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克氏原螯虾染色体及其核型 总被引:2,自引:1,他引:1
染色体是遗传物质的载体,是研究细胞遗传学的基础,为研究克氏原螯虾染色体及其核型,实验以性未成熟雄性个体的精巢为材料,采用低渗和空气干燥常规方法制备细胞分裂中期染色体标本,研究了克氏原螯虾染色体及核型。Giemsa和DAPI染色后在显微镜下观察到清晰的精母细胞减数分裂中期二价体和精原细胞有丝分裂中期染色体时相。对减数分裂中期二价体及有丝分裂中期染色体进行了数目上的统计。结果显示,克氏原螯虾二倍与单倍染色体数目分别为2N=188和N=94。由于有丝分裂染色体形状微小,核型分析困难,故选取减数分裂中期二价体,根据长度及着丝点位置对其进行了初步核型分析,核型公式为N=55M+22(SM,ST)+17T,未发现异形性染色体。 相似文献
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团头鲂核型与DNA含量分析研究 总被引:3,自引:1,他引:3
采用PHA体内培养法,取鱼体肾细胞用空气干燥法制备团头鲂染色体标本。经核型分析,团头鲂的核型为2n=48,26m 18sm 4st,臂数(NF)为92。用流式细胞仪测量外周血红血球细胞核的DNA含量为2.66pg/N。实验结果分析表明团头舫染色体数及DNA含量是稳定的,其核型公式与有关文献的报道略有差异。 相似文献
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根据对虾流网结构特点设计兼有捕虾和接获网上掉虾功能的专用网具,研究了对虾流网作业全过程的掉虾数量;同时还对暂养模拟掉虾和对虾在网上直接死亡率作了调查;并研究了流网掉下对虾的成活率。所得结果为调整渤海区秋季对虾汛的捕捞结构,实行以流网代替拖网作业的管理决策提供了科学依据。 相似文献
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以精巢为材料,研究了细螯沼虾有丝分裂染色体及减数分裂二价体组型。细螯沼虾染色体数目2n=100,n=50;有丝分裂中期染色体小,呈点状,无法进行核型分析;减数分裂双线期二价体呈棒状,着丝点清晰,染色体总臂数NF=172,核型公式为N=30M+6SM+14ST,T。此外,本文还对沼虾属的核型演化关系进行了初步探讨。 相似文献
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Md. Kawser Ahmed Shamima Sultana Sadeka Halim Md. Monirul Islam 《Aquaculture Economics & Management (Blackwell Science)》2016,20(3):272-282
The present study analyzes the prawn marketing chain before and after the implementation of a Danish-funded project (GNAEP) in three coastal districts of greater Noakhali, southeast region of Bangladesh. The results reveal that, before GNAEP, there was a longer prawn marketing chain with a number of intermediaries who used to share a considerable amount of market margin. However, after implementation of GNAEP, the prawn marketing chain has become shorter with a significant reduction of intermediaries which facilitates direct selling of prawns to processing plants through local Community Based Organizations (CBOs). The present prawn marketing system in the regions is in favor of prawn farmers. Farmers have greater advantages because 1) CBOs provide reasonable market price and actual weight, 2) CBOs can bargain with processing plants as the former are aware of the latest international market prices through Marketing Information System 3) number of intermediaries is lowered and 4) transport and preservation costs are reduced. The displaced intermediaries, some of whom are powerful persons in the society, have again started to influence the prawn market in different ways. This fact has opened up another discussion on how the power structure is shifting in this region and how they are affecting prawn marketing. 相似文献
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Nesar Ahmed Faisal Ahammed Catherine Lecouffe 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):335-353
An investigation was carried out in Mymensingh region of Bangladesh to understand current practices of freshwater prawn (Macrobrachium rosenbergii) marketing systems. Prawn marketing is almost exclusively maintained by the private sector, where the livelihoods of a considerable number of people are associated with prawn distribution and marketing systems. The market chain from producers to consumers passes through a number of intermediaries. The prawn is a highly valued product in international markets; most of the prawns (60%) are therefore exported, particularly to the USA, Japan and Europe. The rest (40%) of the under-sized prawns are sold to local markets in Mymensingh. The price of prawn depends on quality, size and weight, and grade. In spite of marketing constraints, livelihood outcomes are positive and most of the households of traders (75%) have improved their social and economic conditions through prawn marketing activities. However, concerns arise about the long-term sustainability of prawn marketing due to poor road and transport facilities, inadequate supply of ice, lack of money and credit facilities, and poor market infrastructure. It is therefore necessary to provide institutional, organizational, and government support for a sustainable prawn market. 相似文献
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Macrobrachium gangeticum (Bate) are commercially valuable prawns that are broadly distributed in the Ganga river that flows from northern to eastern India. We studied embryonic development from cleavage (blastomeres), segmentation, formation of optic vesicle, eye pigment development to larva formation, as these data are largely unknown in this species. We conducted this study using mature M. gangeticum broodstock placed in freshwater tanks. Just after spawning, females were kept in separate aerated tanks, where fecundity was estimated from the total number of eggs. Thereafter, egg samples from berried females were used to study their embryonic stages. The correlation coefficient between size and prawn weight, egg weight, egg number, body weight and egg mass of different sizes of prawns was analysed. Our results show that an increase in prawn size led to an increase in egg weight and egg number while decreases in body weight:egg mass ratio was noticed. Further results indicate that an increase in prawn weight had a positive impact on egg weight and egg number. The embryo development stages were used in this study as a tool to evaluate the development process of the prawn in a hatchery environment. 相似文献
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Md Abdul Wahab Sk Ahmad‐Al‐Nahid Nesar Ahmed Mohammad M Haque Mahmudul Karim 《Aquaculture Research》2012,43(7):970-983
Giant river prawn (Macrobrachium rosenbergii) farming plays an important role in the economy of Bangladesh. Presently, it is cultured in around 50 000 ha area with total annual production of 23 240 t. Traditional extensive prawn farming has been expanding over the last three decades through the introduction and adoption of improved culture systems, such as culture of prawn‐carps, prawn‐shrimp‐fish and prawn‐fish‐rice as concurrent and rotational systems. Efforts for the development of improved techniques on broodstock management, seed production and rearing and grow‐out of prawn have been made over the last decade. The outcomes are low‐cost feed for broodstock, production of post‐larvae in net cages (hapa), all‐male prawn culture, periphyton based prawn‐tilapia culture, C/N based prawn culture, organic prawn farming, prawn‐mola culture and prawn‐carp‐mola polyculture. Despite the development of culture technologies, a number of challenges for sustainable development of prawn farming need to be overcome to realize the potentials of this promising sector. Good aquaculture practises at all levels and application of measures for quality control and food safety would ensure sustainable development of prawn farming in Bangladesh. 相似文献
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Siddhartha Dasgupta Kathy J. Davis Ferdinand F. Wirth 《Aquaculture Economics & Management (Blackwell Science)》2013,17(1):3-16
This paper evaluated consumer perceptions of cooked freshwater prawn sold in festivals. Data were collected from prawn consumers attending the Kentucky State Fair and Garrett's Festival (in Lexington, Kentucky) on knowledge of prawn, seafood consumption frequency, proclivity of purchasing locally grown food, etc. A conjoint experiment was conducted in which respondents rated nine hypothetical plates of cooked prawn, differing from one another by the number of prawns, price, cooking style, and the presence or absence of side items. Results from data analyses indicated that the Garrett's Festival respondents were more educated and had more knowledge of prawns than the State Fair respondents. The State Fair respondents, while indifferent to the prawn cooking style, considered the product's price to be more important than the Garrett's Festival respondents. All results suggest that vendors would be more successful in dedicated prawn festivals than participating in festivals of general interest, such as the State Fair. 相似文献
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Freshwater prawn farming in Bangladesh: history, present status and future prospects 总被引:1,自引:0,他引:1
Within the overall agro-based economy in Bangladesh, freshwater prawn ( Macrobrachium rosenbergii ) farming is currently one of the most important sectors of the national economy. During the last two decades, its development has attracted considerable attention for its export potential. Freshwater prawn farming offers diverse livelihood opportunities for a large number of rural poor. Although the prospects for prawn farming are positive, it requires some research and development activities for long-term sustainability. This paper provides an overview of freshwater prawn farming in Bangladesh. 相似文献
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<正> 我国山西、陕西、新疆、内蒙、青海等地分布着大量的内陆盐湖,这些盐湖面积大的上万亩,小者也有数百亩,由于种种原因,盐湖的开发利用目前仅限于制取盐化产品或在一些盐度较低的湖泊中试养鲤、鲫等鱼类,利用率较低.为进一步开发利用这些 相似文献
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Nesar Ahmed Catherine Lecouffe Edward H. Allison James F. Muir 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3):246-269
A conceptual framework, drawn from an approach to poverty reduction known as the Sustainable Livelihoods Approach (SLA), is applied to understanding the role of freshwater prawn (Macrobrachium rosenbergii) marketing systems in southwest Bangladesh. Freshwater prawn marketing potentially provides economic returns and social benefits to the rural poor. Although the potential benefits are great, a number of constraints were identified for the long-term sustainability of prawn marketing systems. The study used the SLA framework as an analytical tool to identify ways to strengthen livelihoods of prawn traders and associated groups. 相似文献