半滑舌鳎早期形态及发育特征

半滑舌鳎卵子为分离的球形浮性卵 ,卵径 1 18-1 3 1mm。卵膜薄、光滑、透明 ,具弹性。多油球 ,一般为 97-12 5个 ,多数在 10 0个左右 ,油球径 0 0 4-0 11mm。在培养水温为 2 0 5-2 2 8℃的条件下 ,卵子授精后 3 7h仔鱼孵出 ,3 0min后仔鱼全部孵出。初孵仔鱼全长 2 56-2 68mm。 1日龄仔鱼 ,出现胸鳍芽。 1 5日龄仔鱼 ,巡游模式基本建立。 2日龄仔鱼 ,逐渐建立外源性摄食关系。 3日龄仔鱼 ,出现鳔泡 ,个体发育进入后期仔鱼期。 18日龄 ,个体发育进入稚鱼期。 2 5日龄稚鱼 ,右眼开始向上移动。 2 7日龄稚鱼 ,右眼已转到头顶。 2 9日龄稚鱼 ,右眼完全转到左侧 ,胸鳍退化 ,各鳍鳍条发育完全。 57日龄 ,个体发育进入幼鱼期。 79日龄幼鱼 ,鳔退化、鳞片发育完全 ,侧线 3条。研究结果表明 :前期仔鱼培育期间 ,除了严格控制适宜的培养水温外 ,仔鱼开口后就应及时投喂一定密度的适口饵料 ,这是苗种培育中不可忽视的重要环节和技术措施之一 ;稚鱼变态期间加强鲜活饵料的投喂是提高稚鱼变态成活率的关键所在。仔鱼孵化后出现的管状感觉器官以及背、臀鳍膜上的泡状结构在早期发育阶段的生态和生理作用尚不清楚。半滑舌鳎成鱼无鳔和无胸鳍 ,而在早期发育期间具有鳔泡和胸鳍 ,这是生物个体发育史中祖先特征的重演     

中国对虾（Penaeus chinensis）4个种群的同工酶遗传变异

采用水平淀粉凝胶电泳技术分析了中国对虾（Penaeuschinensis）黄渤海沿岸种群（YP）、朝鲜半岛西海岸种群（KP）和2个养殖种群（CP1和CP2）的同工酶遗传变异水平。每个种群随机选取50尾中国对虾进行同工酶检测。在所分析的12种同工酶编码的20个基因位点中,有4个是多态位点。4个种群的多态位点比例（P0.99）分别为15%、20%、10%和20%。种群平均杂合度（观测值）（Ho）分别为0.014±0.007、0.020±0.010、0.010±0.007和0.033±0.017。4个种群的位点有效等位基因数（Ne）分别为1.015±0.008、1.023±0.011、1.011±0.007和1.042±0.022。杂合子平衡偏离指数（D）分别为+0.037、-0.030、-0.098和-0.030。2个地理种群（YP和KP）的遗传相似性系数（I）和遗传距离（D     

长江三峡地区上震旦统稳定同位素异常及地层意义

三峡地区广泛发育的上震旦统,及下伏的南沱组和古城组冰碛层,有良好的生物地层控制及全球对比意义。新秭归城附近的雾河剖面,自南沱组顶部到水井沱组下部出露有利于化学地层学研究的一系列碳酸盐岩沉积,对这一剖面的碳,氧,锶同位素研究发现：1）碳,锶和氧同位素在陡山沱组顶部到灯影组底部存在明显异常;2）碳同位素在寒武系-前寒武系界线附近有负异常;3）碳同位素和锶同位素在剖面上的演化具有全球对比意义;4）陡山沱组顶部到灯影组底部的碳,锶同位素异常,与可能存在末远古纪的冰期,即所谓的“后Marinoan冰期”有关。     

Shifts in bacterial community composition associated with increased carbon cycling in a mosaic of phytoplankton blooms

Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify preferences in the degradation of DOM of different reactivity for taxa associated with contrasting blooms. We used the spatial and temporal variability provided by this natural laboratory to demonstrate that the magnitude of bacterial production is linked to the extent of compositional changes. Our results suggest that partitioning of the DOM resource could be a mechanism that structures bacterial communities with a positive feedback on carbon cycling. Our study, focused on bacterial carbon processing, highlights the potential role of diversity as a driving force for the cycling of biogeochemical elements.     

Identification of differential genes in the ovary relative to the testis and their expression patterns in half-smooth tongue sole (Cynoglossus semilaevis)

Half-smooth tongue sole (Cynoglossus semilaevis) is a rare marine flatfish whose mature ovary and testis greatly differ in volume and weight. The length and weight of mature females are over twice greater than those of mature males. To obtain sufficient information on gonad differentiation and the relationship between gonad development and growth in the fish, we compared gene expression between the ovary and testis using suppression subtractive hybridization (SSH). Testis cDNAs are subtracted from...     

Maturation and persistence of the anti-SARS-CoV-2 memory B cell response

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Monophyly of Anthozoa (Cnidaria): why do nuclear and mitochondrial phylogenies disagree?

The phylum Cnidaria is usually divided into five classes: Anthozoa, Cubozoa, Hydrozoa, Scyphozoa and Staurozoa. The class Anthozoa is subdivided into two subclasses: Hexacorallia and Octocorallia. Morphological and molecular studies based on nuclear rDNA and recent phylogenomic studies support the monophyly of Anthozoa. On the other hand, molecular studies based on mitochondrial markers, including two recent studies based on mitogenomic data, supported the paraphyly of Anthozoa, and positioned Octocorallia as sister group to Medusozoa (the monophyletic group of Cubozoa, Hydrozoa and Scyphozoa). On the basis of 51 nuclear orthologs from four hexacorallians, four octocorallians, two hydrozoans and one scyphozoan (with poriferans and Homo sapiens as out‐groups), we built a multilocus alignment of 9 873 amino acids, which aimed at minimizing missing data and hidden paralogy, in order to understand the discrepancy between nuclear and mitochondrial phylogenies. Our phylogenetic analyses strongly supported the monophyly of Anthozoa. We compared the level of substitution saturation between our data set, the data sets of two recent phylogenomic studies and one of a mitogenomic study. We found that mitochondrial DNA is more saturated than nuclear DNA at all the phylogenetic levels studied. Our results emphasize the need for a good evaluation of phylogenetic signal.