Predicting the potential distribution of the amphibian pathogen Batrachochytrium dendrobatidis in East and Southeast Asia.

Batrachochytrium dendrobatidis (Bd) is the pathogen responsible for chytridiomycosis, a disease that is associated with a worldwide amphibian population decline. In this study, we predicted the potential distribution of Bd in East and Southeast Asia based on limited occurrence data. Our goal was to design an effective survey area where efforts to detect the pathogen can be focused. We generated ecological niche models using the maximum-entropy approach, with alleviation of multicollinearity and spatial autocorrelation. We applied eigenvector-based spatial filters as independent variables, in addition to environmental variables, to resolve spatial autocorrelation, and compared the model's accuracy and the degree of spatial autocorrelation with those of a model estimated using only environmental variables. We were able to identify areas of high suitability for Bd with accuracy. Among the environmental variables, factors related to temperature and precipitation were more effective in predicting the potential distribution of Bd than factors related to land use and cover type. Our study successfully predicted the potential distribution of Bd in East and Southeast Asia. This information should now be used to prioritize survey areas and generate a surveillance program to detect the pathogen.

Larval masquerade: a new species of paedomorphic salamander (Caudata: Plethodontidae: Eurycea) from the Ouachita Mountains of North America.

Species with truncated developmental patterns may go undetected if they resemble the juveniles of their close relatives. Herein we present an example of this phenomenon with the description of a highly divergent, relict species of stream-dwelling plethodontid salamander from the Ouachita Mountains of North America. Both mitochondrial and nuclear sequence data show that this new species is most closely related to its syntopic relative, Eurycea multiplicata. Interestingly, E. multiplicata exhibits the ancestral biphasic (metamorphic) life cycle, whereas the new species maintains an aquatic larval form throughout life (paedomorphic) and superficially resembles larval E. multiplicata. The new species is the first known paedomorphic plethodontid from the Ouachita Mountains, and the most divergent paedomorphic salamander discovered in over seventy years. This species represents an independent instance of the evolution of paedomorphosis associated with a porous streambed, which may facilitate vertical seasonal movements. This new species currently has an extremely limited known distribution and is of immediate conservation concern.

Batrachochytrium dendrobatidis haplotypes on the hellbender Cryptobranchus alleganiensis are identical to global strains.

To determine whether the chytrid fungus Batrachochytrium dendrobatidis (Bd) found on the hellbender Cryptobranchus alleganiensis in the southern US is endemic or exotic, we identified the genetic type of this fungus using partial DNA sequences of the internal transcribed spacer (ITS) region. We identified 3 genetic types, which are found on Japanese amphibians other than the Japanese giant salamander Andrias japonicus, a species that belongs to the same family (Cryptobranchidae) as hellbenders. The fungus collected from hellbenders exhibited low genetic diversity and matched the common Bd genetic types which have been detected from around the world. These results support that the chytrid fungus on the hellbender is a novel pathogen, as proposed by previous studies. Although we have not observed disease symptoms directly linked to this fungus on this endangered salamander, further evaluation of the influence of this exotic fungus on this species is warranted.

Disease state associated with chronic toe lesions in hellbenders may alter anti-chytrid skin defenses.

Hellbenders (Cryptobranchus alleganiensis) are large, aquatic salamanders from the eastern United States. Both subspecies, eastern and Ozark hellbenders, have experienced declines resulting in federal listing of Ozark hellbenders. The globally distributed chytrid fungus, Batrachochytrium dendrobatidis (Bd) has been detected in both subspecies, and Batrachochytrium salamandrivorans (Bsal) poses a new threat if introduced into North America. Ozark hellbenders also suffer a high prevalence of toe lesions of unknown etiology, with changes in host immunocompetence hypothesized to contribute. Antimicrobial peptides (AMPs) secreted from dermal granular glands may play a role in hellbender health. We collected skin secretions from free-ranging hellbenders and enriched them for small cationic peptides used for growth inhibition assays against Bd and Bsal. Generalized linear mixed models revealed the presence of active toe lesions as the strongest and only significant predictor of decreased Bd inhibition by skin peptides. We also found skin secretions were more inhibitory of Bsal than Bd. MALDI-TOF mass spectrometry revealed candidate peptides responsible for anti-chytrid activity. Results support the hypothesis that hellbender skin secretions are important for innate immunity against chytrid pathogens, and decreased production or release of skin peptides may be linked to other sub-lethal effects of disease associated with toe lesions.

Evaluation of Severity and Factors Contributing to Foot Lesions in Endangered Ozark Hellbenders, Cryptobranchus alleganiensis bishopi.

Arkansas populations of Ozark Hellbenders, Cryptobranchus alleganiensis bishopi have declined precipitously over the past few decades and are now limited to a single river. Biologists have also observed an increase of distal limb lesions with unidentified etiology and unknown role in morbidity and mortality of the species in this location. We documented lesions and collected associated individual size class data and pathogen samples in Ozark Hellbenders of Arkansas (n = 73) from 2011 to 2014 with the following two objectives: (1) document spatiotemporal patterns and severity of lesions present in this last remaining Arkansas Ozark Hellbender population, and (2) determine if host factors and infection status are associated with lesion severity. A scoring system was created from 0 to 7 based on lesion observations. Linear mixed model regressions followed by AICc model evaluation were used to determine associations among infection status for amphibian pathogens Batrachochytrium dendrobatidis (Bd) and Ranavirus as well as individual biometrics on lesion score. We discovered 93.2% of Hellbenders had lesions characterized by digit swelling that often progressed toward toe-tip ulceration. In severe cases we observed digital necrosis progressing to digit loss. Any recaptured individuals had the same or worse lesion score from previous captures. The top predictive model for lesion severity included individual mass and Bd infection status with a significant, positive association of Bd with increased lesion severity (ß = 0.87 ± 0.39 S.E., C.I.: 0.11, 1.63). Our findings highlight a widespread and progressive disease that is an important factor to consider for the future of Ozark Hellbenders. This syndrome is presumptively multifactorial, and future studies will benefit from investigating several factors of host, infectious agents, and environment and their roles in disease manifestation for the purpose of developing effective, multi-faceted conservation strategies. A summary of potential etiologies and mechanisms is provided that may explain observed lesion distribution and that will be applicable to future disease and epidemiological investigations.

GEOGRAPHIC AND INDIVIDUAL DETERMINANTS OF IMPORTANT AMPHIBIAN PATHOGENS IN HELLBENDERS (CRYPTOBRANCHUS ALLEGANIENSIS) IN TENNESSEE AND ARKANSAS, USA.

Wildlife diseases are a major threat for species conservation and there is a growing need to implement disease surveillance programs to protect species of concern. Globally, amphibian populations have suffered considerable losses from disease, particularly from chytrid fungi (Batrachochytrium dendrobatidis [Bd] and Batrachochytrium salamandrivorans [Bsal]) and ranavirus. Hellbenders (Cryptobranchus alleganiensis) are large riverine salamanders historically found throughout several watersheds of the eastern and midwestern US. Populations of both subspecies (Ozark hellbender, Cryptobranchus alleganiensis bishopi; eastern hellbender, Cryptobranchus alleganiensis alleganiensis) have experienced precipitous declines over at least the past five decades, and emerging pathogens are hypothesized to play a role. We surveyed Ozark hellbender populations in Arkansas (AR) and eastern hellbender populations in Middle Tennessee (MTN) and East Tennessee (ETN) for both chytrid fungi and ranavirus from swabs and tail tissue, respectively, from 2011 to 2017. Overall, we detected Bd on hellbenders from nine out of 15 rivers, with total prevalence of 26.7% (54/ 202) that varied regionally (AR: 33%, 28/86; MTN: 11%, 4/36; ETN: 28%, 22/80). Ranavirus prevalence (9.0%, 18/200) was comparatively lower than Bd, with less regional variation in prevalence (AR: 6%, 5/ 85; MTN: 11%, 4/36; ETN: 10%, 8/79). We did not detect Bsal in any hellbender populations. We detected a significant negative correlation between body condition score and probability of ranavirus infection (ß=-0.13, SE=0.06, 95% confidence interval: -0.24, -0.02). Evaluation of infection load of positive individuals revealed different trends than prevalence alone for both ranavirus and Bd, with MTN having a significantly greater average ranaviral load than both other regions. We documented a variety of lesions that likely have multiple etiologies on hellbenders located within all geographic regions. Our data represent a multiyear pathogen dataset across several regions of C. alleganiensis, and we emphasize the need for continued pathogen surveillance.