The sedimentation of salmonid spawning gravels in the Hampshire Avon catchment,UK: implications for the dissolved oxygen content of intragravel water and embryo survival

The accumulation of sediment within salmonid redd gravels can have a detrimental impact on the development of salmonid embryos; therefore, redd sedimentation represents a potential limiting factor for salmonid reproduction. The links between redd sedimentation, the dissolved oxygen content of intragravel water and salmonid embryo survival within the upper and middle parts of the Hampshire Avon catchment in southern England are explored. Measurements of surface and intragravel water quality and redd properties were undertaken for artificial redds constructed at known spawning sites. Salmonid embryos were also planted into artificial redds adjacent to the monitoring equipment. The rate of sedimentation of the newly cleaned redd gravels demonstrated a non‐linear decrease over time, which is attributed to a particle‐size‐selective depositional process. The results of the study confirm that low embryo survival and low dissolved oxygen concentrations in intragravel water can be attributed to the accumulation of sediment within the redd gravels. This was found to produce a reduction in redd permeability, which limited the interchange of surface and intragravel water and, therefore, the supply of dissolved oxygen to the intragravel environment. In view of the diminished status of salmonids within many of the UK's chalk rivers and streams, the results highlight the need for management initiatives aimed at reducing redd sedimentation and thereby optimizing salmonid embryo incubation success. Copyright © 2006 John Wiley & Sons, Ltd.     

Impact assessment of modified clay on embryo-larval stages of turbot Scophthalmus maximus L.

Using modified clay is one of the most promising methods for the mitigation of harmful algal blooms(HABs).However,the environmental impact of modified clay has become a subject of global concern.In this study,turbot(Scophthalmus maximus L.)embryos were used as a model to assess the effect of modified clay on this sensitive stage of fish development.Results show that the 24 and 48h LC 50(median lethal concentrations)of the modified clay were 1.70 and 1.65 g/L,and the safe concentration was 0.47 g/L,which is much higher than the concentration used to treat HAB.The modified clay did not affect significantly the hatchability of turbot embryos but when the concentration exceeded 0.50 g/L,the deformity rate of newly hatched larvae increased significantly.The total length,specific growth rate(SGR)and yolk sac absorption rate of larvae reached their peaks at 0.50 g/L and then gradually decreased as the concentration of modified clay increased.Therefore,a moderate amount of modified clay does not harm the survival and hatching of turbot embryos,or the growth and development of newly hatched larvae.     

Embryo dune development on a large,actively accreting macrotidal beach: Calais,North Sea coast of France

Sediment budget data from an 18‐month topographic survey were analysed with data from brief experiments on wind parameters, beach moisture contents, bedforms and sand mobilization in order to monitor conditions and patterns of embryo dune development over a flat 150–1000 m wide accreting upper beach. The surface conditions over the upper beach locally affect aeolian transport, but net dune development over time depends on sustained strong winds and their orientation. Incoming marine sand supplied by storms and onshore winds is reorganized by the dominant offshore to longshore winds into elongated embryo dunes over this upper beach, imprinting a regional morphology of long‐term longshore dune ridge development. Copyright © 2006 John Wiley & Sons, Ltd.     

日本蟳繁殖生物学的初步研Ⅱ.雄性繁殖习性及胚胎发育

根据精巢形态、切片组织学观察及扫描电镜观察 ,可将日本虫寻的精巢发育划分为三期 :未发育期、发育期与成熟期。通过扫描电镜观察可知 ,它的精子为无鞭毛精子 ,呈圆球形 ,大小为 30 μm。并运用实地调查、解剖、分析样本及光镜观察等手段 ,对其性腺形状、交配行为及胚胎发育等作了初步的描述。     

金钱鱼早期发育的观察

金钱鱼Scatophagus argus是一种具有观赏和食用价值的重要海水经济鱼类。文章对金钱鱼受精卵的胚胎发育过程和胚后不同发育阶段的形态特征进行了观察和描述,并对其仔、稚鱼饵料摄食情况作了初步观测。结果显示,在海水温度27.0~28.5℃、盐度26‰、pH为8.10~8.25的条件下,金钱鱼受精卵历时21h 30min完成整个胚胎发育过程孵化出膜。刚破膜仔鱼全长1.60±0.04mm,4h后全长1.79±0.04mm;卵黄囊椭圆球形,长径0.63±0.03mm,短径0.38±0.02mm。在水温28.0~29.0℃、盐度22‰~26‰海水中,1日龄仔鱼全长2.23±0.05mm,体高0.47±0.02mm,卵黄囊明显吸收;5日龄仔鱼全长2.85±0.07mm,卵黄囊和油球吸收完毕,仔鱼口裂0.17~0.18mm,开始摄取粒径0.10~0.12mm的轮虫幼体;9日龄仔鱼全长3.25±0.04mm,腹鳍鳍棘原基形成,胃肠充满饵料食物,消化吸收能力增强,仔鱼群体完全进入异养生长阶段;15日龄仔鱼全长3.72±0.03mm,腹鳍伸展,出现一对雏形鳍棘,仔鱼活力极强,可轻易摄食0.12~0.18mm的轮虫和桡足类幼体;32日龄的稚鱼尾部细小黑色素粒密集,体侧出现4条褐色横纹,背鳍、臀鳍和腹鳍鳍棘及鳍条基本发育完整,颅骨后下方两侧长出一对三叶状特异形骨结节突起,口裂约0.50mm,主食桡足类和硅藻,并能够摄食少量软性配合饲料。本研究可为金钱鱼繁育生产和早期形态鉴别提供生物学依据。     

Effects of temperature and salinity on the development of embryos and larvae of the veined rapa whelk Rapana venosa （Valenciennes, 1846）

The major population of the veined rapa whelk Rapana venosa(Valenciennes, 1846), which is an important fishery resource, is facing a large decline in China. We studied the effects of incubation temperature(16–34℃ at salinity 30) and salinity(5–45 at 25℃) on the incubation period and subsequent larval development. In the temperature experiment, the shortest incubation period was 12 days at 34℃, the lower temperature limit was 16℃, the longest mean shell length(1 193±17 μm) occurred at 25℃ and the highest survival rate 72.28%±5.62% was observed at 28℃. In the salinity experiment, the shortest incubation period was 15 days at 25. The salinity tolerance range was 15–40, the longest mean shell length(855±9 μm) and the highest survival rate 72.93%±4.85% were both observed at 35. This study demonstrated that, during the egg–mass stage, temperature and salinity regimes infl uence later growth and survival of larvae. These observations deepen our understanding of the ecology and conservation of natural populations of Rapana venosa.     

山东冰雹形成机制及雹云催化技术模拟——个例研究

利用中国科学院大气物理研究所开发的三维全弹性冰雹云模式,对2006年7月5日山东境内一次以冰雹、雷雨大风为主的强对流过程进行模拟,分析了冰雹的形成机制。结果表明:79%左右的冰雹胚胎是霰,雹胚以霰为主,霰主要来自于冰雪晶与过冷雨水碰撞冻结以及雪的自动转换过程,霰形成后主要靠碰并过冷云水、雨水增长,而冰雹主要质量来源是霰的自动转化以及碰并过冷云水增长。人工催化试验表明:在强对流云中冰雹含量达到0.1 g·m^-3前1～4 min进行催化,能有效抑制冰雹粒子的增长,在过冷水含量中心(5.5 km)上方1.0～1.5 km催化防雹效果较好,在其下方催化防雹效果较差;剂量越大防雹效果越好。AgI主要以凝华核的作用产生人工冰晶,冰晶凝华增长导致过冷云水含量降低。催化后雹胚特别是霰胚的数量增多,对过冷云水的竞争增强,其平均尺度、质量均减小,降低了雹胚向冰雹的转化率。冰雹碰并过冷云水增长也被减弱,导致冰雹总质量进一步减少。     

山东沿岸六线鱼早期发育的研究

六线鱼(Hexagrammos otakil J &. S)属袖形目、六线鱼亚目、六线鱼科,为冷温性近海底层鱼类,分布于黄、渤海、日本、朝鲜及俄罗斯远东诸海[1].六线鱼为沿岸浅海定居性鱼类,食物链较短、耐低温、适应能力较强、肉质细嫩,颇受我国北方地区养殖业者和消费者欢迎.     

似刺鳊鮈发育过程中同工酶变化及组织分布特征分析

运用高pH不连续聚丙烯酰胺凝胶(PAGE)电泳技术分析了似刺鳊鮈胚胎、仔鱼发育过程中5种同工酶变化,并对成鱼的9种组织同工酶分布特征进行了检测。结果发现:除醇脱氢酶(ADH)外,其他4种酶(EST、LDH、MDH、SOD)在发育过程中均被检出,且呈现明显的阶段性特征;在成鱼的4种同工酶也存在明显的组织特异性。4种酶共检测到9个基因位点。     

波纹龙虾胚胎的离体培养及发育观察

对波纹龙虾不同发育时期的胚胎进行离体培养和显微观察。结果表明,初始培育的离体胚胎愈接近孵化期,其孵化率愈高(最高达80.0%);波纹龙虾胚胎发育经历受精卵、卵裂期、囊胚期、原肠期、中眼色素形成期、复眼色素形成期、心跳期、破膜前期和出膜期;胚胎在发育过程中颜色变化:橙红→深橙红→砖红→灰白→接近透明。