Parasite Haplosporidium Nelsoni Research Articles

江苏海门蛎岈山牡蛎礁生态现状评价

PDF HTML阅读 XML下载 导出引用 引用提醒 江苏海门蛎岈山牡蛎礁生态现状评价 DOI: 10.5846/stxb201510102048 作者: 作者单位: 农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,农业部东海与远洋渔业资源开发利用重点实验室 中国水产科学研究院东海水产研究所 上海,江苏海门蛎岈山国家级海洋公园管理处 江苏海门,江苏海门蛎岈山国家级海洋公园管理处 江苏海门,江苏海门蛎岈山国家级海洋公园管理处 江苏海门,江苏海门蛎岈山国家级海洋公园管理处 江苏海门,江苏海门蛎岈山国家级海洋公园管理处 江苏海门,江苏海门蛎岈山国家级海洋公园管理处 江苏海门 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏海门蛎岈山国家级海洋公园管理处项目；中央级公益性科研院所（东海水产研究所）基本科研业务费项目（2014G01，2015M01）；国家公益性行业（农业）科研专项经费项目（201303047）；国家自然科学基金面上项目（31170508） Ecological status of a natural intertidal oyster reef in Haimen County, Jiangsu Province Author: Affiliation: Key Lab of East China Sea and Marine Fishery Resource Exploitation and Utilization, Ministry of Agriculture, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, 200090, Shanghai, China,,,,,,,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于2013-2014年间的生态调查结果，评价了江苏海门蛎岈山牡蛎礁的生态现状。无人机航拍结果显示，江苏海门蛎岈山分布有750个潮间带区牡蛎礁斑块，总面积约为201519.37 m2；与2003年相比，海门蛎岈山牡蛎礁面积约下降了38.8%。活体牡蛎的平均盖度约为66%，2013年5和9月熊本牡蛎Crassostrea sikamea的平均密度分别为（2199±363）个/m2和（2894±330）个/m2。2013年5月海门蛎岈山熊本牡蛎种群的平均肥满度（CI）和性腺指数（GI）分别为（9.76±0.95）%和（1013±82）mg/g，均显著低于浙江象山港养殖的熊本牡蛎种群（P < 0.05）。海门蛎岈山熊本牡蛎的单倍体多样性和核苷酸多样性指数分别为0.119和0.00028，均高于长江口野生种群和浙江象山港养殖种群。海门蛎岈山熊本牡蛎种群受到尼氏单孢子虫（Haplosporidium nelson）的轻度浸染，其感染率（17.2%）低于浙江象山港养殖群体（47.3%）。泥沙沉积和人类捕捞是江苏海门蛎岈山牡蛎礁面临的主要胁迫因子，今后牡蛎礁恢复的重点是增加附着底物的数量。 Abstract:Oyster reefs are important coastal habitats because they provide ecosystem services such as water filtration, habitat provision, shoreline stabilization, and nutrient retention. The Liyashan oyster reef is located inshore of the Dongzhao Port, Haimen County, Jiangsu Province, and it is a natural intertidal reef. The oyster reef supports abundant species and high fishery production, and it is a major spawning ground for the roughskin sculpin, Trachidermus fasciatus, which is listed as a second-grade state protection animal. However, there is limited information on the ecological status of the natural oyster reef. In this study, we mapped the reef footprint and monitored oyster populations (species, density, biomass, size-frequency, body condition, genetic diversity, and parasite infection) at the Liyashan oyster reef on the basis of field investigations conducted in 2013 and 2014 and compared the metrics to those of farmed oysters. Aerial photos obtained using an unmanned plane indicate that the natural oyster reef is composed of 750 intertidal reef patches, and the area of a patch ranges from 0.98 m2 to 16330 m2. The total area of the intertidal reef is approximately 0.201 km2. However, the aerial footprint of the natural reef has declined by approximately 39% in the past decade because of sedimentation. Mean cover for live oysters was 66%, and mean densities of the oyster Crassostrea sikamea were between 2199 and 2894 ind./m2. The percentage of oyster spats with respect to size-frequency distribution was greater in September than in May, showing high recruitment of oyster larvae in the summer. Mean flesh content, condition index, and gonad index of C. sikamea were (32.15±1.80)%, (9.76±0.95)%, and (600±116) mg/g, respectively. These values were significantly lower at the Liyashan natural oyster reef than at nearby aquaculture sites ((36.50±2.34)%, (15.24±1.04)%, and (1013±82) mg/g, respectively) in Xiangshan Bay, Zhejiang Province. Haplotype diversity and nucleotide diversity index of the C. sikamea population at Liyashan were 0.119 and 0.00028, respectively, and were greater than the values observed at the aquaculture sites. The oyster population had been slightly infected by the parasite Haplosporidium nelsoni, and the infection frequency (17.2%) was lower at the natural reef than at the aquaculture sites (47.3%). The natural oyster reef is rapidly degrading because of heavy sedimentation. The oyster population at the reef had lower body condition, greater genetic diversity, and lower gonad index and parasite infections than those at the aquaculture sites. To protect this important biogenic reef, greater restoration efforts should be initiated to promote the oyster population and reef functions by supplementing hard substrates. 参考文献 相似文献 引证文献

Haplosporidium nelsoni (MSX) in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China

The protozoan parasite Haplosporidium nelsoni (MSX) was identified in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China by histopathologic examination, polymerase chain reaction (PCR) amplification, and in situ hybridization (ISH) assay. H. nelsoni plasmodia-like structures were identified in the digestive glands of scallops by histologic examination, but no parasite spores were observed. PCR using the Hap-F2, R2 primer pair produced a sequence with 100% homology with the corresponding small subunit rDNA region of H. nelsoni. An ISH assay using the oligonucleotide probe MSX1347 produced a positive reaction with the Japanese scallop parasite. This is the first report of H. nelsoni in P. yessoensis in China.

Declining impact of an introduced pathogen: ­Haplosporidium nelsoni in the oyster Crassostrea virginica in Chesapeake Bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 432:1-15 (2011) - DOI: https://doi.org/10.3354/meps09221 FEATURE ARTICLE Declining impact of an introduced pathogen: ­Haplosporidium nelsoni in the oyster Crassostrea virginica in Chesapeake Bay Ryan B. Carnegie*, Eugene M. Burreson Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, Virginia 23062, USA *Email: carnegie@vims.edu ABSTRACT: Disease caused by the parasite Haplosporidium nelsoni has devastated Crassostrea virginica in Chesapeake Bay, exacerbating effects of overharvesting and adversely impacting the ecology of the bay. H. nelsoni is thought to persist as an impediment to oyster restoration because strong reproductive contributions from oysters in low-salinity refugia from parasitism have prevented ­development of disease resistance. On the contrary, long-term data indicate that while infection pressure on naïve sentinels has grown, H. nelsoni levels in wild oysters have fallen, with prevalence typically below 20% and advanced infections uncommon. A transplant experiment comparing naïve sentinels with oysters from ­disease-enzootic populations indicated that these observations ­represent true disease resistance, and its ­geo­graphical ­distribution was revealed by annual fall surveys, and by intensive sampling in 2007 and 2008. Re­sistance is best developed in the small, polyhaline Lynnhaven River, where salinities are never low enough to suppress H. nelsoni. Resistance gradually decreases up the large tributaries and the bay, as revealed by infections reaching higher levels further upstream when drought allows H. nelsoni to colonize unselected oyster populations. Elevated disease in small oysters from the Rappahannock River suggests that a non-resistant component of the population persists due to reproductive contributions from unselected oysters in upriver sanctuaries from disease selection, and from ­susceptible but pre-disease oysters in the lower river. Contributions of these unselected oysters notwithstanding, our results point to substantial reproduction by resistant oysters in disease-enzootic waters, and suggest that reefs in mesohaline-polyhaline salinities, and not only those in disease-free lower mesohaline areas, should be the focus of conservation and restoration efforts. KEY WORDS: Haplosporidium nelsoni · Multinucleated sphere X disease · MSX · Crassostrea virginica · Disease ­resistance · Oyster restoration Full text in pdf format Information about this Feature Article NextCite this article as: Carnegie RB, Burreson EM (2011) Declining impact of an introduced pathogen: ­Haplosporidium nelsoni in the oyster Crassostrea virginica in Chesapeake Bay. Mar Ecol Prog Ser 432:1-15. https://doi.org/10.3354/meps09221 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 432. Online publication date: June 27, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

A 1-year investigation of the parasite Haplosporidium nelsoni (MSX) in the Pacific oyster Crassostrea gigas from Dayaowan Bay, China

The infection prevalence of the protozoan parasite Haplosporidium nelsoni (MSX) in Pacific oysters (Crassostrea gigas), collected from Dayaowan Bay on the north coast of the Yellow Sea, China, was investigated in 2007. The traditional histological method of diagnosing H. nelsoni infection in oysters was compared to that of polymerase chain reaction (PCR). Histology and the first PCR analysis detected infection in 21 (a total of 240 oysters) (8.75%) oysters, and the second PCR revealed infection in 26 oysters (10.83%). Only local or epithelial infections were found; no systemic infections were detected. Infection by H. nelsoni mostly occurred from April through October, and the monthly prevalence ranged from 5% to 25%, with a peak in August. These results suggest that the prevalence of the parasite is low in Dayaowan Bay. The prevalence of H. nelsoni is thought to be controlled in some way by temperature and salinity.

Detection of Haplosporidium nelsoni in Pacific oyster Crassostrea gigas in Japan.

One hundred spat of Crassostrea gigas obtained from a coastal area in north-eastern Japan were examined for the protistan parasite Haplosporidium nelsoni. Haplosporidium-like plasmodia were histologically observed in two spat and positively reacted with a H. nelsoni-specific probe in in situ hybridization. Four spat including the two spat in which the plasmodia were found showed positive reaction in PCR analysis for the detection of H. nelsoni.The small subunit ribosomal RNA sequence amplified from the spat was virtually identical (99.7%) to the sequence of H. nelsoni previously reported. These results demonstrate that H. nelsoni is distributed in Japan.

Increased Virulence in an Introduced Pathogen: Haplosporidium nelsoni (MSX) in the Eastern Oyster Crassostrea virginica.

The protistan parasite Haplosporidium nelsoni has caused extensive mortality in the eastern oyster Crassostrea virginica along the mid-Atlantic coast of the United States since 1957. The origin of H. nelsoni has remained unresolved. Molecular diagnostic tools were used to examine the hypothesis that a haplosporidian parasite in the Pacific oyster C. gigas is H. nelsoni. A DNA probe specific for H. nelsoni reacted positively in in situ hybridizations with haplosporidian plasmodia from C. gigas collected in Korea, Japan, and California. Primers that specifically amplify H. nelsoni DNA in the polymerase chain reaction amplified product from Californian C. gigas infected with the haplosporidian parasite. The DNA sequence of the 565-base pair amplified product was identical to the H. nelsoni sequence except for a single nucleotide transition, a similarity of 99.8%. These results are conclusive evidence that the parasite in C. gigas is H. nelsoni and strongly support previous speculation that the parasite was introduced into Californian populations of C. gigas from Japan. Results also support previous speculation that H. nelsoni was introduced from the Pacific Ocean to C. virginica on the East Coast of the United States, likely with known importations of C. gigas. These results document greatly increased virulence in a naive host-parasite association and reinforce potential dangers of intentional, but improper, introductions of exotic marine organisms for aquaculture or resource restoration.

Cellular Responses of Oysters Infected with Haplosporidium nelsoni: Changes in Circulating and Tissue-Infiltrating Hemocytes

The protozoan parasite Haplosporidium nelsoni (MSX) elicits an inflammatory-type response in oysters, Crassostrea virginica. We assayed circulating hemocytes of oysters exposed to H. nelsoni to quantify the effects of parasitism, selection for resistance, and season on total and differential counts. All factors had a significant (P < 0.02) effect on total counts, but explained relatively little of the overall variance [season (12%) > selection (4%) > infection (2%)]. Circulating hemocyte densities increased with infection intensity in resistant animals, but were depressed in susceptible oysters with light infections. Counts in both groups were lowest in August and highest in May, at which times densities in susceptible oysters were reduced (P < 0.02) compared to those in resistant animals. No differences existed in November. Susceptible oysters may be more debilitated by infections than resistant animals, resulting in impaired circulation and depressed cell counts. The number of tissue-infiltrating hemocytes increased with infection intensity (P < 0.0001), but showed no statistically significant (P > 0.05) association with numbers of circulating hemocytes in individual oysters. Size-frequency analysis with a Coulter counter indicated that the proportion of large cells (presumed to be granular hemocytes) was lower (P < 0.0001) in susceptible oysters, which were also heavily infected, compared to resistant oysters, which had very few infections. The loss of granular hemocytes may stem from degranulation associated with tissue damage and inflammation. Present evidence suggests that the principal role of the hemocyte response in MSX disease is to plug lesions, remove debris, and repair tissues and that these functions may help oysters survive infection.

Lectin binding characteristics of haemocytes and parasites in the oyster, Crassostrea virginicd, infected with Haplosporidium nelsoni (MSX)

Lectin-binding surface receptors on haemocytes from host oysters were compared with those on plasmodial stages of the ascetosporan parasite Haplosporidium nelsoni (MSX). Haemocytes were agglutinated, in descending order of strength, by WGA, HPA, LPA, ConA, and CFA. GMA, PHA, and RMA lectins failed to agglutinate at 100 micrograms/ml, the highest concentration tested. These results indicate that haemocytes contain surface receptors resembling N-acetyl-D-glucosamine and alpha-methylmannopyranoside. Fluorescent (FITC) labelled ConA and WGA also bound to H. nelsoni plasmodia, but parasites were commonly excluded from clumps of agglutinated haemocytes, except for those that were apparently trapped passively in large aggregates. Although seasonal variations existed, agglutination titres for all reacting lectins were 2- to 8-fold higher for cells from systemically infected oysters compared to control oysters not manifesting systemic infections. Preincubation of lectins in serum from control animals reduced agglutination titres 6- to 9-fold, whereas incubation in serum from systemically infected oysters reduced titres only 4- to 6-fold. The loss of lectin-like molecules from the serum of systemically infected animals, and the concurrent increase of lectin receptors in the haemocytes population, is probably related to known changes in haemocytes composition and the loss of serum glycoproteins in diseased animals. Antigenic similarities were detected between surface receptors on oyster haemocytes and those on H. nelsoni plasmodia, which may help explain the failure of oyster haemocytes to phagocytose this parasite.

“Panning”, a technique for enrichment of the oyster parasite Haplosporidium nelsoni (MSX)

Plasmodial stages of the parasite Haplosporidium nelsoni (MSX) were enriched an average eight-fold with recovery of 60 to 80% using a process known as “panning” of hemolymph from infected oysters ( Crassostrea virginica). The method takes advantage of the greater adherence of hemocytes, compared to parasites, to inert surfaces. Hemolymph from infected oysters was layered onto a Petri dish and cells were allowed to settle for 30 min. Nonadhering cells were gently washed, decanted, and placed in a second Petri dish. Maximum enrichment and recovery of parasites were obtained after three panning cycles. Viability, estimated by trypan blue dye exclusion, was greater than 95%. Parasite-to-hemocyte ratios before panning were highly correlated to those after panning, but correlation decreased with each incubation. Initial concentration of parasites, which ranged from 1.4 to 5 × 10 5/ml, was also significantly correlated with the percentage recovery. We suggest that other extracellular invertebrate protozoans may also be enriched by the same method, which is much simpler, gentler, and less expensive than most other cell separation procedures.

Influence of selective breeding, geographic origin, and disease on gametogenesis and sex ratios of oysters, Crassostrea virginica, exposed to the parasite Haplosporidium nelsoni (MSX)

The recent spread and intensification of Haplosporidium nelsoni (MSX) disease in oysters, Crassostrea virginica, along the Atlantic coast of the United States has heightened interest in the use of disease-resistant strains in aquaculture and increased the need for understanding all facets of how selective breeding affects oyster performance, including reproduction. Resistance does not prevent infection, but involves an ability to restrict parasite development and to tolerate infections. We examined selected and unselected oysters, from three geographical locations, all exposed to H. nelsoni infection, to determine the influence of selection, strain origin, and parasitism on gametogenesis. Gonadal development was most frequently correlated with geographic origin of oysters: northern strains (from Long Island Sound) ripened and spawned earlier than southern strains (from the James River), even after several generations of selection at a single location in Delaware Bay. Parasitism was associated with impaired gonadal development in May when gametogenesis was occurring, but not in August, when spawning was underway. Selection for disease resistance was associated with improved gametogenic development, but only in oysters with few or no patent infections. Both parasite burden and selection for resistance were correlated with gametogenesis only in strains from the two southern-most locations, the James River and Delaware Bay, and never in those from Long Island Sound. We suggest that our observations resulted from interference by H. nelsoni in energy acquisition, storage, and conversion cycles of the oyster, which, in turn, differed seasonally according to geographic origin. Gonad development appeared to be more sensitive to parasitism when gametes were in the formative stage rather than after they had matured. Thus, southern strains, which were still in the early stages of gametogenesis when they experienced typical high parasite loads in late May, showed significantly greater inhibition than northern strains, which already had well-developed gonads at the same time. In contrast to most reports that environmental stress correlates with an increased ratio of males to females, we found a three-fold increase in the proportion of females among H. nelsoni-infected oysters compared to uninfected oysters. There was no evidence of sex-associated differential infection or mortality rates and we suggest that parasitism inhibits the development of male gametes more than female gametes.

Effects of sublethal infection by the parasite Haplosporidium nelsoni (MSX) on gameto-genesis, spawning, and sex ratios of oysters in Delaware Bay, USA

manuscript. This study was funded by the National Marine Fisheries Service under PL 88-309 (to H. Haskin), by the New Jersey Department of Environmental Protection, and by a fellowship from the Comision Asesora de Investigacion Cientiifica y Tecnica de Espatia to A. J. F. This is New Jersey Agricultural Experiment Station Publication No. D 32504-2-87, supported by state funds.

Infection and Mortality Patterns in Strains of Oysters Crassostrea virginica Selected for Resistance to the Parasite Haplosporidium nelsoni (MSX)

Strains of oysters Crassostrea virginica resistant to mortality caused by the parasite Haplosporidium nelsoni (MSX) were developed and tested through 6 generations. In addition, strains in each generation were followed for up to 6 yr of continuous exposure to the parasite in nature. Selected strains responded to challenge by the parasite with gradually improved survival in successive generations. They were slower to develop patent infections than were unselected groups and were able to delay mortality after infections did develop, but under repeated exposure most oysters eventually died with H. nelsoni parasitism. Many selected strains, however, reached market size before significant mortalities occurred. The data suggest that resistance to H. nelsoni mortality is under the influence of many genes. No clear defense mechanism has been described and we hypothesize that resistance to H. nelsoni may, in part, involve a physiological state in which selected oysters temporarily fail to provide a suitable habitat for the parasite. Temporary insusceptibility would, in this view, be followed by an increased ability to tolerate the parasite when conditions for its development are present. Selection would then favor individuals that are able to prolong periods of insusceptibility and/or to carry out basic life processes while parasitized.

Comparison of hemolymph proteins from resistant and susceptible oysters, Crassostrea virginica, exposed to the parasite Haplosporidium nelsoni (MSX)

Serum protein constituents in laboratory-reared stocks of oysters, Crassostrea virginica, susceptible to mortality caused by the parasite Haplosporidium nelsoni (MSX) were compared with constituents in resistant oysters exposed to the same level of infection activity. Virtually all of the susceptible oysters became infected and 71% died by the end of the 9-month study, while only half of the resistant group had patent H. nelsoni infections and only 7% died. Total serum protein concentrations fell sharply and in approximate proportion to disease intensity in oysters with systemic H. nelsoni infections. Oysters with heavy parasitism had about one-third the protein levels of uninfected individuals. When infections were confined to the gill, however, as was the case with mortality-resistant oysters, there was no depression of protein levels. In all oysters examined, SDS electrophoresis showed three rapidly migrating proteins, with molecular weights between 25,000 and 75,000, that comprised nearly all the total protein. Up to 12 larger proteins, with molecular weights up to 500,000, were also present, but with considerable individual variability in number and concentration. There was no obvious correlation of electrophoresis patterns with H. nelsoni disease or with genetic background. Results of the study suggest that depletion of certain metabolic substrates such as circulating protein and/or interruption of biosynthetic pathways by the parasite may be a primary cause of death in infected oysters.

Chronic infections of Haplosporidium nelsoni (MSX) in the oyster Crassostrea virginica

Oysters inhabiting areas enzootic for the parasite Haplosporidium nelsoni (MSX) are exposed to infective particles each summer, and it is often difficult to distinguish newly acquired lesions from older infections. To study long-term parasitism without the complication of new infections, MSX-infected oysters were moved from Delaware Bay to a disease-free area on the New Jersey coast. Because infections seen after the transfer were acquired in Delaware Bay during a known infective period, it was possible to determine how long oysters remained infected and how they were affected by chronic parasitism. Chronic infections displayed the same seasonal cycle (high levels in winter and late spring, low levels in summer and early spring) that occurs in enzootic areas with annual reinfection. Within individual oysters, chronic MSX became localized, relapsed into general infections, and then became localized again in a sequence that was probably controlled by temperature. Some experimental oysters survived with MSX for at least 4 years. Hemocytosis persisted in these oysters, and their poor condition suggested that chronically infected individuals would have lowered resistance to additional stress.