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1.
Manila clam Ruditapes philippinarum is one of the most important benthic animals in the coastal north Pacific region, where clam populations have been mixed genetically through trade and aquaculture activities. Accordingly, identification of the genetically different clam populations has become one of the most important issues to manage interbreeding of the local and introduced clam populations. To identify genetically different populations of clam populations, we developed 11 expressed sequence tag (EST)-microsatellite loci (i.e., simple sequence repeat, SSR) from 1,128 clam hemocyte cDNA clones challenged by the protozoan parasite Perkinsus olseni. Genotype analysis using the markers developed in this study demonstrated that clams from a tidal flat on the west coast contained 6 to 19 alleles per locus, and a population from Jeju Island had 4 to 20 alleles per locus. The expected heterozygosity of the 2 clam populations ranged from 0.472 to 0.919 for clams from the west coast, and 0.494 to 0.919 for clams from Jeju Island, respectively. Among the 11 loci discovered in this study, 7 loci significantly deviated from the Hardy-Weinberg equilibrium after Bonferroni correction. The 5 loci developed in this study also successfully amplified the SSRs of R. variegatus, a clam species taxonomically very close to R. philippinarum, from Hong Kong and Jeju Island. We believe that the 11 novel polymorphic SSR developed in this study can be utilized successfully in Manila clam genetic diversity analysis, as well as in genetic discrimination of different clam populations.  相似文献   

2.
The distribution of the Manila clam Ruditapes philippinarum, which is often dominant in intertidal zones, is influenced by both environmental and biological conditions. However, there have been few comprehensive studies on the interactive effects of these two groups of factors. The present study examined the environmental and biological parameters determining the population dynamics of the clams that is a dominant component of the intertidal communities of Euhangri and Padori on the west coast of Korean peninsula. We collected R. philippinarum and other members of the macrobenthos (> 1 mm long) monthly from 0.25 m2 quadrats deployed in the intertidal zones at Euhangri, Taean, and Padori during the period from August 2013 to January 2015. Physicochemical parameters of the water and sediment were measured at the same time. Water temperature and salinity is high and low in the summer to winter, respectively. While mean grain size of the sediment was higher at Euhangri than at Padori, total mean density of R. philippinarum was higher at Euhangri (325 ind./ 0.25 m2 at Padori vs. 194 ind./0.25 m2 at Euhangri). Settled spat (< 10 mm in length) density was much higher at Euhangri than at Padori (132 vs. 12 individuals/0.25m2, respectively). R. philippinarum spats settled down on the sediment at Euhangri in October and grew continually until the following May, when they reached adult size. Spats that settled down at Padori between March and April were not able to reach the adult stage. As the density of the adult population increased, the condition index of individual clams decreased, but as the population density of the spat increased the body condition index increased. The chlorophyll a content of the sediments at Padori exceeded that at Euhangri and decreased as the population of R. philippinarum increased. The shapes of R. philippinarum shells at Euhangri were more prolate than those at Padori, and the condition index at Euhangri exceeded that at Padori, indicating better growth conditions at Euhangri. The condition index and density of R. philippinarum were affected by the amount of chlorophyll a in the water column and in the sediment. The recruitment success of spats was negatively influenced by spat density. We suggest that regulation of habitat conditions for R. philippinarum, including the food supply, will optimize production of these commercial clams.  相似文献   

3.
Cellular and humoral immune parameters are often used as biomarkers to trace environmental and physiological stresses in marine bivalves. In this study, we compared various immune parameters of Manila clams (Ruditapes philippinarum) under normal conditions and under a high level of desiccation, using flow cytometry. The immune parameters analyzed included, total hemocyte count, hemocyte mortality, hemocyte DNA damage, reactive oxygen species (ROS) production, and phagocytosis activity. Total hemocyte count, hemocyte DNA damage, and hemocyte mortality were significantly elevated among clams under high desiccation stress, while phagocytosis activity and spontaneous ROS production were significantly lower compared to those parameters of the control clams (p<0.05). These data suggest that the immune parameters analyzed in this study well reflect the physiological status of clams.  相似文献   

4.
Pathologic condition of Manila clam, Ruditapes philippinarum collected from Haeju off the west coast of North Korea in February and March 2007 was investigated in this study. The diagnostics included a protozoan parasite, Perkinsus olseni, the brown ring disease (BRD) caused by bacteria Vibrio tapetis and metazoan parasites Trematod and Cestod. P. olseni infection was examined using histology and Ray’s fluid thioglycollate medium (RFTM) assay along with Choi’s NaOH digestion technique. Trematode and cestode infection was also examined from the histology. A total of 140 clams with 35–45 mm in shell length (2–3 years old) were analyzed. Condition factor (CF), a ratio of the wet tissue weight to the shell dry weight, ranged from 0.445±0.074 (February) to 0.544±0.132 (March). Total body burden of P. olseni (i.e. infection intensity) ranged from 18,644±37,755 (February) to 26,933±80,611 cells/g wet tissue (March) with the prevalence of 76.7–43.3% (March) respectively. Prevalence of trematode and cestode infection in February and March varied 22.5–25.0 and 15.0–22.5% respectively. Infection intensity of V. tapetis ranged 1–2 and the prevalence was 1.4 (February) and 5.7% (March). Prevalence and infection intensity of P. olseni in clams from Haeju was comparatively lower than those of clams reported on the west coast of Korea. BRD and the other metazoan parasite infection were also relatively lower or similar to the condition of the clams reported previously. CF of Haeju clams was also relatively higher than the clams in Gyeonggi Bay and Taean, suggesting that Haeju clams had relatively better pathologic and health condition.  相似文献   

5.
We have examined the vertical distributions of planktonic bivalve larvae, particularly the clam Ruditapes philippinarum and the mussel Musculista senhousia which are common and abundant on tidal flats of eastern Ariake Bay, southern Japan. Submersible pumping gear was used to take samples at 2 stations every 2 hours during the spring tide over a whole tidal cycle and/or through daytime and nighttime. Water samples were pumped up from 3 to 5 depths from the surface to sea bottom. Regardless of tidal cycles, D-shaped larvae were concentrated near the surface, while umbo larvae were found at the surface to intermediate depths. On average, these larval densities were significantly higher at the station close to the shore than the offshore station, with no significant difference between daytime and nighttime and between flood and ebb tides at each station. The velocity and direction of water movement at both stations revealed remarkable difference between the surface and bottom waters. The larvae at the surface may quickly disperse and be transported elsewhere, while those in water close to the sea bottom may tend to be retained.  相似文献   

6.
为了解TYR基因与蛤仔免疫的关系,本实验利用荧光定量PCR技术研究了菲律宾蛤仔五个群体(白蛤、白斑马蛤、斑马蛤、养殖和野生群体)的鳃组织和肝胰腺组织在LPS胁迫下TYR基因在不同时间(0 h、3 h、12 h、24 h、48 h)的表达特性。结果表明,在LPS注射后鳃组织中TYR6基因表达水平在白蛤和白斑马蛤3 h、6 h、12 h,野生蛤仔3 h,斑马蛤3 h、6 h,养殖群体6 h、12 h显著上调(P0.05),3h野生蛤仔和斑马蛤达到峰值, 6 h白蛤、白斑马蛤、养殖群体达到峰值(P0.05);在肝胰腺中,养殖群体和白斑马蛤6 h,白蛤6 h、24 h,野生群体24 h,斑马蛤3 h显著上调, 3 h野生蛤仔和斑马蛤达到峰值,6h养殖群体、白蛤、白斑马达到峰值(P0.05);鳃组织中TYR10基因表达水平在白蛤、野生群体和白斑马蛤3 h,养殖群体3 h、6 h,斑马蛤3 h、12 h显著上调(P0.05),肝胰腺组织中TYR10基因表达水平在白蛤3 h,野生群体3 h、6 h、12 h,斑马蛤、养殖群体6 h显著上调(P0.05),推测TYR基因在五个菲律宾蛤仔群体的鳃和肝胰腺中参与了免疫应答。通过对TYR基因的氨基酸序列进行二级结构分析和系统发育树分析,找到两个铜离子结合位点和6个组氨酸残基,并发现TYR6基因和长牡蛎同源性最高,为39.43%, TYR10基因和大珠母贝同源性最高,为51.04%。本文首次探讨在LPS胁迫下菲律宾蛤仔TYR基因的表达特性,为进一步探究TYR基因与菲律宾蛤仔免疫应答机制提供参考。  相似文献   

7.
The fishery yield of Manila clams, Ruditapes philippinarum, increased considerably in the 1970s but has decreased rapidly since the middle 1980s on extensive intertidal sand flats in Ariake Sound (Kyushu, Japan). A survey conducted in 2004 on a 3.4-km2 sand flat located in the central part of the Sound (Shirakawa sand flat) revealed four dominant species: two thalassinidean shrimps (Upogebia major and Nihonotrypaea japonica), which are deep-reaching burrow dwellers with strong bioturbation activities, and two bivalves (Mactra veneriformis and R. philippinarum). All four species belong to a phytoplankton (diatom)-feeding guild. In the late 1970s, the Manila clam population prevailed in high densities over the entire sand flat, whereas its distribution was restricted to the lowest quarter of the shore in 2004. In contrast, the population sizes and zones of occurrence of the other phytoplankton feeders have expanded in the absence of R. philippinarum, perhaps an indication of competitive release. After establishment, effects of the thalassinidean shrimps on sediment stability appear to have further reduced clam abundances. Across the sand flat in 2004, wet weight population biomass estimates for N. japonica, U. major, M. veneriformis, and R. philippinarum (whole body for shrimps and soft tissue for bivalves) were 304, 111, 378, and 234 tonnes, respectively. Based on Manila clam fishery yield records from Shirakawa, the carrying capacity of the Shirakawa sand flat in the late 1970s was estimated to be two times greater than the sum value for the whole phytoplankton-feeding guild in 2004. It is hypothesized that (1) the amount of phytoplankton determines the carrying capacity for the benthic community on the Shirakawa sand flat, with both phytoplankton and benthic biomass at maxima in the late 1970s, and (2) the subsequent increases in competition for space have caused further declines in the Manila clam population biomass to approximately one-eighth of its past value.  相似文献   

8.
The present study focuses on the influence of target strength (TS) changes in the swimming angle of the hairtail (Trichiurus lepturus). We measured in-situ TS at 38 and 120 kHz with luring lamps at a fishing ground for jigging boats near the coastal waters of Jeju-do in Korea. Swimming angle and size of hairtails were measured using an acoustic camera. Results showed that mean preanal length was estimated to be 13.5 cm (SD = 2.7 cm) and mean swimming tilt angle was estimated to be 43.9° (SD = 17.6°). The mean TS values were ?35.7 and ?41.2 dB at 38 and 120 kHz, respectively. The results will assist in understanding the influence of swimming angle on the TS of hairtails and, thus, improve the accuracy of biomass estimates.  相似文献   

9.
To explore the effects of temperature changes on dinoflagellate bloom succession in the coastal waters of the East China Sea, changes in the growth, photophysiology, and Rubisco gene expression of Prorocentrum donghaiense and Karenia mikimotoi, two harmful algal species, were investigated at different temperatures (16 to 28°C). The maximal specific growth rate and the maximal mRNA expression of Rubisco gene in P. donghaiense and K. mikimotoi occurred at 20 and 24°C, respectively. The photosynthetic activity of P. donghaiense was generally stable, but K. mikimotoi photosynthesis increased when temperatures rose from 16 to 28°C. The effective photochemical efficiency (F q ′ /F m ′ ) and the maximal relative electron transfer rate (rETRmax) of K. mikimotoi increased significantly with increasing temperature, and the lowest and highest values occurred at 16 and 28°C, respectively. It seems that P. donghaiense has higher photosynthetic capacity than K. mikimotoi due to its higher F q ′ /F m ′ , rETRmax, and photosynthetic efficiency (α). However, K. mikimotoi has a higher growth rate than P. donghaiense. These results suggest that the photosynthetic activity and genetic responses of dinoflagellates are species-dependent. It is likely that temperature changes affect species composition during blooms, leading to the observed patterns of bloom succession.  相似文献   

10.
研究利用中型生物扰动系统 (AFS)对胶州湾薛家岛潮间带菲律宾蛤仔 (Ruditapesphilippinarum)养殖断面和非养殖断面的中潮和低潮 4个站位的生物沉降和沉积物的再悬浮过程进行测定。结果表明生物沉降作用与大型滤食性双壳类动物 -菲律宾蛤仔的丰度呈显著的正相关关系 (r=0 .984 ,P<0 .0 5 ) ,养殖断面的生物沉降作用要明显地大于非养殖断面。在菲律宾蛤仔的低密度区 ,生物沉降的作用小于自然沉降 ,而在其养殖的高密度区 ,生物沉降率约为自然沉降率的4倍。薛家岛潮间带沉积物的临界侵蚀速率为 17.4～ 2 0 .4 cm/ s。沉积物的稳定性与所测生物因子的关系不密切 (P>0 .0 5 )。作者推测两个断面中潮站位沉积物的相对易侵蚀性 ,可能是由于此处环境受到某些大型动物及高潮带人工养殖带来的扰动所致  相似文献   

11.
A laboratory-based microcosm experiment was carried out to examine both the behavioral and antioxidant response of the clam Gomphina veneriformis under the conditions of 3 types of burial material(sand,silt,silt-sand mixture) with 3 burial depths(5 cm,15 cm,30 cm).The concentration of dissolved oxygen decreased significantly after 3 d of burial in all experimental groups.In silt and sand-silt mixture groups,the interstitial water quality became worsened with lower pH,and higher NH_4~+-N concentration,where clam mortality occurred simultaneously.However,clam samples in all sand groups and 5 cm,15 cm sand-silt mixture groups survived well for 8 d.Obviously fewer individuals left in the bottom sand in the 15 cm,30 cm silt groups and 30 cm sand-silt mixture groups than in the 5 cm groups.Therefore,it suggests that adding silt and increasing burial depth could stimulate the vertical movement of organisms and cause lethal effects.It was found that the burial depth was the key factor that influenced the activities of antioxidant enzymes,such as superoxide dismutase(SOD) and catalase(CAT).The SOD and CAT activities in the gills and hepatopancreases of organisms both showed significant upregulation in 30 cm burial depth after buried for 8 d.Higher enzyme activities were found in gills than in hepatopancreases,which indicated that the gills of the bivalve G.veneriformis were more susceptible to burial effects than hepatopancreases.Overall,this study shows that sediment burial could cause effects on the biological behavior and antioxidant enzyme activities.  相似文献   

12.
The current study was carried out from May 2014 to April 2015 to estimate the stock status of P. viridis in Marudu Bay. The gonad development was monitored by histological examination, while the population parameters including asymptotic length (L∞), growth coefficient (K), mortality rate (Z, F and M), exploitation level (E) and recruitment of P. viridis were estimated using the lengthfrequency data. Results of the current study demonstrated that P. viridis in Marudu Bay spawned throughout the year with two major peaks, one in April to May and another one in October to December. The recruitment pattern was continuous with the peak in May to June 2014, which corresponded to the first spawning peak in April. However, no significant recruitment was observed from the second spawning peak due to the difference in spawning timing between male and female populations. The estimated asymptotic length (L∞), growth coefficient (K), total mortality (Z), natural mortality (M), fishing mortality (F) and growth performance (ф) of P. viridis in Marudu Bay were estimate to be 117 mm, 0.97 yr-1, 4.39 yr-1, 1.23 yr-1, 3.16 yr-1 and 4.123, respectively. The exponent b of the lengthweight relationship was 2.4 and exploitation level (E) was 0.72. The high mortality, low condition indices and negative allometric of P. viridis in Marudu Bay is caused by a lack of suitable food in the surrounding water.  相似文献   

13.
Determining the taxonomic status of the red algal genus Chondracanthus based on morphological characters is challenging due to the similarity and high degree of plasticity of the thallus. Since the taxonomic history of several Chondracanthus species remains unclear, we analyzed the plastid rbcL and mitochondrial COI genes of the specimens from Korea and Japan, in combination with morphological observations, to examine their phylogenetic relationships. Our results confirmed the distinction of C. okamurae, which is separated from C. intermedius, and identified a novel species, C. cincinnus sp. nov. Three species (C. okamurae, C. intermedius and C. cincinnus) formed a monophyletic clade with C. tenellus. C. okamurae is distinguished by linear, narrow, cylindrical to compressed, slightly recurved axes, and a high-intertidal to subtidal distribution. It was collected from Korea and Japan, while C. intermedius was identified from Japan only. A new species, Chondracanthus cincinnus sp. nov., is characterized by linear, compressed, strongly recurved axes, and a low-intertidal to subtidal distiribution. Based on the molecular phylogeny using rbcL and COI data, we herein resurrect C. okamurae as a distinct species and identify C. cincinnus as a new species.  相似文献   

14.
菲律宾蛤仔(Ruditapesphilippinarum)是重要的海洋经济贝类和海水养殖品种,具有较强的表型可塑性特点,不同地理群体之间存在表型差异。本研究根据实测数据建立了胶州湾与天鹅湖菲律宾蛤仔壳长(SL)与壳高(SH)、壳宽(SW)和活体重(W)的回归方程,定量分析了两个地理群体的形态学差异。由于其近似圆形的形态使得所能测量的外部指标较少,限制了传统形态测量学在其地理群体判别中的应用。本研究提出了将传统形态测量学和广义线性模型(GLM)相结合的方法,建立了判别菲律宾蛤仔地理群体的逻辑斯蒂(Logistic)回归方程。结果表明:菲律宾蛤仔的天鹅湖群体比胶州湾群体具有更高的SH/SL和SW/SL比值,壳形椭圆较圆且隆起程度高,"凸"形明显;基于GLM模型的Logistic回归能够快速准确地判别菲律宾蛤仔的地理群体归属,判别正确率高达94.23%。本研究为双壳类物种地理群体判别提供了新的分析方法和技术手段。  相似文献   

15.
金属硫蛋白(Metallothionein,MT)是一类富含半胱氨酸的小分子蛋白质,参与机体重金属解毒和金属元素代谢等生理过程。本研究采用RACE技术,克隆获得了菲律宾蛤仔(Ruditapes philippinarum)金属硫蛋白(RpMT)的全长cDNA序列。RpMT的cDNA全长为570bp,编码75个氨基酸,包含15个MT所特有的Cys-Xn-Cys结构。采用实时荧光定量PCR技术,分析了两种壳色菲律宾蛤仔(白蛤和斑马蛤)RpMT基因在Cd2+暴露后的表达变化。结果发现:Cd2+急性和亚慢性暴露均可导致两种壳色蛤仔消化腺和鳃组织RpMT基因表达量的显著上调;暴露后两种壳色蛤仔鳃组织RpMT基因表达量的增加幅度均高于消化腺组织,且以白蛤鳃组织基因表达水平的上调幅度较高。上述结果表明,RpMT可能在菲律宾蛤仔抵御Cd2+胁迫过程中发挥了重要作用。  相似文献   

16.
Clam Ruditapes decussates was used as a biomonitoring organism to measure the potential impact of pollution. The present study investigated histological alterations of R. decussates following a long-term exposure to a sublethal-level of pesticides Reldan and Roundup. The clams were taken to the laboratory and kept for days to adjust to a continuous closed flow system with quality water control. After the adjustment period, clams were exposed either to sublethal concentrations of Reldan (0.6 μl L?1) or Roundup (1.1 μl L?1) for 90 days. Clams were taken to determine the histological damage at 30, 60 and 90 days. Most histological alterations were highly localized in the glandular cells of the gills, mantle tissues and digestive gland; secretions of glandular cells were found to be increased by increasing the time of exposure. Histopathological results showed the activation of resistance mechanisms that allowed the clams to survive under sublethal stresses. Thus, histological changes on localized tissues were sensitive and they have positive correlation to the time of exposure to the pesticides, suggesting that they may serve as biomarkers for Reldan and Roundup exposures.  相似文献   

17.
Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae-Masan Bay, Korea have been nearly annual events for many years. However, excluding some Alexandrium species responsible for PSP, there are no critical reports on the morphology of Alexandrium species in this bay. To identify the Alexandrium species based on detailed morphological features, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment trap samples were analyzed. Four species of Alexandrium were identified: Alexandrium affine, A. fundyense, A. catenella, and A. insuetum. Morphological features of these species were basically consistent with those outlined in previous studies. However, the ventral pore and the connecting pore on the sulcal plate, which have been accepted as diagnostic characteristics for the identification of A. fundyense and A. catenella, need to be reevaluated, indicating that useful morphological features for identifying these two species should be recommended to avoid confusion in the classification of species in genus Alexandrium.  相似文献   

18.
Vestimentiferan tubeworms acquire their symbionts through horizontal transmission from the surrounding environment. In the present study, we constructed a 16S rRNA gene clone library to investigate the phylogenetic relationship between diverse microbes in the sediment and symbiotic bacteria in the trophosome of the tubeworm, Lamellibrachia satsuma, from Kagoshima Bay, Japan. Two symbiotic bacterial phylotypes belonging to the classes γ- and ε-Proteobacteria were found from this tubeworm trophosome. They were very closely related to the symbionts of several other marine invertebrates. The most predominant bacteria in the sediment were ε-Proteobacteria. A broad diversity of bacteria belonged to non-proteobacterial phyla such as Planctomycetes, Acidobacteria, and Chloroflexi was observed. The presence of sulfur oxidizers (i.e., ε-Proteobacteria and γ-Proteobacteria) and sulfur reducers (i.e., δ-Proteobacteria) may play a significant role in the sulfur cycle in these habitats and provide multiple sources of nutrition to the cold-seep communities. Closely related clones of ε-Proteobacteria symbiont in the species level and of γ-Proteobacteria symbiont in the genus level were found in the surrounding sediment. The similarity of symbiont clones of L. satsuma with other symbionts and free-living bacteria suggests the possibility of opportunistic symbiosis in ε-Proteobacteria and the co-evolution of γ-Proteobacteria having occurred after symbiosis with the tubeworms.  相似文献   

19.
The Eulerian-Lagrangian method (ELM) has been used by many ocean models as the solution of the advection equation, but the numerical error caused by interpolation imposes restriction on its accuracy. In the present study, hybrid N-order Lagrangian interpolation ELM (LiELM) is put forward in which the N-order Lagrangian interpolation is used at first, then the lower order Lagrangian interpolation is applied in the points where the interpolation results are abnormally higher or lower. The calculation results of a step-shaped salinity advection model are analyzed, which show that higher order (N=3-8) LiELM can reduce the mean numerical error of salinity calculation, but the numerical oscillation error is still significant. Even number order LiELM makes larger numerical oscillation error than its adjacent odd number order LiELM. Hybrid N-order LiELM can remove numerical oscillation, and it significantly reduces the mean numerical error when N is even and the current is in fixed direction, while it makes less effect on mean numerical error when N is odd or the current direction changes periodically. Hybrid odd number order LiELM makes less mean numerical error than its adjacent even number order LiELM when the current is in the fixed direction, while the mean numerical error decreases as N increases when the current direction changes periodically, so odd number of N may be better for application. Among various types of Hybrid N-order LiELM, the scheme reducing N-order directly to 1st-order may be the optimal for synthetic selection of accuracy and computational efficiency.  相似文献   

20.
The Manila clam, Ruditapes philippinarum, has maintained small‐sized populations in a semi‐enclosed brackish lake along the Sea of Japan, the Honjo area of Lake Nakaumi, although the environment and biota of this area have changed dramatically due to a large‐scale reclamation project. There should be underlying processes that enable the restoration of this species from small‐sized populations, such as the existence of source (i.e. reproductive) populations in other areas and depth zones of the lake. However, there has been no robust, properly designed evaluation of the distribution of the Manila clam in the subtidal sand flats. In order to elucidate the possible mechanisms that allow for the persistence of populations of the Manila clam, we examined the spatiotemporal and vertical variation in distributions of 0‐age clams in the subtidal zone of sand flats. Seasonal effects on population variations showed erratic changes among depth zones without a decreasing trend along the depth gradient. Further, many local populations became extinct even in the shallower zones due to seasonal (summer) hypoxia at deeper zones and hypoxia by the accumulation of key benthic species (Asian mussel and decaying macroalgae) in mats at shallower zones. A few surviving local populations were stable with a spatial‐fragmental (patchy) distribution, associated with fragmented accumulations of Asian mussels and macroalgae. Efforts to maintain stable populations and to restore this species in the subtidal area may depend on these small, restricted, patchy local populations. These findings suggest that high fertility and productivity of the Manila clam as well as patchy distribution of small populations may contribute to the maintenance of the population and the avoidance of extinction (by spatially diffusing the risk of extinction) in harsh environments resulting from the reclamation project.  相似文献   

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