Determining thresholds of low soil temperature for ecophysiological traits of black spruce and jack pine seedlings

Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysiological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce (Picea mariana) and jack pine (Pinus banksiana) seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35°C soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE) and specific l...     

Variables affecting Suillus luteus fructification in ponderosa pine plantations of Patagonia (Argentina)

Suillus luteus is the most abundant wild edible mushroom harvested in Patagonian pine plantations from Argentina. Their fruitbodies are unevenly distributed in plantations but no studies have been carried out to investigate and quantify the macro- and micro-level environmental factors affecting their fructification in productive patches. The objective of this study was to determine the biotic and abiotic micro-environmental factors affecting the productivity of S. luteus fructification. The study was conducted in an even-aged (17–18 years) Pinus ponderosa plantation with sandy loam soil, very common in the region. Twelve plots with fructifications and 12 with no fructification were randomly selected to make comparative measurements. Crown cover (CROWN), percentage of herbaceous + small-shrubs cover (HERB) and species composition, percentage of duff cover (DUFFC), percentage of bare soil (BARE), decomposed + non-decomposed duff depth (TDUFFD), soil water content (SOILH), soil texture, pH in water, pH in NaF, organic matter percentage (OM), total nitrogen percentage, available phosphorus content, S–SO₄²⁻ content, and exchangeable cations including Ca, Mg, K and Na were determined. Multiple logistic regression was used to select variables that explain presence or absence of fructifications, and a principal component analysis to further analyze the relationship between herbaceous species cover and fructification. The occurrence of fructifications was associated with a group of highly correlated variables (high HERB, OM and SOILH and low CROWN, DUFFC and TDUFFD), all determined by the irregular tree spatial pattern in plantation that impacts the quantity of light and water reaching the soil. Those variables related with chemical and physical soil properties, with the exception of OM and SOILH, explained little variation in the data set. The principal component analysis showed that plots with fructification presented higher Acaena ovalifolia and Stipa sp. cover, and that plots without fructification presented higher CROWN and TDUFFD. Pruning and thinning prior to complete canopy closure would maintain light and water reaching the soil and preventing duff accumulation by stimulating decomposition. If ponderosa plantations are managed for high production of S. luteus fructification, silvicultural treatments that include thinning should be implemented earlier.     

Effects of synthetic kisspeptin peptides and GnRH analogue on oocyte growth and circulating sex steroids in prepubertal female chub mackerel (Scomber japonicus)

In recent years, kisspeptin peptides, encoded by kiss genes have been used to manipulate reproductive processes in farmed animals, including fish. Our previous studies demonstrated that the chub mackerel brain expresses kiss1 and kiss2 and intramuscular injection of synthetic Kiss1 pentadecapeptide (Kiss1‐15) but not Kiss2 dodecapeptide (Kiss2‐12) accelerates spermatogenesis in prepubertal male chub mackerel (Scomber japonicus). In the present study, we evaluated their effects in prepubertal female chub mackerel. The gonadosomatic index (GSI) values of experimental fish did not show any significant changes. Condition factor (CF) values increased significantly in Kiss1‐15 treated fish, in comparison with control and GnRH analogue (GnRHa) injected fish. Histologically, only perinucleolar oocytes were found in all experimental fish. However, Kiss and GnRHa treated fish showed a significant increase in the perinucleolar oocyte diameter, in comparison with the control fish. Gene expression analyses revealed decreased expression of gnrh1 in the telencephalon‐preoptic region of the brain of Kiss2‐12 and GnRHa injected fish, in comparison with control fish. In contrast, GnRHa injected fish exhibited higher levels of fshβ in the pituitary, with no changes in the levels of lhβ among different treatments. Levels of circulating sex steroids, testosterone, and estradiol‐17β were significantly higher in Kiss1‐15 injected fish, in comparison with control fish. These results indicate that synthetic kisspeptin peptides and GnRHa can induce oocyte growth in prepubertal female chub mackerel.     

马鲛鱼冷链流通过程中感官和鲜度变化的相关性分析

为研究4℃冷链马鲛鱼在流通和贮藏中感官与鲜度指标及各指标相关性随时间变化的情况,本试验采用理化指标(包括挥发性盐基氮、pH值、硫代巴比妥酸值、组胺的含量变化)、微生物指标(菌落总数)和感官评价相结合的综合评价方法对马鲛鱼冷链流通过程的品质进行分析,并进一步探讨马鲛鱼冷链贮藏期间感官和品质变化的相关性。结果表明,随着流通、贮藏时间的延长,冷链马鲛鱼各鲜度指标相关的各物质含量均呈递增趋势,感官品质下降,菌落总数增加,其货架期约168 h。此外,除硫代巴比妥酸值(TBA)外,其余鲜度指标和微生物指标以及感官评价之间具有显著相关性(P<0.05)。本研究为马鲛鱼冷链条件的优化及选取合适的新鲜度评价指标提供了一定的参考依据和理论基础。     

数据不确定性对西北太平洋两种混栖鲐生长研究的影响

依据2020-2023年“淞航”号渔业资源科研调查与生产船围网的鲐调查数据,着重分析了种类鉴定不确定性和不同数据来源（是否基于渔业生产获取的数据）对日本鲐（Scomber japonicus）和澳洲鲐（S. australasicus）生长特征的影响。研究发现,生产船样本肥满度略小于“淞航”号,且“淞航”号样本体质量增长更快,摄食情况相对较好。叉长-体质量关系的拟合结果表明,相同叉长下,澳洲鲐体质量小于日本鲐;不同数据来源与不同物种所求a值范围为1.886×10-6-6.721×10-5,b值多数大于3。a值变化较大,说明西北太平洋2021-2023年际水域环境变化较大;除2020年生产船日本鲐b值较小（b=2.66）,为负异速增长外,其余均为正异速增长。依据混合效应模型对样本的叉长-体质量关系进行异质性分析,结果表明数据来源与年份对日本鲐与澳洲鲐生长研究结果的影响更显著,物种间差异不显著。因此根据本文的结论,在基于生长等生活史特征的相关鱼种资源评估和管理的过程中,建议充分考虑时间差异和不同数据来源导致的不确定性,而不是采用恒定的、缺乏时间变化和数据来源考虑的生活史参数;此外鉴于实际操作的可行性和成本,暂时可不区分日本鲐和澳洲鲐,但仍然建议在科学研究过程中进一步探讨可能的影响。     

东、黄海日本鲭种群鉴定和划分的研究进展

分布于东、黄海的日本鲭(Scomber japoncus)在我国海洋渔业中具有重要的地位,随着中韩、中日渔业协定的生效,开展日本鲭等重要经济鱼类的种群归属研究显得尤为重要。关于东、黄海日本鲭种群划分,20世纪中日两国学者利用标志放流和渔业调查数据分别进行了研判,但中日间以及国内对其种群划分存在不同见解。21世纪以来,中国一些研究者利用形态框架法和分子遗传学方法对前辈的种群划分进行了验证并提供了一些证据,但分析结果值得商榷。总结相关研究结果,多数中国学者将分布于东、黄海的日本鲭划分为东海西部种群、五岛西部种群和闽南—粤东地方种群,也有中国学者将其划分为东海群系和闽南—粤东地方种群;日本学者将分布于东海不同越冬场日本鲭归属为对马暖流群系,也有日本学者将分布于东、黄海和日本海西部的日本鲭划分为九州西部群系和东海西部群系。针对东、黄海日本鲭种群划分存在的不同观点,今后研究者应同时利用目前较为先进的、相对可操作的鱼类框架形态和分子遗传等判别技术,增加产卵场样本采集覆盖面,以获得判别东、黄海日本鲭种群相对最为科学的证据。     

Comparison of horse mackerel and tilapia surimi gel based on rheological and <Superscript>1</Superscript>H NMR relaxation properties

ABSTRACT:   Horse mackerel and tilapia surimi were subjected to six different heat and pressure treatments in order to compare gelation characteristics of easy- and difficult-setting gels, that is, temperature dependence, by observing rheological properties and microscopic molecular mobility. The stress–relaxation and proton spin–spin relaxation time (¹H T ₂) of water were measured for all treated gels. Horse mackerel gel demonstrated higher elasticity, large distribution of the stress–relaxation process, and smaller water ¹H T ₂ than tilapia in both heat and pressure treatments. The water ¹H T ₂ was steeply increased in the pressure treatment at around 294 MPa for both fishes. In contrast, the ¹H T ₂ rarely changed in the heat treatment in spite of the considerable change in rheological properties. From the experimental results, it is considered that the gelation of horse mackerel (easy setting) surimi is induced by highly unfolding and re-aggregation of protein, which contributes to the formation of a strong network structure compared with tilapia in both heat and pressure treatments, and that pressure treatments hardly improve the gel strength of tilapia (difficult setting) surimi. The water ¹H T ₂ measurement was used effectively in order to study gelation characteristics of easy- and difficult-setting fish through observing its molecular dynamics.     

Comparison of Proximate Composition and Fatty Acid Profile of On-Growing and Wild Mediterranean Horse Mackerel (Trachurus mediterraneus)

ABSTRACT

On-growing of horse mackerel is not known in the world. Recently, we have initiated on-growing of the Mediterranean horse mackerel in the Black Sea. Therefore, we aim to compare proximate composition and fatty acid profile of on-growing and wild horse mackerels to evaluate the effect on their nutritional value. Captured horse mackerels less than 13 cm were kept on-growing in sea cages and fed sea bass feed for a year in the southern Turkish Black Sea. Results showed seasonal variations in the proximate contents and fatty acid profile of both on-growing and wild fish groups (p < 0.05). Protein contents of the wild horse mackerel group were significantly higher than the on-growing mackerel group, while the opposite situation was observed for lipid contents (p < 0.05). Despite higher eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels (as fatty acid methyl esters %) of wild horse mackerel in comparison with on-growing group, much higher EPA + DHA contents were accounted for in on-growing fish in the edible portion resulting from higher lipid contents of these samples. The results suggest that lower amounts of fish meat, 50–90 g, from on-growing mackerel would cover the daily suggested value of EPA + DHA; this level is calculated as 51–150 g for wild fish meat.     

鲐鱼鱼精中5′-脱氧核苷酸的分离工艺

论述了用桔青霉PenicilliumcitrinumM71菌株 ,经液体培养制得的 5′ -磷酸二酯酶降解鲐鱼鱼精DNA成5′ -脱氧核苷酸的分离工艺。分离采用 2 0 1× 8阴离子交换树脂 ,具体条件为 :柱床高 1 0 5mm ,柱床直径 45mm ,样品浓度 2 1 3mg·mL-1,洗脱流速 0 .5mL·cm-2 ·min-1。分离结果表明 ,采用 0 .0 0 5MHCl 0 .0 4MNaCl作洗脱剂 ,流速为 0 .7mL·cm-2 ·min-1时 ,四种 5’ -脱氧核苷酸组分能完全被洗脱下来 ,且呈一个大峰 ,同其它成分分开 ,再先后采用 0 .0 0 1 8MHCl、0 .0 0 2 8MHCl、0 .0 36MNaCl(pH6 .0 )、0 .0 0 5MHCl 0 .0 2MNaCl作洗脱剂时 ,则能分别将dCMP、dAMP、TMP、dGMP完全分离