高浓度硅藻对桡足类繁殖的抑制作用

硅藻作为海洋浮游植物重要的组分 ,一直被看作是桡足类主要的食物来源。但近 10年来许多现场和实验室研究表明 :硅藻 ,特别是高浓度硅藻对桡足类的繁殖具有抑制作用。目前 ,对于抑制作用的机制存在着两种假设 :硅藻细胞缺乏某种关键营养物质或自身产生某种有毒物质阻碍了桡足类繁殖过程。大量的室内实验发现 :关键营养物缺乏使桡足类产卵率降低 ,对于硅藻细胞化学组成的分析表明这种物质可能是某些不饱和脂肪酸。而高浓度硅藻是否会产生毒性物质影响桡足类孵化率则存在很大的分歧。许多室内和野外实验证据显示当硅藻浓度很高时 ,桡足类孵化率显著降低 ,表现为大量未孵化的卵和畸形无节幼体。对硅藻溶出液的分析发现其中含有的不饱和醛类可能正是阻碍胚胎发育的物质。但也有一些室内和现场实验的结果表明并非所有的硅藻和桡足类之间都存在这种抑制作用。目前研究结果大多来自于室内实验 ,在自然海区中的作用机制和影响程度尚不清楚 ,但是如果这一现象在自然海区中普遍存在 ,传统上关于“硅藻——桡足类——鱼类”的海洋经典食物链观点势必存在极大的缺陷。文章针对这一问题分析了目前研究进展和将来工作前景     

海洋浮游桡足类滞育的研究进展

海洋桡足类在海洋生态系统中占有重要的地位,其重要的生理现象一滞育是影响其种群数量变动的重要因子。本文对海洋桡足类滞育的形式、滞育的意义、滞育卵的孵化与发育以及诱导桡足类滞育的环境因子等方面的研究进行了综述,同时还提出了今后研究的方向,以期对桡足类滞育机制的研究提供新的思路。     

桡足类滞育规律研究

首次提出用滞育指数对桡足类滞育能力进行相对量化处理 ,并对 10 2种桡足类的滞育能力同迁移能力、体长、栖息地之间的关系进行了数学分析 ,初步得出了滞育在桡足类中的分布规律 :在桡足类中滞育与迁移呈负相关 ,两者之间存在一定程度的置换 ;个体较小的桡足类一般具有较强的滞育能力和较弱的迁移能力 ,个体较大的桡足类一般具有较弱的滞育能力和较强的迁移能力 ;淡水桡足类一般比海洋桡足类具有较强的滞育能力。最后探讨了这种分布模式的成因     

河北白洋淀的枝角类和桡足类

白洋淀在河北省中部,位于东经115°38′～116°07′,北纬38°43′～39°02′之间;是华北平原最大和最典型的淡水湖泊湿地.湖内浮游动物种类丰富,但不同时期由于种种原因其种类又存在着差异.笔者于2005～2007年曾17次对白洋淀8个样点枝角类和桡足类进行了调查.     

植食性浮游桡足类摄食生态学研究进展

由于浮游动物在调节海洋生物生产中的关键作用,对其摄食生态学的研究一直是海洋生态学研究的重点。总结了近年关于浮游动物主要类群－桡足类对浮游植物摄食的研究进展及其在海洋生态系统动力学研究中的重要意义。主要包括：影响植食怀桡足类摄食强度的主要因素,饵料对于桡足类种群变动的影响;现场测定桡足类摄食率的方法以及海洋生态系统动力学研究中需要关注的问题。     

武汉东湖桡足类的生态学演变

根据１９６２－１９６３,１９７４－１９７５,１９７９－１９９１年在武汉东湖进行的调查资料,考察了过去三十年内在东湖两个代表性采样站桡足类的种类组成及现存量的变化。结果表明：桡足类种类数由６０年代的１４种减少为９０年代的７种,Ｉ、Ⅱ站在种类组成的差别趋于消失。统计结果表明,东湖桡足类现存量以８０年代初、中期较高。但在水平分布格局上却发生了根本变化,由１９８７年前的Ｉ站现存量高于Ⅱ站,至１９８７年后Ⅱ站高于Ｉ站。本文还就影响东湖桡足类演变的生态因子进行了讨论。     

拓林湾浮游桡足类生态研究

2000年7月至2001年7月的周年调查结果表明,粤东柘林湾浮游桡足类29属57种,其中,强额拟哲水蚤Paracalanus crassirostris和短角长腹剑水蚤Oithona brevicornis为优势种,合计占浮游桡足类总个体数的66.7%.柘林湾是一个浮游桡足类相对丰富的海湾,年均总个体数达5.4×10³ind.·m^-3.浮游桡足类的种类数和总个体数均表现为湾外大于湾内的平面分布格局,周年变化基本上为单峰型,高峰期位于5~10月,最低谷位于冬季1月。     

淡水桡足类生物量的测算

本研究测定了16种哲水蚤、5种剑水蚤成体体长-湿重值和13种哲水蚤、4种剑水蚤成体体长-干重值,并应用统计方法推导出相应的体长-体重关系方程式。文中对这方程式的应用作了扼要的讨论。另外,测定了4种哲水蚤、3种剑水蚤卵的干、湿重值和三个不同水域里的无节幼体的干、湿重值。     

河口近海桡足类休眠卵生态学研究进展

桡足类是水域生态系统的关键类群,在物质循环、能量流动和信息传递中起着重要作用.休眠卵是桡足类的重要生存策略,在抵抗不利环境、维持种群延续等方面起着重要作用.本文综述了河口近海桡足类休眠卵种类组成及其分布、休眠卵存活时间、休眠卵萌发率和沉积物中休眠卵丰度以及对水体的潜在补充量及其影响因素等.对河口近海桡足类休眠卵生态学研究提出了展望,以期为相关研究提供新的思路.     

长江口桡足类数量分布与变动

于1999年枯水期(2～3月份)、丰水期(8月份)、2000年枯水期(2～3月份)对长江河口浮游动物桡足类采样调查,研究了长江河口桡足类的数量分布与变动.结果表明:1999年枯水期,桡足类在整个长江河口区的平均数量相对不大,为76ind/m3,但却占同期浮游动物平均数量的95.61%;1999年丰水期桡足类平均数量为254ind/m3,占同期浮游动物平均数量的84.29%;2000年枯水期桡足类平均数量为97ind/m3,占同期浮游动物总数量的84.46%.从优势度看,1999、2000年枯水期主要优势种为华哲水蚤(Sinocalanus sinensis);1999年丰水期主要优势种为火腿许水蚤(Schmackeria poplesia).虫肢歪水蚤(Tortanus vermiculus)、真刺唇角水蚤(Labidocera euchaeta)则在枯、丰水期均为优势种.从种类数看,桡点类在1999年、2000年枯水期均为14种,1999年丰水期为枯水期的近2倍,达25种.对于长江河口主要桡足类而言,华哲水蚤的季节变化明显,适宜生活在盐度较低水域.虫肢歪水蚤数量年际变化较大,其适盐范围比华哲水蚤较宽、较高.真刺唇角水蚤的适盐范围与虫肢歪水蚤相似且更高一些,但该种在枯水期数量较少,丰水期数量较多,变化显著,更适宜在较高温时生长.火腿许水蚤适盐范围宽,能适应很大范围盐度变化,枯水期数量少,丰水期数量大,较高温度生长良好.     

Cocoon production,morphology, hatching pattern and fecundity in seven tropical earthworm species — a laboratory-based investigation

Data on the reproductive biology of seven Indian species of earthworms, viz.Perionyx excavatus Perrier,Lampito mauritii Kinberg,Polypheretima elongata (Perrier),Pontoscolex corethrurus (Muller),Eutyphoeus gammiei (Beddard),Dichogaster modiglianii (Rosa) andDrawida nepalensis Michaelsen are presented. The peregrine earthworms such asPerionyx excavatus, Pontoscolex corethrurus, Dichogaster modiglianii, andPolypheretima elongata are considered to be continuous breeders with high fecundity. NativeLampito mauritii andDrawida nepalensis are semi-continuous andEutyphoeus gammiei discrete breeders. There is a dramatic increase in cocoon production by most earthworm species of Tripura in the summer and monsoon with a corresponding peak during April and July. Cocoon production decreased or ceased during winter. Temperature affected the incubation period of cocoons. With increase in temperature, incubation period increased in the endogeic worms,Pontoscolex corethrurus, Polypheretima elongata andDrawida nepalensis and decreased in the epigeic worms,Perionyx excavatus andDichogaster modiglianii, within a temperature range between 28–32°C under laboratory conditions. There was a significant(P < 0.05) positive correlation between number of hatchlings per cocoon and incubation period inLampito mauritii. High rate of cocoon production, short development time with high hatching success, as well as continuous breeding strategies in the epigeic speciesPerionyx excavatus andDichogaster modiglianii and the top soil endogeic species,Pontoscolex corethrurus,Drawida nepalensis andLampito mauritii, indicate their possible usefulness in vermiculture. The giant anecic worm,Eutyphoeus gammiei, which has a very long cocoon development time, discrete breeding strategy and very low rate of cocoon production, is not a suitable species for vermiculture.     

外生菌根真菌的共生互作和宿主选择机制研究进展

外生菌根真菌作为树木的共生伙伴,是森林生态系统重要组成部分,在森林天然更新、植物抗逆性形成、协助植物吸收限制性营养等方面扮演重要角色。真菌和植物跨界共生具有复杂的分子互作过程,在共生的不同阶段有不同的分子互作机制,其调控反馈网络还有许多未知。基因组与转录组研究技术和方法的进步,为一些新的信号分子、效应蛋白以及相关通路的发现提供了可能。真菌与宿主植物之间营养转移调控对共生的影响也逐渐受到关注,营养相关的转运蛋白对共生的建立和维持提供了物质基础。真菌的宿主选择机制是值得重点关注的领域,由于外生菌根真菌的多谱系起源和演化史中存在多次宿主转换事件,真菌演化出多样的应对机制用来区分相容性宿主、不相容性宿主和非宿主。通过对不同真菌与宿主植物的组学研究,宿主选择机制研究取得了一定进展。本文对近十年来国内外的研究报道进行梳理与总结,并对未来在该领域的探索方向做出展望。     

微生物镉解毒机制及微生物-植物互作修复研究进展

镉(cadmium,Cd)是引起粮食减产的主要金属之一,具有高溶解性及高迁移性,易被植物吸收和积累。微生物长期在镉胁迫的条件下进化出一系列的镉解毒机制。微生物对镉的解毒包括抑制Cd(Ⅱ)的进入、促进Cd(Ⅱ)的外排,以及将进入胞内的Cd(Ⅱ)进行“扣押”。微生物的Cd(Ⅱ)钝化是通过细胞吸附和胞外沉淀将游离态的Cd(Ⅱ)进行钝化,这类微生物具有较强的土壤镉污染治理潜力。本文主要介绍微生物的镉解毒机制、微生物-微生物互作、微生物-植物互作机制及其在镉污染生物修复中应用的最新研究进展。     

Low breeding success of the little egret (Egretta garzetta) near residential areas and in colonies exposed to gales: a comparison of colony in Sichuan,Southwest China,with literature

The breeding biology of the little egret (Egretta garzetta) was studied in 20 nests within the mixed-species breeding colonies at Nanchong, Sichuan, Southwest China, in 2006. By measuring a set of physical characteristics of vegetation at the nests and at a set of 20 randomly chosen sites we showed that birds preferentially used taller trees in areas with fewer shrubs of higher species diversity. Nests at lower locations in trees had marginally lower hatching success due to their destruction by humans; this destruction contributed marginally significantly to lowering of the total nesting success in all studied nests. Although gale winds also had a negative effect on breeding success, the anthropogenic influences were a greater factor in reproductive failure. We found similar effects in our review of literature on breeding success of the little egret from various geographical areas. Our results may be of use by conservation organizations in their actions to protect colonies of the little egret.     

Evaluating the use of spawning success to estimate reproductive success in a Caribbean reef fish

Observations on egg batch production by known female Stegastes partitus and the fates of those egg batches within the nests of known males revealed that spawning success was not a reliable predictor of hatching success and, hence, reproductive success because of high egg batch mortality. Moreover, while numbers of eggs per batch increased with increasing female length, both inter- and intra-individual variation in batch size was considerable, demonstrating that spawning events cannot be considered equivalent. These two findings indicate that spawning success cannot be assumed to provide a direct quantitative substitute for a measure of reproductive success in this benthic spawning reef fish.     

Reproduction, molting, and growth of two Mexican uniparental forms of the tadpole shrimp Triops (Branchiopoda: Notostraca) under a recirculating culture system

Two forms (here called short and long) of the tadpole shrimp Triops from the Baja California peninsula (Mexico) exhibit interesting features for aquacultural purposes; rapid growth, early maturation (six days) and uniparental reproduction via cysts (i.e. drought-resistant dormant eggs). The use of Triops for aquaculture depends on the standard production of viable cysts. Basic information on the reproductive potential of Triops is scarce. Using a recirculating system, we studied, through two culture tests, the cyst production, frequency of molting, and growth rate of the two Mexican forms. For each form, individual data were obtained from five specimens in Test 1 over 15 days, and from 10 specimens in Test 2 over 20 days. Hatching response of cysts produced in Test 1 was also studied. The short-form showed a high fecundity depositing groups of cysts from the ovisacs several times a day. The mean cyst production per day was 156–306 (Test 1 & 2), and the mean total cyst production was 2028 (range 728–3193) (Test 1), and 5821 (range 4136–7554) (Test 2). The maximum number of cysts deposited by one short-form individual in a day was 1231 (Test 2). The reproductive performance of the long-form was poor. The mean cyst production per day was only 4.2–7.9 (Test 1 & 2). The short-form molted every 2.5–2.8 days and the long-form molted every 2.8–3.7 days. The mean growth rate calculated from the standard length (mm d^–1) of the short-form was 0.43–0.84 (Test 1 & 2), and in the long-form the values were 0.84–1.25 (Test 1 & 2). The poor cyst production of the long-form may be explained by inadequate food resources that did not fulfill the nutritional requirements for reproduction. Given its prolific uniparental reproduction (vs. biparental reproduction), the short-form Triops appears as a good potential candidate for aquaculture.     

Exposure of eggs to solar UV‐B leads to reduced hatching rates in two sparid fishes,red sea bream Pagrus major and black sea bream Acanthopagrus schlegeli

Hatching success was examined under exposure to solar ultraviolet radiation (UVR) using filters to give three different light conditions [C1: UV‐B, UV‐A and photosynthetically active radiation (PAR), C2: UV‐A and PAR, C3: PAR] in red Pagrus major and black Acanthopagrus schlegeli sea bream. Hatching rate of both species was reduced by an exposure over a 2 day period to UVR and was not significantly different between two species under the three light conditions.     

扬子鳄(Alligator sinensis)卵体积和重量估算及其对孵化成功率的影响

收集了安徽省扬子鳄国家级自然保护区2004、2006、2007年的800枚扬子鳄卵和2007年的188条幼鳄的相关数据.经统计分析,得到卵的体积、重量的回归方程(V=0.537LB2 1.151,R2=0.960;W=0.593LB2-0.541,R2=0.975)和估算公式(V=0.553LB2,F=0.267,P=0.606＞0.05;W=0.585LB2,F=0.003,P=0.960＞0.05).公式V=0.553LB2 估算出的卵的体积与实际体积相比,误差小于3%;公式W=0.585LB2估算的卵的重量与实际鲜重相比,误差小于2%.基于卵的体积和重量推导公式,还探讨卵的体积、重量与孵化成功率和繁殖成功率之间的关系,结果表明,扬子鳄卵的体积、重量对孵化成功率和繁殖成功率均有明显的影响,较大的卵孵化出幼鳄的几率及成活率都更高.