Evidence of cormorant‐induced mortality,disparate migration strategies and repeatable circadian rhythm in the endangered North Sea houting (Coregonus oxyrinchus): A telemetry study mapping the postspawning migration

Life history theory predicts a trade‐off between migration and residency where migration is favoured when it infers elevated fitness. Although migration to more favourable environments may offer higher growth rates, migrants often experience increased mortality due to predation. Here, we investigated mortality and migration behaviour of the North Sea houting (Coregonus oxyrinchus), an anadromous salmonid endemic to the Wadden Sea. We used acoustic telemetry to map the migration of the only remaining indigenous population by applying stationary hydrophones combined with manual tracking. Data suggested a total mortality of 26%, with 30% of the total mortality attributed to predation by great cormorants (Phalacrocorax carbo sinensis), highlighting that North Sea houting conservation could be jeopardised by increased cormorant predation. Risk of cormorant predation was size‐dependent, with smaller fish suffering higher risk of predation. The study found North Sea houting to exhibit disparate migration strategies and identified a lentic area in the estuary as an important habitat. Two newly established artificial lakes within the river system significantly reduced the migration speeds, possibly indicating constrained navigation through the lakes. The migration into the Wadden Sea correlated with temperature perhaps indicating osmoregulatory constraints of sea entry. Unlike many salmonid species, migration occurred both day and night. Moreover, fish exhibited repeatable individual differences in diel activity patterns, suggesting that individuals differ consistently in their migratory activity throughout the 24‐hr period. Our study provides novel information on salmonid migration, which is crucial for the development of science‐based conservation strategies.     

Movement behaviour of large female yellow European eel (Anguilla anguilla L.) in a freshwater polder area

Due to a recruitment decline of more than 90% in 30 years, the European eel (Anguilla anguilla L.) has been classified by IUCN as critically endangered. Although the species has been studied intensively to obtain knowledge to improve management, studies about the resident yellow stage are relatively scarce. In this study, 52 large female yellow eels were tagged with acoustic transmitters in a Belgian polder system and tracked by a network of 23 automatic listening stations. We studied both circadian and seasonal movement patterns and the effect of environmental variables on these patterns. Large female yellow eels were most active at night in late summer and early autumn. A generalised linear mixed model showed that their movement is only slightly influenced by environmental variables. Moreover, as yellow eels show high site fidelity (i.e., the majority was detected only in the habitat type of their catch‐release location), they do not encounter many human‐induced connectivity problems in polder systems, which makes these systems highly suitable as eel growth habitat. These results can contribute to an effective eel management regarding habitat protection and restoration.     

基于“流水线”的茄果类种苗半自动嫁接机研究

阐述了国内外茄果类种苗半自动嫁接机存在的作业生产率过低的问题,针对国内种苗嫁接环境,以茄果类种苗为作业对象,提出了基于"流水线"的半自动嫁接作业模式,选取适合机械化操作的贴接嫁接法,分析了生产节拍、作业工序与作业生产率的关系,最终将夹持、切削、拢苗、对接、上夹和下苗6个工序合理分配至4个工位。进行了整机嫁接作业试验,结果表明基于"流水线"的嫁接生产模式可实现1000株/h的嫁接生产率,有效提高了作业效率。     

定苗时间对峦大杉1年生苗木生长的影响

探究定苗时间对峦大杉苗期生长动态与生长节律影响,优化定苗时间,为育苗提供理论与技术支持。以当年生峦大杉幼苗为试验材料,开展不同定苗时间试验,采用定株观测并应用Logistic方程拟合生长动态的方法,分析定苗时间对苗木生长动态和生长节律的影响效应。研究结果表明,定苗时间影响苗高地径生长效应随处理时间推移而显现,是个动态过程。Logistic方程能够很好地拟合峦大杉苗木生长。定苗时间显著影响苗高、地径线性生长速率、最大线性生长速率和线性生长量,但对苗高地径线性生长始期、终期、线性生长持续期无显著性影响;苗高生长初期定苗较其他处理显著提高苗高和地径的线性生长量线性生长速率、最大线性生长速率,建议增加速生期的养分和水分供给以提高苗木质量。峦大杉合理定苗时间是苗高生长初期（6月30日）。     

低频声波频率下瘤背石磺CaM-like、CaMKII基因的表达及功能

长期栖息于潮间带的动物能够感知当地的潮汐规律,形成潮汐记忆的能力。本研究以栖息于潮间带的瘤背石磺(Onchidium reevesii)为对象,研究其通过感知潮汐来临时产生的低频声音来调节其行为与潮汐节律相协调的分子机制。通过RACE-PCR技术克隆到CaM-like基因的cDNA序列,并进行生物信息学分析和qRT-PCR实验。结果显示,瘤背石磺CaM-like基因的cDNA全长2321 bp,包括5′非编码区(UTR)366 bp,3′非编码区(UTR)1337 bp,618 bp的开放阅读框编码206个氨基酸;预测该基因编码的多肽链的原子数量是3165,分子量约为23029.64 kD,理论等电点4.64,分子式是C_(1018)H_(1544)N_(274)O_(320)S_9。N端信号肽由29个氨基酸组成。氨基酸序列比对构建系统进化树,结果显示瘤背石磺CaM-like基因与静水椎实螺(Lymnaea stagnalis)、光滑双脐螺(Biomphalaria glabrata)的CaM-like基因的亲缘关系最接近,这与传统形态学分类相吻合。在实验室内模拟潮汐中低频声音刺激瘤背石磺,应用qRT-PCR检测CaM-like基因在不同组织的分布情况,结果显示CaM-like mRNA在瘤背石磺不同组织均有表达,但神经节部位的表达量显著高于背部皮肤、腹足、肠、肝胰腺、口器和蛋白腺等组织(P0.05),推测其可能参与神经系统的可塑性调节。荧光定量结果显示CaM-like、CaMKII基因分别在25 Hz和50 Hz低频声波下刺激12.4 h表达量较高,初步推测其能感知25～50 Hz声波频率。这可能与栖息于潮间带中的瘤背石磺长期感知12.4 h半日潮潮汐周期节律,形成潮汐记忆有关。本研究将为进一步深入了解瘤背石磺感知潮汐节律的分子机制奠定基础,也为探究海洋动物由海洋向陆地进化过程中对环境的适应机制提供依据。     

虫害诱导家榆挥发物的日释放节律分析

以家榆为试验对象,分析挥发物的组分与日释放节律,结果表明:家榆的挥发物共有24种化合物,包含有醇类、烷类、酯类和萜烯类等。挥发物的释放存在昼高夜低的现象,在上午时释放量会迅速增加,到中午达到最大,然后在下午、晚上逐渐减少;在由明转暗时,挥发物的释放有一个短暂的爆发。挥发物的日夜释放节律与害虫天敌的活动规律相符,可能是植物发挥主动防御的结果。     

Coexisting invasive gobies reveal no evidence for temporal and trophic niche differentiation in the sublittoral habitat of Lake Erhai,China

Niche differentiation facilitates the coexistence of species within a community through avoidance of competition via mechanisms involving spatial, temporal and/or trophic dimensions. Where invasive species coexist in their non‐native range, niche differentiation could allow their persistence at higher levels of abundance. Here, we tested whether there was temporal and/or trophic niche differentiation between two congeneric invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) in the sublittoral habitat of Lake Erhai (south‐west China) through quantifying their diel and seasonal rhythm of locomotion activities, feeding activities and diet composition. Both species displayed two similar diel peaks in activity and two main feeding periods (6:00–10:00 and 18:00–22:00), with rhythms of locomotion and feeding activity not differing significantly between the species in each season. Their diets had a high degree of overlap, being primarily composed of macrozooplankton, aquatic insects and shrimp larvae, with no diel changes across the seasons. Thus, in this habitat, there was no clear temporal or trophic niche differentiation between the invasive congeners, indicating their coexistence with high temporal and trophic overlap. In conjunction with data from the littoral and profundal habitats, the gobies revealed different strategies across the habitats (e.g. spatial segregation, trophic niche differentiation) that minimised their competitive interactions and promoted their coexistence. This suggests that the interactions of invasive fishes during the integration into native communities can be context dependent, varying according to factors including habitat and the availability of food resources.     

广藿香中PTS基因不同时间点的表达分析

利用荧光定量PCR技术,分析1天中8个时间点广藿香叶片百秋李醇合成酶基因的表达情况。结果表明,6∶00,9∶00,12∶00和15∶00时间点的PTS基因表达量较低,0∶00,3∶00,18∶00和21∶00的表达量均显著高于前4个时间点,其中,时间点3∶00的表达量最高,表明PTS基因的转录从夜间开始积累,黎明前达到最高峰,之后转录水平逐渐下降。     

天然更新伯乐树的生长过程初步分析

解析1株天然林中148年生伯乐树倒木树干，表明其树高连年生长量在65年生时达到最大值，和树高年平均生长量曲线相交于80年生时；胸径连年生长量在70年生时达到最大值，与胸径年平均生长量相交于95-100年生时；而材积连年生长量的最大值出现在80年生时，与材积年平均生长量于135-140年间相交，此时可以认为是伯乐树的材积数量成熟年龄。     

北京地区泌乳牛夏季鼓膜温度昼夜节律及影响因素研究

【目的】 试验旨在揭示北京地区荷斯坦泌乳牛鼓膜温度的群体特征及其随昼夜和环境温湿度指数（temperature-humidity index,THI）的变化规律,探究中度热应激下泌乳牛鼓膜温度的影响因素及其与直肠温度的关系。【方法】 2021年8月对北京地区某规模化牧场638头荷斯坦泌乳牛的鼓膜温度、直肠温度及环境温湿度进行测定,并对其进行描述性统计;对161头荷斯坦泌乳牛6 h鼓膜温度和直肠温度进行相关性分析;利用混合线性模型分析THI、测定时间、胎次、泌乳阶段和繁殖状态等因素对鼓膜温度和直肠温度的影响。【结果】 北京地区荷斯坦泌乳牛夏季鼓膜平均温度为（39.01±0.40）℃;测定时间内THI为76.11~83.18,此时泌乳牛处于中度热应激。泌乳牛鼓膜温度昼夜变化较大,昼夜节律表现为上午低、下午和傍晚均较高且在早晨和下午出现不正常峰值,鼓膜温度的变化滞后于THI变化。鼓膜温度与直肠温度呈显著正相关关系（P<0.05,r＝0.35）,且两种体温均随着THI的升高而升高,回归系数分别为0.09（P<0.05,R²=0.09）和0.10（P<0.05,R²=0.08）。测定时间和胎次对泌乳牛鼓膜温度有显著影响（P<0.05）,胎次和泌乳阶段对泌乳牛直肠温度有显著影响（P<0.05）,且THI对两部位温度的回归均显著（P<0.05）。【结论】 本研究揭示了奶牛体温的节律变化和影响因素,鼓膜温度可有效反映奶牛实时体温,可为精细化管理牛群提供理论依据。