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Amphibian breeding phenology has generally been associated with temperature and rainfall, but these variables are not able to explain all of the variation in the timing of amphibian migrations, mating and spawning. This thesis examines some additional, previously under-acknowledged geophysical variables that may affect amphibian breeding phenology: lunar phase and the K-index of geomagnetic activity. A serendipitous observation of a large earthquake during the amphibian breeding season enabled a rare record of animal behaviour prior to an earthquake and led to an investigation into the effect of seismicity on amphibians. Data were collected on breeding migrations at three sites in the UK and Italy for frogs (Rana temporaria) and toads (Bufo bufo). Additional data were collated from published literature. Data on the arrivals of two newt species (Triturus cristatus and Lissotriton helveticus) were also analysed. Lunar phase was found to be important in Rana temporaria and Bufo bufo, with more individuals migrating, in amplexus and spawning around the full moon. Newts' response to the full moon was less clear. A meta-analysis of published data revealed that the effect of the lunar cycle on amphibians may be more prevalent than previously supposed and is species-specific, depending on the unique ecology of each species. The effects of the K- index on amphibian reproduction are unclear because of the low number of days when geomagnetism was high. Five days before a large earthquake in L' Aquila, Italy the majority of toads left the breeding site, only re- appearing when the earthquake was over. Numbers of toads were significantly correlated with days since the earthquake but not with weather variables. Finally I attempted to use the variables of interest (two measures of moon phase, plus the K-index of magnetic activity), along with weather variables to construct statistical models of amphibian breeding phenology and to predict arrivals and spawning / amplexus in single years based on the models. This met with variable success; there was a high variability between years in the ability of the models to predict breeding phenology, which could be due to site-specific factors, unmeasured environmental variables, or an endogenous component to breeding phenology.

Aspects of tile breeding biology of the Common Frog, Rana temporaria temporaria L., were studied in relation to altitude. Work centred on 55 breeding ponds in northern England, ranging in altitude from 86 to 838m. A chemical temperature integration technique was used to measure pond and soil temperatures at a series of sites. The temperature fell by approximately 0.4 C for every l00m increase in altitude. Between 1974 and 1977 spawning was always later at higher altitudes. By delaying spawning, highland embryos were less likely to encounter lethally low temperatures. Highland female frogs were about five per cent smaller in snout-vent length than lowland females and produced 707 eggs on average, less than half the mean number of 1,586 eggs produced by lowland frogs. These differences were thought to be due to the short growing season and possibly to the lack of food at higher altitudes. At 6 C the eggs from highland females developed four per cent faster than those from lowland females. Highland eggs had a lower lethal limit for normal development of 2.8 C; one Celsius degree below the limit for lowland eggs. The mucopolysaccharide capsules covering the eggs of Common Frogs act as insulators, keeping the embryos warmer on average than the surrounding water. This is thought to be of importance as Common Frogs breed early in the year when pond temperatures are often close to the lower lethal limit. The volume of the capsules and their insulating efficiency varied in different pond waters. The concentration of the ions in the pond water used as the culture medium was found to be the major factor influencing capsular swelling, but the valency of the ions, the temperature and pH of the water were also important. These findings were discussed in terms of their adaptive significance.

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The ultrastructural organisation of frog heart muscle was investigated using electron microscopy and related techniques. As far as possible, stincture was related to function, with particular emphasis being placed on calcium movements in contraction and relaxation. A basic description of the tissue is presented. Certain features of the cells, such as small size, flattened profiles, the presence of large intercellular clefts and sarcolemmal specialisations, indicate a high degree of reliance on the external medium. Irregularly distributed, short, tubular invaginations were found, which were condidered to increase the efficiency of the movement of solutes within the cell, and possibly to be primitive analogues of T-systems. Pinocytotic vesicles were found to be common and to pinch off from the sarcolemma and move into the cell taking materials from the bathing medium. Apparently anomalous vacuoles were found to be autophagic, and to arise from vacuolating mitochondria and from lysosomal degradation of organelles. Tlie application of cryo-ultramicrotomy to frog myocardium is discussed. Intracellular calcium was investigated using electron probe microanalysis. Close correlation between observed and expected ratios of calcium distribution in myofibrils and reasonable correlation between the absolute calcium content of the tissue foimd by two different methods, indicated the reasonable validity of calcixim localisation in conventionally prepared electron microscope specimens. Relative calcium levels in different organelles following induction of different physiological states, implicated the sarcoplasmic reticulum as a major intracellular site of calcium of activation, although mitochondria where also found to be involved in calcium fluxes, Myofibrillar H lines were found to be sites of calcium concentration, and nuclei, specific granules and mast cells were foimd to be high in calcium. Frog heart muscle organisation is discussed in relation to other myocardia and to the mode of action of striated muscle.

The gross and microscopic structure of the breast-shoulder apparatus is described in 9 salientian families representing 92 genera and 243 species. From this the Anura are divided into two groups: those with and those without posteriorly directed epicoracoid horns.

There is limited research regarding amphibian distribution and status in rural upland habitats in Britain. Previous studies suggest potential influences on distribution and abundance arising from habitat modification and acidification. However, the extent to which these factors influence distribution at the landscape level is unclear. This study aimed to evaluate whether particular features of the aquatic and terrestrial habitat influence distribution and breeding ecology of common frogs (Rana temporaria L.) in rural upland areas. In particular, the extent to which aquatic and early terrestrial life-stages might be impacted upon by the quality of their respective habitats was investigated. Common frogs were found to be widespread and ubiquitous throughout the study area. No evidence was found to suggest that any specific biotic or abiotic feature of either the aquatic or terrestrial habitat significantly influenced distribution and relative abundance of breeding adults. However, reproductive success was found to be significantly impacted upon by acidity in coniferous and hilltop habitats. It is probable that juvenile recruitment at some ponds is chronically reduced and populations are maintained through immigration. Recruitment in improved habitats was highly variable between ponds and between years, although it was not possible to elucidate precise controls on larval populations in the natural habitats studied. Significant differences in physical condition at metamorphosis among wild populations were demonstrated. This may signify possible differences in future growth, life-fitness and dispersal ability between populations, or at least between natal ponds. Dispersal by new juveniles is potentially affected by the vegetation structure surrounding breeding ponds. Intra- and interspecific differences in behaviour regarding microhabitat use were demonstrated. Rural upland habitats can be valuable habitats for amphibians and the common frog in particular. However, further research is required to better understand rates of recruitment and immigration and how terrestrial habitats mediate juvenile survival and dispersal.

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No description available.

No description available.