不同植物油对大规格吉富罗非鱼生长性能、组织脂肪酸组成的影响

本试验旨在探究大规格吉富罗非鱼(GIFT)对不同植物油的利用效果,筛选出大规格吉富罗非鱼饲料中合适的植物脂肪源。分别以大豆油(SO)、棕榈油(PO)、棉籽油(CO)、菜籽油(RO)、磷脂油(SL)和大豆油∶棕榈油∶棉籽油∶菜籽油∶磷脂油=1∶1∶1∶1∶1的混合油(MIX)为脂肪源配制6种等氮等脂的试验饲料,饲喂初始体重为(229.92±0.31)g的吉富罗非鱼8周。每种试验饲料投喂4个网箱(重复),每个网箱放养50尾。结果表明:对于增重率和特定生长率,棉籽油组和混合油组显著低于菜籽油组(P0.05)。菜籽油组饲料系数显著低于混合油组(P0.05),其他各组间无显著差异(P0.05)。混合油组蛋白质效率显著低于菜籽油组和磷脂油组(P0.05)。混合油组肝体指数显著高于棕榈油组和菜籽油组(P0.05)。大豆油组、菜籽油组、棕榈油组和磷脂油组在增重率、特定生长率和饲料系数方面没有显著差异(P0.05)。大豆油组和菜籽油组肌肉饱和脂肪酸总量显著低于其他各组(P0.05)。对于肌肉中n-3系脂肪酸/n-6系脂肪酸,菜籽油组显著高于其他各组(P0.05),棉籽油显著低于其他各组(P0.05)。棉籽油组肝脏饱和脂肪酸总量显著高于其他各组(P0.05),菜籽油组则显著低于其他各组(P0.05);对于肝脏n-3/n-6,菜籽油组显著高于其他各组(P0.05)。各组肌肉脂肪酸组成与饲料脂肪酸组成的相关系数均高于肝脏脂肪酸组成与饲料脂肪酸组成的相关系数。在饲料脂肪酸组成与肌肉或肝脏脂肪酸组成的相关系数中,均以棕榈油组最大,磷脂油组最小。由此得出,大豆油、棕榈油、菜籽油和磷脂油可以作为大规格吉富罗非鱼(体重为230~790 g)饲料中良好的脂肪源。大规格吉富罗非鱼肌肉中脂肪酸组成一定程度上被饲料脂肪酸组成影响,但肝脏脂肪酸组成与饲料脂肪酸组成的相关性较小。     

干旱区矿区不同立地类型土壤种子库特征

矿区的自然或人工植被恢复是维持生物多样性及生态系统稳定的重要途径。通过室外萌发法对金昌镍铜矿区7种不同立地生境土壤种子库的研究表明:该区域土壤中物种丰富度较高,包括16科47属,共56种植物,分别为:藜科(Chenopodiaceae)、禾本科(Gramineae)、菊科(Compositae)、柽柳科(Tamaricaceae)、苋科(Amaranthaceae)、马齿苋科(Portulacaceae)、豆科(Leguminosae)、十字花科(Cruciferae)、车前科(Plantaginaceae)、胡颓子科(Elaeagnaceae)、蒺藜科(Zygophyllaceae)、莎草科(Cyperaceae)、大戟科(Euphorbiaceae)、紫草科(Boraginaceae)、蔷薇科(Rosaceae)、茄科(Solanaceae);植物组成以一年生草本植物占绝对优势(89.3%),多年生草本植物次之(7.54%),灌木种最少(2.59%)。土壤种子平均储量412粒·m~(-2),不同立地类型土壤种子库储量差异显著,与其他荒漠地区比较,土壤种子库储量偏低;土壤种子库物种Simpson多样性指数为:新尾矿周边自然植被区龙首矿自然植被区龙首矿开采废弃地供暖公司柽柳林地。     

Organic Chemical Characterization of Decomposing Plant Litter: A Comparison of Methods

There are two common methods to characterize organic chemical composition of decomposing plant litter, a forest products method and a forage fiber method. These methods divide litter into a few fractions based on extractions using different solvents. In this study, equivalencies were established between the fractions of the methods. Some of the equivalencies were based on similarities in the fractionation methods, whereas some were estimated empirically. The equivalencies gave similar chemical composition for different litter types as measurements. The results were also comparable to, or for certain fractions even better than, those obtained using earlier conversion equations. The equivalencies established are suitable for converting the forage fiber fractions to the forest products fractions in litter decomposition studies. Thus, they increase possibilities to exchange data on litter chemical characteristics across the methods in decomposition studies.     

Dynamics of extracellular DNA decomposition and bacterial community composition in soil

Microbial necromass is an important source of stabilized organic matter in soil, yet the decomposition dynamics of necromass constituents have not been adequately characterized. This includes DNA, a nutrient-rich molecule that when released into the environment as extracellular DNA (eDNA) can be readily used by soil microorganisms. However, the ecological relevance of eDNA as a nutrient source for soil microorganisms is relatively unknown. To address these deficits, we performed a laboratory experiment wherein soils were amended with ¹³C-labeled eDNA and clay minerals known to interact with DNA (kaolinite and montmorillonite). The amount of eDNA-carbon remaining in the soil declined exponentially over time. Kaolinite amendment decreased eDNA decomposition rates and, after 30 days, retained a higher fraction of eDNA-carbon (∼70% remaining) than control or montmorillonite soils (∼40% remaining), indicating that clay mineral sorption can stabilize eDNA-derived carbon in soil. Sequencing of bacterial 16S rRNA genes showed that during the incubation the relative abundance of the added eDNA's sequence decreased by 98%, 92% and 99% in the control, montmorillonite, and kaolinite amended soils respectively. These results suggest that the fraction of eDNA-carbon that remained in the soil was incorporated into microbial biomass, firmly bound to soil constituents, or fragmented and no longer amenable to sequencing. In addition, the eDNA amendment affected the composition of the bacterial community. Specifically, the relative abundance of select phyla (Planctomycetes and TM7) and genera (e.g., Arthrobacter and Nocardioides) were elevated in soils that received eDNA, suggesting these groups may be particularly effective at degrading eDNA and using it for growth. Taken together, these results indicate that while eDNA is consumed by bacteria in soil, a fraction of eDNA material is resistant to decomposition, particularly when stabilized by soil minerals, suggesting a substantial amount of recalcitrant eDNA could accumulate over time.     

5个椰子品种形态特征的比较研究

对5个椰子品种茎、叶、花的23个形态特征进行了比较研究。结果表明:有15个数量性状和5个质量性状在5个品种间有显著性差异,而小叶形状、小叶边缘颜色和小叶边缘形状这3个性状在品种间无显著性差异。通过综合分析这20个性状,可以将供试品种进行初步区分。     

Soil microarthropods are only weakly impacted after 13 years of repeated drought treatment in wet and dry heathland soils

Studies of biological responses in the terrestrial environment to rapid changes in climate have mostly been concerned with aboveground biota, whereas less is known of belowground organisms. The present study focuses on mites and springtails of heathland ecosystems and how the microarthropod community has responded to simulated climate change in a long-term field experiment. Increased temperature and repeated drought was applied for 13 years to field plots located in Wales, The Netherlands and Denmark representing sites of contrasting climatic conditions with respect to precipitation and temperature. This approach provided an opportunity to study biological responses on a local (within sites) and regional scale. Warming treatments increasing night time temperature (0.3–1 °C higher than ambient at 5 cm soil depth) had no detectable effects on the microarthropod communities. Increased intensity and frequency of drought had only weak persistent effects on springtail species composition, but practically no effect on major mite groups (Oribatida, Prostigmata or Mesostigmata) suggesting that ecosystem functions of microarthropods may only be transiently impacted by repeated spring or summer drought.     

Mineral Composition and Soil-Plant Relationships for Common Guava (Psidium guajava L.) and Yellow Strawberry Guava (Psidium cattleianum var. lucidum) Tree Parts and Fruits

The mineral compositions of the fruit and tree parts of common guava, Psidium guajava L., and strawberry guava, Psidium cattleianum var. lucidum, were determined. The study occurred during three seasons at six locations in Hawaii to assess guava as feed for livestock. Guava bark contained the greatest concentrations of calcium (Ca) and ash; leaves the greatest concentrations of magnesium (Mg), sulfur (S), sodium (Na), boron (B), and manganese (Mn); and the shoots had the greatest concentrations of nitrogen (N), phosphorus (P), and potassium (K). The leaves and the shoots had the greatest concentrations of copper (Cu) and iron (Fe). Between guava and waiwi, guava had greater concentrations of most minerals except for Na in all plant parts, and Mg and ash in the leaves. Guava leaves and shoots meet the macromineral requirements for various phases of sheep, goat, and beef cattle life cycles with the exception of P and Na. Guava shoots do not meet Mn requirements for lactating cows.     

Effects of salinity on the growth and proximate composition of selected tropical marine periphytic diatoms and cyanobacteria

Marine periphytic cyanobacteria and diatoms have been examined as a potential source of feed supplement for rearing aquatic larvae in the aquaculture industry. Culture of the periphytic diatom Amphora sp., Navicula sp., Cymbella sp. and the cyanobacteria Oscillatoria sp. at different salinities showed significant changes in biomass and specific growth rates. Diatoms growth was significantly higher at 35 g L⁻¹, while for cyanobacteria growth was better at 25 g L⁻¹. Significantly higher levels of protein and lipid were found in diatoms at low salinities (15–25 g L⁻¹) and an increase in carbohydrate at high salinities (30–35 g L⁻¹). Conversely, cyanobacteria showed a significantly higher lipid content at 30–35 g L⁻¹ compared with other salinity levels but no significant changes were observed in the protein and carbohydrate contents at different salinity levels. The present findings can be taken into consideration when culturing marine periphytic Amphora sp., Navicula sp., Cymbella sp. and Oscillatoria sp. to provide appropriate levels of protein, lipid and carbohydrate as feed supplement as well as for bioremediation in aquaculture.     

Changes of Intramuscular Fat Composition,Lipid Oxidation and Lipase Activity in Biceps femoris and Semimembranosus of Xuanwei Ham During Controlled Salting Stages

Fatty acid composition of neutral lipids （NLs）, phospholipids （PLs） and free fatty acids （FFAs） from intramuscular fat （IMF）, lipid oxidation and lipase activity in muscle Semimembranosus （SM） and msucle Biceps femoris （BF） of dry-cured Xuanwei ham during the 90-d salting stages were analysed. The salt content increased from 0.34 to 3.52%in BF and from 0.10 to 5.42%in SM during the 90 d salting stage, respectively. PLs of IMF in both BF and SM decreased 54.70%（P〈0.001） and 34.64%（P〈0.05）, furthermore, the saturated fatty acids （SFA）, monounsaturated fatty acids （MUFA） and polyunsaturated fatty acids （PUFA） of PLs in both muscles were hydrolysed almost isochronously. FFAs were increased from 0.46 g 100 g-1 lipids to 2.92 g 100 g-1 lipids in BF at the end of salting, which was lower than SM （from 1.29 g 100 g-1 lipids to 9.70 g 100 g-1 lipids）. The activities of acid lipase, neutral lipase and acid phospholipase all remained active in the 90 d. The thiobarbituric acid reactive substances （TBARS） was slowly increased to 1.34 mg kg-1 muscle in BF and to 2.44 mg kg-1 muscle in SM during the salting stage. In conclusion, the controlled salting process prompted the hydrolysis of PLs of IMF notably and increased the lipid oxidation of muscles within some limits.