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1.
The penaeid prawns Fenneropenaeus indicus and Metapenaeus monoceros support shallow-water prawn fisheries in the south-west Indian Ocean. They are sympatric and have similar life histories, including developmental stages that depend on estuarine and marine habitats and a short dispersal duration. Nevertheless, M. monoceros juveniles display a more generalist habitat preference in estuaries and recruit to offshore habitats during a different season than F. indicus. We hypothesised that these differences would affect dispersal patterns, leading to dissimilar geographic genetic structure between the two taxa. Given their short dispersal phase, we also hypothesised that the Mozambique Channel would form a barrier to dispersal between the southeastern African mainland and Madagascar sites. Population differentiation was assessed based on analysis of mitochondrial DNA control-region sequences. Both species displayed high haplotype and low nucleotide diversity. Pairwise ?ST statistics supported the existence of admixed populations along the African mainland sites for both species, with geographic distance isolating populations at the extremes of the sampled range (Kenya and east coast of South Africa). The Madagascar population differed significantly from African mainland populations. The concordant patterns in population differentiation suggest that F. indicus and M. monoceros can be considered as single African stocks, or fisheries management units.  相似文献   

2.
Lichia amia is an important coastal recreational fishery species with a cosmopolitan distribution in the eastern Atlantic. In southern Africa, it is distributed from southern Angola to northern KwaZulu-Natal in South Africa. A recent biological survey revealed differences between Angolan and South African individuals suggesting that they may represent separate stocks. As fishery management decisions should be based on accurate knowledge of population structure, an initial survey of the genetic substructuring of L. amia was conducted on samples collected in southern Angola and South Africa. Assessment of genetic diversity and population structure was conducted using a fragment of the mitochondrial Control Region. Obtained genetic diversity levels were within the expected range for marine teleosts (h = 0.867, π = 0.007), and two deeply divergent (southern Angolan and South African) populations were identified (average φ ST = 0.78) across the Benguela Current system. These results suggest that Angolan and South African L. amia should be managed as two independent stocks. This work represents the first assessment of population genetic substructuring across the Benguela Current of a valuable coastal fishery resource, and has application for future fisheries management.  相似文献   

3.
The collector sea urchin Tripneustes gratilla has been identified as a species with potential for aquaculture production in South Africa. The species’ roe is considered a culinary delicacy in Asia and Europe. However, T. gratilla remains genetically uncharacterised in South Africa. Therefore, the purpose of this study was to provide baseline genetic information consisting of estimates of genetic diversity and population stratification, which may aid in future sustainable use of this urchin resource. A total of 22 species-specific microsatellite markers were used for the genetic characterisation of T. gratilla samples from along the South African coast, at Haga Haga, Coffee Bay, Hibberdene, Ballito Bay and Sodwana Bay. A moderate level of genetic diversity was observed, with an average number of alleles of 7.89 and an average effective number of alleles of 6.57, as well as an average observed heterozygosity of 0.55. Population differentiation tests suggest that the geographically representative samples form part of a single, large interbreeding population, with a global Fst estimate of 0.02 (p > 0.05). This finding is likely explained by high levels of gene flow between these locations caused by extensive larval dispersal during the planktonic larval stage. The panmixia observed within these natural populations of T. gratilla indicate that they could be managed as a single genetic stock.  相似文献   

4.
The study investigated the global and regional phylogeography of the yellowtail kingfish Seriola lalandi by examining genetic diversity and population genetic structure of this species at inter-and intra-ocean level and on a regional scale. DNA fragments of two mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit I (COI) and one nuclear gene, recombination activating gene 1 (RAG1), were sequenced to investigate the global-scale phylogeography of this species. The population genetic structure within the South Pacific, as well as along the South African coastline, was examined further using six microsatellite markers. Three distinct clades were identified for S. lalandi, which correspond with previously described subspecies of the North-East Pacific, North-West Pacific and the Southern Hemisphere. Within the latter, additional divergence was observed between the South Pacific and the South-East Atlantic regions. Divergence estimates were indicative of a Pacific origin for S. lalandi populations, because of Pleistocene vicariant events. Microsatellite analyses revealed overall significant genetic differentiation between South African and South Pacific samples. This corroborates recent findings on the global phylogeography of the species. No population differentiation was observed within South Africa, indicating high levels of gene flow.  相似文献   

5.
Genetic studies on South African marine fishes have shown that many species exist as single, well-mixed stocks throughout their core distribution. The black musselcracker or poenskop Cymatoceps nasutus is a slow-growing, late-maturing and long-lived sparid (Perciformes: Sparidae) that is endemic to South African coastal waters. Conventional tagging studies suggest that it is resident, with limited connectivity between different regions along the coast. Mitochondrial and nuclear DNA were used to investigate the genetic structure of C. nasutus along the South African coastline and showed evidence of at least two populations. Samples collected from the Tsitsikamma Marine Protected Area on the South Coast to KwaZulu-Natal on the East Coast showed no significant population structure over much of the distribution. Gene flow for C. nasutus within this region is not limited by geographic distance and appears to be unaffected by various oceanographic barriers and biogeographical boundaries. Samples from the Western Cape to the west of Tsitsikamma, however, showed moderate to substantial differentiation for both markers, which may be influenced by a temperature barrier – a coldwater ridge – along the South Coast. These data provide the first genetic assessment of this South African sparid, and suggest that a two-stock management strategy would be appropriate for the species.  相似文献   

6.
The Asian green mussel Perna viridis is an invasive Indo-Pacific species recently reported from South African harbours. To verify the invasion, a phylogenetic (and morphological) analysis of green-shelled mussels (n = 39), found in six South African harbours, was conducted using the mitochondrial cytochrome c oxidase subunit I gene (COI). Estimates of genetic distances using the neighbour-joining analysis identified P. viridis only from Durban Harbour. All other green mussels were more than 3.2% divergent from P. viridis and were identified as green-shelled variants of indigenous P. perna. The only reliable morphological differences distinguishing the two species were the poorly developed mantle papillae and the wavy pallial line in P. viridis. The confirmed occurrence of P. viridis in a South African harbour suggests that there is a possible threat of the species becoming established and then spreading onto the open coast and competing with indigenous P. perna.  相似文献   

7.
Pelagia noctiluca is thought to have a global distribution, yet our understanding of genetic connectivity across the range of this problem animal is poor. Here, we investigate the genetic structure of populations off southern Africa using mitochondrial COI and nuclear ITS1 and ITS2 genes, and compare the results to recent work conducted in the North-East Atlantic. Analyses showed significant differentiation between the southern and northern Atlantic population groups (COI Φ st = 0.72, ITS2 Φ st = 0.23, p < 0.001), which suggests historical rather than contemporary gene flow. Southern African samples showed high haplotypic (h = 1) and low nucleotide (π = 0.008) diversity, similar to those from Europe. Phylogenetic analyses suggest South African samples to have diverged earlier than those from the northern Atlantic.  相似文献   

8.
Cetacean research, in terms of the number of papers, and areas for which data are available, has expanded considerably in the southern African subregion in the past decade, especially in the South-West Indian Ocean. We review cetacean research within this subregion from the 1800s to the present to provide an overview of findings, investigate trends and identify knowledge gaps. Data are presented separately for large whales (those subject to commercial whaling) and smaller cetaceans, and are separated by era and ocean basin. Over 550 peer-reviewed papers and books were identified relating to research on cetaceans within the subregion. More than half (284) have been produced since 1990 and 193 relate specifically to South African waters. The most-studied species are those that are most accessible due to their coastal distributions (southern right whale Eubalaena australis: 45 papers, humpback whale Megaptera novaeangliae: 31 papers, killer whales Orcinus orca: 27 papers, Indo-Pacific bottlenose dolphin Tursiops aduncus: 30 papers, Indo-Pacific humpback dolphin Sousa chinensis (plumbea form): 25 papers) and/or were hunted commercially (sperm whale Physeter macrocephalus: 25 papers). Identified conservation concerns vary throughout the subregion, but include bycatch and directed hunts, oil and gas development, ecotourism activities, shifts in prey resources, and noise and chemical pollution. The inshore stocks of Bryde's whales Balaenoptera edeni, the Indo-Pacific humpback dolphin and the Atlantic humpback dolphin S. teuszii were identified as the populations of highest conservation concern, although there are considerable knowledge gaps relating to deep-water species and almost no data (even on species occurrence) are available for several areas and countries.  相似文献   

9.
中国沿海不同地区泥蚶(Tegillarca granosa)的遗传多样性分析   总被引：1，自引：0，他引：1  
以采自海南海口、广西防城港、广西北海、广东湛江、福建漳州、山东荣成、山东威海7个地理群体62个泥蚶个体为材料,获取592bp线粒体COI基因片段序列,并进行遗传多样性及分化分析。多态性遗传参数统计显示:62个个体共检测出103个多态性位点,定义了26个单倍型;总群体单倍型多样性指数为0.834,核苷酸多样性指数为0.01665,平均核苷酸差异数为9.85772。7个群体均显示出较丰富的遗传多样性,群体内遗传距离及群体内遗传多样性参数显示中国沿海泥蚶遗传多样性由北向南呈升高趋势,而群体内遗传分化系数也呈现升高的趋势。基于26个单倍型COI序列构建的NJ树和UPGMA树以及基于群体间遗传距离构建的UPGMA树显示,荣成群体和威海群体亲缘关系较近,聚成一小支,而后与漳州群体相聚,然而南方类群并没有聚为独立的一支。  相似文献   

10.
Molecular population genetic analysis has provided evidence that the copepod, Calanus finmarchicus, of the Labrador Current, Gulf of St Lawrence, Scotian Shelf, Gulf of Maine, and Georges Bank constitute a single, interbreeding population. The DNA sequence of a 350 base pair portion of the mitochondrial large subunit (16S) ribosomal RNA (rRNA) gene was determined for a total of 72 individuals collected in 1992, and 110 individuals collected in 1993 from these regions. There was significant heterogeneity in haplotype frequencies among the samples collected in 1992, but this heterogeneity did not resolve into regional patterns. The only regional differences seen were between pooled samples of the western N. Atlantic and those of the Norwegian Sea. There were no significant differences in haplotype frequencies among the samples collected in 1993, and fewer haplotypes were observed in these samples. Intraspecific molecular variation was typical of other marine species: there were 29 haplotypes among the 182 individuals sequenced. The frequency distribution of the haplotypes was highly skewed: 128 individuals shared one haplotype and 19 individuals were unique. There were 24 variable sites among the 350 bases sequenced; estimated nucleotide diversity was 0.0042. The genetic character of C. finmarchicus populations in the western N. Atlantic was stable over time in that three of the haplotypes (including the most abundant) occurred in both 1992 and 1993. However, haplotype frequencies differed significantly between the two years. The lack of regional structure in the 1992 samples and the genetic homogeneity of samples collected in 1993 across the domain from the Labrador Current to the Gulf of St Lawrence to Georges Bank and the Gulf of Maine indicated that there is significant gene flow across this region. The persistent genetic pattern suggests that the Gulf of St Lawrence may be an important source region for recruitment of C. finmarchicus to Georges Bank. Determination of zooplankton dispersal patterns within high gene flow species will provide information that may not be determined by conventional oceanographic analyses.  相似文献   

11.
Spatial variability in phenotypic characteristics within a fish population may be used to infer the existence of multiple stocks, and knowledge of the population structure of exploited species is important for their sustainable management. In this study we investigated geographic variability in meristic (vertebral count) and morphometric (body shape) characteristics of sardine Sardinops sagax from three southern African regions: Namibia, the South African west coast, and the South African south coast. There were significant regional differences in vertebral counts, with Namibian fish tending to have more vertebrae than South African fish, but with no difference between sardine off the South African west and south coasts. Body shape was characterised using morphometric landmarks, and shape changes were investigated using geometric morphometrics, with influences on fish shape assessed using multivariate regressions. To remove the effects of allometry, the 22 shape variables (represented by Procrustes coordinates) were regressed against fish size (represented by centroid size). There was a significant allometric effect, which was removed by using the residuals of these regressions in further analyses. A multivariate multiple regression was applied to the 22 size-corrected shape variables and to three covariates: condition factor, stomach fullness and fat stage. The significant influence of these covariates was removed by using the residuals from this regression in a canonical variate analysis, where corrected shape variables were classified in relation to region, year and sex. The Mahalanobis distances from the canonical variate analysis differed significantly for most combinations of classifier variables, with clear separations among the three regions. Sardinops sagax off Namibia had thicker bodies and more contracted tail regions than South African fish, whereas S. sagax off the South African south coast had thinner bodies and smaller heads than those off the west coast. These results support the hypothesis of multiple sardine stocks around southern Africa.  相似文献   

12.
Marthasterias glacialis are found in the cool-temperate waters of the north-eastern Atlantic Ocean, in the subtropical waters of the Mediterranean Sea and along the south-western tip of Africa. The South African Marthasterias population includes two morphotypes, a smooth, spineless rarispina form and a spiny africana form, that have been described as separate species, subspecies, or forma by various authors over the past century. To test whether these two morphotypes represent separate species, and whether either, or both, are conspecific with the North-East Atlantic species, 78 Marthasterias were collected from the Cape Peninsula of South Africa. Morphological comparisons between individuals of the two forms showed no significant clustering of samples, indicating that there is no morphological separation of the two South African forms into distinct groupings. The africana and rarispina forms were also shown to be genetically indistinguishable, using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene and the nuclear internal transcribed spacer 1 (ITS1). In addition, the COI sequences were also compared to those from European specimens, and phylogenetic reconstruction and intra- and interspecific levels of divergence suggested that the South African specimens form a single group that is genetically distinct from the European M. glacialis. Although the allopatric distribution, high genetic divergence (more than 3% for the COI fragment) and morphological differences suggest that the South African form should be raised to species status under the name Marthasterias africana, further work must assess an independent genetic marker (nuclear) to support raising the COI clade to species level. True M. glacialis have a spine-armament pattern of a series of three or more regular spine rows down the length of each arm, whereas M. africana are either covered in many irregularly spaced spines, or have an extraordinarily bare surface with only two spine rows per arm. Marthasterias africana may also have an actinal spine simulating the presence of a third inferomarginal spine. This work tentatively resolves the taxonomic dispute, elucidates the separation and amalgamation of the two African forms and suggests a single, uniquely South African Marthasterias species that might be distinct from the north Atlantic M. glacialis, although further analyses to test reproductive isolation between the North-East Atlantic and South African forms are required.  相似文献   

13.
The increasing exploitation of mangrove forests, without any sustainable planning, has been seriously compromising the survival of this ecosystem and of its exclusive resources. Scylla serrata is one of the most commercially exploited crabs inhabiting mangroves and estuaries of the Indo-Pacific region. This species is extensively harvested, mainly for selling to the tourist market, and, as a consequence, its populations are in constant decline. The aim of the present study was to assess the level of genetic exchange of S. serrata within the Western Indian Ocean (WIO), using a population genetic structure approach. To achieve this goal, we reconstructed the intra-specific geographic pattern of genetic variation by partial sequencing the mitochondrial DNA cytochrome oxidase subunit I, in samples from seven mangrove sites of the WIO. Our data set then encompassed all the sequences for the same genetic marker deposited in Genbank and corresponding to samples from South East Asia, Australia and some Pacific Islands: this allowed us to estimate the level of connectivity among S. serrata populations within its distribution area.  相似文献   

14.
During a cruise in March 1988 dedicated to investigation of the marine resources of South Africa's continental slope, 62 species in 22 families of Cephalopoda were collected from the Cape Canyon and Cape Point Valley. Multivariate analysis revealed a clear distinction between cephalopods of the upper and lower continental slope in both benthic and epibenthic habitats. Todaropsis eblanae and Todarodes angolensis were indicator species for the upper slope benthic, from 300 to 500 m, but on the lower slope, in 700–900 m of water, they were replaced by Histioteuthis miranda and Opisthoteuthis agassizii. In the epibenthic, both upper and lower slopes were dominated by Abraliopsis gilchristi and Lycoteuthis ?diadema, but other species characteristic of the lower slope were the oceanic species Mastigoteuthis hjorti, Ctenopteryx sicula and Taonius sp. A. Cranchia scabra indicated the presence of oceanic water at stations 700–900 m deep. Other species of significance in the catches were Todarodes filippovae, Histioteuthis macrohista, Rossia enigmatica and Bathypolypus valdiviae. Species affinities indicate that the cephalopod fauna of the southern African continental slope includes the following zoogeographic components: southern African endemic, circum-Subantarctic species associated with Antarctic Intermediate Water, circum-global southern tropical/subtropical, tropical Indo-Pacific and cosmopolitan tropical/subtropical.  相似文献   

15.
为了解栉孔扇贝(Chlamys farreri)、虾夷扇贝(Patinopecten yessoensis)及其杂交子代(F1)的种群遗传多样性和遗传结构,对3个群体的线粒体COI和Cytb基因的部分序列进行了扩增和分析。经比对分别获得781bp和725bp核苷酸片段,74个样本共检测到47个单倍型;F1群体的单倍型数、单倍型多样性指数、核苷酸多样性及平均核苷酸差异数都是最高的,而双亲的较低;F1和栉孔扇贝间的遗传距离最小,其次为栉孔扇贝和虾夷扇贝群体之间,F1和虾夷扇贝群体之间的遗传距离最大;F1和栉孔扇贝之间的遗传分化系数较小而两者间的基因流比较大,F1和栉孔扇贝与虾夷扇贝之间的遗传分化系数较大而基因流较小,说明栉孔扇贝和虾夷扇贝群体群体很早就发生了遗传分化;采用UPGMA法和简化的中介网络法构建的系统树表明,3个群体的所有个体被分为2个族群,栉孔扇贝和F1交叉聚为一类,虾夷扇贝独自聚为一类,2个分支间没有交叉;使用特异性引物分别对3个群体进行PCR扩增检验,结果栉孔扇贝的特异引物能在杂交子代中扩增,而虾夷扇贝的特异引物不能在子代中扩增出条带,说明栉孔扇贝和虾夷扇贝杂交,其子代的线粒体遗传模式为严格的母系遗传。本研究结果表明杂种优势的形成与线粒体遗传多样性的变化有关。  相似文献   

16.
采用微卫星DNA分子标记方法对中国南部沿海多鳞鱚(Sillago sihama)广西北海、广东湛江、汕尾及海南三亚4个野生地理群体进行了遗传多样性及遗传分化等研究。结果表明:(1)用于研究的34对微卫星引物在4个群体中具有丰富的多态性,有效等位基因数介于1.71—20.46之间,多态信息含量PIC介于0.40—0.95之间。4个群体总的平均期望杂合度(He)为0.598,观测杂合度(Ho)为0.572,SY群体的杂合度最大(He=0.606,Ho=0.623),SW群体的最小(He=0.586,Ho=0.508)。(2)群体间F-统计量分析表明,群体遗传分化处于高度分化水平(Fst平均值为0.306);基于奈氏遗传距离(DA)构建的NJ和UPGMA聚类树均显示地理位置相邻的群体聚在一起。  相似文献   

17.
Penaeus semisulcatus, the green tiger prawn, is an ecologically and economically important penaeid shrimp in the Indo‐West Pacific region, especially in rice‐shrimp farming and capture fisheries in Bangladesh and Sri Lanka, respectively. Genetic variation and phylogeography of samples of this species from Bangladesh and Sri Lanka were studied utilizing different mitochondrial DNA markers, i.e. cytochrome oxidase subunit 1 (CO1), control region (CR) and 16S rRNA genes. No evidence of population structure was observed in Bangladesh, but distinct variations were found among the Sri Lankan samples (ΦST = 0.04, p = .002; FST = 0.07, p = .001), with the western sample differing from the northwestern and southern samples. The Bangladesh population had lower genetic diversity than two of the three Sri Lanka populations. The phylogeography of P. semisulcatus revealed two distinct mitochondrial DNA (mtDNA) lineages, one in the Western Pacific Ocean and second in the Indian Ocean. The Bangladesh samples showed highest levels of similarity with samples from Sri Lanka, India and Malaysia, with the Bangladesh and Sri Lanka populations sharing the most common recent ancestry. Among the Indian Ocean samples, high levels of variation were observed in the samples from Iran, indicating admixture of two distinct mtDNA lineages, one shared by the populations from the Bay of Bengal and the other possibly originating from Eastern Africa. The genetic and phylogeographic information obtained in this study will be useful in appropriate planning for management and conservation of shrimp fisheries in Bangladesh and Sri Lanka, and in the Indo‐West Pacific region.  相似文献   

18.
The red seaweed genus Asparagopsis Montagne (Bonnemaisoniales) contains two widely introduced species that are considered notorious seaweed invaders worldwide, Asparagopsis armata and A. taxiformis, both characterised by heteromorphic, diplo-haplontic life histories. To uncover cryptic introductions of Asparagopsis along the South African coastline and identify ‘Falkenbergia’ isolates (i.e. tetrasporophytic life-history phase morphologically identical between species), the mitochon-drial cox2–3 spacer was sequenced from gametophytes of Asparagopsis taxiformis from Scottburgh, KwaZulu-Natal, on the East Coast, Knysna Lagoon on the South Coast and from tetrasporophytes, otherwise unidentifiable to species level, collected from False Bay near Cape Town on the South-West Coast and Tsitsikamma on the South Coast. Only tetrasporophytes of the temperate Asparagopsis armata were encountered from the Cape Peninsula (Cape Town) probably as far east as to Port St Johns, Eastern Cape province. This is considered an introduced species, and was first collected at Kommetjie (Cape Peninsula) in 1935. Gametophytes of the warm-temperate to tropical A. taxiformis were first collected at Reunion Rocks near Durban in 1984; the KwaZulu-Natal material studied here belongs to an Atlantic Mediterranean cryptic lineage. This taxon is an ecological dominant in some intertidal and shallow subtidal areas in northern KwaZulu-Natal, and is thus considered ‘introduced’ and ‘invasive’. In contrast, A. taxiformis gametophytes, collected in Knysna Lagoon in 2008, clustered with individuals of Indo-Pacific lineage 2. The latter is considered a major invasive lineage in the western Mediterranean, but at present is categorised as introduced in South Africa. This study provides molecular evidence of three independent, cryptic introductions in South Africa, one of them probably very recent, and this is discussed with respect to potential vectors responsible for transport.  相似文献   

19.
Yi  Chang Ho  Kim  Won 《Ocean Science Journal》2020,55(1):99-113

The solitary ascidian, Ciona savignyi (Ascidiacea, Enterogona) is a notorious marine invader still expanding its habitat range worldwide. This species is considered native to the North West Pacific, but its indigeneity in Korean coastal waters has been questioned because of outdated taxonomic records and its inhabitation of oceanographically marginal areas. To clarify their cryptic invasion state, 247 individual C. savignyi samples were collected from 12 harbors and marinas on the Korean coast, and a 744 bp region of mitochondrial DNA (mtDNA) cytochrome c oxidase subunit I gene was sequenced and analyzed. Our analyses of population genetic structure and demographic history provided considerable pieces of evidence supporting their long-term establishment on the Korean coasts: differentiated population genetic structure, sequentially arrayed star-shape haplotype network, neutrality test results of past population expansions, and post-glacial colonization pattern of demography. Consequently, we concluded that C. savignyi populations on the Korean Coast are indigenous rather than exotic. These results could be used as reference data for further phylogeo graphic and demographic studies of problematic Ciona species, and to clarify and resolve similar cryptic invasion states of the other Korean coastal marine organisms. This study is the first to resolve the cryptic in vasion state of Korean marine organisms using genetic analysis.

  相似文献   

20.
Catches of South African sardine Sardinops sagax have declined in recent years from about 200 000 t harvested annually during the period 2002–2006 to less than 100 000 t. Consequently, some companies are now importing sardine from sources elsewhere in the world to meet local demand for canned sardine and bait. This importation has the potential for the introduction of sardine pathogens, in particular the pilchard herpesvirus (PHV), which could have a negative impact on the currently small South African sardine population. The aims of the current study were to determine whether PHV is present in the local sardine population and to assess the extent to which sardine is being imported into the country and whether imported fish are from countries where the virus is known to be endemic. Fish sampled from South Africa’s western (n = 150), southern (n = 182) and eastern (n = 96) putative stocks of S. sagax were analysed for the presence of PHV using real-time quantitative polymerase chain reaction (qPCR). The origin and amount of potentially infected material imported into South Africa during the period 2010–2014 was also assessed. None of the South African sardine collected during this study tested positive for PHV, suggesting that active PHV was not prevalent in the local population of S. sagax at the time of this study. Between 56 000 and 71 000 t of frozen sardine was imported annually into South Africa from countries where S. sagax occurs, including some from areas (Australia and New Zealand) where sardine infection by PHV is known to be endemic. Hence, it is plausible that the PHV pathogen, capable of perpetuating infections in local sardine populations, could be imported into South Africa along with the importation of frozen sardine. Should local sardine be naïve to the virus, as suggested by this study, then the population is at risk of infection and precautions against such must be taken.  相似文献   

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