京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18104号 / 理博第3982号 / 新制||理||1574(附属図書館) / 30962 / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 森 哲, 教授 沼田 英治, 教授 疋田 努 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The arroyo toad (Anaxyrus californicus) is a federally endangered species found on Fort Hunter Liggett, Monterey County, California. The species was discovered in 1996 and was determined to occupy 26.7 km of the San Antonio River from approximately 2.4 km northwest of the San Antonio Mission de Padua, to the river delta above the San Antonio Reservoir. The construction of the San Antonio Reservoir dam in 1963 isolated this northern population of arroyo toads. Through time, the Fort Hunter Liggett landscape has changed drastically. The land was heavily grazed by cattle until 1991, which considerably reduced vegetation in riparian areas. Military training following acquisition of the land in 1940 far exceeded current allowable training. Fire was used extensively to reduce unfavorable vegetation, and as a result, extreme tree loss occurred through the ranges. Today cattle grazing is prohibited and military activity is restricted from riparian corridors. While riparian vegetation continues to recover in the San Antonio River, habitat for breeding arroyo toads has become less suitable. To improve conservation efforts and management of this endangered species, I have provided a thorough assessment of the life history of arroyo toads specific to Fort Hunter Liggett and identified the status and current threats to the population on the installation. I have also prepared a habitat assessment of the San Antonio River in the arroyo toad range, quantified habitat conversion, and identified areas that may no longer provide suitable breeding habitat for the species. The research conducted for this report is preliminary to restoration efforts that are inevitable to ensure recovery of the endangered species at Fort Hunter Liggett.

Mercury (Hg) is an important environmental contaminant due to its global distribution, tendency to bioaccumulate, and toxicity to wildlife. However, Hg has received little attention in amphibians compared to other vertebrates, despite the fact that amphibian population declines have been documented worldwide and environmental contaminants are believed to contribute to some declines. During my dissertation research, I used a pluralistic approach which combined field studies and manipulative laboratory and mesocosm experiments to examine the bioaccumulation and ecological effects of environmentally relevant Hg exposure routes acting at various early life stages in amphibians. By collecting amphibians in the field at the Hg-contaminated South River, VA, I confirmed that amphibians exhibiting different life histories and occupying different ecological niches (Plethodon cinereus, Eurycea bislineata, and Bufo americanus) can bioaccumulate sufficient levels of Hg to warrant concern (Chapter 2) and female Bufo americanus transfer accumulated Hg to their eggs (Chapter 3). Maternal transfer of contaminants is a parental effect which typically has negative consequences for offspring because early development is a critical organizational period in the ontogeny of vertebrates. Through laboratory observations and mesocosm experiments, I examined the short and long-term effects of maternal contaminant exposure on offspring, and found the negative effects of maternal Hg exposure manifested either immediately at the embryonic stage or later during the larval stage, depending on the year in which the study was conducted (Chapters 4 and 5). Lastly, using a factorial laboratory experiment, I examined whether the latent effects of maternal transfer of contaminants manifests differently depending on the environment in which offspring develop, and found both maternal and dietary Hg exposure independently produced negative, but different, sublethal effects on larval development. Most importantly, maternal exposure to Hg combined with high dietary Hg exposure later in ontogeny had a lethal effect in larvae (Chapter 6). This study is one of the first to demonstrate that the latent effects of maternally transferred contaminants may be exacerbated by further exposure later in ontogeny, findings that may have important implications for both wildlife and human health. / Ph. D.

The geographic isolation of populations can result in a metapopulation effect where regional dynamics of extinction and colonization are more important to population viability than local dynamics of individuals' birth or death. When this partial isolation is maintained for many generations genetic variability can be geographically structured. Populations of temperate-zone anuran amphibians are often considered to be geographically isolated on relatively small spatial scales due to the animals presumed high site fidelity and strict dependence on moisture for respiration and breeding. As a result, temperate, pond-breeding anuran amphibian populations are considered likely candidates to test hypotheses of metapopulation theory, movement and phylogeography. Using data from the Fowler's toad, (Bufo fowleri) I test the applicability of metapopulation theory, the likelihood of limited movement and the strength of phylogeographic structure. Specifically, I show that the generalization of the amphibians-as-metapopulations paradigm, due to their limited dispersal capabilities, is not supported (I). Bufo fowleri movement is well described by an inverse power function. Whereas most individuals do not move, some move long distances. There is no sex bias to this movement and I propose the hypothesis that the animals moving the longest distances are aided by the passive action of lake currents (II). B. fowleri juveniles are not a dispersal stage. They move neither farther nor faster than adults. The observation of predominantly juvenile contribution to a dispersal pool is due to their abundance---there are simply many more juveniles than adults (III). My observations of amphibian population turnover do not support the predictions of two specific metapopulation models when parameterized on a local (<10km) or regional scale (~300km) (IV). B. fowleri populations in Canada exhibit both shallow and deep phylogeographic structure. The shallow divisions are geo

In this paper I focused on the examination of chosen localities inside the hybrid zone of the fire-bellied toads, where the occurrence of these species and their hybrids was confirmed in previous research. The goal is to follow the development of these habitats, suitable for the presence of a threatened species, and trends in quantities of these toads. Another aim was to calculate the hybrid index of each individual based on the ventral spots and so to classify the populations on each locality according to species.

No description available.

The western toad (Anaxyrus boreas, formerly Bufo boreas) is one of many amphibian species considered to be at risk of extinction (COSEWIC status is Special Concern). I examined habitat use patterns of the western toad using several methods to gain a better understanding of its habitat requirements. I examined the relationship between relative abundance of the western toad and two sympatric amphibian species (wood frog, Lithobates sylvaticus; and boreal chorus frog, Pseudacris maculata) and habitat features at eight scales of spatial extent at 24 wetlands in the Lake Utikuma region of Alberta, Canada. I radio-tracked adult western toads in three study areas in the Aspen Parkland and Boreal regions of north-central Alberta to examine 1) whether patterns of habitat selection change with different scales of spatial extent, spatial resolution, habitat composition, temporal period, and between males and females during the active period, 2) habitat used for hibernation, and 3) factors influencing the timing and nature of movements to hibernation sites. I found that the abundance of the three amphibian species was best described at different spatial extents and was related to the biology of each species. Resource Selection Function (RSF) models, created using radio-telemetry data, indicated that habitat selection was scale-dependent for western toads; differences in selection were observed among study designs, study areas, time periods, and sexes. Predictive ability did not differ significantly among study designs. However, models that were created using a fine-grained map and home-range spatial extent generally produced models with greater predictive ability than models using a coarse-grained map or population-range extent. During the active season toads selected open habitat types such as wet shrub, disturbed grass, and crop/hay fields. Western toads hibernated terrestrially in pre-existing tunnels and the majority of toads hibernated in forest stands dominated by spruce. Toads used hibernation sites 1461936 m from breeding ponds and 68% of hibernacula were communal. Arrival at and entry into hibernation sites was influenced by temperature and/or day length; larger toads moved to hibernation sites later in the year. My research results can be used to identify and protect habitat for western toads in Canada. / Environmental Biology and Ecology

No description available.

Submitted by Ana Damasceno (ana.damasceno@unipampa.edu.br) on 2016-06-24T17:05:01Z No. of bitstreams: 1 Atividade biológica do veneno de Rhinella Icterica Anura Bufonidae sobre o sistema nervoso de vertebrados.pdf: 3606718 bytes, checksum: 4fa3e0cd0db679c55769dcfec4b36b6d (MD5) / Approved for entry into archive by Ana Damasceno (ana.damasceno@unipampa.edu.br) on 2016-07-21T18:23:37Z (GMT) No. of bitstreams: 1 Atividade biológica do veneno de Rhinella Icterica Anura Bufonidae sobre o sistema nervoso de vertebrados.pdf: 3606718 bytes, checksum: 4fa3e0cd0db679c55769dcfec4b36b6d (MD5) / Made available in DSpace on 2016-07-21T18:23:38Z (GMT). No. of bitstreams: 1 Atividade biológica do veneno de Rhinella Icterica Anura Bufonidae sobre o sistema nervoso de vertebrados.pdf: 3606718 bytes, checksum: 4fa3e0cd0db679c55769dcfec4b36b6d (MD5) Previous issue date: 2016-03-03 / Os venenos animais são fontes de compostos bioativos com aplicabilidade terapêutica. Os anuros produzem através de glândulas paratóides, uma secreção venenosa rica em compostos de diversas classes químicas, as quais apresentam uma série de atividades farmacológicas de nteresse biotecnológico. Os sapos da espécie Rhinella icterica (Spix, 1824), pertencem a um grupo de animais venenosos presentes no bioma Pampa com carência de estudos macológicos e toxicológicos. Para os ensaios biológicos, os sapos foram coletados na região de Derrubadas, no estado do Rio Grande do Sul. O veneno foi extraído manualmente por compressão das glândulas paratóides, tratado por extração metanólica seguida de liofilização e então foi chamado de MERIV. A neurobiologia do veneno foi avaliada sobre a junção neuromuscular de aves, através da preparação biventer cervicis de pintainhos (BCP) e, através da análise das desidrogenases em fatias hipocampais de camundongos. A incubação de MERIV (5, 10, 20, 40 µg/mL) e Digoxina (6,5; 13; 26 e 52 nM) em fatias hipocampais de camundongos, induziram um efeito dose dependente na viabilidade celular. Apenas MERIV (5 µg/mL) e Digoxina (6,5 e 13 nM) provocaram aumento significativo da viabilidade celular de 36 ± 10%, 52 ± 7% e 57 ± 13%, p<0.05, respectivamente, enquanto nas demais concentrações houve decréscimo na viabilidade celular quando comparados com o controle Hepes (n=6). Em preparações euromusculares BCP, MERIV (5, 10 µg/mL) produziu um efeito facilitatório de 60 ± 15% e 46 ± 6%, respectivamente, seguido de bloqueio neuromuscular em 120 min de registro (n=6, p<0.05). De forma semelhante, a incubação dos músculos com Digoxina 52 nM ou Ouabaína 0,2 nM mimetizou a atividade de MERIV com aumento da amplitude de contração por 19 ± 4% e 27 ± 6%, e diminuição da contração muscular de 80 ± 4% e 91 ± 5%, respectivamente (n=5, p<0.05). MERIV também demonstrouatividade digitalic-like com inibição de 39 ± 3% da Na+,K+-ATPase (n=4, p<0.05). Em BPC, quando MERIV foi incubado 20 min antes da d-Tubocurarina 1,45 µM, houve um reforço do bloqueio neuromuscular, o qual foi completo em 80 min. Enquanto que em preparações BCP curarizadas, MERIV aumentou o tempo de bloqueio em 50 min, semelhante a ação de drogas anticolinesterásicas. Juntos, esses dados indicam que o extrato metanólico do veneno de R. icterica é capaz de interferir com a neurotransmissão provavelmente via inibição das enzimas acetilcolinesterase e Na+-K+- TPase. / Animal poisons are sources of bioactive compounds with therapeutic applicability. Anurans through parotid glands produce a poisonous secretion rich in compounds of different chemicalclasses, that have a range of pharmacological activities of biotechnological interest. oads of the species Rhinella icterica (Spix, 1824), belong to a group of poisonous animals present in the Pampa biome that still need to pharmacological and toxicological studies. Venom collection was made by milking toads obtained at Derrubadas region, Rio Grande do Sul state. The venom was previously treated by methanol extraction followed by lyophilization (thus called MERIV), before the biological assays. The venom neurobiology was evaluated on chicks neuromuscular junction by preparation biventer cervicis (BCP), and by function of mitochondrial dehydrogenases in hippocampal brain slices from mice. Incubation of MERIV (5, 10, 20 and 40 μg/mL) or digoxin (6.5, 13, 26 and 52 nM) with mice hippocampal brain slices induced a dose-dependent effect on cell viability. At low concentration MERIV (5 μg/mL) and digoxin (6.5 and 13 nM) induced a corresponding significative increases in cell viability, 36 ± 10%, 52 ± 7% and 57 ± 13% (p<0.05), respectively, while at higher concentrations there were a decrease in cell viability compared with control Hepes (n=6). In chicks neuromuscular preparation BCP, MERIV (5, 10 µg/mL) produced a facilitatory effect of 60 ± 15% and 46 ± 6%, respectively, followed by neuromuscular blockade in 120 min recordings (n=6, p <0.05). The incubation of BCP with digoxin (52 nM) or ouabain (0.2 nM) mimicked the venom activity by increasing the amplitude of the twitches by 19 ± 4% and 27 ± 6%, respectively, followed by a depression in muscle contraction recorded for 120 min ( 80 ± 4% and 91± 5%, p<0.05, respectively, n=5). MERIV also demonstrated digitalic-like activity inhibiting 39 ± 3% of Na+,K+-ATPase (n = 4, p <0.05). In BCP, when MERIV was incubated for 20 min before d-Tubocurarine (1.45 μM), there was a reinforcement of the neuromuscular blockade, wich was complete at 80 min. However, in preparations “curarizadas”, incubated with d-Tubocurarine (1.45 μM) before MERIV, there was a increase in the blocking time at 50 min, similar to the action of acetylcholinesterase drugs. Altogether, these data indicate that the methanolic extract from R. icterica venom is able to interfere in neurotransmission, probably by inhibiting the enzymes acetylcholinesterase and Na+,K+- ATPase.

<p>Dispersal is an important factor in animal ecology. Anurans (frogs and toads) are often philopatric (home loving) but some specimens in a population usually have the capacity to disperse relatively long distances. In this study I investigated the colonization of newly constructed ponds in the southwest of Sweden by three anuran species: The common toad (Bufo bufo), the moor frog (Rana arvalis) and the common frog (Rana temporaria). The ponds were constructed between two and five years ago and were now as frequently occupied as older source ponds in the area. For the common toad and the common frog there was no correlation between distance to source populations and degree of colonization. The moor frog was more common in ponds that were situated in the vicinity of older source ponds with ample populations. The main impression was that these species rapidly colonize newly constructed ponds, at least within moderate distances from source populations. There were some differences between the species though and it seems like the moor frog have more limited dispersal abilities than the other two species.</p>