梭梭种群分子生态学研究

中国是受沙漠化影响最严重的国家之一。梭梭(Haloxylon ammodendronBunge)是藜科梭梭属多年生小乔木或灌木，作为荒漠地区主要的建群种和优良固沙植物，梭梭在维持荒漠生态系统的结构与功能、防止土地沙漠化、改善小气候方面具有十分重要的作用。近年来，由于不合理地开发利用，大面积的天然梭梭林衰退甚至死亡。然而，我们对于梭梭种群的空间分布和遗传结构所知甚少。本文拟通过对自然梭梭种群的空间格局、遗传结构、遗传结构的空间分布、以及种子种群与地面植被种群的遗传比较的研究，探讨种群的空间结构特征及成因，评价种群遗传多样性水平，了解遗传多样性在种群内、种群间的分布情况以及在空间上的分布格局，预测种群的遗传潜能，并为制定合理的保护、利用策略提供理论依据。 1．对古尔班通古特沙漠东南部地区处于不同演替阶段的四个梭梭种群的分布格局和种群动态进行了考察。结果表明，不同样地中梭梭种群的幼苗（<0.5m）和幼树( 0,5-lm)均呈聚集分布，样地A、B、D中的成熟个体(>1m)也呈聚集分布，样地c中的成熟个体呈随机分布，从整个种群来看，所有梭梭种群均呈聚集分布。种群的龄级结构图表明样地A和c中的梭梭种群表现为稳定型结构，可进行持续更新，虽然样地D中的种群幼苗和幼树数量较少，但这种现象是暂时的，种群仍具有持续更新的能力，样地B中的种群表现为衰退型结构。 2．利用空间自相关分析检测上述四个种群的空间遗传结构，结果表明，四个种群中的成株均无显著的空间自相关。虽然梭梭的种子散布能力有限，但花粉流有可能是空间遗传结构不显著的原因之一;另一个可能的解释是在种群更新和发展过程中，由于种内竞争的增强而发生了自疏现象。 3．利用ISSR标记对新疆和内蒙古境内共9个种群的遗传结构进行研究。8个引物共扩增出219条带，其中184条(84%)具多态性，种群的遗传多样性水平较高，通过AMOVA分析表明大部分遗传多样性分布在种群内，区域间、种群间的遗传变异均很小。梭梭种群较高的遗传多样性水平可能源于对异质、高胁迫环境的长期适应，而种群间遗传分异低的主要原因是种群间存在强大的基因流。 4．对5个梭梭种群的地面植被和种子库的遗传结构进行了比较分析，并调查了其中3个种群地面植被和种子库的空间遗传结构。结果表明，在所有种群中，地面植被和种子库的遗传多样性水平相似，而地面植被的遗传分异高于种子库的遗传分异：二者在遗传结构的空间分布上也不相同，地面植被种群无显著的空间自相关，而种子库种群在第一距离级上( 0-10 m)呈显著正相关。研究结果表明梭梭种群的种子库有能力保持种群的遗传多样性并减弱种群的遗传分化。 5．研究结果建议，由于现存梭梭种群和其潜在种群（种子种群）仍保持了较高的遗传多样性，种群间的基因交换并没有受到阻碍，因此对梭梭的保护可以与生态恢复工作同时进行。在具体工作中，应充分考虑种群的遗传结构特征及其空间格局，选取适合的种群或种子资源进行恢复与重建，并保持一定水平的种群大小，才能实现种群的稳定发展以及在高胁迫环境中的长期存活。 荒漠生态系统植被结构简单，环境压力大，对荒漠地区主要建群种和优势种植物的空间分布和遗传结构进行研究对于探讨在胁迫环境中各种进化力量（如选择、突变、迁移、漂变）的作用机制有重要意义，并为荒漠生态系统的恢复与重建工作提供了有价值的信息。在本文中，对荒漠植物在较大地理范围内的遗传结构研究、通过空间自相关分析进行种群的空间遗传结构研究、地面植被种群与种子库种群在遗传结构、空间遗传结构上的比较研究在国内均为首例。这些研究结果为进一步深入探讨荒漠植物生态适应与进化的分子机制奠定了基础。

Suitability of rich-fish culture under mono and polyculture systems in the boro rice ecosystem

An experiment was conducted in farmers’ fields under Paikgacha thana, Khulna to study the suitability of integrated rice-cum-fish culture. Three treatments namely T1 (Puntius gonionotus), T2 (Puntius gonionotus and Cyprinus carpio) and T3 ( Cyprinus carpio) were included for the study each having three replicates. The fish were stocked at a density of 3750/ha in all the rice plots. The physicochemical parameters of water viz., water depth, temperature, dissolved oxygen, pH, salinity, nitrate and phosphate etc. recorded during the study period were found within optimum range. Of the two cultured species C. carpio attained the highest average individual weight (160g) and survival (81.06%). With respect to biomass and income, highest average fish production and net profit per hectare (306.74kg and Tk. 8177.91) were obtained in T2 and the lowest (184.17kg and Tk. 2049.41) obtained in T1 and a significant variation (p<0.05) in fish production was observed among the treatments while for rice production, it was insignificant. The cost benefit ratio of fish production found were 1:1.29, 1:2.14 and 1:1.90 for T1, T2 and T3, respectively.

Population dynamics of the ribbon fish, Lepturacanthus savala (Cuvier 1829) from the north-eastern part of the Bay of Bengal

Population parameters of Lepturacanthus savala from the trawl catches in the north-eastern part of the Bay of Bengal, Bangladesh were investigated based on length frequency data, using complete ELEFAN computer program. The asymptotic length (Lα) and growth constant (K) were estimated to be 106.50 cm (total length) and 0.80/year respectively. Based on these growth parameters, the total mortality (Z) was estimated to be 1.89. The estimated values for natural mortality (M) and fishing mortality (F) were 1.08 and 0.81 respectively. The estimated value for the exploitation rate (E) using the length converted catch curve was 0.43. The recruitment pattern showed two peaks per year. The estimated sizes of L. savala at 25, 50 and 75% probabilities of capture were 57.49, 60.39 and 63.28 cm respectively. The estimated length weight relationship for combined sex was W=0.00093 TL(super)2.97

Growth performance of Chlorella ellipsoidea as biomicrocapsule using supernatant of digested sugar mill waste effluent

Biomicrocapsules mean microscopic living organisms which carry important nutrients, very essential for the growth and development of aquatic organisms as well as other animals. Among these biomicrocapsules, Chlorella ellipsoidea, an important green microalga (Chlorophyceae) which contains 40-45% crude protein, 12-16% crude lipid, 14-15% minerals, colour pigments, vitamins and carotene. The microalga, C. ellipsoidea was cultured in four different dilutions of supernatant of digested sugar mill effluent (DSME) i.e. 25, 50, 75 and 100% DSME and Bold basal medium (BBM) as control in laboratory condition. Maximum cell growth and chlorophyll a content of C. ellipsoidea were obtained on l0th day of culture in supernatant of 50% diluted DSME followed by those of this biomicrocapsule grown in BBM, and 75, 25 and 100% DSME at stationary phase. Cell number had highly (p<0.01) direct correlation with chlorophyll a (r = 0.889) of C. ellipsoidea, and optical density (r = 0.926) of media. Chlorophyll a was also highly (p<0.01) and directly correlated with optical density (r= 0.877) of media. The specific growth rates (µ/day) of cell and chlorophyll a of C. ellipsoidea grown in supernatant of 50% DSME were significantly (p<0.01) varied from those of C. ellipsoidea cultured in BBM followed by other DSME. Total biomass of C. ellipsoidea cultured in supernatant of 50% DSME was found significantly (p<0.01) higher than that of this microalga cultured in BBM, and supernatant of 25, 75 and 100% DSME. Similar trend was also observed in the case of optical density. The physico-chemical properties of media were varied with the growth of cell of this microalga. It was recorded that cell number, chlorophyll a of biomicrocapsule, and optical density of media were highly (p<0.01) and directly correlated with pH, hardness and alkalinity, and inversely correlated with nitrate-N. Crude protein and crude lipid of C. ellipsoidea grown in supernatant of 50% DSME were significantly (p<0.01) higher than those of C. ellipsoidea cultured in other DSME and BBM. Due to best growth performance exhibited by this microalga grown in supernatant of 50% DSME, it may be used to grow in supernatant of 50% DSME to get more essential nutrients than that cultured in supernatant of other DSME media.

中华眼镜蛇膜毒素与McAb偶联物对白血病细胞的杀伤作用

用中华眼镜蛇膜毒素(CT)与抗人T细胞McAb Wu71偶联制备免疫毒素Wu71CT。经SDS-聚丙烯酰胺凝胶电泳、免疫双扩散和间接免疫荧光检测, 证实结合物中Ab和CT均保持活性。实验表明Wu71:CT有较好的特异性杀伤作用。扫描电镜显示, 免疫毒素作用下的CEM靶细胞膜破列、 萎缩、崩溃, 而非靶细胞大部分保持完整。 图4参12

Studies on the occurrence and growth rates of two intertidal fouling bryozoans in the Mattancherry channel of Cochin harbour, south-west coast of India

Occurrence and growth rates of two species of intertidal fouling bryozoans namely Electra bengalensis (Stoliczka) and Electra crustulanta (Pallas) are presented in this paper. The former was a typically marine form, settling on panels only during the high saline conditions of the pre-monsoon period and were absent during the low salinity conditions of the monsoon period, while the latter appeared to be a typical brackish water form settling on panels during the low saline conditions existing during the monsoon and post-monsoon periods and were totally absent during the pre-monsoon months. Regression co-efficient of the former was higher than that of the latter suggesting more pronounced growth in Electra bengalensis. Maximum growth for this species was noticed during March, April and May (pre-monsoon) while for the other species growth was more or less similar during monsoon and post-monsoon months (June-January) showing that the species was at home in oligohaline and mesohaline waters.

云南微小按蚊随机扩增多态DNA及遗传分化关系

对来自云南昭通、景洪、元阳、潞西和镇康等5个地区的25只雌按蚊,及4只雄按蚊进行随机扩增多态DNA分析。从使用的20个随机引物中,选择其中扩增谱带清晰的12个引物进行分析。结果发现,只有2个引物获得的RAPD谱带呈单型,其余均表现为不同程度的多态型。UPGMA法构建的分子系统树表明该29只微小按蚊实际上可以归并为显著不同的5个组,分别对应于它们的地理来源,说明云南微小按蚊群体间的基因流程度不高,不同地理群体间存在显著的遗传分化。

Prices on Indian frozen shrimp in U.S. market: a note on seasonal variation

The supply and consumption of shrimp follow a more or less regular seasonal pattern. Like agricultural products, fishery products have also their period of heavy and less productions on which depend their price movements. The prices of shrimp in any particular market reflect this seasonal behaviour quite often.

Molecular basis of albinism in the rhesus monkey

Sequence analysis of the tyrosinase (TYR) coding region from one albino rhesus monkey (Macaca mulatta) family revealed that the two monkeys with phenotype similar to human TYR-negative oculocutaneous albinism (OCA) were homozygous for a missense mutation (S184TER) in exon 1 at codon 184. The offspring of one of the albino monkey (''Kangkang'') are all heterozygous for the S184TER mutation, but the S184TER mutation was not observed in 93 control individuals. We conclude that the point mutation is responsible and sufficient to generate the albino rhesus monkey phenotype. The rough age of the S184TER nonsense mutation may be about 0.8 million years using a rate of 0.16% per million years. (C) 2000 Elsevier Science B.V. All rights reserved.