The Influence of Environmental Conditions and Co-Occurring Parasites on Blood Physiology in Eastern Hellbenders (Cryptobranchus alleganiensis)
| dc.contributor.author | Slack, Katherine Louise | en |
| dc.contributor.committeechair | Hopkins, William A. | en |
| dc.contributor.committeemember | Moore, Ignacio T. | en |
| dc.contributor.committeemember | Escobar Quinonez, Luis E. | en |
| dc.contributor.department | Fish and Wildlife Conservation | en |
| dc.date.accessioned | 2024-12-03T09:00:10Z | en |
| dc.date.available | 2024-12-03T09:00:10Z | en |
| dc.date.issued | 2024-12-02 | en |
| dc.description.abstract | Climate change, habitat degradation, and infectious disease are major drivers of global amphibian declines. Amphibians are particularly susceptible to these factors due to their unique physiology and habitat requirements. Thus, investigating components of amphibian physiology and evaluating the influence of environmental conditions, perceived threats, and encounters with infectious agents is essential to conserving imperiled amphibian species. Here, I measured hematocrit, hemoglobin, relative proportions of polychromatic red blood cells, and white blood cell differentials in a wild population of male Eastern Hellbender salamanders (<i>Cryptobranchus alleganiensis</i>) which remain with their nest for up to ~8 months and have frequent encounters with parasitic leeches (<i>Placobdella appalachiensis</i>) that transmit hematophagous endoparasites (Trypanosoma sp.), often resulting in coinfection. Results indicate that hematocrit and hemoglobin increase in response to acute stress and with temperature. Additionally, the magnitude of the stress-induced hemoconcentration response was greater at lower temperatures. Hellbenders exhibited an increase in the proportion of neutrophils and eosinophils in circulation as temperatures decreased while the proportions of lymphocytes and basophils had an inverse effect. Furthermore, the proportion of neutrophil precursors also increased as temperature decreased, which signifies recruitment of innate immune cells during seasonally cold periods. Coinfection of the leech and trypanosome parasites resulted in decreased hematocrit and hemoglobin and a marked increase in polychromatic red blood cells which is indicative of regenerative anemia in the hellbender host. However, these effects were not present in individuals only infected with trypanosomes, implicating the leech vector as the key contributor to anemia in hellbenders. Moreover, the proportion of neutrophils and eosinophils increased, while lymphocytes decreased, in response to leech attachment. However, as parasitemia of leeches and trypanosomes increased concurrently, the proportion of lymphocytes increase in circulation while neutrophils and eosinophils decrease, underscoring the complexities associated with coinfection and multi-parasite interactions. Together, this research provides novel insights into the blood physiology of an imperiled salamander by establishing reference values essential for population surveillance while also describing how these values fluctuate across season and in response to extrinsic factors, with an emphasis on co-occurring hematophagous parasites. | en |
| dc.description.abstractgeneral | While large losses of biodiversity are a global trend among vertebrate populations, amphibian species are most at risk of extinction due to the compounding effects of infectious disease, habitat degradation, and climate change. Understanding how these factors impact the health, condition, and survival of imperiled species is vital to monitoring populations and developing successful conservation strategies. Here, I used hematological metrics that are associated with respiratory, metabolic, and immune responses to monitor a wild population of imperiled eastern hellbender salamanders (<i>Cryptobranchus alleganiensis</i>). Eastern hellbenders are fully aquatic giant salamanders that engage in an ~8-month solitary paternal care period and have faced precipitous declines in recent decades. Furthermore, hellbender populations in southwest Virginia harbor parasitic leeches (<i>Placobdella appalachiensis</i>) which act as vectors for blood-feeding endoparasites (Trypanosoma sp.), frequently leading to coinfection. My aim was to gain mechanistic insight into how hellbender blood physiology varies with environmental conditions, how they respond to potential threats like acute stressors, and how parasites and coinfection impact their health. Through my research, I discovered fascinating insights into the physiology of hellbenders. When faced with environmental temperature changes and acute stress, hellbenders adapt by modulating the red blood cell concentration in their blood, enhancing blood-oxygen-carrying capacity, to meet increased metabolic demands. Furthermore, white blood cell parameters of hellbenders exhibit seasonal changes, which may indicate an increased reliance on mechanisms of innate immune responses during colder temperatures, when cells associated with adaptive immune responses are less active. My study also revealed that coinfection of the leech vector and trypanosome parasites in hellbenders can trigger immune responses and lead to regenerative anemia in the host. However, the pathologies associated with anemia in hellbenders were attributed to the leech vector rather than the trypanosome parasite it transmits. These findings shed light on the physiology of amphibians and have important implications for population surveillance, particularly in identifying potential environmental factors that threaten imperiled species. | en |
| dc.description.degree | Master of Science | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:39727 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/123712 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | hellbender | en |
| dc.subject | hematology | en |
| dc.subject | parasite | en |
| dc.subject | coinfection | en |
| dc.subject | anemia | en |
| dc.subject | stress | en |
| dc.subject | season | en |
| dc.subject | temperature | en |
| dc.title | The Influence of Environmental Conditions and Co-Occurring Parasites on Blood Physiology in Eastern Hellbenders (<i>Cryptobranchus alleganiensis</i>) | en |
| dc.type | Thesis | en |
| thesis.degree.discipline | Fisheries and Wildlife Science | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |
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