Prevalence of Batrachochytrium dendrobatidis in immature eastern hellbenders Cryptobranchus alleganiensis from North Carolina, USA.

Batrachochytrium dendrobatidis (Bd) has been detected in wild hellbender Cryptobranchus alleganiensis populations, with rare instances of chytridiomycosis and Bd-induced mortality. To date, Bd surveillance in hellbender populations has been disproportionately focused on adult age classes. A lingering question is whether Bd might contribute to hellbender declines through disproportionate negative effects on immature age classes. The objective of this study was to quantify Bd prevalence and load in immature hellbenders in western North Carolina, USA. We conducted field surveys during 2018 and 2019 and collected 88 skin swabs from 84 hellbenders spanning 3 age classes. Bd was detected on 11% of individuals, including 8 larvae and 1 juvenile. We did not detect symptoms of chytridiomycosis or a decline in body condition in Bd-positive hellbenders. Load varied from approximately 1-153 zoospore equivalents for the 9 Bd-positive hellbenders and was not associated with size class of the individual. While hellbenders appeared to be abundant in each survey reach, more work is needed to determine whether Bd may increase the vulnerability of immature hellbenders to anthropogenic stressors.

Development and characterization of 33 novel polymorphic microsatellite markers for the brown tree snake Boiga irregularis.

BACKGROUND: Boiga irregularis is a widespread invasive species on Guam and has led to extirpation of most of the island's native avifauna. There are presently no microsatellite markers for this invasive species, hence we developed highly polymorphic microsatellite markers to allow for robust population genetic studies on Guam. FINDINGS: We isolated and characterized 33 microsatellite loci for the brown tree snake, B. irregularis. The loci were screened across 32 individuals from Guam. The number of alleles per locus ranged from three to ten, with an average of 4.62. The expected (He) and observed heterozygosity (Ho) ranged from 0.294 to 0.856 and from 0.031 to 0.813, with an average of 0.648 and 0.524, respectively. Significant deviations from Hardy-Weinberg equilibrium were detected at seven loci after Bonferoni correction. Probability of identity values ranged from 0.043 to 0.539. CONCLUSIONS: These genetic markers are useful for understanding a suite of post-invasion population genetic parameters, sources of invasions, and effectiveness of management strategies for this invasive species.

Genetic analysis reveals multiple parentage in captive reared eastern hellbender salamanders (Cryptobranchus alleganiensis).

Information on the parentage of captive reared clutches is vital for conservation head-starting programs. Molecular methods, such as genotyping individuals with hyper-variable markers, can elucidate the genealogical contribution of captive-reared, reintroduced individuals to native populations. In this study, we used 12 polymorphic microsatellite loci to infer parentage of a clutch of 18 eastern hellbenders collected from a single nest from Buffalo Creek, West Virginia, subsequently reared in captivity, and used for translocations in Indiana. Collectively, these markers successfully detected the presence of multiple parentage for this species of conservation concern presently used in captive management programs in zoos across many states. This study highlights the need for genetic analysis of captive reared clutches used in translocations to minimize the loss of genetic diversity and potential for genetic swamping at release sites.

Population genetics of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) across multiple spatial scales.

Conservation genetics is a powerful tool to assess the population structure of species and provides a framework for informing management of freshwater ecosystems. As lotic habitats become fragmented, the need to assess gene flow for species of conservation management becomes a priority. The eastern hellbender (Cryptobranchus alleganiensis alleganiensis) is a large, fully aquatic paedamorphic salamander. Many populations are experiencing declines throughout their geographic range, yet the genetic ramifications of these declines are currently unknown. To this end, we examined levels of genetic variation and genetic structure at both range-wide and drainage (hierarchical) scales. We collected 1,203 individuals from 77 rivers throughout nine states from June 2007 to August 2011. Levels of genetic diversity were relatively high among all sampling locations. We detected significant genetic structure across populations (Fst values ranged from 0.001 between rivers within a single watershed to 0.218 between states). We identified two genetically differentiated groups at the range-wide scale: 1) the Ohio River drainage and 2) the Tennessee River drainage. An analysis of molecular variance (AMOVA) based on landscape-scale sampling of basins within the Tennessee River drainage revealed the majority of genetic variation (∼94-98%) occurs within rivers. Eastern hellbenders show a strong pattern of isolation by stream distance (IBSD) at the drainage level. Understanding levels of genetic variation and differentiation at multiple spatial and biological scales will enable natural resource managers to make more informed decisions and plan effective conservation strategies for cryptic, lotic species.

Health and habitat quality assessment for the eastern hellbender (Cryptobranchus alleganiensis alleganiensis) in Indiana, USA.

The eastern hellbender (Cryptobranchus alleganiensis alleganiensis) has experienced precipitous population declines throughout its range. Numerous factors are speculated to be involved, but no empirical evidence has been presented for any. We implemented a population-wide health assessment in Indiana, USA, examining both the physical well-being of individuals and the quality of their habitat. Physicochemical parameters were analyzed directly in the field and later in the laboratory, when appropriate. Samples were collected June 2008-October 2008 and June 2009-September 2009 for reproductive analysis, blood screening, and disease prevalence. Of 27 chemicals screened in water samples, three were found in the study site, including atrazine. Atrazine was found at levels reported to cause reproductive problems in other amphibians. Vitellogenin was detected only in females and proved a reliable indicator of sex. Sperm parameters were generally of high quality and similar to other populations. Most plasma parameters were similar between sexes, although there were significant differences in calcium and potassium concentrations. Abnormalities were common, occurring in 68% of individuals. No hemoparasites were found, but amphibian chytrid fungus (Batrachochytrium dendrobatidis) was detected on one individual. Our findings establish a baseline for hematology and water-quality parameters that can be used as a model for evaluating population health throughout the hellbender range.