Dataset Information

Morphological and molecular characterization of a new species of leech (Glossiphoniidae, Hirudinida): Implications for the health of its imperiled amphibian host (Cryptobranchus alleganiensis).

ABSTRACT: The hellbender (Cryptobranchus alleganiensis) is among the most intriguing and imperiled amphibians in North America. Since the 1970s and 80s, western populations of the Ozark and eastern subspecies in Missouri have declined by nearly 80%. As a result of population declines, the Ozark hellbender was recently federally protected as an endangered species, and the eastern subspecies was granted protection under CITES. Although habitat degradation is probably the biggest threat to hellbender populations, recent evidence suggests that pathogens including chytrid fungus and "flesh-eating" bacteria may also contribute to declines in Ozark hellbenders. Leeches, which are very common on Ozark hellbenders, have recently been implicated as possible vectors of disease among Ozark hellbenders but have not been described in eastern hellbenders or outside of Missouri and Arkansas. We discovered a population of leeches on eastern hellbenders in southwest Virginia and confirmed that the species of leech is within the genus Placobdella, but is morphologically and genetically distinct from all previously described leech species. We named the new species Placobdella appalachiensis sp. n. Moser and Hopkins, based on the mountainous region in which it was discovered. Our surveys over a three consecutive year period suggested that this leech species may be patchily distributed and/or have a narrow geographic range. We consistently detected leeches at one site (mean prevalence in 80 hellbenders = 27.5%; median intensity = 3.0 leeches per parasitized hellbender [range 1 - >250 leeches]) during three years of surveys, but we never found leeches in any of our other seven study sites in two streams (mean prevalence in 139 hellbenders = 0%). We found a significant positive relationship between hellbender body size and the intensity of parasitism, and we suggest the possibility that the behavioral ecology of adults leading up to reproduction may increase their encounter rates with parasites. We discuss the potential conservation implications of discovery of leeches in this stream, and make recommendations for future mitigation and monitoring efforts.

SUBMITTER: Hopkins WA

PROVIDER: S-EPMC3935429 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Publications

Morphological and molecular characterization of a new species of leech (Glossiphoniidae, Hirudinida): Implications for the health of its imperiled amphibian host (Cryptobranchus alleganiensis).

Hopkins William A WA Moser William E WE Garst David W DW Richardson Dennis J DJ Hammond Charlotte I CI Lazo-Wasem Eric A EA

ZooKeys 20140207 378

The hellbender (Cryptobranchus alleganiensis) is among the most intriguing and imperiled amphibians in North America. Since the 1970s and 80s, western populations of the Ozark and eastern subspecies in Missouri have declined by nearly 80%. As a result of population declines, the Ozark hellbender was recently federally protected as an endangered species, and the eastern subspecies was granted protection under CITES. Although habitat degradation is probably the biggest threat to hellbender populat ...[more]

PMID: 24574854

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Project description: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 environmental 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.

Project description: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.

Dataset Information

Morphological and molecular characterization of a new species of leech (Glossiphoniidae, Hirudinida): Implications for the health of its imperiled amphibian host (Cryptobranchus alleganiensis).

Publications

Morphological and molecular characterization of a new species of leech (Glossiphoniidae, Hirudinida): Implications for the health of its imperiled amphibian host (Cryptobranchus alleganiensis).

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