Fecundity and spawning season of striped mullet (Mugil cephalus L.) in South Carolina estuaries

Fecundity in striped mullet (Mugil cephalus) from South Carolina correlated highly with length and weight, but not with age. Oocyte counts ranged from 4.47 × 105 to 2.52 × 106 in 1998 for fish ranging in size from 331 mm to 600 mm total length, 2.13 × 105to 3.89 × 106in 1999 for fish ranging in size from 332 mm to 588 mm total length, and 3.89 × 105 to 3.01 × 106 in 2000 for fish ranging in size from 325 mm to 592 mm total length. The striped mullet in this study had a high degree of variability in the size-at-age relation-ship; this variability was indicative of varied growth rates and compounded the errors in estimating fecundity at age. The stronger relationship of fecundity to fish size allowed a much better predictive model for potential fecundity in striped mullet. By comparing fecundity with other measures of reproductive activity, such as the gonadosomatic index, histological examination, and the measurement of mean oocyte diameters, we determined that none of these methods by themselves were adequate to determine the extent of reproductive development. Histological examinations and oocyte diameter measurements revealed that fecundity counts could be made once developing oocytes reached 0.400 μm or larger. Striped mullet are isochronal spawners; therefore fecundity estimates for this species are easier to determine because oocytes develop at approximately the same rate upon reaching 400 μm. This uniform development made oocytes that were to be spawned easier to count. When fecundity counts were used in conjunction with histological examination, oocyte diameter measurements, and gonadosomatic index, a more complete measure of reproductive potential and the timing of the spawning season was possible. In addition, it was determined that striped mullet that recruit into South Carolina estuaries spawn from October through April.

辽河三角洲芦苇湿地生态系统水碳通量动态及其控制机制

全球变化背景下人类生存环境及社会经济的可持续发展要求，使得水循环和碳循环成为科学研究的关注点。湿地与森林、海洋并称为全球三大生态系统，与生态平衡、人类生存和经济社会可持续发展息息相关，特别是湿地的碳汇功能使得其在全球碳循环中具有重要作用。我国湿地面积占亚洲第一位，世界第四位，占世界湿地面积的11.9% 。但是，与森林、草地与农田等生态系统相比，湿地水碳循环控制机制研究的甚少，制约着湿地生态系统的水碳管理。 本论文基于2005~2007 年盘锦芦苇湿地生态系统野外观测站的涡度相关系统的水碳通量和气象环境因子的连续观测数据，结合芦苇湿地生态系统的生物学调查资料，较系统地分析了芦苇湿地生态系统水汽通量和碳通量的动态特征，探讨了不同时间尺度芦苇湿地生态系统水汽通量和碳通量的环境控制机制。主要结论如下： (1)芦苇湿地生态系统蒸散的日、季变化显著。2005~2007 年盘锦芦苇湿地生态系统的年蒸散量分别为432、480 和445 mm。非生长季(11 月~次年4 月)对全年蒸散量的贡献约13~16%，表明在湿地蒸散年总量的估算中不能忽略非生长季的贡献。 (2)关于动力作用和热力作用对芦苇湿地蒸散的贡献表明，能量是驱动芦苇湿地蒸散的重要因素，在小时至月尺度上均起着主导作用；时间尺度越长，能量因子对蒸散变异的解释率越大。仅温度就能解释蒸散月总量变异的95%左右。但是，随着时间尺度的降低，水分条件如饱和水汽压差、相对湿度，对芦苇湿地蒸散的作用逐渐显现。降雨和蒸散的变化虽然没有统计上的相关性，但短时段的降雨可能导致雨后蒸散增强，而持续多天的阴雨天气却能导致蒸散量连续下降。 (3)基于芦苇湿地生态系统作物系数(kc)具有显著日间变异的事实，发展了耦合气温、相对湿度和净辐射影响的芦苇湿地日作物系数模型，弥补了国际粮农组织建议的蒸发散估算模型FAO56 缺乏适宜湿地作物系数的不足。 (4)芦苇湿地生态系统呼吸呈单峰型季节变化，2005~2007 年生态系统呼吸的年总量分别为834、894 和872 g C m-2 yr-1，非生长季芦苇湿地的生态系统呼吸碳排放量为102~136 g C m-2 season-1，占全年生态系统呼吸总量的12~16%。这说明，非生长季湿地生态系统的碳排放通量不可忽视。温度是小时至月尺度的生态系统呼吸控制因子；同时，生物因素也对芦苇湿地生态系统呼吸有显著影响。生态系统呼吸对温度的响应呈指数函数关系，二者间的响应受土壤水分的影响。当表层土壤含水量(5 cm) 为20~25%时，芦苇湿地生态系统呼吸的潜力(Reco,10)最大。生态系统呼吸的日值与地上生物量、叶面积指数呈对数正相关，而与冠层高度呈显著二次曲线关系。生态系统呼吸的年际差异并不是由温度变化引起，而与植被生长状况密切相关。 (5)芦苇湿地生态系统的净碳交换季节变化明显，变化范围在-12.9~4.2 g C m-2 day-1 之间。一般在5~9 月表现为大气CO2 的汇，其余月份为碳源。其中，净碳吸收最大的月份为6、7 月，而净碳排放最大的月份为4、10 月。2005~2007 年的年碳收支分别为-55、-230 和-53 g C m-2 yr-1，呈碳汇。 (6)不同时间尺度的净碳交换控制因子不同。小时尺度上，影响芦苇湿地生态系统净碳交换的环境因子主要是光合有效辐射(PAR) 。芦苇湿地生态系统光合作用的光响应参数(α、Amax 和Reco)随温度指数上升，而与叶面积指数呈线性正相关。光响应参数的这种显著季节波动表明，在生态系统碳循环模型中不应该将生态系统的光合作用参数视为常数，应该考虑采用光响应参数与环境和生物因子间的定量关系来反映光合作用光响应参数动态。日尺度上，温度是芦苇湿地碳交换的主要控制因子，湿地净碳交换在15℃左右由正值变为负值，芦苇湿地由碳源变为碳汇。除温度外，饱和水汽压差对日尺度净碳交换波动也有影响，二者呈二次曲线关系(U 型)，当饱和水汽压差在0.8 kPa 附近时，芦苇湿地净碳吸收达到最大。月尺度上，影响芦苇湿地净碳交换的主要环境因子依然是温度，二者间表现出“非对称响应”特征。 (7)对芦苇湿地碳交换各组分间的关系分析表明，芦苇湿地生态系统呼吸和净碳交换均受总光合生产力的显著影响，即通过光合作用产物来源控制。

Sox2基因3'非翻译区保守元件对基因表达的调控作用

转录因子Sox2是脊椎动物早期发育中最早表达的神经系统特异性基因之一,同时在干细胞的维持中也起着关键作用.通过生物信息学分析,作者发现在脊椎动物Sox2 mRNA 3'非翻译区中存在4段非常保守的富含AU的区域.将这些片段按照不同的组合克隆到GFP和荧光素酶两种报告基因载体中,在非洲爪蟾胚胎和培养细胞中检测了这些片段对报告基因表达的影响.结果显示,Sox2的3'UTR可影响报告基因的表达水平,特别是其中的保守片段2可显著提高报告基因的表达水平,表明Sox2 3'非翻译区有可能参与Sox2表达的转录后调控.

The genetic structure and phylogenetics of pikeperch (Sander lucioperca) Anzali and Amirkolaye wetlands and perch (Perca fluviatilis) populations in Aras Dam and south-west of the Caspian Sea

The genetic structure of pikeperch (Sander lucioperca) and perch (Perca fluviatilis) populations was studied using microsatellite technique. A total of 207 specimens of adult pikeperch were collected from Aras dam (57 specimens), Anzali wetland (50 specimens), Talesh (50 specimens) and Chaboksar (50 specimens) coasts. Also a total of 158 specimens of adult perch were collected from Anzali (Abkenar (50 specimens)and Hendekhale(48 specimens)) and Amirkolaye(60 specimens) wetlands. About 2 g of each specimen's dorsal fin was removed, stored in 96% ethyl alcohol and transferred to the genetic laboratory of the International Sturgeon Research Institute. Genomic DNA was extracted using ammonium-acetate method. The quality and quantity of DNA was assessed using 1% agarose gel electrophoresis. Polymerase Chain Reaction (PCR) was conducted on the target DNA using 15 pairs of microsatellite primers. PCR products were electrophoresed on poly acryl amide gels (6%) that were stained that were stained using silver nitrate. DNA bands were analyzed with BioCapt software. Allele count and frequency, genetic diversity, expected and observed heterozygosity , allele number and the effective allele number, genetic similarity and genetic distance, Fst, Rst, Hardy Weinberg Equilibrium based on X2 and Analysis of Molecular Variance (AMOVA) at 10% confidence level was calculated using the Gene Alex software. Dendogram for genetic distances and identities were calculated using TFPGA program for any level of hierarchy. The results for P. fluviatilis showed that from 15 pair of primers that were examined 6 polymorphic and 7 monomorphic loci were produced, while 2 loci didn't produce any DNA bands. Mean allele number was 4.1±1.1 and mean observed and expected heterozygosity was 0.56±0.12 and 0.58±0.14 respectively. It was also seen that specimens from all regions were not in Hardy Weinberg Equilibrium in some of loci (P<0.001). Highest Fst (0.095) with Nm=2.37 was observed between Hendekhale and Amirkolaye and the lowest Fst (0.004) with Nm=59.31 was observed between Abkenar and Hendekhale. According to AMOVA Significant difference (P<0.05) was observed between recorded Rst in the studied regions in Anzali and Amirkolaye lagoons. In another words there are two distinct populations of this species in Anzali and Amirkolaye lagoons. The highest genetic distance (0.181) and lowest genetic resemblance (0.834) were observed between specimens from Hendekhale and Amirkolaye and the lowest genetic distance (0.099) and highest genetic 176 resemblance (0.981) were observed between specimens from Abkenar and Hendekhale. Based on the genetic dendogram tree derived by applying UPGMA algorithm, specimens from Anzali and Amirkolaye wetlands have the same ancestor. On the other hand there is no noticeable genetic distance between the specimens of these two regions. Also the results for S. lucioperca showed that from 15 pair of primers that were examined 6 polymorphic and 7 monomorphic loci were produced, while 2 loci didn't produce any DNA bands. Mean allele number was 3.0±0.6 and mean observed and expected heterozygosity was 0.52±0.21 and 0.50±0.14 respectively. It was also seen that specimens from all regions were not in Hardy Weinberg Equilibrium in some of loci (P<0.001). Highest Fst (0.093) with Nm=2.43 was observed between Aras dam and Anzali wetland and the lowest Fst (0.022) with Nm=11.27 was observed between Talesh and Chaboksar coasts. Significant differences (P<0.05) were observed between recorded Rst in the studied regions exept for Talesh and Chaboksar Coasts. In another words there are three distinct populations of this species in Caspian sea, Anzali wetland and Aras dam. Highest genetic distance (0.110) and lowest genetic resemblance (0.896) were observed between specimens from Aras dam and Anzali wetland and the lowest genetic distance (0.034) and highest genetic resemblance (0.966) were observed between specimens from Talesh and Chaboksar coasts. Based on the genetic dendogram tree derived by applying UPGMA algorithm, specimens from Talesh and Chaboksar coasts have the lowest genetic distance. On the other hand the main population of this species belongs to Anzali wetland. Phylogenetic relationship of these two species was inferred using mitochondrial cytochrome b gene sequencing. For this purpose 2 specimens of P. fluviatilis from Anzali wetland, 2 specimens of S. lucioperca from Aras dam and 2 specimens of S. lucioperca from Anzali wetland were sequenced and submitted in Gene Bank. These sequences were aligned with Clustal W. The phylogenic relationships were assessed with Mega 4. The results of evolutionary history studies of these species using Neighbor-Joining and Maximum Parsimony methods showed that the evolutionary origin of pikeperch in Aras Dam and Anzali wetland is common. On the other hand these two species had common ancestor in about 4 million years ago. Also different sequences of any region specimens are supposed as different haplotypes. 177 As a conclusion the results of this study showed that microsatellite and mtDNA sequencing methods respectively are effective in genetic structure and phylogenic studies of P. fluviatilis and S. lucioperca.

Development of zona-free hamster ova to blastocysts in vitro

The zona pellucida (ZP) enclosing the mammalian ovum is important for its protection and for initial stages of fertilization, but the role of the ZP during embryo development is less clear. This study was designed to investigate if the hamster ZP is needed for embryo development from 1-cell to blastocyst in vitro, and to compare methods for removing the ZP. A total of 395 hamster pronucleate ova were collected 10 h post activation from superovulated, mated female hamsters. The ZP was removed from some ova using either 0.05% pronase, 0.05% trypsin or acid Tyrode's solution. To prevent ZP-free ova from sticking together, they were cultured singly in 30-50 muL drops of HECM-6 culture medium together with ZP-intact ova as controls. There was no significant difference among treatment groups in embryo development to blastocyst: 36/87 (42%) in the ZP intact group; 35/75 (47%) in the pronase-treated ZP-free group; 37/74 (50%) in the trypsin-treated ZP-free group; and 37/71 (52%) in the acid-treated ZP-free group. These results indicate that 1) the ZP is unnecessary for hamster embryo development in vitro from the pronucleate ovum stage to blastocyst; 2) none of the three ZP-removal methods was detrimental to embryo development; 3) embryos do not need to be cultured in groups during in vitro development from 1-cell to blastocyst. (C) 2000 by Elsevier Science Inc.

Fabrication of excitonic luminescent inorganic-organic hybrid nano- and microcrystals

Inorganic-organic (IO) hybrid nano- and microcrystals are fabricated by a low-cost, environmentally friendly and easily scaled-up route. Lead(II) iodide (PbI 2) nano/microcrystals are obtained by solvothermal techniques and subsequent IO hybrid (C 12H 25NH 3) 2PbI 4 crystals are produced by intercalation of the organic moiety. The hexagonally shaped crystals obtained range in size from 20 nm to ∼7 μm. Sequential stacking of inorganic/organic layers in these IO hybrid crystals results in strong room-temperature exciton photoluminescence, wherein the excitons are confined within the inorganic sheets. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

略论长江渔具渔法与渔业资源保护

长江流域是我国重要的渔业产区,渔业资源极为丰富。而长江上现存的各种类型的渔具渔法的大量使用则是长江渔业资源过度开发利用的重要原因之一。在指出了我国现行有效的关于长江渔具渔法使用的法律法规的相关规定的基础上,提出了如何正确、合理使用渔具渔法的观点;既要充分利用长江渔业资源,又必须有效地保护长江鱼类,达到持续利用和发展的目的。