220 resultados para Clam


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The name Ernest Ingersoll is well-known to many shellfishery biologists as the author of two outstanding monographs on the shellfisheries of the United States and Canada in the 1880's. The first (Ingersoll, 1881a), entitled "A Report on the Oyster-Industry of the United States," was a 252-page description of historical and contemporary oyster fishing' marketing methods, and statistical data in the eastern provinces of Canada and the coastal states of the United States. The second (Ingersoll, 1887), entitled "The Oyster, Scallop, Clam, Mussel, and Abalone Industries," was a l20-page summary of the first monograph about oysters as well as a history and description of contemporary methods and statistical data of the other shellfisheries. Although Ingersoll was, by profession, a naturalist and author but only briefly a shellfish scientist, these monographs are regarded as benchmarks, providing the principal descriptions of shellfisheries in North America in the 1700's and 1800's.

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Through research aimed at understanding the coastal environment, surveys designed to help manage the resource, and national programs to monitor environmental condition, we see a picture of a dynamic ecosystem that is Cape Romain National Wildlife Refuge (CRNWR). Currently, there are efforts underway to protect threatened species; monitor fish populations; and quantify the biological, physical, and chemical characteristics of this environment. The potential impacts to this system are just now being understood as ecological responses to human modification are observed and explained. As a starting point, this document compiles existing information about Cape Romain NWR in five topic areas and addresses the potential impacts to the Refuge. This review is intended to serve as a stepping stone to developing a research agenda in support of management of the Refuge. There are various sources of information on which to build a framework for monitoring conditions and detecting change to this environment. For instance, information on basic ecological function in estuarine environments has evolved over several decades. Long-term surveys of Southeast fisheries exist, as well as shellfish and sediment contaminants data from estuaries. Environmental monitoring and biological surveys at the Refuge continue. Recently, studies that examine the impacts to similar coastal habitats have been undertaken. This document puts past studies and ongoing work in context for Refuge managers and researchers. This report recommends that the next phase of this resource characterization focus on: • compiling relevant tabular and spatial data, as identified here, into a Geographic Information System (GIS) framework • assessing the abundance and diversity of fisheries utilizing CRNWR • delineating additional data layers, such as intertidal habitats and subtidal clam beds, from low-level aerial photography, hard copy maps, and other sources • continued inventories of plant and animal species dependent on the Refuge • monitoring physical and chemical environmental parameters using the methodology employed at National Estuarine Research Reserve System (NERRS) and other coastal sites, where appropriate • further definition of the potential risks to the Refuge and preparing responses to likely impacts.

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Post larvae of tiger prawn (Penaeus monodon) of the size 10-12 mm were stocked at the rate of 10 lakhs/ha in a manured cement nursary pond which was initially fertilized with chemical manures. Water exchange was attended once in a week. Artificial feeding was given in the form of minced clam meat. After a month, the pond was harvested. The juveniles which have grown to 40-46 mm size were recovered. The percentage of survival from post larvae to juveniles was 85.45%.

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Historical survey maps of Maryland oyster bars, crab bottoms, and clam beds, by county and watershed. PDF includes two index maps and forty-two survey maps scanned from microfilm.

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An experiment was conducted for a period of 28 days using 7-day old C. batrachus larvae of initial total length (±S.D.) of 7.4 ± 0.49 mm and weight (±S.D.) of 2.8 ± 0.75 mg. Five test diets viz. diets I, II, III, IV and V were prepared. Diet I was formulated using 30% fish meal (FM), 20% soybean meal (SM) and 20% Baker's yeast (BY), diet III using 15% FM, 20% SM, 15% cotton seed meal and 30% BY and diet IV using 20% FM, 30% BY and 30% powdered milk. The remaining two diets (diets II and V) were prepared using minced clam meat (96%) and BY (90%) respectively as the sole source of protein. Three replications were used for each treatment. The larvae fed on diet II exhibited significantly (P<0.05) better length gain and specific growth rate (SGR) than those of the larvae fed on diet III and there was no significant difference among the length gain and SGR of the larvae fed on diet I,II,IV and V. The larvae fed on diet II also showed significantly better weight gain and survival than those of the larvae fed on other diets. There was no significant difference between the condition factor of the larvae fed on diet II and IV. However, the larvae fed on diet II showed better condition factor than those of the larvae fed on other diets.

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Rate and pattern of spoilage of some of the economically important edible species of shell fishes Mytilus edulis (Mussel), Villorita cornucopia (Clam), Neptunus pelagicus (Crab) and Scylla serrata (Crab) have been discussed in this communication. Chemical indices used for objective evaluation of quality were water extractable nitrogen (WEN), non-protein nitrogen (NPN), free α-amino nitrogen (α - NH2 -N), glycogen, lactic acid and inorganic phosphorus in addition to the subjective tests. No significant difference in the spoilage pattern of the species during ice storage was observed and these species could be preserved in ice in organoleptic acceptable condition up to 8 days, 9 days, 8 days and 11 days respectively.

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Prawn, crab and clam meat were processed in experimental ca s having reduced internal tin coating of 5.6 GSM. Conventional cans having 11.2 GSM tin coating were used as control. Results showed that experimental cans behaved normally when used for canning prawns, provided the lacquer film was perfect with no exposure of metal. When there was a discontinuity in lacquer film exposing the metal blackening took place in such areas. Areas subjected to severe strains like the lock seam side and expansion rings on can ends were found to be more prone to blackening. Experimental cans were found unsuitable for canning crab meat or clam meat because in both cases the can wall as well as the contents underwent discoloration, in all cases.

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A fingernail clam, Sphaerium lacustre, was studied in subtropical Lake Donghu from June 1999 to May 2000. The S. lacustre population was characterized by a single annual reproduction period starting in March and ending in October; the population comprised three size groups, of which the 1999 cohort was dominant. The annual average density and biomass were 100.2 ind./m(2) and 12.11 g/m(2), respectively The annual production was 43.02 wet weight g/m(2), and the corresponding annual production/biomass ratio was 3.55.

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Seed rearing is an important part in large scale clam culture industry. Since the nutritional history affects early development in bivalve, the condition of larval nutrition plays a key role in successful seed rearing. So far, the molecular mechanism of nutrient uptake in bivalve larvae is unclear. As one of the important proteolytic enzymes, cathepsin B of several organisms has been reported to be involved in digestion. We intended to analyze whether cathepsin B is involved in larval nutrient metabolism in the economic bivalve, clam Meretrix meretrix. The full length of M. meretrix cathepsin B (MmeCB) cDNA was cloned, which is 1647 bp with an open reading frame of 1014 bp. The deduced amino acid sequence encoded a preproenzyme of 337 residues with Cys-114, His-282 and Asn-302 composing cathepsin B activity center. The temporal and spatial expressions of MmeCB mRNA were examined from trochophore to post larva stages by whole mount in situ hybridization. In trochophore stage, no detectable signal was found. In the later three stages, MmeCB mRNA was detected in the digestive gland, suggesting a possible role of MmeCB in digestion. Moreover, MmeCB mRNA was also observed in the epidermal cells in D-veligers. Cathepsin B specific inhibitor (CA074 methyl ester) was applied to block the activity of cathepsin B in unfed larvae. The average shell lengths of treated larvae were smaller than that in control groups. The results of mRNA epidermal distribution and inhibitor treatment in D-veligers indicated that MmeCB may be also associated with other pathway of nutrient metabolism in larval epidermis. The overall results in this paper revealed that MmeCB might play a role in larval nutrient metabolism. (C) 2008 Elsevier B.V. All rights reserved.

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采用体外药物诱导的方法,研究了5-羟色胺(5-hydroxytryptamine,5-HT)诱导的硬壳蛤卵母细胞成熟过程中cAMP信号通路的作用。结果表明,5-HT (0.01—100µM)均能够显著地诱导硬壳蛤卵母细胞的成熟。磷酸二酯酶抑制剂—咖啡因、茶碱和IBMX(3-异丁基-1-甲基黄嘌呤)可以单独抑制卵母细胞的自发成熟,但效果不显著。10mM的咖啡因和茶碱以及5mM的IBMX能够显著地抑制5-HT的诱导效果。dbcAMP(双丁酰基环腺苷一磷酸)不但能够抑制卵母细胞的自发成熟,而且还可以抑制5-HT诱导的成熟。因此,cAMP信号通路参与了5-HT诱导的硬壳蛤卵母细胞的成熟过程,并且该信号通路起着负调控的作用。 研究了PLC(磷脂酶C)和PKC(蛋白激酶C)的激活剂/抑制剂对5-羟色胺诱导的卵母细胞成熟的影响。高浓度的新霉素(PLC抑制剂)可以抑制5-HT诱导的卵母细胞的成熟,而DMBA(9,10-Dimethy-1,2-benzanthracene,9,10–二甲基胆蒽,PLC激活剂)则能够促进成熟。PMA(phorbol 12-myristate 13-acetate,佛波十四烷酸乙酸酯,PKC激活剂)能够抑制5-HT诱导的成熟,而Spingosine(PKC抑制剂)则可以促进卵母细胞的成熟。从而推测,5-HT诱导的卵母细胞成熟需要磷脂酰肌醇信号通路的激活。PLC浓度的降低能够抑制5-HT诱导的卵母细胞成熟;PKC浓度的降低则会促进卵母细胞的成熟。因此,在硬壳蛤卵母细胞的成熟过程中,PLC起促进的作用,DAG(二酰肌甘油)–PKC通路则起抑制的作用。 细胞外高浓度Ca2+能够促进硬壳蛤卵母细胞的成熟,Ca2+离子载体A23187也可以促进硬壳蛤卵母细胞的成熟。1-100µM异搏定(Verapamil,钙离子通道阻断剂)能够抑制卵母细胞的成熟,而100µM的Verapamil能够完全抑制其成熟。上述结果表明细胞外Ca2+对硬壳蛤卵母细胞的成熟是必需的,而且起到促进卵母细胞成熟的作用。三氟拉嗪(TFP,Ca2+与CaM结合的拮抗剂)能够抑制卵母细胞的成熟,高浓度的三氟拉嗪(1mM)能够完全抑制卵母细胞的成熟。说明CaM起到促进卵母细胞成熟的作用。可见,Ca2+通过与CaM的相互作用,共同起到促进硬壳蛤卵母细胞成熟的作用。 5-HT诱导成熟的卵母细胞可以完成受精过程,其受精过程以及幼虫发育情况与正常受精发育过程类似,没有显著差异。高浓度的新霉素可以抑制受精过程,而茶碱和咖啡因对受精没有影响。从而推测,磷脂酰肌醇信号通路参与了硬壳蛤卵母细胞的受精过程,而cAMP信号通路可能没有参与受精过程。 发现硬壳蛤的性腺发育与我国常见的双壳类如泥蚶相似。硬壳蛤卵母细胞中卵黄粒主要由线粒体、高尔基液泡、内质网和微吞饮泡形成。

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贝类养殖是我国海水养殖业中最重要的组成部分之一。贝类人工大规模养殖中的关键环节是种苗的人工繁育,早期幼虫能否正常生长发育,对幼虫变态和变态后生长率及成活率有很大的影响,直接关系到生产产量和经济效益,所以,了解幼虫发育机制对于生产实践具有重要的指导意义。 文蛤(Meretrix meretrix)是一种在东亚各国沿海和滩涂地区广泛分布的双壳贝类,是我国一种重要的经济品种。本论文以文蛤幼虫为研究对象,分别对文蛤幼虫发育过程中贝壳形成相关的铁蛋白(MmeFer)、营养及变态相关的组织蛋白酶B(MmeCB)及变态过程中细胞凋亡相关的caspase三个基因进行了克隆,分析了基因及编码蛋白在担轮幼虫期(L1)、D形幼虫期(L2)、壳顶幼虫期(L3)和稚贝期(L4)的时空表达特征,解析了其可能的功能,并研究了相应酶类的特异性抑制剂作用对幼虫发育过程的影响,进行了目标蛋白的功能验证,详述如下: 研究结果显示,在文蛤胚胎发育到原肠胚时放入不含铁离子的人工海水中培养,发育成无壳的畸形,随着人工海水中铁离子添加浓度的升高,幼虫长出壳状组织接近正常状态;而发育到L1期幼虫放入不含铁离子的人工海水中培养却可以发育出正常的壳,推测铁和铁代谢相关蛋白在幼虫贝壳初始形成有重要的作用。根据构建的文蛤幼虫cDNA文库中提供的序列信息,从文蛤中克隆了与铁离子代谢密切相关的铁蛋白(MmeFer)的全长cDNA 序列;通过Real time PCR发现,MmeFer mRNA的表达量在贝壳形成前后有明显改变;整体原位杂交结果显示MmeFer mRNA在L1期的表达部位刚好是贝壳生成的起始部位,推断文蛤铁蛋白与文蛤幼虫贝壳初始形成密切相关。 利用文蛤幼虫cDNA文库中的EST信息在幼虫中克隆到文蛤组织蛋白酶B(MmeCB)全长cDNA序列;通过整体原位杂交分析发现MmeCB mRNA在L2至L4期幼虫的消化腺部位表达,而且在L2期的幼虫表皮也有表达,说明MmeCB可能和幼虫消化相关,而且可能参与幼虫从表皮摄取营养的过程。利用MmeCB特异性抑制剂(CA074Me)处理饥饿幼虫,发现其生长受到明显抑制,验证了MmeCB参与幼虫表皮营养代谢的推论。利用免疫组织化学技术,研究了MmeCB蛋白在文蛤幼虫中的时空分布,发现其在L2期幼虫表面和胃部有阳性信号,而在L3期,MmeCB在幼虫面盘基部有强烈的表达,提示MmeCB在文蛤幼虫中不仅起到营养的作用,而且可能和幼虫附着变态有关。利用CA074Me分别处理文蛤胚胎和变态期幼虫,发现抑制MmeCB的活性对胚胎发育和幼虫变态都有显著影响。研究结果提示MmeCB在幼虫发育各阶段均具有重要的生物学功能。 根据caspase在不同物种中的保守区域设计简并引物,在文蛤幼虫中扩增到cDNA序列片段;检测有活性的caspase在文蛤幼虫各发育时期的分布部位,发现其在L1至L3期幼虫中都有分布,说明整个幼虫形态变化过程中都有caspase的参与;细胞凋亡检测结果显示,幼虫主要发生细胞凋亡的部位在L3期幼虫的面盘,即变态过程中要退化的器官,说明细胞凋亡可能是文蛤幼虫变态过程中面盘退化的主要机制;用caspase特异性抑制剂处理变态前幼虫,发现幼虫变态率下降,初步验证了caspase在文蛤幼虫变态过程中的作用。 通过对上述三种基因的研究,分别探讨了文蛤幼虫发育阶段中的几个主要事件(L1期到L2期的贝壳形成、L2到L3期的幼虫营养摄食及L3到L4期的附着变态)相关的基因及其功能,为研究贝类生长发育调控的分子机理提供了新的线索。

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Accumulation and distributions of aliphatic and polyaromatic hydrocarbons (PAHs) and heavy metals were measured in tissues of the clam Ruditapes philippinarum collected from 5 sites in Jiaozhou Bay, Qingdao, China. The concentrations of total aliphatic hydrocarbon and PAHs ranged from 570 to 2 574 ng/gdw (gram dry weight) and from 276 to 939 ng/gdw, in the most and least polluted sites, respectively. The bio-accumulation of hydrocarbons and PAHs in the clams appeared to be selective. Aliphatic hydrocarbons were predominantly represented by short chain (< nC(23)) n-alkanes, suggesting that petroleum hydrocarbons were likely the major contamination source. The selective uptake of 3 and 4 ring PAHs, such as naphthalene, fluorene, phenanthrene, fluoranthene and pyrene, by the clams was probably related to the physiological and bio-kinetic processes that were energetically favorable for uptake of compounds with fewer rings. Accumulation of the metals Cd, Cu, Zn, Pb, Cr, Hg, and As in the clam tissues also showed high variability, ranging from 0.043 to 87 A mu g/gdw. Among the 7 detected metals, Zn, Cd, Cu, and As had a particularly high potential of accumulation in R. philippinarum. In general, a positive correlation was found between the tissue concentrations and sediment concentrations of hydrocarbons and of some metals. Our study suggests that moderate contamination with polyaromatic hydrocarbons, and low to moderate contamination with metals, currently exists for clam R. philippinarum in Jiaozhou Bay, in comparison with other regional studies. A long-term monitoring program is certainly needed for assessment of the potential ecological influence and toxicity of these contaminants of R. philippinarum in Jiaozhou Bay.

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In many molluses, it has been found that Ca2+ signaling pathway is involved in the resumption of meiotic maturation in oocytes. To better understand the possible role of Ca2+ signaling pathway in regulating meiotic maturation in oocytes of the northern quahog Mercenaria mercenaria, free extracellular Ca2+, A23187 (calcium ionophore), verapamil (calcium channel blocker), and trifluoperazin (calmodulin antagonist) were used to incubate oocytes or serotonin-induced oocytes by pharmacological methods. Results show that extracellular Ca2+ (50 similar to 200 mM) and A23187 (1 similar to 10 mu M) can stimulate the meiotic maturation. In addition, verapamil (1 similar to 100 mu M) and trifluoperazin (10 similar to 1,000 mu M) could inhibit serotonin-induced oocyte maturation. Therefore, Ca2+ is essential for the reinitiation of meiotic maturation in oocytes of the northern quahog. Moreover, an increase i [Ca2+]i can promote meiotic maturation.

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Manila clams (Ruditapes philippinarum) and sediments were collected bimonthly during 2007 at five locations in Jiaozhou Bay near Qingdao, China, to determine heavy metal concentrations and to assess the validation of R. philippinarum as a metal biomonitor. Concentrations of heavy metals in clam soft tissues ranged between 0.75 and 3.31, 0.89 and 15.20, 5.70 and 26.03, 52.12 and 110.33, 10.30 and 72.34, 9.64 and 28.60, and 3.15 and 52.75 mu g g (-aEuro parts per thousand 1) dry weight for Cd, Pb, Cu, Zn, Mn, Cr, and Ni, respectively. Most of the highest values occurred at the northeast bay and the lowest values occurred at the western part. Regarding seasonal variation, relatively high tissue metal concentrations were observed during October or December. A similar pattern was also found in habitat sediments. There was a strong correlation between the concentrations of Cd, Pb, Zn, Mn, Cr, and Ni in soft tissues and surrounding sediments. It is indicated that R. philippinarum could be used as a biomonitor for heavy metal contamination in Jiaozhou Bay.

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Suspended particulate matter (SPM), sediments and clams were collected at three sites in Jiaozhou Bay to assess the magnitude of trace metal pollution in the area. Metal concentrations in SPM (Cu: 40.11-203; Zn: 118-447; Pb: 50.1-132; Cd: 0.55-4.39; Cr: 147.6-288; Mn: 762-1670 mu g/g), sediments (Cu: 17.64-34.26; Zn: 80.79-110; Pb: 24.57-49.59; Cd: 0.099-0.324; Cr: 41.6-88.1; Mn: 343-520 mu g/g) and bivalves (Cu: 6.41-19.76; Zn: 35.5-85.5; Pb: 0.31-1.01; Cd: 0.51-0.67; Mn: 27.45-67.6 mu g/g) are comparable to those reported for other moderately polluted world environments. SPM showed a less clear pattern. Metal concentrations in sediments displayed a clear geographical trend with values increasing with proximity to major urban centers. The clams (on dry weight) showed a complex pattern due to the variability introduced by age-related factors. Cd showed an apparent reverse industrial trend with higher concentrations in clams collected at distant stations. Zn, Pb and Mn showed no clear geographical pattern, whereas Cu increased in the clams collected in the most industrialized area. In addition, the bioaccumulation factors (BAF) were calculated. The result indicated that the studied Ruditapes philippinarum in Jiaozhou Bay possessed different bioaccumulation capacities for Cd, Zn, Cu, Pb and Mn, and Cd, Zn had a relatively high assimilation of those metals from sediment particles. A significant relationship with clam age was observed for Zn (positive) and Cu (negative) suggesting different physiological requirements for both metals with age. Trace metal concentrations measured in the tissue of the investigated clam were in the range considered safe by the WHO for human use.