Institute of Hydrobiology, Chinese Academy Of Sciences
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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
Chlorocladiella gen. nov. (Pithophoraceae, Cladophorales, Chlorophyta), Including Four New Species From Various Freshwater Habitats in China(1)
No full textSamples of Pithophoraceae, collected in diverse freshwater and damp terrestrial habitats from tropical and subtropical China, were characterized morphologically and ultrastructurally, and their phylogenetic position was determined based on nuclear ribosomal DNA sequences. Our phylogenetic analysis resolved a novel lineage of Pithophoraceae, sister to Aegagropilopsis. Based on our phylogenetic results, morphological observations and comparative rDNA ITS2 secondary structure analysis, we propose Chlorocladiella gen. nov., characterized by a well-developed system of prostrate filaments, and describe four new species, C. cochlea sp. nov., C. erecta sp. nov., C. medogensis sp. nov., and C. pisformis sp. nov. Two species were found growing on damp soil, which is an unusual habitat for cladophoralean green algae, indicating that the diversity of Cladophorales in terrestrial habitats may be greater than currently recognized
Human disturbance and long-term changes in fish taxonomic, functional and phylogenetic diversity in the Yellow River, China
No full textDramatic environmental changes and species invasions are increasingly threatening the diverse fish fauna of the Yellow River, China. This study examines temporal changes in the alpha and beta components of fish taxonomic, functional and phylogenetic diversity in relation to anthropogenic environmental changes over the past 50 years. We hypothesized that temporal trends in multifaceted components of diversity would be highly congruent, but that the relative importance of anthropogenic disturbances would differ in shaping spatial patterns of fish diversity. We found that all three components of alpha diversity increased over time but at different rates (19.1%, 21.3% and 15.3% for taxonomic, functional and phylogenetic diversity, respectively). Fish faunas of the Yellow River have also become homogenized over time, but this was much greater for functional and phylogenetic components of beta diversity than for taxonomic diversity (change in beta diversity = - 0.11, - 0.24 and - 0.02, respectively). Temporal changes in alpha and beta diversity were strongly related to invasion of non-native fish species and changes in temperature, sediment load, reservoir capacity and aquaculture area. Our results underscore the ongoing need for threat mitigation (particularly relating to dams and aquaculture) to conserve the unique biodiversity of one of the world's largest rivers
鱼类应激应对策略及其在抗逆育种中的应用
No full text发展现代水产种业,引领水产养殖绿色发展,成为未来水产养殖业可持续发展的保障。应鼓励产业选育推广优质、高效、多抗、安全的水产养殖新品种,由单纯高产品种转向适宜生态化、集约化养殖模式的优质高效、节料节药、抗逆性强、适应性广的品种。本文分析了当前水产种业存在的一些问题,剖析了优质、高效、多抗水产养殖品种的耐应激本质,围绕应激反应、应激恢复、应激应对方式在畜禽种业中的应用案例等,提出了环境限制育种理念和未来综合性抗逆育种技术发展方向,助推水产养殖业的可持续发展。</p
Ectothermic omnivores increase herbivory in response to rising temperature
No full textHigher temperatures as a consequence of global climate change may considerably alter trophic interactions. Ectothermic herbivores and carnivores generally ingest more food with rising temperature as their metabolic rates increase with rising temperature. However, omnivorous ectotherms may respond in two ways: quantitatively by consuming more food and qualitatively by altering their degree of herbivory or carnivory through a diet shift. We hypothesize that rising temperature will increase herbivory of ectothermic omnivores as herbivory increases towards the equator. We tested the hypothesis in a freshwater model system in which ectothermic omnivores are prevalent, by applying two approaches, a temperature manipulation experiment and a literature study. We performed feeding trials with a juvenile aquatic ectothermic omnivore (pond snail Lymnaea stagnalis) at different temperatures ranging from 12 to 27 degrees C, supplying them with both animal food and plant material, and directly quantified their consumption rates over time. The results showed that snails cultured at high temperatures (> 21 degrees C) increased the proportion of plant material in their diets after 17 days, which supports our hypothesis. In the literature survey, we found that rising temperature increased herbivory in multiple aquatic animal taxa, including zooplankton, amphibians, crayfish, fish and snails. This suggests that aquatic ectothermic omnivores might commonly increase herbivory with rising temperature. The mechanisms underlying this temperature-induced diet shift are not sufficiently explained by current theories related to the physiology, metabolism and stoichiometry of omnivores. We propose to incorporate the animals' ontogenetic development in the temperature metabolic stoichiometry hypothesis as a complementary explanation for the diet shift, namely that the diet shift could be due to faster development of the ectotherms and an earlier ontogenetic diet shift at higher temperatures. We conclude that future global warming will most likely alter food webs by increasing the top-down control of aquatic herbivores and omnivores on primary producers
Ectothermic omnivores increase herbivory in response to rising temperature
No full textHigher temperatures as a consequence of global climate change may considerably alter trophic interactions. Ectothermic herbivores and carnivores generally ingest more food with rising temperature as their metabolic rates increase with rising temperature. However, omnivorous ectotherms may respond in two ways: quantitatively by consuming more food and qualitatively by altering their degree of herbivory or carnivory through a diet shift. We hypothesize that rising temperature will increase herbivory of ectothermic omnivores as herbivory increases towards the equator. We tested the hypothesis in a freshwater model system in which ectothermic omnivores are prevalent, by applying two approaches, a temperature manipulation experiment and a literature study. We performed feeding trials with a juvenile aquatic ectothermic omnivore (pond snail Lymnaea stagnalis) at different temperatures ranging from 12 to 27 degrees C, supplying them with both animal food and plant material, and directly quantified their consumption rates over time. The results showed that snails cultured at high temperatures (> 21 degrees C) increased the proportion of plant material in their diets after 17 days, which supports our hypothesis. In the literature survey, we found that rising temperature increased herbivory in multiple aquatic animal taxa, including zooplankton, amphibians, crayfish, fish and snails. This suggests that aquatic ectothermic omnivores might commonly increase herbivory with rising temperature. The mechanisms underlying this temperature-induced diet shift are not sufficiently explained by current theories related to the physiology, metabolism and stoichiometry of omnivores. We propose to incorporate the animals' ontogenetic development in the temperature metabolic stoichiometry hypothesis as a complementary explanation for the diet shift, namely that the diet shift could be due to faster development of the ectotherms and an earlier ontogenetic diet shift at higher temperatures. We conclude that future global warming will most likely alter food webs by increasing the top-down control of aquatic herbivores and omnivores on primary producers
Effect of the complete replacement of dietary fish meal by soybean meal on histopathology and immune response of the hindgut in grass carp (Ctenopharyngodon idellus)
No full textA 14-day experiment was conducted to explore the pathological process and immune response of soybean meal (SBM) induced enteritis (SBMIE) in grass carp (Ctenopharyngodon idellus). The complete replacement of dietary fish meal (FM) with SBM resulted in a remarkable reduction in final body weight, weight gain ratio, and feed conversion efficiency (p < 0.05). The typical histopathological changes of SBMIE appeared starting at day 4, and progressively increased in severity until day 8, then gradually subsided after day 11. The course of SBMIE could be divided into incubation period (days 1-2), prodromal period (days 3-6), symptomatic period (days 7-10), and convalescent period (days 11-14). Transcription levels of pro-inflammatory cytokines, including IL-1 beta, TNF-alpha, IL-6, IL-8, IL-17A/F1 and IFN-gamma 2, were up-regulated during the prodromal period, and then down-regulated during the convalescent period. Transcript levels of anti-inflammatory cytokines (IL-10 and TGF beta 1) and their receptors (IL-10RI and T beta RII), were up-regulated during the prodromal and convalescent periods. Transcript levels of MHCII beta, lg mu, Ig tau, TCR delta, TCR beta, CD4, and CD8 alpha were altered in SBMIE. Furthermore, expression levels of T-bet, IFN-gamma 2, ROR gamma 2 and IL-17A/F1 were significantly increased in the initiation of enteritis, whereas the transcript levels of Foxp3 and IL-2/15Ra were significantly up-regulated in the repair of enteritis. In conclusion, grass carp SBMIE is regulated by the adjustment of SBM-based diet intake, and the changes of the above-mentioned genes expression suggest that these genes may be involved in SBMIE
Almond Shell-Derived, Biochar-Supported, Nano-Zero-Valent Iron Composite for Aqueous Hexavalent Chromium Removal: Performance and Mechanisms
No full textNano-zero-valent iron biochar derived from almond shell (nZVI-ASBC) was used for hexavalent chromium (CR) removal. Experiments showed that pH was the main factor (p < 0.01) that affected the experimental results. At a dosage of 10 mg.L-1 and pH of 2-6, in the first 60 min, nZVI-ASBC exhibited a removal efficiency of 99.8%, which was approximately 20% higher than the removal yield at pH 7-11. Fourier transform infrared spectroscopy results indicated N-H was the main functional group that influenced the chemisorption process. The pseudo second-order dynamics and Langmuir isotherm models proved to be the most suitable. Thermodynamic studies showed that the reaction was exothermic and spontaneous at low temperatures (T < 317 K). Various interaction mechanisms, including adsorption and reduction, were adopted for the removal of Cr(VI) using the nZVI-ASBC composite. The findings showed that the BC-modified nZVI prepared with almond shell exerts a good effect and could be used for the removal of Cr(VI)
In Primitive Zebrafish, MHC Class II Expression Is Regulated by IFN-gamma, IRF1, and Two Forms of CIITA
No full textMammalian CIITA isoforms are tightly regulated by independent promoters. These promotors are induced by IFN-g through JAK-STAT signaling pathway. The induction of CIITA controls the expression of MHC class II (MHCII) and Ag presentation to the adaptive immune system. In the current study, to our knowledge, we first identified two independent promoters, p1 and p2, in the zebrafish ( Danio rerio) that control the expression of the two variants of CIITA, CIITA variant 1 (CIITAv1), and CIITA variant 2 (CIITAv2), respectively. Moreover, although IRF1 in an IFN-gamma signaling pathway induced CIITAv2, which has two ISRE motifs in its promoter, CIITAv1 expression was not induced by this signal. Further, the transcription of MHCII DAB was controlled by IRF1 via two distinct mechanisms: 1) the transcription of MHCII DAB was controlled by IRF1 indirectly through the two ISREs in p2; and 2) directly via the ISRE in MHCII DAB promoter. We also found that IRF1 associated with CIITAv1 and CIITAv2 via protein-protein interactions to synergistically drive the transcription of MHCII DAB. The IFN-gamma-IRF1-CIITA-MHCII signaling cascade was functional in early life stages of CIITA(-/-) and IRF1(-/-) zebrafish. Our findings imply that the immune system develops early in fishes and that the IFN-g signaling cascade-induced CIITA and MHCII DAB is conserved in teleost fishes and mammals