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91.
The canonical Wnt pathway is recurrently used during embryogenesis and adult life. To track the cellular output of Wnt signaling in a living organism, we designed a hormone-inducible Wnt responsive system, capable to dynamically and specifically report Wnt pathway activities through eGFP expression. In contrast to previous in vivo reporters, our system essentially avoids interference of consecutive signals by remaining dormant until addition of hormone, which makes it a valuable tool to map canonical Wnt signaling in post-embryonic stages. Transgenic Xenopus laevis embryos were analyzed revealing at tadpole stage in specific tissues and organs cell populations with high Wnt pathway activity. 相似文献
92.
根据2012-2013年在南沙群岛西南部和北部湾口海域春秋两个航次的调查资料, 分析了该海域鱼类种类组成、相对重要性指数和物种多样性等特征。结果表明, 两个航次调查共鉴定鱼类504种, 隶属于2纲31目129科294属; 其中北部湾口海域出现鱼类301种, 南沙群岛西南部海域出现鱼类357种。优势种数量较少, 多以中小型鱼类为主, 且季节间变化较大。春季多样性指数高于秋季, 这主要是因为春季出现的大量鱼类为补充群体, 而许多种类在秋季有向较深海区移动的趋势; 南沙群岛西南部海域多样性指数高于北部湾口海域, 这主要是由于南沙群岛西南部海域受水温和洋流的影响较大造成的。更替指数和迁移指数显示, 秋季鱼类群落结构稳定性要低于春季, 而且两个季节的鱼类群落结构都偏离平衡状态, 主要是由鱼类的洄游和不同适温性鱼类的迁入迁出造成的。综合来看, 南沙群岛西南部海域鱼类物种多样性和群落结构稳定性均高于北部湾口海域, 在努力控制资源可捕量范围的同时, 可合理开发南海中南部海域的渔业资源。 相似文献
93.
94.
The contrasting effects of short‐ and long‐term habitat drainage on the population dynamics of freshwater turtles in a human‐dominated landscape 下载免费PDF全文
Zoey Owen‐Jones Pauline Priol Stephanie Thienpont Marc Cheylan Gabrielle Sauret Christophe Coïc Aurélien Besnard 《Freshwater Biology》2016,61(1):121-132
95.
Dongyan Han Qiuyun Ma Kindong Richard Chunxia Gao 《Zeitschrift fur angewandte Ichthyologie》2021,37(2):347-349
The present study provides the length-weight relationships (LWRs) for 10 marine fish species collected from the coastal waters of the East China Sea by bottom trawl surveys. The open width of the sampling net was 40 m and the mesh size of the codend was 20 mm. Specimens were collected from November 2015 to November 2019 at seasonal intervals. The measurement accuracy of weight and length were 0.1 grams and 0.1 centimeters, respectively. This study provides new information of LWRs for nine species which have not yet been reported in FishBase. Also, this study updates the information of maximum length for two species. 相似文献
96.
《Harmful algae》2014
Dinoflagellates belonging to the genus Gambierdiscus are the causative agent of ciguatera fish poisoning (CFP). This syndrome, which is widespread in tropical and subtropical regions, has recently been reported also in temperate latitudes. Taxonomic studies of Gambierdiscus have yet to completely couple the morphological features of member species with their genetics. In this study, the cellular and nuclear morphology of a single strain of one species of Gambierdiscus was determined in cells grown under different culture conditions. The results showed a wide-ranging variability of cell sizes, together with a clear relationship between cell size and nuclear morphology. Thus, small cells were associated with round to oval or slightly U-shaped nuclei and large cells with obviously U-shaped nuclei. Most cells exhibited the typical anterio-posteriorly compressed lenticular, shape of Gambierdiscus, with the exception of a few small globular-shaped specimens. In all cells, regardless of their size, the arrangement of the thecal plates was typical of lenticular Gambierdiscus. Dividing cells were consistently the largest. In these cells, nuclear morphology, karyokinesis, and cytokinesis were characterized. Cells underwent division only during the dark period, thus demonstrating their spontaneous synchronized division. Cellular forms related to the sexual cycle were also present in the cultures and included gamete pairs and putative meiotic planozygotes. The effect of the culture medium was studied by means of principal component analyses, which showed a positive correlation between the medium used and nuclear size and shape but not cell size. 相似文献
97.
Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes? 总被引:5,自引:1,他引:5
SUSANA ROMO MARÍA-JOSÉ VILLENA MARÍA SAHUQUILLO JUAN M. SORIA MARIO GIMÉNEZ TERESA ALFONSO EDUARDO VICENTE MARIA R. MIRACLE 《Freshwater Biology》2005,50(10):1706-1717
1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long‐term limnological data set to document changes in the food‐web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L?1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents from ricefields. 3. Chlorophyll a concentration was reduced by half (annual mean of 180 μg L?1). Cyanobacteria abundance remained high but its composition changed towards smaller species, both filamentous and chroococcal forms. 4. Cladocera abundance increased and reached peaks twice a year (December to March and July to September). After nutrient reduction, short‐term clear‐water phases (up to 5 weeks) occurred during February to March in several years, concomitant with annual flushing of the lake and lower fish densities. The abundance of Cladocera in winter contrasted with the spring peaks observed in northern restored shallow lakes. The zooplankton to phytoplankton biomass ratio remained lower than in northern temperate shallow lakes, probably because of fish predation on zooplankton. 5. Improvement of the water quality of Lake Albufera remained insufficient to counteract littoral reed regression or improve underwater light allowing submerged plants re‐colonise the lake. 6. Sewage diversion from Lake Albufera impacted the food web through the plankton, but higher trophic levels, such as fish and waterfowl, were affected to a lesser degree. Although the fish species present in the lake are mainly omnivorous, long‐term data on commercial fish captures indicated that fish communities changed in response to nutrient level and trophic structure as has been observed in restored shallow lakes at northern latitudes. 7. Phosphorus concentrations produced similar phytoplankton biomass in Lake Albufera as in more northern shallow lakes with abundant planktivorous fish and small zooplankton. However, in Lake Albufera, high average concentrations were maintained throughout the year. Overall, results suggest that nutrient control may be a greater priority in eutrophicated warm shallow lakes than in similar lakes at higher latitudes. 相似文献
98.
Difference in the predation impact enhanced by morphological divergence between introduced fish populations 总被引:1,自引:0,他引:1
RYUJI YONEKURA YUKIHIRO KOHMATSU† MASAHIDE YUMA‡ 《Biological journal of the Linnean Society. Linnean Society of London》2007,91(4):601-610
The strength of predation impact on recipient environments may vary among introduced populations due to their local adaptations to different prey. We examined whether functional diversification associated with morphological differences may be observed among the introduced populations of invasive bluegill sunfish Lepomis macrochirus (Perciformes, Centrarchidae) in Japan. The two examined populations are morphologically different, although they were recently derived from a common American source and colonized in different lakes. We performed a laboratory experiment wherein these populations were fed the benthic (chironomid larva) and the pelagic prey (daphnid zooplankton). The results revealed that a population colonizing in a shallower lake and foraging on benthic invertebrates in the wild had a greater impact on the benthic prey, whereas the other population colonizing in a deeper lake and foraging on crustacean zooplankton have consumed the pelagic prey more efficiently. A series of regression analyses showed that morphological differences among individuals were responsible for these population differences. The evidence obtained suggests that morphological adaptations by introduced bluegill populations enhance the strength of predation impact on a prey resource consumed in a relevant environment, but reduce the impact on the other prey. Thus, although the introduced Japanese populations were recently derived from a common ancestor, the predation impacts on the native prey community vary due to morphological adaptations to different prey. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 601–610. 相似文献
99.
Olivier Beauchard Quiterie Duron Thierry Oberdorff Sébastien Brosse 《Global Ecology and Biogeography》2011,20(3):407-414
Aim We tested whether coarse‐grained occurrence data can be used to detect climatic niche shifts between native and non‐native ranges for a set of widely introduced freshwater fishes. Location World‐wide. Methods We used a global database of freshwater fish occurrences at the river basin scale to identify native and non‐native ranges for 18 of the most widely introduced fish species. We also examined climatic conditions within each river basin using fine‐grained climate data. We combined this information to test whether climatic niche shifts have occurred between native and non‐native ranges. We defined climatic niche shifts as instances where the ranges of a climatic variable within native and non‐native basins exhibit zero overlap. Results We detected at least one climatic niche shift for each of the 18 studied species. However, we did not detect common patterns in the thermal preference or biogeographic origin of the non‐native fish, hence suggesting a species‐specific response. Main conclusions Coarse‐grained occurrence data can be used to detect climatic niche shifts. They also enable the identification of the species experiencing niche shifts, although the mechanisms responsible for these shifts (e.g. local adaptation, dispersal limitation or physiological constraints) have yet to be determined. Furthermore, the coarse‐grained approach, which highlights regions where climatic niche shifts have occurred, can be used to select specific river basins for more detailed, fine‐grained studies. 相似文献
100.
For more than 20 years scientists of the ‘Food-chain studies’ Group of the former Limnological Institute have been studying
interactions within the pelagic food web. Purpose of research was to explain the structure and dynamics of the zooplankton
and fish communities in lakes and reservoirs in relation to biotic and abiotic environmental factors. A so-called multi-species
approach was used, in which all common and abundant species within a specific ecosystem were studied on the individual and
population level with the same degree of detail. The recent results and the scientific approach used are evaluated and the
main gaps in knowledge about food-web dynamics in shallow eutrophic lakes are identified and discussed. It is concluded that
instead of the purely functional approach used so far, future studies should also include evolutionary aspects which determine
the success of an organism in a given environment and that more attention should be paid to central questions in ‘community
ecology’.
This paper is based on a lecture given by the first author for the Netherlands Society of Aquatic Ecology on May 12th, 1992,
in Amsterdam, The Netherlands. 相似文献