °C. Fluorescence microscopy, element mapping via NanoSIMS and μ-XRF, sulfur XANES analyses, and δ34S measurements were performed on the experimentally altered shell segments. Changes in elemental compositions and δ34S of sulfate in the post-alteration solutions were also determined. Results indicate clear differences between the δ34S values of the CAS (+21‰, V-CDT) that reflects ambient seawater sulfate and the organically bound sulfur that is isotopically lighter (+14.8‰, V-CDT or less). Carbonate associated sulfate is primarily incorporated in the mineral phase of the shell, whereas reduced sulfur phases are mainly found within the intrashell organic matter. Hydrothermal alteration experiments at 100 °C resulted in minimal changes of sulfur within the bivalve shells. In contrast, the 175 °C experiments triggered decomposition of intrashell organic matrices which then led to extensive diagenetic alteration in both the shell microstructure and chemistry. Changes in total concentration, speciation, and spatial distribution of sulfur reflect the diagenetic processes that occurred within the shells. Preferential incorporation of CAS in a neomorphic calcite phase with Mg/Ca ratios of 0.13–0.21 was observed. Due to its presence in both organic and inorganic phases and its multiple oxidation states with different isotopic compositions we conclude that sulfur is a useful and sensitive proxy for diagenetic alteration in biogenic aragonite.
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