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81.
Photoperiodic time measurement is a well-documented adaptation of multicellular plants and animals to seasonal changes in the environment, but it is unclear whether unicellular organisms can exhibit bona fide photoperiodic responses. We demonstrate that the occurrence of zygospore germination of the unicellular alga Chlamydomonas is a genuine photoperiodic response. Germination efficiency is enhanced in long days as compared with short days. While the total amount of light exposure influences the efficiency of germination, the photoperiod is a significant cue for germination. The developmental stage that senses the photoperiod is just prior to mating and during the first days of zygospore development, so there may be a critical window of zygospore maturation that is regulated by photoperiod. Because zygospores are resistant to freezing injury, whereas vegetative cells are not, it is likely that the suppression of germination by short days is an adaptive response for overwintering of Chlamydomonas. Therefore, Chlamydomonas is a single-celled organism that is capable of photoperiodic responses. 相似文献
82.
83.
18S rRNA phylogeny of sea spiders with emphasis on the position of Rhynchothoracidae 总被引:2,自引:1,他引:1
Koichiro?Nakamura Yasunori?KanoEmail author Nobuo?Suzuki Takashi?Namatame Akinori?Kosaku 《Marine Biology》2007,153(2):213-223
The phylogenetic relationships among all living families of sea spiders (Arthropoda: Pycnogonida) are investigated using nearly
complete 18S rRNA sequences from 57 ingroup species and five chelicerates under the Bayesian and maximum likelihood methods.
Monophyly of Colossendeidae, Pycnogonidae, Phoxichilidiidae, Endeidae and Pallenopsidae is consistently supported. However,
the genera formerly classified in the family Ammotheidae are split up into two distantly related groups. The genera Ascorhynchus and Eurycyde (here recognized as Ascorhynchidae) are possibly an early offshoot of sea spiders, whereas other ammotheids constitute a
robust terminal clade with Pallenopsidae, Phoxichilidiidae and Endeidae. This topology also opposes the prevalent assumption
of successive losses and simplification of three kinds of cephalic appendages like in a previous cladistic analysis. At least
three independent losses are suggested for palps by the inferred topology, and both chelifores and female ovigers may have
been lost twice. Our knowledge of early ontogeny and internal anatomy is more congruent with the present 18S rRNA data. The
families Callipallenidae and Nymphonidae with unique “attaching larvae” are grouped together in present molecular trees, suggesting
that extended paternal care of offspring evolved only once in Pycnogonida. Confident clustering of Pycnogonidae and Rhynchothoracidae
indicates that the number of female genital pores is an evolutionary conservative character. 相似文献
84.
Ai Leon Kazunori Kohyama Kazuyuki Yagi Yusuke Takata Hiroshi Obara 《Mitigation and Adaptation Strategies for Global Change》2017,22(1):85-98
Cultivated wetland rice fields are a source of methane (CH4) emissions. To estimate CH4 emissions and develop policies to reduce such emissions, information on water management at the farm level is crucial. It is known that farmers implement midseason drainage (MD) to increase rice yields and save water. However, little is known about whether MD is carried out in soils where CH4 emissions are high and how part-time status will influence management. The objective of this study is to identify factors that determine MD implementation using a binomial logistic regression model based on a farm-level survey in Japan and to indicate possible changes in estimates of CH4 emissions, accounting for current water management practices. The implementation rates were significantly higher where the soil types were classified as having the potential for high CH4 emissions. Under current water management practices, the duration of MD and the percentage of continuous flooding were 5 to 7 days longer and approximately 7 % higher, respectively, than the values used by the Greenhouse Gas Inventory Office of Japan, which in turn are used to report greenhouse gas emissions to the United Nations Framework Convention on Climate Change. By accounting for current water conditions with the Tier 2 method, this study indicates that national estimates of CH4 emissions from rice straw application areas could be lowered by 12.7 %. These results may contribute to the development of a mitigation policy that will help to further reduce CH4 emissions. 相似文献
85.
Investigation of the possible sources of heavy metal contamination in lagoon and canal water in the tannery industrial area in Dhaka, Bangladesh 总被引:2,自引:0,他引:2
86.
Both the UK and Japan are densely populated islands with relatively short rivers. Therefore, both countries are likely to be highly exposed to contaminants emanating from their human populations. This review considered how effective the different sewage treatment facilities of the two countries are at removing steroid estrogens from the effluent. The methods of estrogen analysis in sewage effluent, the number and importance of different sewage treatment types, and their apparent effectiveness at removing estrogens were all considered. In both countries, the activated sludge treatment was dominant in terms of people served and water discharged. The analytical techniques used by those studying estrogen concentrations in effluents in both countries were broadly similar. Activated sludge plant (ASP) effluent in the UK typically contained around 2 ng/L estradiol (E2) and 8 ng/L estrone (E1), while Japanese ASPs typically reported E2 as below detection, and 10 ng/L E1 in their effluents. When estrogenic bioassays were used in Japan, they typically record an estrogenic potency of 10 ng/L E2 equivalents. Even taking into account ethinylestradiol (EE2) (not found in Japanese effluents), the overall estrogenicity of British sewage effluents would appear to be the same as that of Japanese sewage effluents (around 10 ng/L E2 equivalents). This suggests that the ASPs serving the large urban communities in Japan and the UK would have effluent of similar estrogenic potencies. Less information is available about the more numerous biological (trickling) filter plants (BFP) in the UK and oxygen ditches (OD) in Japan which tend to serve smaller, more rural communities. The available data would suggest that the BFPs are significantly less efficient than the ODs at removing E1. This would suggest that in similar circumstances, British headwaters (where this sewage treatment plant (STP) type is often found) might be more at risk from endocrine disruption than their Japanese counterparts. Overall, the apparently higher incidence of endocrine disruption in British wild fish than in Japanese wild fish cannot be attributed to differences in the efficiency of their respective STPs. 相似文献
87.
Zoogeographical aspects of rocky-intertidal molluscan fauna of the Pacific coasts of Japan 总被引:1,自引:0,他引:1
Intertidal molluscan faunas were studied on the exposed rocky shores of the Pacific coasts of Japan (excluding Hokkaido) to determine distribution patterns and latitudinal gradients of taxa. Collections were made at spring low tide in 1980. Five types of distribution patterns were found: tropical, tropical-temperate, warm-temperate, temperate, and boreal. Many examples of parallel species displacement, the term which Thorson (1957) proposed and generalized, were found. Latitudinal gradients of molluscan taxon were observed. Frequency of the Archaeogastropoda in gastropods increases northward, while frequency of the Mesogastropoda and the Neogastropoda decreases. Frequency of predatory gastropods decreases northward, and that of herbivorous ones increases. Commonness indices show that the molluscan fauna of the study sites situated within the wide area between the Kanto and Kyushu are closely related with each other, and they can be regarded as one province. The Tohoku district is less related with this region, and the Okinawa district is the least related. 相似文献
88.
Keisuke Satoh Yosuke Tanaka Masachika Masujima Makoto Okazaki Yoshiki Kato Hiroshi Shono Kentaro Suzuki 《Marine Biology》2013,160(3):691-702
We tested the hypothesis that a large body size and rapid growth rate affect the survival of larval Pacific bluefin tuna, Thunnus orientalis (PBT), and analyzed larval growth in relation to environmental conditions. Seven high density larval patches of PBT were tracked with reference buoys in the northwestern Pacific Ocean for 28–171 h in May–June from 2004 to 2008. The otolith radii and daily growth rates of the survivor larvae (collected on later tracking days of each tracking session) tended to be larger and more rapid, respectively, than those of original larvae (collected on earlier tracking days). A large body size was found to positively affect the survival of larval PBT, as did a rapid growth rate, even at an early larval stage (7 days after hatching). Generalized linear modeling showed that the otolith radius was influenced positively by the sea temperature, stratification parameter and food density, while the growth rate was influenced positively by the sea temperature and food density. 相似文献
89.
Yukari Suzuki Lina G. Kawaguchi Dulee T. Munidasa Yukihiko Toquenaga 《Behavioral ecology and sociobiology》2009,63(9):1353-1362
We proposed “foundress-max” hypothesis that a bumble bee foundress chooses her nest site to maximize her energy intake rate
from nectar. To examine the hypothesis, we estimated the maximum energy intake rate at each site in the study area and compared
the distribution of the maximum energy intake rates with those of actual nest sites. We also calculated rank correlations
of the maximum energy intake rate with the number of nest-searching foundresses at 54 sites. The nest locations supported
the foundress-max hypothesis, but the number of nest-searching foundresses did not. This could be attributed to the density
of food sites: many food sites may attract many foundresses. Therefore, we subsequently proposed “foundress-sum” hypothesis
that a foundress chooses her nest site to maximize the sum of energy intake rates. The nest locations supported the foundress-max
hypothesis more than the foundress-sum hypothesis. A profitable food site would affect foundresses’ nest site selection. 相似文献
90.
Kamrun Nahar Motiar Rahman Mirza Hasanuzzaman Md. Mahabub Alam Anisur Rahman Toshisada Suzuki Masayuki Fujita 《Environmental science and pollution research international》2016,23(21):21206-21218
The role of exogenous spermine (0.25 mM Spm, a type of polyamine (PA) in reducing Cd uptake and alleviating Cd toxicity (containing 1 and 1.5 mM CdCl2 in the growing media) effects was studied in the mung bean (Vigna radiata L. cv. BARI Mung-2) plant. Exogenously applied Spm reduced Cd content, accumulation, and translocation in different plant parts. Increasing phytochelatin content, exogenous Spm reduced Cd accumulation and translocation. Spm application reduced the Cd-induced oxidative damage which was reflected from the reduction of H2O2 content, O2 ?– generation rate, lipoxygenase (LOX) activity, and lipid peroxidation level and also reflected from the reduction of spots of H2O2 and O2 ?– from mung bean leaves (compared to control treatment). Spm pretreatment increased non-enzymatic antioxidant contents (ascorbate, AsA, and glutathione, GSH) and activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) which reduced oxidative stress. The cytotoxicity of methylglyoxal (MG) is also reduced by exogenous Spm because it enhanced glyoxalase system enzymes and components. Through osmoregulation, Spm maintained a better water status of Cd-affected mung bean seedlings. Spm prevented the chl damage and increased its content. Exogenous Spm also modulated the endogenous free PAs level which might have the roles in improving physiological processes including antioxidant capacity, osmoregulation, and Cd and MG detoxification capacity. The overall Spm-induced tolerance of mung bean seedlings to Cd toxicity was reflected through improved growth of mung bean seedlings. 相似文献