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Jeffrey T. Briggler - One of the best experts on this subject based on the ideXlab platform.

  • Captivity-Induced Changes in the Skin Microbial Communities of Hellbenders ( Cryptobranchus Alleganiensis )
    Microbial ecology, 2018
    Co-Authors: Obed Hernandez-gomez, Jeffrey T. Briggler, Rod N Williams
    Abstract:

    Variation in environmental conditions can result in disparate associations between hosts and microbial symbionts. As such, it is imperative to evaluate how environmental variables (e.g., habitat quality) can influence host-associated microbiome composition. Within wildlife conservation programs, captive conditions can negatively influence the establishment and maintenance of “wild-type” microbiotas within a host. Alternative microbial communities can result in the proliferation of disease among captive stock or upon reintroduction. Hellbenders (Cryptobranchus Alleganiensis) are a threatened salamander for which extensive captive management is currently employed. Using metabarcoding, we characterized the skin microbiota of wild and captive hellbenders from two subspecies in the state of Missouri, the eastern (C. a. Alleganiensis) and the Ozark hellbender (C. a. bishopi). Both subspecies in our study included wild adults and captive juveniles that were collected from the wild as eggs. Our objectives were to investigate differences in the skin microbial communities’ richness/diversity, composition, and functional profiles of microbes between wild and captive individuals. Captive eastern hellbenders possessed richer communities than wild cohorts, whereas the opposite pattern was observed within the Ozark subspecies. We found significant microbial community structure between wild and captive populations of both subspecies. Microbiota structure translated into differences in the predicted metagenome of wild and captive individuals as well. As such, we can expect captive hellbenders to experience alternative microbial structure and function upon reintroduction into the wild. Our study provides a baseline for the effect of captivity on the skin microbial communities of hellbenders, and highlights the need to incorporate microbiota management in current captive-rearing programs.

  • augmentation programme for the endangered ozark hellbender Cryptobranchus Alleganiensis bishopi in missouri
    International Zoo Yearbook, 2017
    Co-Authors: Jeff Ettling, M D Wanner, A S Pedigo, J L Kenkel, K R Noble, Jeffrey T. Briggler
    Abstract:

    The Ozark hellbender Cryptobranchus Alleganiensis bishopi is an endangered aquatic salamander that inhabits cold-water streams in the Ozark Highlands of Missouri and Arkansas in the USA. As a result of the drastic population declines over the past 40+ years, with a prominent shift in age structure (large, mature individuals predominate; young classes virtually absent), the Ozark Hellbender Working Group (OHWG) was established in 2001 to develop a conservation strategy for the species. The OHWG comprises representatives from state and federal agencies, Saint Louis Zoo (MO, USA), universities and interested individuals. Based on data from the Hellbender Population and Viability Assessment it was determined that without intervention, including a captive-propagation, head-start and augmentation programme, it was highly likely (>96% probability) that the species would go extinct within the next 75 years. Inter-agency collaboration has facilitated significant progress since the inception of the captive-propagation programme in 2002. The joint strategy of the world's first captive breeding of Ozark hellbenders in 2011 and subsequent captive breeding in the 2012–2015 period, together with the hatching and rearing of wild-collected eggs, means 6737 larvae/juveniles have been produced and/or reared at the Saint Louis Zoo. Since 2008, 3138 juvenile Ozark hellbenders reared at Saint Louis Zoo have been released into the wild in Missouri to augment remaining populations in four different streams (Bryant Creek, North Fork of the White River, Current River and Eleven Point River). Based on the success of the captive-propagation programme, post-release survival and dedicated individuals of various organizations the future of the Ozark hellbender is looking optimistic.

  • Redescription of Placobdella cryptobranchii 1 Redescription and molecular characterization of Placobdella cryptobranchii (Johnson &
    2016
    Co-Authors: William E. Moser, Jeffrey T. Briggler, William A. Hopkins, Chawna D. Schuette, Dennis J. Richardson, Charlotte I. Hammond, Eric A. Lazo-wasem
    Abstract:

    Placobdella cryptobranchii (Johnson & Klemm, 1977) was originally described from specimens collected from Ozark Hellbenders (Cryptobranchus Alleganiensis bishopi) from the North Fork of the White River i

  • within river gene flow in the hellbender Cryptobranchus Alleganiensis and implications for restorative release
    Conservation Genetics, 2014
    Co-Authors: Sheena M Feist, Jeffrey T. Briggler, Jeffrey B Koppelman, Lori S Eggert
    Abstract:

    Understanding how populations are genetically and demographically connected is beneficial for species management, since gene flow and dispersal contribute to genetic diversity and population persistence. For hellbenders (Cryptobranchus Alleganiensis), an aquatic salamander species experiencing dramatic declines in population size, fine-scale (i.e. within river) patterns of genetic diversity and gene flow are not well understood. Previous findings indicate that hellbenders are habitat specialists that exhibit extreme site fidelity and low vagility, suggesting that gene flow is restricted among the several, discrete habitat patches within a river. Using 15 polymorphic microsatellite loci and 497 hellbender samples from four Missouri rivers, we assessed fine-scale patterns of genetic diversity in order to infer population connectivity and aid in population management. Results indicate moderate levels of genetic variation (HO = 0.66–0.78) with little differentiation among habitat patches (avg. FST = 0.002) and no evidence of isolation by distance. Our data suggest that hellbender gene flow has been extensive even among habitat patches separated by distances greater than >100 km. These results are useful for hellbender management, especially in terms of making informed decisions regarding restorative releases of captively propagated individuals.

  • Relating resource use to body condition and survival of Ozark hellbenders Cryptobranchus Alleganiensis bishopi
    Endangered Species Research, 2013
    Co-Authors: Christopher R. Ayers, Jeffrey T. Briggler, Catherine M. Bodinof, Jerrold L. Belant, J. Millspaugh
    Abstract:

    Endangered species conservation requires the understanding of factors affecting animal condition and performance. However, commonly investigated resource-use metrics such as habitat selection may not accurately predict biological outcomes because some components of habitats are more important to animals than others. We examined individual level resource− outcome relationships and the relationship between 2 biological outcome metrics — body condition and fate — in Ozark hellbenders Cryptobranchus Alleganiensis bishopi, which were recently included on the US Endangered Species List by the United States Fish and Wildlife Service. Our regression models included proportional use of a stream substrate, average distance to cover, distance moved, and water temperature as predictors of daily change in body condition or fate of captive-reared, radio-marked released hellbender populations in 2 sections of the North Fork of the White River in Missouri in 2008−2009. Distance moved between observations helped predict change in body condition, but no variable predicted fate well. We infer that resource use of selected substrate features did not predict biological outcomes in the short term. Our results indicate that energetic metrics such as distance moved can predict biological outcomes better than use of substrate features. Body condition did not correlate with fate and may be a poor indicator of an animal’s ability to survive and reproduce. These investigations improve our understanding of influences on biological outcomes in hellbenders, which may improve efficacy of management and conservation of this species through efforts to increase abundance of important resources to improve hellbender condition and performance.

Rod N Williams - One of the best experts on this subject based on the ideXlab platform.

  • movement and habitat use of eastern hellbenders Cryptobranchus Alleganiensis Alleganiensis following population augmentation
    Herpetologica, 2018
    Co-Authors: Emily B Mccallen, Bart T Kraus, Nick G Burgmeier, Songlin Fei, Rod N Williams
    Abstract:

    Abstract With amphibian declines at crisis levels, translocations, including population augmentations, are commonly used for amphibian conservation. Eastern Hellbenders (Cryptobranchus Alleganiensis Alleganiensis) have declined to low densities in many areas of their range, making them ideal candidates for population augmentation. Both wild adults and captive-reared juveniles have been used for augmentations, but their suitability has never been directly compared. Herein, we use radio telemetry with Eastern Hellbenders to examine patterns of site fidelity, movement, and habitat use over a 2-yr period for adult residents, wild adult translocates, and captive-reared juvenile translocates. We used generalized linear models and generalized linear mixed models to identify temporal trends and explore the effects of residential status (resident vs. translocate) and origin/age (captive-reared juveniles vs. wild adults) on various ecological and behavioral traits relating to habitat. Site fidelity was high in adul...

  • Captivity-Induced Changes in the Skin Microbial Communities of Hellbenders ( Cryptobranchus Alleganiensis )
    Microbial ecology, 2018
    Co-Authors: Obed Hernandez-gomez, Jeffrey T. Briggler, Rod N Williams
    Abstract:

    Variation in environmental conditions can result in disparate associations between hosts and microbial symbionts. As such, it is imperative to evaluate how environmental variables (e.g., habitat quality) can influence host-associated microbiome composition. Within wildlife conservation programs, captive conditions can negatively influence the establishment and maintenance of “wild-type” microbiotas within a host. Alternative microbial communities can result in the proliferation of disease among captive stock or upon reintroduction. Hellbenders (Cryptobranchus Alleganiensis) are a threatened salamander for which extensive captive management is currently employed. Using metabarcoding, we characterized the skin microbiota of wild and captive hellbenders from two subspecies in the state of Missouri, the eastern (C. a. Alleganiensis) and the Ozark hellbender (C. a. bishopi). Both subspecies in our study included wild adults and captive juveniles that were collected from the wild as eggs. Our objectives were to investigate differences in the skin microbial communities’ richness/diversity, composition, and functional profiles of microbes between wild and captive individuals. Captive eastern hellbenders possessed richer communities than wild cohorts, whereas the opposite pattern was observed within the Ozark subspecies. We found significant microbial community structure between wild and captive populations of both subspecies. Microbiota structure translated into differences in the predicted metagenome of wild and captive individuals as well. As such, we can expect captive hellbenders to experience alternative microbial structure and function upon reintroduction into the wild. Our study provides a baseline for the effect of captivity on the skin microbial communities of hellbenders, and highlights the need to incorporate microbiota management in current captive-rearing programs.

  • Training for Translocation: Predator Conditioning Induces Behavioral Plasticity and Physiological Changes in Captive Eastern Hellbenders (Cryptobranchus Alleganiensis Alleganiensis) (Cryptobranchidae, Amphibia)
    MDPI AG, 2018
    Co-Authors: Erin K. Kenison, Rod N Williams
    Abstract:

    Translocations are stressful, especially when captive animals are naïve to natural stimuli. Captive eastern hellbenders (Cryptobranchus Alleganiensis Alleganiensis) identify predatory fish as threats, but may be more vulnerable to predation and stress because of inexperience with them. We investigated the use of predator conditioning to prepare hellbenders, behaviorally and physiologically, for the presence of a common predator, largemouth bass (Micropterus salmoides). We reared hellbenders for 30 d with and without continuous exposure to largemouth bass kairomones and heterospecific alarm cues and found conditioned hellbenders became less active compared to unconditioned individuals (p = 0.017). After conditioning, we exposed hellbenders to water, a low concentration of kairomones, or a high concentration of kairomones in a closed respirometer system. We measured activity within respirometer chambers and routine metabolic rate. We found unconditioned hellbenders exposed to low and high concentrations of kairomones were 41% and 119% more active than conditioned animals (p = 0.002 and p < 0.001). Moreover, conditioned individuals had on average 6.5% lower metabolic rates across all three kairomone concentrations compared to unconditioned individuals (p = 0.017). Our data suggest that predator conditioning induces behavioral avoidance tactics and physiological changes that could improve future translocation efforts for hellbenders and other imperiled species

  • Cutaneous Microbial Community Variation across Populations of Eastern Hellbenders (Cryptobranchus Alleganiensis Alleganiensis).
    Frontiers in microbiology, 2017
    Co-Authors: Obed Hernandez-gomez, Jason T. Hoverman, Rod N Williams
    Abstract:

    Multicellular hosts maintain complex associations with microbial communities. While microbial communities often serve important functional roles for their hosts, our understanding of the local and regional processes that structure these communities remains limited. Metacommunity analyses provide a promising tool for investigating mechanisms shaping microbiome heterogeneity, which is essential for predicting functional variation between hosts. Using a metacommunity framework, we examined heterogeneity in the skin microbiome of the eastern hellbender (Cryptobranchus Alleganiensis Alleganiensis). Hellbenders are broadly distributed throughout river systems in the eastern United States, but are present in specific environment locations throughout their range. The large range of the species and history of population fragmentation suggest that local and regional processes contribute to the distribution of cutaneous symbiont diversity. Therefore, we characterized the skin and environmental bacterial communities at eight rivers throughout the range of the species. We observed variation among hellbender populations in skin microbial community diversity and proportion of shared operational taxonomic units (OTUs) between animal and river water communities. Among populations sampled, we noted significant clumped OTU turnover (i.e., Clementsian structure) resulting in unique cutaneous communities. In addition, we observed a significant positive correlation between skin community divergence and hellbender population genetic divergence. Host-population skin community dissimilarity did not correlate strongly with distance between sampling locations, indicating a weak spatial effect on the distribution of symbionts. These results suggest that species sorting mechanisms (i.e., local processes) structure local skin microbial communities in hellbenders. The variation in skin community composition observed among host populations foreshadows a similar pattern in important functional characteristics (e.g, resistance to dysbiosis). Future work should focus on investigating forces shaping microbiome structure in eastern hellbenders, examining functional variation among populations, and evaluating effectiveness of microbiome management recommendations.

  • Genetic confirmation of filial cannibalism in North America’s giant salamander, the Eastern hellbender Cryptobranchus Alleganiensis Alleganiensis
    2017
    Co-Authors: Shem D Unger, Rod N Williams
    Abstract:

    Genetic confirmation of filial cannibalism in North America’s giant salamander, the Eastern hellbender Cryptobranchus Alleganiensis Alleganiensis

William A. Hopkins - One of the best experts on this subject based on the ideXlab platform.

  • the influence of multiscale habitat variables and population density on artificial shelter use by hellbenders Cryptobranchus Alleganiensis
    Herpetologica, 2020
    Co-Authors: Sky T Button, Catherine Bodinof M Jachowski, Brian F Case, Jordy Groffen, William A. Hopkins
    Abstract:

    Recently, artificial shelters have been proposed as a novel tool to monitor Hellbenders (Cryptobranchus Alleganiensis) and other cryptobranchid salamanders. Factors that influence artificial shelter use by Hellbenders have not been identified, but are important for maximizing the utility of these shelters as monitoring tools. To identify these factors, in 2013–2018 we deployed 438 artificial shelters across 10 stream reaches inhabited by Hellbenders, within three rivers in the upper Tennessee River Basin. We hypothesized that occupancy and nesting would depend on shelter placement, and would be greatest in reaches with relatively high densities of adult/subadult Hellbenders (i.e., >1.5 individuals per 100 m2). We placed shelters in locations representing a range of instream conditions, but avoided microhabitats that were not suitable for Hellbenders. We monitored shelter occupancy by Hellbenders every 2–8 wk, and surveyed shelters for nests every 2–5 d during their breeding season. We quantified densities of adult/subadult Hellbenders and 10 habitat variables across multiple spatial scales. Hellbenders occupied 46% of artificial shelters, and nested in 17% of artificial shelters that were in place for at least one breeding season. Hellbenders were most likely to occupy and nest in shelters placed in portions of those reaches that were ≥50 cm deep with high densities of adult/subadult individuals. Among the variables we considered, population density was the most important factor influencing shelter occupancy by Hellbenders. Shelter nesting was most influenced by water depth, but also by population density and time since shelter installation. Both occupancy and nesting in shelters increased for 2–3 yr following shelter deployment. Our results provide evidence that artificial shelters constitute efficient tools in some streams for monitoring the occurrence and reproduction of Hellbenders.

  • Cortisol is the predominant glucocorticoid in the giant paedomorphic hellbender salamander (Cryptobranchus Alleganiensis).
    General and comparative endocrinology, 2019
    Co-Authors: William A. Hopkins, Michelle L. Beck, Sarah E. Durant, W. Keith Ray, Richard F. Helm, L. Michael Romero
    Abstract:

    Corticosterone is widely regarded to be the predominant glucocorticoid produced in amphibians. However, we recently described unusually low baseline and stress-induced corticosterone profiles in eastern hellbenders (Cryptobranchus Alleganiensis Alleganiensis), a giant, fully aquatic salamander. Here, we hypothesized that hellbenders might also produce cortisol, the predominant glucocorticoid used by fishes and non-rodent mammals. To test our hypothesis, we collected plasma samples in two field experiments and analyzed them using multiple analytical techniques to determine how plasma concentrations of cortisol and corticosterone co-varied after 1) physical restraint and 2) injection with adrenocorticotropic hormone (ACTH), the pituitary hormone responsible for triggering the release of glucocorticoids from amphibian interrenal glands. Using liquid chromatography-mass spectrometry, we found that baseline and restraint-induced plasma concentrations of cortisol were more than five times those of corticosterone. We then demonstrated that plasma concentrations of both glucocorticoids increased in response to ACTH in a dose-dependent manner, but cortisol concentrations were consistently higher (up to 10-fold) than corticosterone. Cortisol and corticosterone concentrations were not correlated with one another at basal or induced conditions. The extremely low plasma concentrations of corticosterone in hellbenders suggests that corticosterone could simply be a byproduct of cortisol production, and raises questions as to whether corticosterone has any distinct physiological function in hellbenders. Our results indicate that hellbenders produce cortisol as their predominant glucocorticoid, supporting a small and inconclusive body of literature indicating that some other amphibians may produce appreciable quantities of cortisol. We hypothesize that the use of cortisol by hellbenders could be an adaptation to their fully aquatic life history due to cortisol's ability to fulfill both mineralocorticoid and glucocorticoid functions, similar to its functions in fishes. Given the large number of amphibian species that are fully aquatic or have aquatic life stages, we suggest that the broadly held assumption that corticosterone is the predominant glucocorticoid in all amphibians requires further scrutiny. Ultimately, multi-species tests of this assumption will reveal the ecological factors that influenced the evolution of endocrine adaptations among amphibian lineages, and may provide insight into convergent evolution of endocrine traits in paedomorphic species.

  • Haematological and immunological characteristics of eastern hellbenders (Cryptobranchus Alleganiensis Alleganiensis) infected and co-infected with endo- and ectoparasites.
    Conservation physiology, 2016
    Co-Authors: William A. Hopkins, Jesse A. Fallon, Michelle L. Beck, Brittney H. Coe, Catherine M. Bodinof Jachowski
    Abstract:

    Disease is among the leading causes of the global decline in amphibian populations. In North America, parasites and pathogens are among the factors implicated in precipitous population declines of the giant hellbender salamander (Cryptobranchus Alleganiensis), but the incidence of infections and the responses of hellbenders to infections remain poorly studied. Here, we document the prevalence of leech and trypanosome infections in a wild population of eastern hellbenders (Cryptobranchus Alleganiensis Alleganiensis) and describe haematological and immunological characteristics of hellbenders harbouring these infections. We hypothesized that hellbenders parasitized by trypanosomes would be anaemic, that individuals infected with either or both parasites would exhibit shifts in white blood cell counts and that hellbenders infected with leeches would exhibit altered plasma bactericidal capacity. We found that 24 and 68% of hellbenders in our sample population were infected with leeches and trypanosomes, respectively, and 20% were co-infected with both parasites. We found no evidence suggestive of anaemia among infected individuals. However, hellbenders infected with either or both parasites exhibited marked shifts in circulating white blood cells that were consistent with predictable responses to parasitic infection. Additionally, we found that hellbenders harbouring leeches had much higher plasma bactericidal capacity than individuals without leeches, and we offer multiple potential mechanistic explanations for this observation. We also found evidence that cellular and serological immune responses to parasites were less robust in juvenile than adult hellbenders. This finding warrants further investigation in light of the demographic characteristics, specifically the scarcity of juvenile age classes, of hellbender populations where disease is a possible contributor to declines. Finally, we describe two methodological advances that will improve future studies seeking to diagnose trypanosome infections and to test the bactericidal capacity of hellbenders and perhaps other amphibians. Our study provides fundamental insights into how hellbenders respond physiologically to endo- and ectoparasites, which could ultimately prove useful for their conservation.

  • Redescription of Placobdella cryptobranchii 1 Redescription and molecular characterization of Placobdella cryptobranchii (Johnson &
    2016
    Co-Authors: William E. Moser, Jeffrey T. Briggler, William A. Hopkins, Chawna D. Schuette, Dennis J. Richardson, Charlotte I. Hammond, Eric A. Lazo-wasem
    Abstract:

    Placobdella cryptobranchii (Johnson & Klemm, 1977) was originally described from specimens collected from Ozark Hellbenders (Cryptobranchus Alleganiensis bishopi) from the North Fork of the White River i

  • Evidence of ectoparasite-induced endocrine disruption in an imperiled giant salamander, the eastern hellbender (Cryptobranchus Alleganiensis)
    Journal of Experimental Biology, 2015
    Co-Authors: Sarah E. Durant, Andrew K. Davis, William A. Hopkins, L. Michael Romero
    Abstract:

    ABSTRACT Parasitic leeches and trypanosomes release chemical signals into their hosts to evade immuno-detection, but it is unknown whether these compounds manipulate host behavior or endocrine physiology. We determined whether parasitic infections with leeches and/or trypanosomes affected the immune and stress response of an imperiled giant species of amphibian, the eastern hellbender ( Cryptobranchus Alleganiensis Daudin). We monitored corticosterone and white blood cell counts in response to restraint and injection with adrenocorticotropin hormone (ACTH) or saline for up to 50 h. The presence of leeches dampened hellbender corticosterone responses to restraint and reduced diel patterns of plasma corticosterone. Injection with ACTH restored the normal inter-renal responses of hellbenders, suggesting that leeches, possibly through neurotransmitters in leech saliva, cause down-regulation of corticosterone release at the level of the pituitary or hypothalamus. Infection with leeches also increased the relative abundance of eosinophils, white blood cells often recruited into circulation in response to parasitic infection. Lastly, neutrophil to lymphocyte (N:L) ratios increased in all animals after 24 h of capture and remained elevated for up to 50 h, but these temporal dynamics did not differ with parasite infection. Trypanosome infection did not affect any aspect of hellbender physiology that we measured. Our findings reveal a previously undocumented host–parasite dynamic. While the functional significance to the parasite is unclear, the physiological and behavioral implications for the host are great, given the important role of glucocorticoids in regulating physiology and behavior.

Yue-wern Huang - One of the best experts on this subject based on the ideXlab platform.

  • Heavy Metals, Hematology, Plasma Chemistry, and Parasites in Adult Hellbenders (Cryptobranchus Alleganiensis)
    Environmental toxicology and chemistry, 2010
    Co-Authors: Chuan-chin Huang, Jeffrey T. Briggler, Paul Ki-souk Nam, Michael J. Mckee, Yue-wern Huang
    Abstract:

    Ozark (Cryptobranchus Alleganiensis bishopi) and eastern hellbenders (C. a. Alleganiensis) from seven rivers in Missouri, USA, were collected to investigate essential information on hematology, parasites, and plasma chemistry and levels of select heavy metals (Hg, Pb, Cd, Cr, and Co) in the animals' blood. The body masses of Ozark hellbenders were much smaller than those of eastern hellbenders. Blood parasites were detected in Ozark hellbenders, but not eastern hellbenders. The higher frequency in occurrence of eosinophils in Ozark hellbenders (8.8-16.8%) than in eastern hellbenders (highest at 6.6%) might result from the infection of parasites. Seven of the 18 hematology and plasma parameters (hematocrit, basophils, eosinophils, K, P, Ca, and chloride) showed significant differences between subspecies. The blood levels of heavy metals Co, Hg, and Pb differed significantly between subspecies. Ozark hellbenders had higher blood levels of Co ( p < 0.001), while blood levels of Hg and Pb were higher in eastern hellbenders. The levels of chromium (Cr) and cadmium (Cd) were not different between subspecies and among rivers. The eastern hellbenders at Niangua River and the Ozark hellbenders at the North Fork of the White River had lower Hg levels compared to eastern and Ozark hellbenders at other sites. All together, our findings provide important baseline information for managing this endangered species. Environ. Toxicol. Chem. 2010;29:1132-1137. # 2010 SETAC

  • Occurrence of Organic Chemicals in Two Rivers Inhabited by Ozark Hellbenders ( Cryptobranchus Alleganiensis bishopi )
    Archives of environmental contamination and toxicology, 2007
    Co-Authors: Mauricio E. Solis, Chih-chin Liu, Paul Ki-souk Nam, Dev K. Niyogi, Janet M. Bandeff, Yue-wern Huang
    Abstract:

    Ozark Hellbender (Cryptobranchus Alleganiensis bishopi) populations are in decrease throughout their native range with rare recruitment of young. Increased estrogenic chemical levels and alterations of physicochemical properties in their habitat may play a significant role in this phenomenon. We report here the first systematic, comprehensive study of organic chemical concentrations and physical and nutrient parameters in two rivers containing Ozark hellbender populations. Water samples were collected monthly from August 2003 to November 2004. Concentrations of 21 organic chemicals were determined using gas chromatography–mass spectrometry. Nine organic chemicals were detected. Benzyl butyl phthalate, dibutyl phthalate, bisphenol A, and β-sitosterol were all detected >85% of the time, with median concentrations of 18 to 234 ng/L and maximum concentrations of 198 to 4141 ng/L. Individually, concentrations of nutrients and organic chemicals were much lower than those shown previously in laboratory and field experiments to have reproductive effects on amphibians. Nevertheless, hellbenders are exposed to a variety of chemicals with potential estrogenic effects. Our study establishes the basis to examine the specific effects of the detected concentrations, alone and in combination, on the Ozark hellbenders.

Max A Nickerson - One of the best experts on this subject based on the ideXlab platform.

  • Do These Crayfish Make Me Look Fat? Body Condition Correlates To Prey Abundance In Three Hellbender (Cryptobranchus Alleganiensis) Populations
    2019
    Co-Authors: Kirsten A. Hecht, Max A Nickerson, Michael J. Freake, Phil Colclough, Katie Stofer
    Abstract:

    AbstractIn ecological studies body condition is often measured as an indicator of animal health or well-being. The Hellbender (Cryptobranchus Alleganiensis) is a threatened salamander species found throughout the montane regions of the eastern United States. Although few young individuals have historically been found in the wild, recent studies in Blue Ridge Physiographic Regions have uncovered larvae in several streams. In Little River, Tennessee, differences in the crayfish population, the principal component of the adult Hellbender diet, was hypothesized as a potential reason for the large number of immature individuals, and lack of large adults. To investigate this hypothesis, we compared body condition of Hellbenders in three streams with different crayfish relative frequencies. Body condition of Hellbenders was positively correlated with crayfish relative frequencies, with Hellbenders in the stream with the highest crayfish relative frequency exhibiting the highest expected mass per total length.

  • Hellbender Salamanders (Cryptobranchus Alleganiensis) Exhibit an Ontogenetic Shift in Microhabitat Use in a Blue Ridge Physiographic Region Stream
    Copeia, 2019
    Co-Authors: Kirsten A. Hecht, Max A Nickerson, Michael J. Freake, Phil Colclough
    Abstract:

    Organisms that experience large changes in body size during the life span often exhibit differences in resource use among life stages. Ontogenetic shifts in habitat use reduce intraspecific competition and predation and are common in lotic organisms. Although information on the immature life stages of the Hellbender (Cryptobranchus Alleganiensis) is limited, this aquatic salamander exhibits ontogenetic shifts in habitat use in some streams, with adults sheltering under large rocks and larvae utilizing interstitial spaces of gravel beds. Due to the geomorphology of Little River, Tennessee, however, limited interstitial spaces within the gravel are often filled with sand. Therefore, we quantified microhabitat parameters for three life stages of Hellbenders (larvae, sub-adult, adult) to determine if an ontogenetic shift in microhabitat occurred in Little River. We found no significant differences in stream substrate at capture sites among the stages, but there was a positive correlation between rock shelters underlain with very coarse gravel and overall Hellbender occupancy. Although we found no difference in water quality parameters and streambed particle size among the stage classes at the sites of capture, there was a significant difference in the average shelter size among all stages, with larvae utilizing the smallest shelters. Based on these results, future Hellbender research and conservation efforts should consider differences in life stage habitat use as well as specific stream particle classes.

  • hellbenders Cryptobranchus Alleganiensis may exhibit an ontogenetic dietary shift
    Southeastern Naturalist, 2017
    Co-Authors: Max A Nickerson, Kirsten Hecht, Phillip B Colclough
    Abstract:

    Abstract Organisms in lotic habitats often experience dietary shifts over their lifetime. The diet of adult Cryptobranchus Alleganiensis (Hellbender) is well studied throughout the species' range, but knowledge regarding the natural history of larval Hellbenders, including dietary information, remains scarce. We obtained non-lethal diet samples from 23 larval Hellbenders. Larval Hellbenders consumed primarily invertebrate prey including mayfly (Ephemeroptera) and caddisfly (Trichoptera) nymphs. Since these items do not comprise a large proportion of the adult diet, Hellbenders may undergo an ontogenetic dietary shift. Therefore, future management and conservation decisions regarding the Hellbender should consider the abundance and density of aquatic insect populations.

  • Hellbender Salamanders (Cryptobranchus Alleganiensis) Exhibit An Ontogenetic Shift In Microhabitat Use In A Blue Ridge Physiographic Region Stream
    2017
    Co-Authors: Kirsten A. Hecht, Max A Nickerson, Michael J. Freake, Phil Colclough
    Abstract:

    Organisms that experience large changes in body size during the life span often exhibit differences in resource use among life stages. Ontogenetic shifts in habitat use reduce intraspecific competition and predation and are common in lotic organisms. Although information on the immature life stages of the Hellbender (Cryptobranchus Alleganiensis) is limited, this aquatic salamander exhibit9s ontogenetic shifts in habitat use in some streams, with adults sheltering under large rocks and larvae utilizing interstitial spaces of gravel beds. Due to the geomorphology of Little River, Tennessee, however, limited interstitial spaces within the gravel are filled with sand. Therefore we quantified microhabitat parameters for three life stages of Hellbenders (larvae, sub-adult, adult) to determine if an ontogenetic shift in microhabitat occurred in this location. We found no significant differences in stream substrate at capture sites among the stages, but there was a positive correlation between rock shelters underlain with very coarse gravel and overall Hellbender occupancy. Although we found no difference in water quality parameters and streambed particle size among the stage classes at the site of capture, there was a significant difference in the average shelter size among all stages, with larvae utilizing the smallest shelters. As the smaller rocks utilized by larvae in Little River could be less secure shelter than the larger rocks used by adults, mortality may be higher in young Hellbenders due to a potential increase in overall predation risk and susceptibility to flooding. Based on these results, future Hellbender research and conservation efforts should consider differences in life stage habitat use as well as specific stream particle classes.

  • 2003 SOUTHEASTERN NATURALIST 2(4):619–629 HABITAT DIFFERENCES AFFECTING AGE CLASS DISTRIBUTIONS OF THE HELLBENDER SALAMANDER, Cryptobranchus Alleganiensis
    2015
    Co-Authors: Max A Nickerson, Kenneth L Krysko, D. Owen
    Abstract:

    ABSTRACT – Hellbender salamander (Cryptobranchus Alleganiensis) popula-tions have received considerable attention over the last few decades and recent studies show declines. We compared C. Alleganiensis populations and habitat characteristics of the Little River (LR) in the Great Smoky Mountain National Park (GSMNP) of Tennessee, with those of the North Fork of the White River (NFWR), Missouri. We also compared the results of two different sampling methods for obtaining small individuals < 20 cm total length (TL) and gilled larvae. There was no significant difference in the frequency of larvae and adults in LR population There were highly significant differences in the frequency of larvae and adults in the NFWR population and in the proportion of larvae and adults between LR and NFWR. The stream bottom substrate, especially the deep gravel beds of the NFWR, provided a more secure larval habitat than in the LR. We believe this secure larval habitat was a major factor in maintaining large adult populations in NFWR. The less secure larval habitat within the LR makes larvae more suscep-tible to capture, and coupled with reduced crayfish populations, translates to fewer adult C. Alleganiensis. Larvae were more efficiently collected by skin-diving than wading and turning rocks in these habitats. With the exception of the LR popula-tion, which is composed of 48 % gilled or gilled size larvae, all recorded populations are almost entirely composed of adult and sub-adult age groups and small larvae, especially gilled larvae are either uncommon or unknown