Sex reversal and growth performance in juvenile females of the freshwater crayfish <Emphasis Type="Italic">Cherax quadricarinatus</Emphasis> (Parastacidae): effect of increasing temperature and androgenic gland extract in the diet

Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature): control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month. The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment, the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic of cultured populations.     

Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?

It is well known that healthy gut microbiota is essential to promote host health and well‐being. The intestinal microbiota of endothermic animals as well as fish are classified as autochthonous or indigenous, when they are able to colonize the host's epithelial surface or are associated with the microvilli, or as allochthonous or transient (associated with digesta or are present in the lumen). Furthermore, the gut microbiota of aquatic animals is more fluidic than that of terrestrial vertebrates and is highly sensitive to dietary changes. In fish, it is demonstrated that [a] dietary form (live feeds or pelleted diets), [b] dietary lipid (lipid levels, lipid sources and polyunsaturated fatty acids), [c] protein sources (soybean meal, krill meal and other meal products), [d] functional glycomic ingredients (chitin and cellulose), [e] nutraceuticals (probiotics, prebiotics, synbiotics and immunostimulants), [f] antibiotics, [g] dietary iron and [h] chromic oxide affect the gut microbiota. Furthermore, some information is available on bacterial colonization of the gut enterocyte surface as a result of dietary manipulation which indicates that changes in indigenous microbial populations may have repercussion on secondary host–microbe interactions. The effect of dietary components on the gut microbiota is important to investigate, as the gastrointestinal tract has been suggested as one of the major routes of infection in fish. Possible interactions between dietary components and the protective microbiota colonizing the digestive tract are discussed.     

Natural bixin as a potential carotenoid for enhancing pigmentation and colour in goldfish (Carassius auratus)

Discovering natural carotenoids for colour enhancement and health benefits of fish is important to develop new feed formulations. We have purified natural bixin from achiote seeds and evaluated the effect of colour enhancing and pigmentation in goldfish. Varying levels of bixin‐based diets were prepared with 420 g kg^?1 of crude protein and 120 g kg^?1 of lipid content. Our results clearly showed that bixin (0.05, 0.10, 0.20 and 0.60 g kg^?1) based diets significantly (P < 0.05) enhanced the skin and fin colour at 30 and 60 days compared to diet without bixin. Interestingly, diet which contains 0.20 g kg^?1 bixin and commercial feed (with astaxanthin) had similar effect on carotenoid deposition in skin. Moreover, total carotenoid deposition in fin was higher than in skin of all bixin‐containing diets. However, 0.60 g kg^?1 bixin‐containing diet had lower specific growth rate (1.01 ± 0.01) and higher feed conversion ratio (2.05 ± 0.19) compared to the control group. The present results demonstrate that achiote bixin can be successfully used as an alternative natural carotenoid source against synthetic astaxanthin in fish feed. Our data indicate that 0.20 g kg^?1 is a suitable dietary level of bixin to ensure strong pigmentation, acceptable growth and feed utilization in goldfish.     

土霉素在黑鲷体内的药物代谢动力学研究

首次报道了黑鲷口服土霉素的药物代谢动力学特征，用高效液相色谱法测定组织中的药物含量，药物在肌肉，血液，肝脏中的平均回归率分别为８５.61%,85.38%,82.005,该方法的检测限可达0.01μg/g，黑鲷１次口服剂量为７５mg/kg的土壤素后，其血液药物浓度－时间数据符合一室开放动力学模型，吸收速率常数（ka)为０.296/h，达峰时间（Ｔamx)为１０.635h,峰浓度（Ｃmax)为１.398μg/ml, 分布半衰期（Ｔ１／２a）为２.339h ,消除半衰期(T1/20β）为46.663h，药时曲线下面积（ＡＵＣ）为１１0.25mg/L.h，黑绸口服药物０.5h后在血液，肥肉，肝脏，肾脏４种组织中就可以检测到药物的存在，药物在１６h的采样点浓度达最高，分别为1.68μg/ml,1.68,2.52,6.77μg/g。     

田间条件下水稻根系分布及其与土壤容重的关系

 采用大田和筒栽方法研究了超高产三系杂交稻协优9308和两系杂交稻两优培九在穗分化期和开花期根系生长和分布及土壤容重对根系分布的影响。结果表明，在田间条件下，土层15 cm内水稻根系占根系总量的89%～98%，深层根系丛间比丛中比例高。不早衰的协优9308根系生长量较两优培九大。土壤容重提高，根系总生长量下降，且深层根系的量和比例下降。就深耕法对水稻根系生长和分布的影响进行了讨论。     

Glu A1和 Glu D1位点高分子量谷蛋白亚基共同缺失对弱筋小麦品质的影响

为了研究高分子量谷蛋白亚基(HMWGS)缺失对小麦品质的影响,以 GluA1和 GluD1位点HMWGS共同缺失材料2GS041410作供体亲本,以弱筋小麦品种扬麦13和扬麦18作轮回亲本进行回交,构建不同遗传背景的BC¹F³和BC²F³群体,测定受体、供体亲本的品质,以及回交群体BC¹F³和BC²F³中 GluA1和 GluD1位点HMWGS共同缺失纯合单株及两位点均正常表达纯合单株的品质。结果表明,供体2GS041410具有较低的SDS沉降值、较短的面团形成时间和稳定时间;在BC¹F³和BC²F³中, GluA1和 GluD1位点HMWGS共同缺失对蛋白含量影响不显著,但可显著或极显著降低SDS沉降值和水溶剂保持力(SRC)。 GluA1和 GluD1位点HMWGS双缺失在弱筋小麦品质育种中具有一定的应用价值。     

Short-term effects of aglime on inorganic- and organic-derived CO2 emissions from two acid soils amended with an ammonium-based fertiliser

Purpose

Aglime application can promote carbon dioxide (CO₂) emissions from acid soils. However, the controlling mechanisms are still poorly understood, particularly the role of fertiliser-ammonium oxidation. This study therefore assessed the effects of aglime on soil inorganic C (SIC)– and soil organic C (SOC)–derived CO₂ emissions from acid soils amended with ammonium.

Materials and methods

Ammonium at three N rates [0% (A0), 0.005% (A1), and 0.2% (A2) w/w] and labelled aglime (Ca¹³CO_3,¹³C 5.94% aa) at three rates [0% (L1), 0.067% (L1), and 0.392% (L2) w/w] were applied to two contrasting acid soils (Nariva series, Mollic Fluvaquents; and Piarco series, Typic Kanhaplaquults) and incubated in 1-l media bottles for 23 days. A calcareous soil (Princes Town series, Aquentic Eutrudepts, carbonate δ¹³C of ??4.79‰) was included as a control that only received ammonium at the three rates.

Results and discussion

The application of ammonium at the A2 rate significantly (p?<?0.05) increased cumulative SIC-CO₂ emissions by 15.8 and 27.1% in comparison to the A0 rate for the Nariva and Piarco soils, respectively, when they were limed at the L2 rate. The lower rate of ammonium (A1), however, had no effect on these emissions, which suggests that enough acidity may not have been generated at this rate to significantly enhance the release of SIC-CO₂. Furthermore, no effect of ammonium rates was observed on SIC-CO₂ emissions from the calcareous soil, which refutes the hypothesis that this amendment plays a greater role in regulating these emissions from calcareous soils compared with acid soils. Also, in contradiction to another hypothesis, the aglime-induced priming effect on SOC decomposition was more apparent in the low-C Piarco soil. This effect was also significantly (p?<?0.05) greater at the L2 rate (above the lime requirement for Piarco), which demonstrates the negative impact that over-liming could have on the sequestration of C in this soil. Our results also showed that ammonium addition may also help to reduce the magnitude of the aglime-induced priming effect in the Piarco soil when it is not over-limed.

Conclusions

Overall, the findings of this study suggest that ammonium fertiliser broadcast at conventional rates may not serve as a significant regulator of SIC-CO₂ emissions from highly to moderately acidic soils amended with aglime. Our findings also indicate a need to consider nitrogen management as an important factor regulating the effects of aglime on SOC-CO₂ emissions.

     

Terrestrial-marine continuum of sedimentary natural organic matter in a mid-latitude estuarine system

Journal of Soils and Sediments - Humic acids (HA) have several environmental roles, but are particularly important in aquatic environments, being recognized as redox active natural organic matter...     

The chemistry of humic and fulvic acids extracted from argentine soils—I. Analytical characteristics

Five humic and three fulvic acids were extracted from Argentine Chestnut, Brunizem, Solod and Solonetz soils and analysed by electrometric, spectroscopic and spectrometric methods. There were great similarities in elementary analysis, functional group content, absorption characteristics in the visible region and in the IR, and in the ESR measurements between the humic acids and, similarly, between the fulvic acids. There were distinct differences between the humic and fulvic acids in C, H, N and O content, distribution of oxygen in functional groups, E₄/E₆ ratios and free radical content.     

Major mechanisms in formation of spodic horizons

Current explanations of the formation of spodic horizons do not accomodate all features of the horizons in their natural state. In this paper, a more complete explanation of major mechanisms is proposed, using two principles of colloid chemistry: (1) organic substances may form hydrophylic colloids with surface charges, and (2) the hydrophylic character and negative surface charges determine the dispersibility of the colloids. The hydrophylic character is due to the presence of hydrophylic radicals as parts of the organic compounds in soils. The surface charges are the result of dissociation of -COOH and possibly phenol-OH radicals.The neutralization of the surface charge can in principle occur: (1) through electrostatic or physical adsorption and (2) through chemisorption. The first case is typical for monovalent alkali cations. The adsorbed cations are distributed in a double layer, which favours dispersion. Chemisorption occurs mostly with polyvalent cations. This process corresponds in reality to the formation of organo-metallic compounds. It results in a relatively complete disappearance of the double layer and in the formation of large immobile “polymerized” organo-metallic compounds. Because these compounds contain much hydrophylic water, they form a gel. Transition into the solid state is accompanied by the loss of most of the hydration water. The dehydration may be induced by a decrease in thickness of the double layer. At a certain stage of the dehydration process, Van der Waals bonds and protonic bridges can form and bring about a certain degree of hydrophoby.In soils, mobile organic substances are formed during breakdown of plant remains. If at the top of the mineral soil enough polyvalent cations, especially Al and Fe, are available, the mobile organic substances formed are immobilized immediately and no migration occurs. In case insufficient amounts of Al and/or Fe are available to completely immobilize the mobile compounds, these cations are complexed by the mobile compounds and transported downward. Immobilization may occur at some depth through supplementary fixation of cations, through dessication or on arrival at a level with different ionic concentration.In nature, spodic horizons range from loose, with many roots, to very cemented with few roots. These differences can be related to changes in microstructure. Loose spodic horizons have a predominance of polymorphic pellets and aggregates, whereas organans or monomorphic coatings prevail in cemented horizons. The former horizons have many features suggesting major biological influences during their formation, viz., high numbers of roots, thorough mixing of the organic units with clay and silt, the presence of pedotubules and relatively young mean residence times. The latter horizons have features consistent with organo-metallic compounds immobilized in a gel-state, viz., the coatings are strongly cracked, indicating the transition of a gel into a solid; they contain much Al or Al plus Fe but very little or no Si, and the mean residence time is considerably higher than in loose horizons.The two processes seem to operate simultaneously during the formation of spodic horizons and their relative intensities determine the composition of each spodic horizon at any moment in its evolution. As long as the biological activity predominates, the horizon remains loose; if the accumulation of mobile organo-metallic compounds starts to prevail, the horizon is gradually cemented and fossilized.