Thesis (M.S.)--East Tennessee State University, 2001. / Original full text available electronically. Includes vita. Includes bibliographical references (leaves 54-58) and abstract.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiv, 138 p. : ill. Advisor: Thomas C. Grubb, Dept. of Evolution, Ecology, and Organismal Biology. Includes bibliographical references (p. 129-138).

Evidence is growing that agrochemicals are playing a role in the decline of amphibians in California. An area of concern is the Sierra Nevada Mountains, where insecticides used in the Central Valley are aerially transported to amphibian habitats. I examined the effects of two of these insecticides, endosulfan and chlorpyrifos, in two experiments on anuran larvae. For the first experiment I exposed Sierra Mountain yellow-legged frog (Rana sierrae) larvae starting at Gosner stage 25 to each insecticide for 63 d to determine median lethal concentrations (LC50) and sublethal effects on growth and development. In the second experiment Sierran treefrog (Pseudacris regilla) larvae were exposed to chlorpyrifos and endosulfan individually and in combination from Gosner stage 25 through metamorphosis to evaluate the interaction between these insecticides. In the first experiment the endosulfan LC50 was 19.8 µg/L (95% confidence interval, 15.3-52.2 µg/L) and the chlorpyrifos LC50 was 595 µg/L (95% confidence interval could not be determined). Endosulfan concentrations greater than 8 µg/L reduced growth but had no effect on time to metamorphosis. No larvae exposed to chlorpyrifos reached metamorphosis. All larvae exposed to greater than 737 µg/L died before the end of the experiment. Growth was reduced above 325 µg/L and cholinesterase was depressed at 737 µg/L compared to controls. In the second experiment the interactive effects of the insecticides depended on concentration and exposure duration. Chlorpyrifos alone did not affect survival or body size after 30 d, even at concentrations greater than the previously reported LC50. Survival and body size decreased with increasing endosulfan concentrations. In combination, 137 µg/L chlorpyrifos inhibited the negative effects of endosulfan on growth and survival and the positive effects of endosulfan on cholinesterase.

The development of alkaline phosphatase (AP) has been studied in two species of Urodele amphibian, Ambystoma qracile and Taricha torosa. The enzyme is present in embryo homogenates at gastrulation and increases immensely in activity as development proceeds to the free-swimming stages. The activity level is a product of two isozymic forms that change quantitatively. Using histochemical detection methods, it was possible to correlate the specific activity and electrophoretic data with histological AP development. Some function of AP were related to the available data. A correlation between substrate specificities and function is proposed which may assist in understanding the role of AP in the process of differentiation / Science, Faculty of / Zoology, Department of / Graduate

The normal breathing pattern recorded in unanaesthetized, lightly re-strained turtles, Chrysemys picta, consisted of periods of continuous breathing interspersed with periods of breath holding. During each ventilatory period, respiratory frequency and tidal volume were controlled separately and independently of breath length, the total inspiratory interval, the active inspiratory interval and the expiratory interval. Increases in pulmonary minute ventilation during hypercapnia were caused by increases in respiratory frequency due solely to shortening of the intervals of breath holding. The frequency of breathing within each ventilatory period remained constant. There was a large variability in inspiratory and expiratory gas flow rates yet tidal volume was maintained within narrow limits by adjustment of the lengths of the active inspiratory and expiratory intervals. This mechanism was dependent upon lung volume information carried within the vagus nerve. Following vagotomy, changes in minute ventilation due to hypercapnia stemmed primarily from changes in tidal volume while changes in respiratory frequency were markedly reduced. Lung volume information carried within the vagus nerve arose from slowly adapting pulmonary stretch receptors. Single fibre nerve activity from pulmonary receptors was recorded from vagal slips in single-pithed tidally ventilated turtles. The major stimulus of these receptors was the change in lung volume throughout each breathing cycle. The rate and degree of change in transpulmonary pressure were without direct effect on receptor discharge. The functional characteristics of these receptors differed only quantitatively from those recorded in pulmonary stretch receptors of mammals and these differences probably stem from the lower body temperature of the turtle and the location of the receptors in the turtle lung. Most receptors were sensitive to CO₂, several sufficiently sensitive that both tonic and phasic receptor discharge were totally inhibited throughout the ventilatory cycle by 5 to 10% CO₂ in the inspired gas. Pulmonary mechanoreceptors in the frog were also shown to be sensitive to. The acute sensitivity to of a few receptors in turtles and frogs parallels that of the intrapulmonary receptors described-in birds and suggests that a pulmonary receptor with distinct mechano- and chemosensitive properties may represent the functional precursor of the variety of pulmonary receptor types which appear in modern day vertebrates. To examine the role of sensitivity of pulmonary receptors in the overall response of turtles to inhaled CO₂, ventilatory responses of unanaesthetized turtles to changes in the intrapulmonary CO₂ content of a vascularly isolated lung (constant PaCO₂ ) and an intact lung were measured during spontaneous breathing. The isocapnic hyperpnea associated with inhalation of CO₂ by the vascularly isolated lung was small and abolished by vagotomy. It is concluded that both inhibition of pulmonary stretch receptor discharge with increasing levels of FICO₂ and a functional increase in central inspiratory volume threshold contributed significantly to tidal volume increases during hypercapnia. The primary ventilatory response of intact turtles to increasing levels of FICO₂ was an increase in respiratory frequency and this response FICO₂ was greatly reduced when CO₂ was inspired only by the vascularly isolated lung. Thus the ventilatory response of turtles to increasing levels of FICO₂ is primarily dependent upon increased levels of arterial CO₂. The effect of vagotomy in producing apneusis in turtles supports suggestions they lack a pneumotaxic centre. The arrhythmic breathing pattern in turtles with intact vagal nerves, however, bears no similarity to the pattern of breathing in mammals with only the pneumotaxic centre ablated. It is concluded that the vagal input from pulmonary receptors to the respiratory centres in turtles is qualitatively similar to that in mammals yet the differences in central integration of lung volume information in turtles and mammals are not due solely to the absence of a pneumotaxic centre in the turtle. Many of the remaining differences may arise from the lower metabolic demand of turtles but how this affects central integration and respiratory pattern generation is unknown. / Science, Faculty of / Zoology, Department of / Graduate

An alarming number of anuran (frog and toad) species are facing the threat of extinction in the wild. In efforts to address this conservation crisis, captive breeding programs are rapidly being established at zoos and research institutions worldwide. However, the captive management of anurans can be challenging, as their reproduction is a tightly regulated hormonal response to environmental stimuli, often unknown or absent in captivity. Consequently, ex-situ breeding efforts tend to be greatly hindered by a paucity of knowledge in anuran reproductive physiology and, for many species on the brink of extinction, time is running out. Assisted reproductive technologies (ARTs), such as exogenous hormone induction of gamete release, artificial fertilization for population augmentation, and cryopreservation for the long-term storage of genetics, have the potential to greatly enhance captive breeding efforts in lieu of natural breeding. Broadly, research aims were to develop assisted reproductive technologies for captive populations of the declining Southern Rocky Mountain boreal toad (Anaxyrus boreas boreas), the critically endangered Mississippi Gopher Frog (Lithobates captio sevosa) and Puerto Rican crested toad (Peltophryne lemur). Specific objectives were to a) trial the efficacy of exogenous hormone treatments on sperm release in male target species by characterizing spermiation response across time; b) investigate methods for increasing sperm longevity through cold-storage and cryopreservation techniques; c) ascertain motility recovery rates and functional capacity of cold-stored and frozen-thawed spermatozoa through artificial fertilization techniques, and; d) apply successfully developed ARTs to determine the feasibility of genetically linking in-situ and ex-situ populations of A. b. boreas, through artificial fertilization of male and female gametes from wild and captive toads, respectively. Research outcomes from this study include the successful development of exogenous hormone protocols, spermiation profiles and sperm cryopreservation techniques for all target species. Additionally, these studies enabled validation of an alternative method for increasing genetic diversity in captive anurans through in-situ-ex-situ gamete linkage. Overall, this research emphasizes the potential value of assisted reproductive technologies as conservation tools for supporting the recovery of endangered frog and toad species worldwide.

Temporary wetlands are important breeding sites for herpetofauna, including species of concern, but are often overlooked in conservation planning and management decisions. I conducted surveys of herpetofauna communities and quantified habitat variables surrounding isolated, upland and stream-connected ephemeral pools on Tombigbee National Forest and Noxubee National Wildlife Refuge in north-central Mississippi from March 2004 ? March 2006 to compare herpetile species assemblages between different classes of temporary wetlands, determine use of pools as reproductive sites for amphibians, and determine faunal-habitat relationships for herpetofauna. Species richness and abundance of terrestrial herpetiles differed significantly between upland and floodplain pools. Upland pools contributed substantially more to the diversity of herpetiles than floodplain pools. Upland pools supported significantly greater abundance of larval Ambystomatid salamanders and central newts (larvae and adults). Forest overstory and ground coverage components influenced amphibian abundance such as abundance of mature trees, standing snags, downed woody debris, and litter depth.

No description available.

abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Typescript (photocopy). / Digitized by Kansas Correctional Industries