首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 687 毫秒
1.
星突江鲽精子的超微结构   总被引:1,自引:0,他引:1       下载免费PDF全文
应用扫描电镜和透射电镜观察了星突江鲽Platichthysstellatus精子的超微结构。星突江鲽的精子由头部、中段和尾部组成。头部呈球形,主要结构为细胞核。核前端无顶体,后端有植入窝,植入窝较浅,凹入深度约为细胞核直径的I/4。核中染色质致密,但存在染色质较浅的头部凹陷和核泡。中段包括中心粒复合体和袖套。近端中心粒的长轴与基体的长轴相互垂直,呈“T”字型排列,基体的长轴与精子的长轴平行。袖套很浅,其最深处只达到线粒体下端的1/3处。在袖套线粒体的外面,具有大量的椭圆形囊泡存在。尾部细长,主要由轴丝构成,为典型的“9+2”微管结构。鞭毛较粗,长有两排侧鳍,侧鳍不对称。鞭毛细胞质中可见大小不一的椭圆形囊泡存在,囊泡的分布不均匀,一侧囊泡数量较多,另一侧偏少。鞭毛的这种结构与精子的运动相适应。  相似文献   

2.
The primary structure of the major protein from the Corpuscles of Stannius (CS) of the Australian eel was elucidated from the cDNA sequence and was found to bear close similarity to the N-terminal amino acid sequence of the presumably homologous salmon hormone, teleocalcin (TC). The cDNA sequence predicted a preproprotein of 263 amino acids. Following removal of a 17 amino acid signal peptide, specific monobasic cleavage at an Arg-Phe bond generates the 231 amino acid mature form of the protein. The isolation and sequence determination of the prosequence confirms that the precursor contains a prosegment of 15 residues. Various fragments of the protein have been synthesized chemically and their biological activity assessed. The N-terminal 1–20 fragment of the mature protein inhibits calcium uptake in fingerling trout, the effect being similar, but not equipotent to salmon teleocalcin. Further, infusion of either the N-terminal 1–20 or the 81–94 fragment at 50 μg/h into the renal artery of conscious sheep, caused significant decreases in systemic plasma potassium concentration and in potassium excretion. The 1–20 fragment also gave rise to a small but significant increase in sodium excretion. Infusion of TC at the same rate results in a significant decrease in plasma potassium and phosphate concentration as well as a significant decrease in potassium excretion. Bovine PTH (1–34) at 100 μg/h causes a small decrease in plasma potassium and phosphate and an increase in plasma calcium concentration, and was the only peptide to cause a significant decrease in calcium excretion.  相似文献   

3.
Yongshun Xiao   《Fisheries Research》2004,70(2-3):311-318
Fishing effort is a function of many (continuous) variables which fishers can manipulate. However, when catch and fishing effort data are analysed using a generalized linear model, individual types of fishing effort usually enter as a composite quantity. But not all quantities can be combined into a composite quantity. Use of such data this way generally leads to a loss of information and incurs a model bias. In this paper, I analyse catch and effort data for the blue swimmer crab off South Australia by a direct use of individual types of fishing effort to extract a relative index of biomass, and use the concept of homogeneous functions to present some of the results. I also give formulae for choosing a combination of different types of fishing effort to effect a specified level of catch in both absolute and relative terms. Assuming that catch follows an independent gamma, normal, negative binomial, or Poisson distribution, fitting of a generalized linear model with a log-link function to the commercial catch and effort data suggests that: (1) the exploitable biomass remained relatively constant from 1 July 1983 to 30 June 1996; (2) the relative instantaneous rate of fishing mortality of a particular sex and age (if gear selectivity was constant over time) slightly increased over time; (3) a 1% increase in the number of days fished gave about 0.85% increase in catch whereas a 1% increase in the number of people on a boat led to only about a 0.45% increase in catch. This implies that use of a composite measure of fishing effort such as boat days and man days when analysing catch and effort data is inappropriate for this fishery. Although a generalized linear model may be a reasonable first-order approximation, catch and effort data are best interpreted through a process model.  相似文献   

4.
大窑湾牡蛎养殖区叶绿素a分布和初级生产力估算   总被引:1,自引:0,他引:1  
根据1997年4-12月间对大窑湾牡蛎湾牡蛎养殖区的生态环境调查结果,讨论了该养殖水域叶绿素a含量分布特征和季节变化,对初级生产力进行估算。结果表明,大窑湾浮筏养殖区叶绿素a含量上于较低水平,平均为1.02mg/m^3。叶绿素a含量分布呈现出明显的季节差异,秋季较高。初级生产力的分布与叶绿素a含量分布存在差异,丰季最高,海水透明度可能是造成这种差异的重要影响因子。  相似文献   

5.
Automated measurement of species and length of fish by computer vision   总被引:2,自引:0,他引:2  
Trials of a computer vision machine (The CatchMeter) for identifying and measuring different species of fish are described. The fish are transported along a conveyor underneath a digital camera. Image processing algorithms: determine the orientation of the fish utilising a moment-invariant method, identify whether the fish is a flatfish or roundfish with 100% accuracy, measure the length with a standard deviation of 1.2 mm and species with up to 99.8% sorting reliability for seven species of fish. The potential application of the system onboard both research and commercial ships is described. The machine can theoretically process up to 30,000 fish/h using a single conveyor based system.  相似文献   

6.
In this study, we undertook a series of experiments to assess different faecal‐collection methods and also the digestibilities of a range of feed ingredients when fed to Tra catfish (Pangasinodon hypothalamus). Apparent digestibility coefficients for dry matter, energy and nitrogen for a reference diet were also determined from faeces collected by way of settlement at 2‐h intervals from 2 to 24 h. No significant effect of sample collection time on the digestibility values was observed. Stripping was attempted, but was not considered a suitable method for collecting digesta from Tra catfish. Dissection collection was also evaluated. Values determined from dissection collection were lower than those from using settlement. In a second experiment, a suite of test ingredients was combined with a reference diet component in a 30 : 70 ratio to determine the ingredients for dry matter, energy and nitrogen digestibilities. Ingredients included were trash‐fish, defatted rice bran, wet full‐fat rice bran, dried full‐fat rice bran, broken rice, cassava, soybean and fish meals. Collection of faeces by settlement was used for determining the digestibility of each of the ingredients. The results showed that Tra catfish can efficiently digest protein and energy from a wide range of feed ingredients and nutrient sources.  相似文献   

7.
This study investigated the effect of acetic acid concentrations from 3 to 8% on the physicochemical and sensory quality of marinated Atlantic and Baltic herring from fresh and frozen-thawed material. The increased concentration of acetic acid was found to exert a strong impact on decreased sensory scores, weight yield, and pH value as well as on an increased brightness parameter of meat. In turn, moisture, protein hydrolysis products (PHB), total volatile bases (TVB) content, and hardness parameter were affected by the higher addition of acid to a lesser extent. Enhanced protein hydrolysis was observed only at acetic acid concentration of 5% or 5–8%, whereas there was a decrease in the content of TVB only at an acid concentration of up to 4–5%. The marinated frozen-thawed fillets, compared to the fresh ones, required a greater addition of acid in the brine, by 1.5%, to reach a similar pH value. The freezing of fish contributed also to a decrease of PHB and free hydroxyproline, along with an increased concentration of acetic acid. The marinades from frozen-thawed herring contained more TVB, had worse color, and hardness parameters, as well as less yield.  相似文献   

8.
褐藻糖胶的提取纯化方法   总被引:4,自引:0,他引:4  
褐藻糖胶是存在于褐藻中的硫酸酯多糖,具有多种生物活性。本文综述了褐藻糖胶的提取、纯化和分级等方面的研究工作。  相似文献   

9.
To determine the urea in milk and thus to get information on the feeding regimen, a method using colour stripes was developped for the extension service in Bavaria. The quantitative results are fairly exact and available within four minutes comparing the colour changes of the stripe with a four-colour-scale. The scale comprises a range from 15 to more than 40 mg urea nitrogen per 100 ml of milk. The resulting colour as a rule lies between two colour shadings. Udder diseases give uncorrect results. The pH values of the milk samples should be situated between 6.6 and 6.9. This test meets the requirements of the extension service in most cases. Thus disturbances of metabolism caused by feeding can be corrected without problems and immediately. The status of lactation seems to have no influence. Most important in this respect are a feed composition adapted to ruminants and a correct ratio between intake of energy and protein.  相似文献   

10.
微量元素对水华发生、发展的影响   总被引:7,自引:0,他引:7  
微量元素作为藻类营养因子的一部分,对藻类生长具有重要作用,而藻类(特别是微囊藻)的大量增长则会造成"水华"现象。本文综述了各种微量元素对水华藻类生长的影响及其影响机理,进而得出结论:微量元素对水华藻类的生长影响趋势为低浓度促进生长,高浓度抑制生长,而藻类对微量元素有一定的富集作用;在微量元素中,铁元素对水华的发生、发展至为重要,在某种情况下有可能成为水华发生、发展的限制因子;其他元素(如稀土元素和重金属元素等)在水华发生、发展中则起辅助作用。  相似文献   

11.
二种微生物制剂对青虾池水质和生长的影响   总被引:2,自引:0,他引:2  
将二种微生物制剂施用于青虾养殖池,观察池塘水质的变化和对青虾规格及产量的影响,结果表明,施用微生物制剂后,池水的溶解氧、总磷增加,氨氮值下降,而COD、pH和总氮则没有明显变化和差异。试验池青虾的生长速度明显要大于对照池,说明微生物制剂可明显改善水环境,提高养殖青虾的产量和规格。  相似文献   

12.
The ability to separate or sequester individual fish identified as requiring further inspection would represent a milestone in the development of inspection and control systems for fish in sea nets. This paper reports work on a technique which enables a visually identified fish to be selectively drawn away from the other fish and towards the camera. The development of a device capable of sequestering the fish thus localised is the subject of future development. The technique for attracting the fish relies on the development of a conditioned response in the whole population which associates a light stimulus with food delivery. This is found to be a relatively easy and rapid process. The target fish is then selectively exposed to this stimulus and so is attracted to the light source while the others remain undisturbed. Tank trials suggest that a target fish can be selectively attracted to the camera with a reliability approaching 70%. Further work is needed to establish whether this concept can be used in sea nets at commercial stocking densities.  相似文献   

13.
为缩短传统育苗时间,开发室内种质保存技术,满足大规模栽培苗种需求,实验用4%的果胶酶和2%纤维素酶混合,将来自于不同月份和不同藻体部位的宽礁膜切段,分别在相同条件下解离成原生质体,详细研究了这些不同部位和不同生长时期细胞的再生、分化和发育途径。根据体细胞后代的外形、有无假根、有无公共膜、细胞大小和排列方式,以及它们最终的发育分化趋势,将宽礁膜原生质体发育方式分为8种结果,既可形成体细胞,也可形成生殖细胞。形成体细胞的发育途径又分3种类型7种结果,即细胞团、畸形苗和正常苗3种类型,其中发育成细胞团的类型又分为规则细胞团和不规则细胞团2种结果,发育成畸形苗的类型又分为假根为主的畸形苗、有类假根的畸形苗、无假根的畸形苗和管状畸形苗4种结果。各种发育类型与藻体的日龄、大小及部位有关,其原生质体直接发育形成正常形态藻体的发育方式只是8种发育结果的一种。  相似文献   

14.
鳜传染性脾肾坏死病毒p31基因结构及序列分析   总被引:3,自引:0,他引:3  
邓敏 《水产学报》2001,25(6):542-546
报道了鳜传染性脾肾坏死病毒(ISKNV)的p31基因结构及其序列分析。对ISKNV DNA HindⅢE酶切片段的序列分析结果发现该序列中含有完整的p31基因,ISKNV p31基因完整读码框为675bp,GC含量为49.78%,等电点为7.61,编码一个长为225aa、分子量为25.3kD的推定蛋白。结果分析发现该基因具有启动动子TATAbox和CAATmotif,下游有反向重复序列可形成茎环,另外还有一段直接重复序列和二联体结构。ISKNV与其它3种虹彩病毒(包括FV3、LCDV-1和EHNV)的p31基因氨基酸序列具有一定的同源性,但ISKNV与它们的同源性不高,序列比较和系统树分析发现ISKNV与蛙病毒属和淋巴囊肿病毒属的病毒都不尽相同。  相似文献   

15.
This study examined the influence of different lupin species and cultivars and their inclusion levels on the physical properties of an extruded diet. Lupin kernel meals were included into a fish diet formulation at 0%, 10%, 20% and 30%. Soybean meal was also included in a series of diets on a similar basis as a reference. The diet mashes were extruded using a laboratory-scale APV19:45 twin-screw extruder. The pellets were examined for radial expansion, bulk density, vacuum oil uptakes, sink rate, shear and crush strengths. Inclusion of lupin kernel meal significantly increased bulk density, sink rate, shear and crush strength of the pellets. With the increase in lupin kernel meal inclusion level, a concomitant decline in vacuum oil uptake and radial expansion was also observed. An assessment of the diet mashes using a Rapid Visco Analyser showed that the inclusion of lupin kernel meals increased the rate and degree of gelatinization of the mash starch content compared with that with a similar inclusion level of soybean meal. The inclusion of lupin kernel meals in the diet mash also improved the water-holding capacity of the extrudate, which has important implications for the reduction in extruder wear.  相似文献   

16.
Male farm animals accept female conspecifics as partners for mating only when they have been imprinted on them. The mating behaviour of the male can be divided into three phases: a) looking for female conspecifics in heat; b) testing the readiness to be served; and c) serving. The male animal can accelerate the development of the heat characteristics by certain behaviour patterns, which cause an effect of pheromones. There is a relationship between duration of the coitus and the sexual potency in every species. Finally masturbation is discussed. Ethologically it is a typical vacuum activity.  相似文献   

17.
沙爱龙 《南方水产》2007,3(6):71-74
主要阐述了流式细胞仪在贝类血细胞分类、血细胞功能、染色体核型分析、倍性检测等研究中的应用,供研究贝类的科技工作者参考。  相似文献   

18.
In Mexico, aquaculture is a growing sector, but it continues to be developed using non‐native species. The natural ecosystems of the lowland humid tropics of southeastern Mexico have been well‐described by ecologists and are host to a very high diversity of species, including a substantial ichthyofauna. Cichlid fish, commonly known in southeast Mexico as ‘mojarras’, are an important fish resource and are widely consumed. Several species are now under considerable pressure and consequently the generation of biotechnology for the culture of native fish species is necessary and worthwhile. This paper examines and describes the experiences and knowledge generated over recent years regarding the aquaculture of native cichlids in the southeast of Mexico. Although the scientific and technological capacity for research and development for native species culture exists, there is an evident lack of information on new technologies among producers, as scientific research is not translating fully into technical assistance. Research and extension should be emphasized in order to develop a comprehensive knowledge base on native species and to enable their cultivation.  相似文献   

19.
In conservation hatcheries, typically a great emphasis is placed on maximizing the effective number of breeders through spawning an appropriate number of spawners, spawning equal numbers of males and females when possible, and by mating either in a single-pair or factorial fashion. A commonly encountered problem, especially in small operations with anadromous salmonids, is a shortage of males at some point during the season, so that some males need to be spawned multiple times. This has an impact on the genetically effective number of breeders, and the commonly used equations for effective number are not applicable. In this paper I derive a relatively simple equation for effective number of breeders when some males are multiply spawned but reproductive contribution within spawning classes are equal: , where i is the number of times a male is spawned, Ni the number of males spawned i times, and μt the mean gametic contribution. I also derive an equation that allows relaxation of the assumption of equal contribution within classes. I then develop a number of simple and accurate approximations for the effective number of breeders. The equations can be applied to any situation in which there are discrete spawning classes in which the average reproductive contribution of any one class can be expressed as a multiple of that of another class.  相似文献   

20.
Abstract. The histopathological effects of intramuscular (i.m.) and intraperitoneal injections of the purified lethal cytolytic toxin of A. salmonicida in Atlantic salmon, Salmo salar L., were restricted to extensive degranulation of eosinophilic granular cells (EGCs) in the gills (both routes) and a limited coagulative necrosis of muscle fibres at the site of i.m. injection. The severity of these lesions did not apparently differ amongst fish that were moribund within 48 h and the surviving fish at 90 h. Previous studies indicate a maximum time to death caused by this toxin of 48 h. Thus, it is difficult to account for death of the fish from the toxin solely on the grounds of the histopathological features. It is suggested that a complex metabolic dysfunction results in death. The mechanism of 'furuncle' formation was demonstrated to result from a combined effect of the cytolysin and the purified 70-kDa protease present in the ECP. When i.m.-injected singly, the purified cytolysin produced a limited coagulative necrosis and the purified protease produced a limited liquefaction and haemorrhaging. In combination, they induced the extensive liquefactive haemorrhagic 'furuncle' characteristic of the whole ECP.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号