Genomic organization of selected genes in the small monogonont rotifer, Brachionus koreanus

Information of genome structure with its size variation may provide important clues for evolutionary processes at lower taxon level in eukaryotes. Here, we analyzed the compact genome structure of the monogonont rotifer, Brachionus koreanus in the light of transphyletic genome comparison and economic genome usage. To confirm the genome compactness of B. koreanus, we compared the genomic structure of several selected genes with those of human and pufferfish. For example, one of the large genes, DNA-dependent protein kinase (DNA-PK) with dimeric protein Ku70 and Ku80, showed high similarity, even though genomic DNA lengths were quite different. The replication protein As (RPAs) as a heterotrimeric protein also showed a compact genomic structure including all the essential domains and motifs in B. koreanus. Regarding transmembrane protein-containing genes, the B. koreanus P-glycoprotein (P-gp) showed exactly the same topology of the TM domain compared to those of human and pufferfish, even though it had a compact genome structure. In addition, the gene structure of an inducible repair enzyme O(6)-methylguanine DNA methyltransferase (O(6)-MGMT) of B. koreanus showed the highest compactness among the genes tested. The objective of this report is to evaluate the potential for whole genome sequencing and functional genomic research using the monogonont rotifer B. koreanus as a non-model organism that plays important roles in aquatic food-webs. Subsequently, we discussed possible reasons for compact genome structures as well as small and fewer introns from several perspectives. We conclude that the small size genome of B. koreanus would make this species potentially useful for comparative genome structure analysis of non-model species through whole genome sequencing and genetic mapping.     

不同藻密度下Cd2+浓度对萼花臂尾轮虫生命表统计学参数的影响

为了比较不同食物密度下污染物浓度对受试生物的慢性毒性,筛选出以轮虫为受试生物对水环境中Cd污染进行监测的敏感指标,研究了在不同斜生栅藻密度(1.0×10⁶、3.0×10⁶和5.0 ×10⁶ cells·ml^-1)下不同浓度(2.5、5.0、10.0、20.0和40.0 μg·L^-1)Cd²⁺对萼花臂尾轮虫生命表统计学参数的影响.结果表明：(25±1) ℃下Cd²⁺对轮虫的24 h LC₅₀为37.7 μg·L^-1.与各藻密度下的对照组相比,当藻密度为1.0×10⁶ cells·ml^-1时,20.0和40.0 μg·L^-1的Cd²⁺显著延长了轮虫的世代时间,5.0 μg·L^-1的Cd²⁺显著提高了轮虫的后代混交率;当藻密度为3.0×10⁶ cells·ml^-1时,除了5.0 μg·L^-1外,其他浓度的Cd²⁺显著降低了轮虫的后代混交率;而当藻密度为5.0×10⁶ cells·ml^-1时,Cd²⁺浓度对轮虫的所有生命表统计学参数均无显著影（P>0.05）.藻密度对轮虫的世代时间、生命期望、净生殖率和后代混交率均有显著影响（P<0.05）,Cd²⁺浓度对轮虫的世代时间和后代混交率有显著影响（P<0.05）,两者交互作用对后代混交率有极显著影响（P<0.01）.轮虫的世代时间和后代混交率是在1.0×10.6和3.0×10.6 cells·ml^-1食物密度下对Cd²⁺污染比较敏感的参数,其中后代混交率最敏感.     

不同温度下新安江水域(屯溪段)轮虫种群动态研究

温度是决定轮虫生活史特征的重要的生态因子之一.应用生命表统计学方法对采自黄山市新安江水域屯溪段的萼花臂尾轮虫在四种不同温度(15℃、20℃、25℃和30℃)下的生命表统计学特征进行了比较研究.结果表明,萼花臂尾轮虫的存活率和繁殖率在不同温度下存在着差异.四种培养温度下,世代时间在15℃时最长,25℃和30℃时最短且无显著差异;内禀增长率在较低温度下(15℃、20℃)较小,在较高的温度下(25℃、30℃)较大;生命期望和平均寿命均在15℃时最长,其余三个温度下无显著差异.温度对萼花臂尾轮虫的净生殖率和后代的混交雌体百分率无显著影响.     

基于rDNA ITS序列分析莲塘湖萼花臂尾轮虫种群遗传结构的季节变化

对采自芜湖市莲塘湖水体中的萼花臂尾轮虫(Brachionus calyciflorus)夏季种群中的30个克隆(S1-S30)和秋季种群中的20个克隆(A1-A20)的rDNA ITS序列进行了分析;以十指臂尾轮虫B.patulus为外群,构建了50个克隆的NJ、MP和ME系统发生树。结果表明:三个系统树均支持将50个克隆分为两个支系;第一支系包括29个夏季采集的单元型(单元型S9除外)和1个秋季采集的单元型A2,第二个支系包括18个秋季采集的单元型(单元型A2除外)和1个夏季采集的单元型S9;两支系间ITS序列差异为5.1%-8.8%;它们应属于两个不同的姐妹种。夏季,莲塘湖水体中的萼花臂尾轮虫种复合体内以第一支系为主构成的姐妹种在相对丰度上占绝对优势,达29/30;而秋季则相反。上述结果表明:浅水湖泊中萼花臂尾轮虫种群密度的季节变动实际上主要在于各姐妹种相对丰度的季节变化;两姐妹种的种群遗传结构季节变化符合重叠模型。     

球形棕囊藻对五种水生动物的急性毒性作用

利用室内半静水法研究球形棕囊藻培养液、藻细胞悬浮液、去藻细胞滤液、藻细胞内容物、藻细胞碎片以及溶血毒素粗提物对卤虫(Artemia sinica)、褶皱臂尾轮虫(Brachionus plicatilis)、蒙古裸腹潘(Moina mongolia)、赤点石斑鱼幼鱼(Epinephelus akaara)和南美白对虾(Penaeus vannamei)5种水生动物的影响,并对其致毒途径进行分析.结果表明,与对照相比,培养液、藻细胞悬浮液处理卤虫,其运动速度下降,培养液、藻细胞悬浮液与毒素粗提物处理轮虫72 h,存活率显著降低(P＜0.05),卤虫、轮虫消化道中充满藻细胞,提示摄食球形棕囊藻可能是引起卤虫、轮虫中毒的主要途径.培养液、滤液和藻细胞内容物对赤点石斑鱼幼鱼均有显著的致死作用,而藻细胞碎片和溶血毒素粗提物对幼鱼的存活无明显影响,表明球形棕囊藻细胞表面并不存在毒性物质,球形棕囊藻可能会分泌有毒物质进入水体,进而影响鱼类的生长.培养液、藻细胞悬浮液、去藻细胞滤液、毒素粗提物处理蒙古裸腹溞72 h虽有死亡,但存活率与对照无显著差异;南美白对虾的情况与蒙古裸腹溞类似,表明球形棕囊藻及相关组分对蒙古裸腹溞和对虾的影响较小.这些结果表明,球形棕囊藻对不同生物的毒害作用不同;摄食和分泌有毒、有害物是球形棕囊藻引致生物中毒的主要途径;除了溶血毒素以外,球形棕囊藻还可能产生其他鱼毒性物质.     

Effects of three organophosphorus pesticides on population growth and sexual reproduction of rotifer Brachionus calyciflorus Pallas

Effects of organophosphorus pesticides including dichlorvos, triazophos and chlorpyrifos on population growth and sexual reproduction of freshwater rotifer Brachionus calyciflorus were studied by 3-d population growth and 4-d resting egg production tests. The results showed that all the three organophosphorus pesticides influenced significantly the population growth rate, the ratio ovigerous females/non-ovigerous females in the rotifer populations and the resting egg production of the rotifers. Both dichlorvos and chlorpyrifos influenced markedly the mictic rate of the rotifers, but triazophos did not. Compared to the controls, both dichlorvos at 10.0–1000.0 μg/L and chlorpyrifos at 0.01–100.0 μg/L increased the population growth rate, but the reverse was also true for dichlorvos and triazophos both at 10000.0 μg/L. Chlorpyrifos at 10000.0 μg/L made the rotifers dead after 24-hr exposure. Dichlorvos and triazophos both at 10000.0 μg/L, and chlorpyrifos at 1000.0 μg/L all increased the ratio ovigerous females/non-ovigerous females. Both dichlorvos at 10000.0 μg/L and chlorpyrifos at 0.1–100.0 μg/L increased the mictic rate. Dichlorvos at 10.0 μg/L and 100.0 μg/L, and triazophos and chlorpyrifos both at 0.1–100.0 μg/L increased the resting egg production. Both population growth rate and ratio ovigerous females/non-ovigerous females are suitable endpoints for assessing the effects of dichlorvos, triazophos and chlorpyrifos, and mictic rate is a suitable endpoint for monitoring the effects of dichlorvos and chlorpyrifos on the reproduction of the rotifers. Both population growth rate and ratio ovigerous females/non-ovigerous females are more sensitive to dichlorvos and chlorpyrifos than mictic rate.     

北京西海萼花臂尾轮虫（Brachionus calyciflorus）种群休眠卵库的遗传分化

利用线粒体细胞色素氧化酶Ⅰ亚基(COI)序列片段(543bp)对孵化自西海萼花臂尾轮虫休眠卵库的46个克隆进行分析,共发现6个单倍型,平均遗传距离为0.032,分别聚在2个分支.选取4个出现频率较高的克隆群,分别对其在3种食物浓度(蛋白核小球藻Chlorella pyrenoidosa,1×106 cells/ml,6×106 cells/ml,12×106 cells/ml)和3种温度(15℃,25℃,35℃;蛋白核小球藻Chlorella pyrenoidosa,6×106 cells/ml)下的适合度特征(R0和rm)以及个体大小(背甲长和背甲宽)进行比较研究.生命表实验结果显示,单倍型与食物浓度的交互作用(R0:P=0.038;rm:P=0.027)以及单倍型与温度的交互作用(R0:P=0.006;rm:P=0.000)对种群增长均有显著影响,这4个单倍型克隆群对环境条件具有不同的偏好,并且各个克隆群对于环境变化有不同的生殖反应.形态测量结果显示,单倍型与温度的交互作用(背甲长:P=0.033;背甲宽:P=0.000)以及单倍型与温度的交互作用(背甲长:P=0.027;背甲宽:P=0.000)对个体大小均有明显的影响.结合生命表及形态数据,探讨了休眠卵库中各个克隆群的生态位及形态分化以及可能对种群结构的动态变化产生的影响.     

利用种群增长研究镜湖夏季萼花臂尾轮虫对水温的适应

运用种群增长实验方法, 在4个温度(20℃、24℃、28℃和32℃)和3个斜生栅藻Scenedesmus obliquus (Turpin) Kuetzing密度(1.0106、2.0106和4.0106 cells/mL)共12个条件组合下研究了镜湖夏季出现的萼花臂尾轮虫(Brachionus calyciflorus Pallas)的种群增长率、平均混交率、平均受精率和休眠卵产量等生殖参数。结果表明, 在各食物密度下, 轮虫种群增长率均在28℃和32℃下最高。平均混交率、平均受精率和休眠卵产量等与温度间的关系因食物密度的不同而异。温度对种群增长率、平均混交率、平均受精率和休眠卵产量均有极显著性影响(P 0.01), 食物密度对种群增长率和休眠卵产量均有极显著性影响(P 0.01), 温度和食物密度的交互作用对平均混交率、平均受精率和休眠卵产量均有极显著性影响(P 0.01)。在1.0106、2.0106和4.0106 cells/mL的斜生栅藻密度以及28℃和32℃下, 轮虫具有较高的种群增长率(1.501.95/d)表明该种群能够适应较高的水温, 水温不是导致其在夏季水体中具有极低的种群密度(远低于1个/L)的直接因素。在种群存在于镜湖水体期间(7月初至12月初), 特别是当水温降至20℃左右时, 其较高的休眠卵产量为该种群在次年的同一时段在水体中重新出现提供了保证。       

Growth of dominant zooplankton species feeding on plankton microflora in Lake Shira

Batch cultures and continuous flow cultures were used to study the growth rates of zooplankton species from Shira lake, the rotifer Brachionus plicatilis Muller and calanoid copepod Arctodiaptomus salinus Daday, which were fed on phytoplankton and bacterioplankton from the lake. Analyses of the birth and survival rates were used to demonstrate that the lake phytoplankton, consisting mostly of cyanobacteria and diatomaceous algae, is inadequotes for optimal realisation of the reproductive potential of B. plicatilis when compared with the bacterial diet. The study revealed that the kinetic growth characteristics of the two zooplankters were similar: B. plicatilis r _max, 0.120 d^–1; S ₀, 0.253; and K _s, 0.114 mg dry mass l^–1; and for A. salinus r _max, 0.129 d^–1; S ₀, 0.240; and K _s, 0.171 mg dry mass l^–1. Fluctuations in natural food concentration reduced the growth rate of both species. Even though the threshold concentration of food for B. plicatilis and A. salinus were quite similar, the copepods were less sensitive to food limitation.     

不同培养条件下萼花臂尾轮虫休眠卵的萌发

为确定萼花臂尾轮虫休眠卵的最适形成条件 ,或为提高特定培养条件下形成的休眠卵的萌发率 ,对不同温度、食物、光照和 pH条件下萼花臂尾轮虫形成的休眠卵进行了萌发研究。发现不同培养条件下形成的休眠卵在不同萌发条件下的萌发历时均为实验开始后的第 1～ 7天 ,萌发率高峰均出现在第 1～ 3天。在萌发温度为15℃～ 30℃范围内 ,2 0℃下形成的休眠卵在 2 0℃的萌发温度下累积萌发率最高 ,为 5 2 5 0± 6 89% ;母体以小球藻为食物时 ,其所产休眠卵的平均累积萌发率为 2 7 92 % ,显著大于以斜生栅藻或蛋白核小球藻和斜生栅藻所组成的混合藻为食物时 ;休眠卵形成和萌发时的光照条件对其累积萌发率无显著的影响 ;pH6 5和 7 5条件下形成的休眠卵的累积萌发率较高 ,分别为 32 5 0± 7 0 7%和 38 75± 15 5 3%。本研究和已报道的研究结果表明 :不同培养条件下形成的休眠卵在不同条件下萌发时均呈同步萌发型式 ;2 0℃和pH7 5分别是武汉东湖萼花臂尾轮虫休眠卵形成的最适温度和最适 pH条件。