京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22281号 / 理博第4595号 / 新制||理||1659(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 沼田 英治, 准教授 森 哲, 教授 曽田 貞滋 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23364号 / 理博第4735号 / 新制||理||1679(附属図書館) / 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 曽田 貞滋, 教授 中川 尚史 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

The function of light in the reproductive cycle in amphibians has not been extensively studied. However, Farner (1965) feels that the small amount of experimental evidence suggests that photoperiod may play a role in the testicular cycle of Rana esculenta. The purpose of this paper is to study the effect of light on the gonads and the gonadotropic hormone forming cells of the adenohypophysis in the newt Taricha granulosa granulosa.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20954号 / 理博第4406号 / 新制||理||1633(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 沼田 英治, 准教授 森 哲, 教授 中川 尚史 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Apple drops were removed from a portion of an apple orchard in September and apples left available in the remainder of the orchard. Presence of apples had little effect on the immature:adult ratio or on body weight. However, adult males and juveniles of both sexes had higher values for reproductive characteristics in November and December in the area with apples available. In a laboratory experiment adult voles fed a rabbit chow diet supplemented with apple consumed less digestible energy but had higher body weights and more body fat, and males had heavier testes than those fed only chow. Adults on a 14L:10D photoperiod had higher values for reproductive characteristics than those on a declining photoperiod. In a third experiment juveniles fed a horse chow diet supplemented with apples had higher body weights and more body fat, initiated and completed molt to adult pelage at higher body weights and had heavier reproductive organs than those given only chow. In these experiments voles with access to apples dia not consume more digestible energy but they grew faster, were in better condition and were more likely to produce offspring. The consumption of apples possibly stimulated the hypothalamus anu;or pituitary gland, increasing synthesis or release of gonadotropins. Adult pine voles on a declining or short photoperiod may be inhibited reproductively because of antigonadotropic substances produced by the pineal gland. Consuming apples could affect the degree of inhibition. It was hypothesized pine voles use both photoperiod and nutrition as cues fox reproduction. / Master of Science

<i>Abutilon</i> x <i>hybridum</i>, flowering maple has the potential to become a profitable floriculture crop. However, growing guidelines need to be developed in order to produce a proportional, well-branched, and uniform-flowering pot plant. The objective of this research project was to form a foundation on which a commercial growing program could be developed. Growing flowering maple under short-day conditions (SD) significantly reduced plant height. Plants grown under SD were nearly half as tall as those plants grown under long-day conditions (LD). Also, plants grown under SD flowered an average of 5 days earlier than those plants grown under LD. Ancymidol at 50 ppm was successful in the reducing the height of nonpinched plants. Chemical pinching agents, including mefluidide and Atrinal, induced more lateral branch development and increased flower production of both seed-grown and cutting-grown plants. As the concentration of mefluidide and Atrinal increased, so did the number of flowers that were produced. Atrinal at 1000 ppm appeared to be the treatment of choice for producing the most aesthetic and marketable flowering maple plant. A foliar application of GA₄₊₇ at 100 ppm was successful in elongating peduncles without producing a disproportional increase in plant height. The peduncles of both seed-grown and cutting-grown plants receiving 100 ppm GA₄₊₇ were nearly twice as long as the controls. Thus, GA could be used to improve the flower display of <i>Abutilon</i>. / M.S.

Photoperiod manipulations are widely used throughout the Atlantic salmon (Salmo salar) farming industry as a means of producing a product of uniform quality all-year round. However, farmers still remain sceptical over their effectiveness to regulate growth and maturation during the on-growing stage. Furthermore, reports of a characteristic growth-dip following light exposure suggest that light may negatively affect the physiological performance of fish in the short-term. Thus, this thesis investigates the effects of light characteristics (spectral quality, intensity and photoperiod) on growth and maturation of salmonid fish and addresses some of the uncertainties surrounding photoperiod use currently reported within the industry. Rainbow trout (Oncorhynchus mykiss) are seemingly an ideal model species for examining photoperiod effects on growth. Consequently, the application of constant light exposure (LL) at two different intensities (28W and 16W) during two different thermal conditions (summer and winter) was examined on individually tagged fish. Feed intake and growth appeared to be related to the ambient water temperature and did not appear to be affected by intensity or photoperiod, although the onset of constant light did appear to initially affect growth rate. This may indicate that LL has a limiting effect on the growth of trout or that the prevailing water temperature at which light is applied may override the photoperiodic effect. Furthermore, the lack of enhanced growth in trout exposed to LL, unlike that demonstrated for other salmonids, suggest that there may be a species-specific response to environmental variables. Thus, questions regarding photoperiod effects should be limited to the species in question. The main source of variation in results observed under photoperiod manipulations stems from the salmon industry. Atlantic salmon post-smolts were reared in seawater tanks and either maintained under a natural photoperiod (NP) or exposed to a simulated natural photoperiod (SNP), constant light superimposed on the natural light (NPLL) or constant light only (LL). Artificial light onset, irrespective of photoperiod, resulted in an apparent trend for a reduced appetite lasting up to 60 days. Furthermore, the onset of constant light resulted in a significant chronic elevation of plasma cortisol levels and changes to growth and thyroid hormone levels, providing direct evidence that constant light exposure induces stress. In addition, fish exposed to SNP failed to exhibit a stress response despite a low feed intake. However, differences in the plasma melatonin levels during twilight times, as compared to NP, suggest that gradual changes in the natural light intensity throughout the day, particularly around dawn and dusk, may be important for synchronizing daily events. No differences in growth were observed between the NP and NPLL regimes, although fish reared in an enclosed regime (SNP and LL) exhibited a significantly lower weight gain than fish in an open environment (NP and NPLL). This further highlights the impact that the rearing environment has on the growth performances of fish and the need for commercially run trials. Advances in lighting technologies and a greater understanding of how light is transformed through the water column have focussed research on the spectral sensitivity of fish. Therefore the lighting efficiency of novel blue narrow bandwidth LED lighting units through the water column and their effects on growth and maturation performances of salmon reared in commercial production cages were compared against the standard metal halide units currently utilized throughout the industry. LL application, irrespective of intensity or spectrum, reduced the numbers of fish maturing as compared to fish reared under a natural photoperiod. However, this was greatest under the standard metal halide units reflecting a greater light penetration and perception as determined by plasma melatonin levels. The metal halide groups exhibited the greatest relative weight gain over the trial period as compared to control fish. No evidence was observed for a growth-dip under metal halide light, although blue lit treatments exhibited an initial significant reduction in food consumption, suggesting a possible welfare issue. Nevertheless, the prototype blue LED units showed possible potential for commercial application by penetrating the water depth at half the distance of the metal halide units for only one eighth the power and one fifth the brightness. However, further tests of these prototype spectral units are required to examine the potential welfare and physiological growth and reproductive effects. These studies have shown that the efficacy of artificial light regimes is largely dependent upon the effectiveness of the light source through the underwater environment and its perception by fish, providing a sufficient intensity is emitted exceeding the physiological threshold level for the species cultured. Moreover, whilst the onset of artificial light may elicit a stress response and demonstrate a trend for a suppression of appetite for salmon reared in experimental tanks, no compelling evidence for a suppression of appetite or growth was found under normal commercial cage conditions. This suggests that the growth-dip observed within the industry may in part be a combination of a physiological response to the onset of light further exaggerated by the farmer’s perception and altered judgement in feeding. In addition, the results obtained from this study have helped to standardize the use of light regimes within the industry. Nevertheless, further studies are necessary to fully elucidate the underlying mechanisms which may govern growth and maturation in fish following the onset of light exposure.