Barton and the forgotten description of Salamandra horrida (Amphibia, Urodela): story of a rediscovery

Cryptobranchus alleganiensis (Sonnini & Latreille, 1801b) was long considered the only species of the genus Cryptobranchus Leuckart, 1821. In this genus, Sabatino & Routman (2009) found eight genetic independent unities isolated from each other, which they treated as Management Units. Later, Hime (2017) recovered five strongly supported species-level lineages within this genus, corresponding more or less to the lineages of Sabatino & Routman (2009). We herein resurrect a valid nomen for one of the lineages of Hime (2017) (Ohio/Allegheny/Susquehanna lineage), the most broadly distributed of the five, which should be named Cryptobranchus horridus (Barton, 1807a). We relate the story of the rediscovery of two forgotten publications of Barton (1807a‒b) preceding that of 1808 so far recognized as the original description of this taxon. We discuss the problem of the onymotope of Cryptobranchus alleganiensis and present logonomic lists for the genus Cryptobranchus and all the taxa described. The nucleospecies of the genus Cryptobranchus is Salamandra horrida Barton, 1807a which is no longer a synonym of Salamandra alleganiensis Sonnini & Latreille, 1801b. The updating of the logonymic lists revealed the forgotten designation of Barnes (1828) for the genus Protonopsis Le Conte, 1824, a synonym of Cryptobranchus. The following nomina can be allocated to three of the five lineages identified by Hime (2017): Cryptobranchus alleganiensis, Cryptobranchus horridus and Cryptobranchus bishopi. Two other lineages require further studies.

Dorsal Skin Microbial Assemblages in Free-ranging Hellbenders, Cryptobranchus Alleganiensis, Associated With Subspecies and Chronic Toe Lesions, but Not With Chytrid Fungal Infection.

BackgroundSkin microbiomes are important components of skin health and have been shown to contribute to immunity in amphibians, especially against the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Hellbenders (Cryptobranchus alleganiensis) are large aquatic amphibians (Order Caudata) native to the eastern United States that have experienced population declines of both the Ozark and eastern subspecies, C. a. bishopi and C. a. alleganiensis, respectively. In addition, ulcerative non-healing toe lesions have become increasingly prevalent in C. a. bishopi, in Arkansas (AR) where populations are now reduced to a single river. To evaluate the potential impacts of both chronic toe lesions and Bd on hellbender health, we compared dorsal skin microbial assemblages based on 16S rRNA gene amplicons between a declining Ozark hellbender population in Arkansas (AR) presenting lesions and a reference, recruiting, lesion-free, population of eastern hellbenders in eastern Tennessee (ETN). We further evaluated effects of mass and life stage across both subspecies, as well as toe lesion severity and Bd infection status within AR, to better understand the associations between microbiomes and disease in a wild salamander.ResultsWe found skin of ETN hellbenders to have greater bacterial alpha diversity compared to AR, with this disparity decreasing as Hill number order increased. Conversely, within AR, animals with more severe lesions had decreased alpha diversity than those with mild lesions, which became more pronounced with increasing Hill number. Further, the average microbial assemblage structure differed between ETN and AR. Specifically, AR communities displayed increased beta diversity compared to those from ETN, which appeared to be linked to toe lesion severity. Neither size class (mass) nor Bd infection status had a significant effect on alpha or beta diversity. Taxonomic analysis revealed ETN to have greater OTU abundance of phylum Cyanobacteria 24.3%) compared to AR (5.9%); whereas AR had increased abundance of Proteobacteria (48.5%), Firmicutes (9.1%), and Synergistetes (1.5%), in comparison to ETN (31.5%, 2.6%, 0.2%, respectively).ConclusionsResults demonstrate that eastern hellbenders of ETN have richer and less dispersed dorsal skin bacterial assemblages compared to Ozark hellbenders of AR. Furthermore, we suggest that increased severity of toe lesions may be linked to systemic changes resulting in skin microbial dysbiosis, independent of Bd infection. Although lesions remain to have an unknown etiology, this study is another step towards understanding skin bacterial microbiomes in hellbenders, and their potential associations with chronic disease.

Landuse and Water Quality Threats to Current and Historical Cryptobranchus Alleganiensis Streams Across Multiple Ecoregions

The hellbender (Cryptobranchus alleganiensis) is a large, long-lived, and fully aquatic salamander species endemic to streams and rivers across 15 states in the Midwest and Eastern United States. Hellbender populations have experienced drastic declines due to habitat degradation, accelerated sedimentation, aquatic contaminants, and infectious diseases. Although declining water quality is often suggested as a major contributing factor to hellbender population declines, few studies have evaluated the presence of aquatic contaminants at sites with current and historical C. alleganiensis populations. We used a novel passive sampling technique to assess the presence and concentration of two herbicides (glyphosate and atrazine) in the water and analyzed heavy metal (cadmium (Cd), mercury (Hg), and lead (Pb)) concentrations in stream sediment samples at 30 sites across a watershed development gradient throughout the C. alleganiensis range in Tennessee (TN) and North Carolina (NC). Our results indicated the presence of atrazine in 23% of our sites. All 30 sites contained Cd and Pb, and 26 sites contained Hg. Levels of glyphosate were too low to detect using our methods. Although percent watershed development was not significantly different among ecoregions, Blue Ridge watersheds were overall less developed than watersheds in the Ridge and Valley and Interior Plateau ecoregions. The model with greatest support suggested that percent watershed development and specific conductivity were negatively correlated with hellbender population status. Because this research focused on assessing the prevalence of commonly encountered aquatic contaminants, our results and study design are broadly applicable to C. alleganiensis populations across the species range.

Stable Isotope Analysis of Ozark Hellbender (Cryptobranchus alleganiensis bishopi) Living and Preserved Museum Tissue Reveals a Shift in Their Generalist Diet Composition

Ozark hellbenders (Cryptobranchus alleganiensis bishopi) have undergone marked population declines across their entire distribution. A variety of ecological life history research has been conducted to determine the cause(s) of the declines. Historically, hellbender diet studies used stomach content examination methods; however, alternative approaches such as less intrusive stable isotope analyses are now options for researchers. The goals of our study were to conduct stable isotope analysis on live and formalin-preserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, Arkansas. Also, we used stable isotope analysis to investigate if Spring River hellbender diets have changed over time. We sampled fish, live hellbenders (non-destructively), and formalin-preserved hellbender tissues from museum collections for stable isotope analysis. We sampled crayfish for assemblage composition and stable isotope analysis. The results of our stable isotope study revealed three main findings: (1) there were no statistically significant differences between hellbender δ13C and δ15N values among sites and hellbender stable C and N isotopes were correlated with body length; (2) traditional δ13C versus δ15N bi-plots and trophic discrimination values did not provide complete discernment in hellbender diets; however, Bayesian MixSIAR models revealed hellbenders to be generalists, and (3) the use of δ13C and δ15N values adjusted historic formalin-fixed and ethanol preserved hellbenders matched well with current crayfish and fish stable isotope values based on Bayesian MixSIAR models. These findings provide important diet information and a possible tool to examine dietary patterns from preserved specimens that may be used for hellbender conservation and management.

Short-term exposure to elevated suspended sediment increases oxygen uptake of gilled larval Eastern Hellbender salamanders (Cryptobranchus alleganiensis)

Freshwater ecosystems are increasingly impacted by anthropogenic elevated levels of suspended sediment that may negatively affect aquatic organisms, including salamanders. While increasing fine sediment in streams has been suggested as a reason for population declines, to date no study has empirically assessed the effect of suspended sediment on gilled larval Eastern Hellbenders (Cryptobranchus alleganiensis Daudin, 1803), a critical life history stage and species of conservation concern. We used custom respirometers to elucidate effects of suspended sediments on larval Hellbender oxygen uptake in trials conducted in situ in Georgia streams. Mean oxygen uptake increased and was significantly higher in trials when larval salamanders were exposed to suspended sediment (mean = 5.06 O2 mg/L, 800 mg/L sediment treatment vs 2.25 O2 mg/L, 0.00 mg/L sediment control). This may indicate elevated physiological stress in response to short term exposure to suspended sediments. Qualitatively, individuals in both groups exhibited rocking behavior in response to low oxygen (hypoxia), albeit at different frequencies (sediment exposure = 7.6 rocks per minute and control = 2.1 rocks per minute). Larval salamanders may be able to temporarily compensate for low oxygen through increased rocking behavior when high suspended sediment loads are present, with future respirometry research needed.