In the amphibian auditory system, a subset of hair cells is known to be frequency tuned via electrical resonance. This tuning is thought to contribute to frequency selectivity of the information leaving the auditory periphery via the auditory afferent fibers. At the same time, while most, if not all, afferent fibers are shown to be frequency tuned, electrical resonance has only been experimentally demonstrated in a subset of amphibian auditory hair cells. In this thesis, we validate and use a novel Zap current method to probe the electrical resonance of the bullfrog amphibian papilla hair cells. We uncover the existence of two previously unknown types of electrically resonant auditory hair cells. We then show the existence of resonant hair cells across the length of amphibian papilla, with the range of frequency tuning that is nearly indistinguishable from that previously reported in the of auditory fibers. Therefore, this work further validates amphibian hair cell frequency resonance as the possible mechanism underlying frequency selectivity of the subsequent stages in auditory signal transduction.

This master’s thesis deals with the analysis of geometric shapes fuselage amfibie SEAGLE and propose optimal shapes for the improvement of hydrodynamic and aerodynamic properties.

My master´s thesis deals with the design of amphibian hull for VUT 001 Marabu aircraft. Part of this work is aerodynamic and hydrodynamics design of hull including flight mechanics with, take of and landing on the water. The last point of work is load calculation of float and landing gear and design of landing gear retraction mechanics.

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Recent models argue that thermal environments are the major cause of ectotherm life-history clines. However, elevational clines in body size in the mountain dusky salamander Desmognathus ocoee (family Plethodontidae) shift from positive at hatching, to negative at metamorphosis to positive again as adults, and so are not consistent with this explanation. The clinal shift from hatching to metamorphosis was investigated by examining the clinal and seasonal feeding patterns of larval salamanders at high and low elevation sites in rockface and woodland habitats. Repeated cohort sampling was also used to examine clinal and seasonal patterns in body size and to estimate average growth rates. Larval growth in both rockface and woodland habitats was tightly correlated with feeding activity. Although temperature was found to vary between high and low elevation sites, the greatest growth occurred in a cold woodland habitat with a high elevation, and the lowest growth occurred in an adjacent rockface habitat. Because this difference in growth cannot be attributed to thermal differences, we conclude that local food resource levels are the predominant source of local differences in growth. These findings, clinal patterns of variation in other predatory salamanders, and experimental analyses in which both food and temperature are orthogonally manipulated, indicate that general models that single out temperature as the principle cause of ectotherm life-history clines should be viewed with caution.

The Puerto Rican coqui frog, Eleutherodactylus coqui, was introduced to Hawaii in the late 1980s via the commercial horticulture trade. Previous research has shown that coquis can change invertebrate communities, but these studies were conducted at small scales using controlled, manipulative experiments. The objective of this research was to determine whether coqui invasions change invertebrate communities at the landscape scale across the island of Hawaii. At each invasion front, we measured environmental variability on either side of the front and removed sites that were too variable across the front to ensure that the impacts we measured were the result of the invasion. After doing this, there remained 15 sites for which we compared invertebrate communities in 30 m x 30 m plots situated on either side of coqui invasion fronts. In each plot, we collected invertebrate samples from three invertebrate communities, the leaf litter, foliage, and flying invertebrate communities. Multivariate analyses show that coqui frogs change leaf litter communities, by reducing microbivore and herbivore abundances. Coqui also change flying community composition, but have no measurable effect on foliage communities. Across sites, we found that coquis reduced the number of leaf litter invertebrates by 27%, and specifically abundant Acari by 36%. We also found that coquis increased the abundance of flying Diptera by 19% across sites. We suggest that the leaf litter community is altered through direct coqui predation and that Diptera increase because of increased frog carcasses and excrement in invaded plots. Results support previous studies conducted in more controlled settings, but add to our understanding of the invasion by demonstrating that coqui effects on invertebrate communities are measurable at the landscape scale.

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The Mississippi gopher frog (MGF, Lithobates sevosa) is a critically endangered amphibian which requires the use of assisted reproductive technologies (ART) to successfully reproduce in captivity. Several challenges to successfully breeding MGFs were investigated to improve reproduction in this species. Accurate identification of biological sex is a necessary first step to reproducing species, thus several non-invasive techniques for sex identification were compared in the weakly dimorphic MGF. Reliably obtaining eggs from female MGFs has also proved difficult, therefore, four exogenous hormone therapies were compared for their success to induce ovulation. Ultrasound imaging was used alongside hormone treatments to improve understanding of ovarian response to hormone treatment. Lastly, short-term cold storage of spermic urine was studied to determine the feasibility of this technique for MGF gamete storage. Findings from these research projects are important for the successful conservation of the MGF by aiding in the production offspring for future reintroduction programs.

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