Institute of Hydrobiology, Chinese Academy Of Sciences
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Swimming features in captive odontocetes: Indicative of animals' emotional state?
No full textCaptive welfare studies in odontocete species have been mostly conducted on bottlenose dolphins (Tursiops truncatus) while the welfare of many other species' -including endangered species- remains poorly studied. More research is needed to find and validate potential indicators of welfare for each species and even for each group. Since captive odontocetes spend most of their time swimming, their swimming features are interesting to study in relation to their welfare state. We first analysed the circular swimming direction bias in three groups of captive odontocetes (Yangtze finless porpoises: Neophocaena asiaeorientalis asiaeorientalis; East-Asian finless porpoises: N. a. sunameri; and bottlenose dolphins, Tursiops truncatus). Second, we studied the effect of environmental and social factors (i.e., time of the day, delay to training, enrichment, potential perturbation, social grouping, public presence and housing pool) on circular swimming, fast swimming, group swimming, synchronous swimming and contact swimming in the three groups. Yangtze finless porpoises exhibited a clockwise swimming bias while East-Asian finless porpoises and bottlenose dolphins swam significantly more in the counter-clockwise direction. Each studied factor significantly impacted the animals' swimming behaviour slightly differently depending on the group. However, some patterns were common for the three groups: animals seemed to be more active in the morning than at noon and in the afternoon, and enrichment seemed to decrease circular swimming, fast swimming and social swimming (i.e., synchronous, contact and group swimming), while potential perturbations (e.g., pool cleaning, noise) seemed to increase it. In addition, behaviour differed for Yangtze finless porpoises and bottlenose dolphins right before the training or when other animals were being trained, suggesting an anticipation of this event or an excited/frustrated state in this context. Social separation also impacted these animals' swimming behaviour with less group swimming but more circular swimming, synchronous swimming and fast swimming when separated. The housing pool had an impact on bottlenose dolphins' behaviour with more circular swimming, more fast swimming and less group swimming when having access to a larger space. The effect of the presence of public was unclear and requires further investigation. From our results, we propose that circular swimming, synchronous swimming and contact swimming could be useful to monitor animals' emotional state, but that additional parameters should be added (e.g., swimming speed) since these behaviours can be expressed both in quiet and relaxed contexts and in stressful ones. In addition, fast swimming can be a useful indicator of stress for porpoises but might be more ambiguous for bottlenose dolphins that engage in intense social play bouts for instance. Finally, group swimming might be a good behaviour to monitor when wanting to investigate reactions to various conditions or events that can potentially be stressful. We suggest that further research should be conducted on other groups of odontocetes to validate our findings
Photo-induced phosphate release during sediment resuspension in shallow lakes: A potential positive feedback mechanism of eutrophication
No full textDissolved phosphate (P-i) can be released during resuspended sediments exposed to sunlight. However, the significance of this phenomenon in the process of eutrophication is not clear. In this study, the behavior of photo-induced P-i release during sediment resuspension in shallow lakes with the different trophic states was investigated. The amount of photo-induced P-i release in the sediment resuspension from Lake Liangzi, Lake Dong, Lake Tangxun and Lake Longyang in China was 0.013, 0.019, 0.032, and 0.048 mg/L, respectively, and increased as the trophic states of the lakes increased. The results of phosphorus speciation analysis showed that the phosphate monoester in the particulate phosphorus is the organic phosphorus species participated in the photochemical reaction. The steady-state concentration of hydroxyl radical ((OH)-O-center dot) in the sediment resuspension also increased along with the trophic states of lakes increased and dissolved organic matter (DOM), nitrate, and Fe3+ presented in sediment resuspension were the main photosensitizers for (OH)-O-center dot production. All these results indicate that the increase of trophic states of lakes leads to the accumulation of organic phosphorus and (OH)-O-center dot, resulting in more dissolved phosphate photo-released, which accelerate the eutrophication process in a form of positive feedback. (C) 2019 Elsevier Ltd. All rights reserved
RNase II binds to RNase E and modulates its endoribonucleolytic activity in the cyanobacterium Anabaena PCC 7120
No full textIn Escherichia co/i, the endoribonuclease E (RNase E) can recruit several other ribonucleases and regulatory proteins via its noncatalytic domain to form an RNA degradosome that controls cellular RNA turnover. Similar RNA degradation complexes have been found in other bacteria; however, their compositions are varied among different bacterial species. In cyanobacteria, only the exoribonuclease PNPase was shown to bind to the noncatalytic domain of RNase E. Here, we showed that AIr1240, a member of the RNB family of exoribonucleases, could be co-isolated with RNase E from the lysate of the cyanobacterium Anabaena PCC 7120. Enzymatic analysis revealed that AIr1240 is an exoribonuclease II (RNase II), as it only degrades nonstructured single-stranded RNA substrates. In contrast to known RNase E-interacting ribonucleases, which bind to the noncatalytic domain of RNase E, the Anabaena RNase II was shown to associate with the catalytic domain of RNase E. Using a strain in which RNase E and RNase II were tagged in situ with GFP and BFP, respectively, we showed that RNase E and RNase II form a compact complex in vivo by a fluorescence resonance energy transfer (FRET) assay. RNase E activity on several synthetic substrates was boosted in the presence of RNase II, suggesting that the activity of RNase E could be regulated by RNase II-RNase E interaction. To our knowledge, Anabaena RNase II is an unusual ribonuclease that interacts with the catalytic domain of RNase E, and it may represent a new type of RNA degradosome and a novel mechanism for regulating the activity of the RNA degradosome. As Anabaena RNase E interacts with RNase II and PNPase via different regions, it is very likely that the three ribonucleases form a large complex and cooperatively regulate RNA metabolism in the cell
Light, but Not Nutrients, Drives Seasonal Congruence of Taxonomic and Functional Diversity of Phytoplankton in a Eutrophic Highland Lake in China
No full textInformation on temporal dynamics of phytoplankton communities and their responses to environmental factors can provide insights into mechanisms driving succession of phytoplankton communities that is useful in programs to manage and or remediate undesirable assemblages. Populations of phytoplankton can be controlled by bottom-up factors such as nutrients and temperature or top-down such as predation by zooplankton. Traditionally, taxonomic diversity based on morphologies has been the measure used for analysis of responses to environmental factors. Recently, according to functional groupings, including functional groups (FG), morpho-FG (MFG), and morphology-based FG (MBFG), functional diversity has been used to represent functional aspects of phytoplankton communities. However, to what extent these taxonomic and functional groupings are congruent at seasonal time-scales and the main environmental factors, which drive succession, have remained less studied. Here, we analyzed absolute and relative proportions of a phytoplankton community during a 3-year period in Lake Erhai, a eutrophic highland lake in China. Alpha diversity and beta diversity, as measured by Shannon-Wiener and Bray-Curtis indices of taxonomic grouping and three functional groupings (FG, MFG, and MBFG) were applied to investigate environmental factors determining diversity. Significant, positive relationships were observed between taxonomic diversity and functional diversity that were strongly linked through seasons. In order to exclude the influence of dominant species' tolerance to extreme environments, the dominant species were excluded one by one, and the results showed that residual communities still exhibited similar patterns of succession. This synchronous temporal pattern was not principally driven by the dominant genera (Microcystis, Psephonema, and Mougeotia). Instead, the entire phytoplankton community assemblages were important in the pattern. Most diversity indices of taxonomic and functional groupings were significantly correlated with solar irradiance, but not nutrient concentrations. Because the lake is eutrophic and there were already sufficient nutrients available, additional nutrients had little effect on seasonal taxonomic and functional diversity of phytoplankton in Lake Erhai.</p
Species richness and biodiversity significance of alpine micro-waterbody systems in Gaoligong Mountain, Northwest Yunnan, China
No full textWater quality, size, connectivity and other physical properties of hydrological systems might have different functions in the formation and maintenance of biodiversity, but this remains mostly unclear due to the lack of undisturbed sites for experimental modelling. Alpine freshwater habitats such as micro-waterbodies (MWB) represent a kind of natural system suitable for biodiversity research. In order to assess potential linkages between environmental factors, connectivity of MWBs and aquatic species richness, we conducted a pilot study in two separated MWB systems located in Gaoligong Mountain, northwest Yunnan province, China. A total of 27 MWBs have been analyzed, including 22 connected and 5 isolated bodies. 13 conventional environmental factors were tested while all kinds of aquatic macro-organisms were collected and classified. Results showed a high environmental heterogeneity among MWBs and significant differences between the two systems but only a few environmental variables such as the depth of soil bottom, total Nitrogen and altitude were related to species richness and the formation of the community structure. As a benefit from the high environmental heterogeneity, the cascaded MWB systems provided divergent habitats able to support species richness at a higher level than the same number of randomly selected MWBs. This finding supports the idea that habitat connectivity matters also in extremely small aquatic ecosystems. Moreover, although still a preliminary result, a polarization effect within connected chains where edge MWBs host higher taxa and endemic taxa richness as well as larger populations, was detectable. This study gives interesting insights on the spatial processes driving community structure and a new prospective for biodiversity conservation. Since alpine MWBs have significant effects on the maintenance of watershed biodiversity, further research on such small and crucial ecosystems is encouraged.</p
Population survey showing hope for population recovery of the critically endangered Yangtze finless porpoise
No full textThe Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), has experienced rapid declines in recent decades. We estimate its abundance based on surveys conducted between November and December 2017 in the main-stem of the Yangtze River and adjacent Poyang and Dongting Lakes. We compare these to published abundance estimates from 2006 and 2012, using a bootstrap resampling approach to make inference about population change over the 2006-2017 time period. Encounter rates of porpoise from additional surveys during this period provided another index for evaluating temporal changes in abundance in Poyang and Dongting Lakes. As of December 2017, free-ranging populations of this species are estimated at 1012 (95%CI: 791-1233) individuals of which 445 (95%CI: 295-595) occur in the main stem of the Yangtze River, 457 (95%CI: 329-634) in Poyang Lake, and 110 (95%CI: 65-187) in Dongting Lake. Porpoise numbers in main-stem of the Yangtze River and Dongting Lake declined rapidly from 2006 to 2012 (mean annual rates of -14% and -12%, respectively). These rates of decline greatly eased from 2012 to 2017 (-2.5% and +3% annual growth, respectively). In Poyang Lake, the encounter rates of porpoise have remained relatively stable between 2006 and 2017. This improved population trajectory was likely a joint consequence of government and public conservation efforts. However, fragmentation of porpoise populations in Yangtze River main-stem and significantly reduced migratory movements between the two adjoining lakes and the Yangtze main stem pose a continued threat to the long-term viability of this species. Further actions to improve habitat connectivity are urgently needed
Efficient generation of zebrafish maternal-zygotic mutants through transplantation of ectopically induced and Cas9/gRNA targeted primordial germ cells
No full textThe clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology has been widely utilized for knocking out genes involved in various biological processes in zebrafish. Despite this technology is efficient for generating different mutations, one of the main drawbacks is low survival rate during embryogenesis when knocking out some embryonic lethal genes. To overcome this problem, we developed a novel strategy using a combination of CRISPR/Cas9 mediated gene knockout with primordial germ cell (PGC) transplantation (PGCT) to facilitate and speed up the process of zebrafish mutant generation, particularly for embryonic lethal genes. Firstly, we optimized the procedure for CRISPR/Cas9 targeted PGCT by increasing the efficiencies of genome mutation in PGCs and induction of PGC fates in donor embryos for PGCT. Secondly, the optimized CRISPR/Cas9 targeted PGCT was utilized for generation of maternal-zygotic (MZ) mutants of tcf7l1a (gene essential for head development), pou5f3 (gene essential for zygotic genome activation) and chd (gene essential for dorsal development) at F-1 generation with relatively high efficiency. Finally, we revealed some novel phenotypes in MZ mutants of tcf7l1a and chd, as MZtcf7l1a showed elevated neural crest development while MZchd had much severer ventralization than its zygotic counterparts. Therefore, this study presents an efficient and powerful method for generating MZ mutants of embryonic lethal genes in zebrafish. It is also feasible to speed up the genome editing in commercial fishes by utilizing a similar approach by surrogate production of CRISPR/Cas9 targeted germ cells. Copyright (C) 2020, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Limited and Science Press. All rights reserved.</p
一头搁浅瑞氏海豚的病理解剖和死因分析
No full text瑞氏海豚在我国大陆沿海搁浅的案例相对较少。2019年7月10日,一头活体瑞氏海豚搁浅于广东省湛江市徐闻县石马角海域,半小时左右死亡。本文描述了该海豚的外部形态特征和骨骼系统,并通过解剖对其死因进行了分析。该瑞氏海豚为成年雌性,体长252.0 cm,体重约130.0 kg;体型消瘦,皮下脂肪层菲薄,体表无明显可致死外伤。头骨长45.6 cm,脊椎式为C7+T12+L23+Ca24 = 66,肋骨12对,V形骨19枚。解剖发现,该海豚的呼吸道和消化道中均存在大量泥沙;前胃内有两只长度超过30 cm的橡胶手套,胃和肠中几乎没有食糜和粪便。推测该瑞氏海豚因误食橡胶手套造成胃部阻塞而无法正常进食和消化,导致脂肪层过度消耗,体力不支而搁浅;在搁浅过程中可能因挣扎导致呼吸道进入大量泥沙引起呼吸不畅,最终死亡。当前难降解的海洋垃圾对海洋哺乳动物,包括以头足类为食的鲸类动物所产生的直接威胁已不容忽视。</p
Diversity dynamics of Devonian terrestrial palynofloras from China: Regional and global significance
No full textThe microfossil-based pattern of the Devonian land plants of China is revised and discussed based on a new, comprehensive dataset. This dataset compiles the chronostratigraphical distribution of 1677 species belonging to 190 genera of spores and pollen from the primary literature, which covers the history of fossil Chinese terrestrial palynofloras. From this, we describe the patterns and biodiversity dynamics using both range-based and sample-based data to illustrate the main fluctuations of Devonian taxonomic richness, including rarefaction by filtering out uneven sampling. Results show that the apparent terrestrial palynofloral diversity of China increases progressively from the Early to Middle Devonian, with a genuine Givetian peak followed by a plateau persisting during the Late Devonian. Results further suggest that sampling effects may strongly influence the perception of biodiversity trends in China, as well as that the observed Late Devonian taxonomic diversification may have been greatly overestimated. Compiled evidence is discussed in the light of the global evolution of marine-terrestrial ecosystems. We hypothesize that the rise of Devonian floras may have played a remarkable role in an oceanic oxygenation event during this Period
Strategies adopted by Aphanizomenon flos-aquae in response to phosphorus deficiency and their role on growth
No full textBackground The N-2-fixing cyanobacterium, Aphanizomenon flos-aquae is a globally distributed bloom causing species that degrades water quality of fresh and marine water bodies. Overcoming phosphorus (P) deficiency is one of the ecological advantages for bloom-forming cyanobacteria. It remains unclear to what extent can A. flos-aquae alleviate P deficiency by regulating P using strategies. Results Based on in situ observations of extracellular alkaline phosphatase (APase) in A. flos-aquae via enzyme-labeled fluorescence in freshwater bodies in China, Poland and Czechia, we further investigated responses of isolated A. flos-aquae to different P supplies (dissolved inorganic P (Pi) as +DIP, dissolved organic alpha-glycerophosphate and beta-glycerophosphate as +DOP alpha and +DOP beta, P-free condition as P-depleted). The significantly negative relationships between percentage of APase producing cells and soluble reactive P concentration in both fields and cultures suggested that the excretion of APase in cyanobacterium was regulated by ambient Pi supply. Suffering from P deficiency in the P-depleted treatments, A. flos-aquae showed the highest APase activity but a vigorous growth at the early culture stage, which might also benefit from the formation of polyphosphate body (PPB) and the decrease of cell P quota. In the +DOP treatments, the coordination of dissolved DOP mineralization and continuous prompt utilization of PPB might contribute to a maintenance but not reproduction of A. flos-aquae when relying on DOP, since the specific growth rate kept around 0 cells L-1 day(-1) at the second half culture period and the highest cell density reached only 13.38% of that in +DIP treatments while photochemical efficiency was comparable during the whole experiment. Luxury uptake of phosphate as PPB in the +DIP treatments was consistent to the canonical view of polyphosphate as P storage. Conclusion Aphanizomenon flos-aquae could achieve an instantaneous growth in response to P deficiency with the coordination of P utilization strategies, while it maintained a long-term sustainable growth but not reproduction under sole DOP supply. Persistent and active reproduction could only be achieved in high Pi supply, which implying that an effective consequence can be expected for combating the bloom of A. flos-aquae when controlling P supply