Comparative phylogeography of two marine species of crustacean: Recent divergence and expansion due to environmental changes

Environmental changes, such as changes in the coastal topography due to Eurasian plate movements, climate oscillation during the Pleistocene, and alteration of ocean currents, have complicated the geographical structure of marine species and deepened their divergence between populations. As two widely distributed species of crustacean (Oratosquilla oratoria and Eriocheir japonica), weak differences were expected due to their high dispersal potential of planktonic larvae with ocean currents. However, results showed a significant genetic divergence between north of China and south of China in the study. In addition, the estimated north–south divergence time (27–30.5 Myr) of mantis shrimp was near the time of the Himalayan movement, and the China–Japan clade divergence time (10.5–11.9 Myr) of mitten crabs was also coincident with the time of the opening of the Sea of Japan. Thus, we hypothesized that environmental changes in the coastal topography contributed to the marine species divergence. Furthermore, based on phylogenetic analysis, network analysis and haplotype distribution, we surmised that mitten crabs originated from a population with the oldest haplotype (H6) and then divided into the north and south populations due to the recent Eurasian plate movements and ocean currents. And lineage of Japan originated from the north population for the opening of the Sea of Japan. While O. oratoria was guessed to originate from two separate populations in the China Sea. The results of “star-like” network, negative values in neutral test, and Tajima's D statistics of two marine species supported a recent rapid population expansion event after the Pleistocene glaciations.     

Metacercarial infections of Paragonimus westermani in freshwater crabs sold in markets in Seoul

Status of metacercarial infections of Paragonimus westermani was observed in freshwater crabs, which were purchased at 3 markets in its peak season of 1990. All of 85 crabs were Eriocheir japonicus. No other species of Eriocheir were found. When crushed muscle and viscera was examined individually, the infection rate was 11.8%; and mean number of metacercariae was 2.1 per infected crab. Unless adequately cooked, freshwater crabs are still potential sources of human paragonimiasis.     

Infection Status of Freshwater Crabs and Crayfish with Metacercariae of Paragonimus westermani in Korea

The present study investigated the infection status of Paragonimus westermani metacercariae in freshwater crabs (n = 363) and crayfish (n = 31) from October 2007 to October 2008 using the crush method. All of the freshwater crabs, Eriocheir japonicus, were negative for P. westermani metacercariae while 10 (32.3%) of the 31 examined crayfish were positive. The 10 positive crayfish were caught in Haenam, Jeollanam-do, and there were 8-59 (mean 28.4) metacrcariae per infected crayfish. These results suggest that P. westermani metacerariae are still transmitted by crayfish enzootically in southern Korea, and that freshwater crabs may transmit metacercariae only on rare occasions.     

利用微卫星分子标记分析四个中华绒螯蟹群体的遗传多样性

利用本实验室克隆的16个和国际上发表的8个微卫星标记,对4个中华绒螯蟹群体(江苏、安徽、辽宁、天津)的遗传多样性进行检测。所检测到的扩增片段长度为80—445bp,在群体间扩增出2—10个等位基因,共计155个等位基因,平均等位基因6.458个。4个中华绒螯蟹群体的平均有效等位基因数(Ne)为4.3491—4.7234,平均观察杂合度(Ho)为0.5690—0.6722,平均期望杂合度(He)为0.7238—0.7546,并通过基因型的P值,确定了7个座位处于Hardy-Weinberg平衡;同时对4个群体的遗传距离进行了估算,聚类分析结果表明,安徽、江苏、天津聚为一支,属于长江河蟹类型,辽河种群单独聚为一支。     

Invasion biology of the Chinese mitten crab Eriochier sinensis: A brief review

The Chinese mitten crab Eriocheir sinensis is a native of freshwater and estuarine habitats along the east coast of Asia. Invasive populations have existed in northern Europe since the early 20th century, and more recently a breeding population has become established in the San Francisco Bay system along the west coast of North America. Ballast water is the most probable vector for both invasions, although there is also potential for escape from ethnic markets and from the ornamental aquarium industry. Invasive populations of mitten crabs have caused millions of dollars in economic and ecological damage. Economic impacts center largely on the burrowing activity of the crabs, which damages stream banks and levees, and the annual spawning migration, which interferes with fishing activities and irrigation projects. Chinese mitten crabs have recently appeared in the Chesapeake and Delaware Bays on the east coast of the USA, and there are confirmed reports of breeding females in both estuaries. The potential for large populations of mitten crabs in these estuaries has not been determined. This paper presents a review of the biology and ecology of native and invasive populations of the species and provides recommendations for research relevant to the prediction of future mitten crab invasions.     

Microsatellite analysis of genetic diversity and population structure of Chinese mitten crab （Eriocheir sinensis）

Chinese mitten crab (Eriocheir sinensis) has higher commercial value as food source than any other species of Eriocheir in China.To evaluate the germplasm resources and characterize the genetic diversity and population structure of the crabs in different water systems,two stocks and two farming populations were assessed with 25 polymorphic microsallite loci available in public GenBank.Basic statistics showed that the average observed heterozygosity (Ho) amongst populations ranged from 0.5789 to 0.6824.However,a remarkable presence of inbreeding and heterozygote deficiencies were observed.To analyze population structure,pairwise FST coefficients explained only ～10.3% variability from the subdivision of mitten crab populations,the remaining variability stems from the subdivision within subpopulations.Although the four populations had slight differentiation,different allelic frequencies resulted in distinct population structures.Two stocks and one farming population were clustered together to the phylogenetic branch of Yangtze crab,with an approximate membership of 95%.Whereas,another fanning population was clustered singly to the phylogenetic branch of the Liaohe crab,with a membership of 97.1%.The tests for individual admixture showed that Yangtze crab had probably been contaminated with individuals from other water systems.Genetic relationships between populations also supported the conclusion that Yangtze crab and Liaohe crab had different gene pools in spite of the origins of the same species.     

Rapid range expansion increases genetic differentiation while causing limited reduction in genetic diversity in a damselfly

Many ectothermic species are currently expanding their geographic range due to global warming. This can modify the population genetic diversity and structure of these species because of genetic drift during the colonization of new areas. Although the genetic signatures of historical range expansions have been investigated in an array of species, the genetic consequences of natural, contemporary range expansions have received little attention, with the only studies available focusing on range expansions along a narrow front. We investigate the genetic consequences of a natural range expansion in the Mediterranean damselfly Coenagrion scitulum, which is currently rapidly expanding along a broad front in different directions. We assessed genetic diversity and genetic structure using 12 microsatellite markers in five centrally located populations and five recently established populations at the edge of the geographic distribution. Our results suggest that, although a marginal significant decrease in the allelic richness was found in the edge populations, genetic diversity has been preserved during the range expansion of this species. Nevertheless, edge populations were genetically more differentiated compared with core populations, suggesting genetic drift during the range expansion. The smaller effective population sizes of the edge populations compared with central populations also suggest a contribution of genetic drift after colonization. We argue and document that range expansion along multiple axes of a broad expansion front generates little reduction in genetic diversity, yet stronger differentiation of the edge populations.     

绒螯蟹触角形态特征及其在分类中的应用

基于光镜和扫描电镜的观察,研究了绒螯蟹触角的形态结构,分析了绒螯蟹第1触角内、外肢节的组成,以及外肢节内侧感觉毛的特点;第2触角内肢节的形状以及极长感觉毛和表面鳞片的特征.探讨了在绒螯蟹系统分类中,触角形态特征作为新的分类性状的可能性.     

Molecular systematics of the Asian mitten crabs,genus Eriocheir (Crustacea: Brachyura)

To help resolve phylogenetic relationships among the mitten crabs, complete sequences of the nuclear DNA internal transcribed spacer (ITS) and portions of the mitochondrial genome corresponding to the cytochrome oxidase I (COI), were sequenced for all Asian mitten crabs of the genus Eriocheir and seven species of the Grapsoidea. The resulting phylogeny supports the establishment of a separate genus Neoeriocheir, but does not provide justification for the recognition of Platyeriocheir. A female mitten crab specimen from the Zhujiang River, China, was considered to be Eriocheir recta (), a species previously synonymized with Eriocheir japonica (de Haan, 1835). In the ITS analysis, a sequence from Eriocheir formosa (from Taiwan) falls within a well-supported E. recta group, which indicates that E. formosa may have to be synonymized with E. recta. Three previously recognized members of the genus, E. japonica, Eriocheir sinensis, and Eriocheir hepuensis constitute a monophyletic sister group to E. recta in all phylogenetic trees. We provide evidence for the conspecific status of these taxa. Phylogenetic trees based on COI and combined COI and ITS sequences indicate that E. japonica consists of three subgroups. Since the name E. japonica (de Haan, 1835) takes precedence over E. sinensis (H. Milne Edwards, 1853) and E. hepuensis, we suggest that these three subgroups correspond to three subspecies of E. japonica: E. j. japonica, E. j. sinensis, and E. j. hepuensis.     

利用RAPD技术对三种绒螯蟹亲缘关系的研究

采用ＲＡＰＤ技术结合一定的形态学研究手段,对中华绒螯蟹,日本绒螯蟹及其合浦亚种进行亲缘关系的研究,为三种绒螯蟹的种及亚种分析重要资料,三种绒螯蟹的第四步足前节长宽比值,与其分类标本吻合或基本吻合,用一组引物,对每种各１０个个体的基因组ＤＮＡ进行扩增,得到一批特异,可重复的扩增图谱,扩增区带的相似率分析表明,中华绒螯蟹与日本绒螯蟹的亲缘关系远,而日本绒螯蟹合浦亚种与日本绒螯蟹近,最后,对文中ＲＡＰＤ     

Population genetic structure of sexual and parthenogenetic damselflies inferred from mitochondrial and nuclear markers

It has been postulated that obligate asexual lineages may persist in the long term if they escape from negative interactions with either sexual lineages or biological enemies; and thus, parthenogenetic populations will be more likely to occur in places that are difficult for sexuals to colonize, or those in which biological interactions are rare, such as islands or island-like habitats. Ischnura hastata is the only known example of natural parthenogenesis within the insect order Odonata, and it represents also a typical example of geographic parthenogenesis, as sexual populations are widely distributed in North America, whereas parthenogenetic populations of this species have only been found at the Azores archipelago. In order to gain insight in the origin and distribution of parthenogenetic I. hastata lineages, we have used microsatellites, mitochondrial and nuclear DNA sequence data, to examine the population genetic structure of this species over a wide geographic area. Our results suggest that sexual populations of I. hastata in North America conform to a large subdivided population that has gone through a recent spatial expansion. A recent single long distance dispersal event, followed by a demographic expansion, is the most parsimonious hypothesis explaining the origin of the parthenogenetic population of this species in the Azores islands.     

A life history model for the San Francisco Estuary population of the Chinese mitten crab, <Emphasis Type="Italic">Eriocheir sinensis</Emphasis> (Decapoda: Grapsoidea)

First discovered in San Francisco Bay in 1992, the Chinese mitten crab,Eriocheir sinensis, has become established over hundreds of km² of the San Francisco Estuary. Ecological and economic impacts of this invasive species motivated our search for a greater understanding of the crabs life history as an important step in better management and control. Data for this life history model comes from the authors research and scientific literature. Juvenile crabs migrate from the Estuary into fresh water where they develop into adults. Environmental signals may stimulate gonad development that is followed by a downstream migration beginning at the end of summer. Mating occurs after the crabs reach saline water. Embryos are carried until hatching, and the larvae undergo five zoeal stages before settlement. Our model projects rates of development at various temperatures and growth increments, supports a minimum of 2 years in low salinity or freshwater habitat, and predicts that most California mitten crabs are at least 3 years old before becoming sexually mature. Environmental factors strongly influence the timing and duration of the crabs life stages, and are discussed in the context of a gradient of development times for worldwide populations of this important invasive species.     

基于线粒体COI基因序列的大豆食心虫中国东北地理种群遗传多样性分析

【目的】大豆食心虫Leguminivora glycinivorella (Matsumura)是一种危害大豆的主要害虫,在中国北方地区危害较重。本研究旨在探讨大豆食心虫在中国东北不同地理种群间的遗传变异。【方法】测定了10个不同地理种群153个个体的线粒体细胞色素氧化酶亚基Ⅰ (mtCOI)基因的657 bp序列,利用DnaSP 5. 0和Arlequin 3. 5. 1. 2等软件对大豆食心虫种群间的遗传多样性、基因流水平和分子变异进行分析。【结果】结果表明：10个地理种群间的COI基因共有36个变异位点和17个单倍型,其中1个单倍型为10个种群所共享。总种群的单倍型多样性指数Hd为0.456,各地理种群单倍型多样度范围在0~0.634之间。总群体的固定系数Fst为0.12545,遗传分化系数Gst为0.06326,总基因流Nm为3.49,且各种群间的基因流均大于1,种群间基因交流的水平较高。【结论】大豆食心虫种群内遗传多样性水平处于中低等水平。总群体和各种群的Tajima’s D检验结果皆不显著,说明中国东北地区大豆食心虫在较近的历史时期内没有出现种群扩张现象。AMOVA分子变异分析结果表明,大豆食心虫的遗传分化主要来自种群内部,而种群间未发生明显的遗传分化。各地理种群的单倍型在系统发育树上和中介网络图上散布在不同的分布群中,缺乏明显的地理分布格局。各种群的遗传距离与地理距离之间没有显著线性相关性,种群间的基因交流并未受到地理距离的影响。     

Effects of temperature and thermal history on neuromuscular properties of two crustacean species

Summary The effect of temperature on the ability of neuromuscular junctions and muscle fibers to contract, release neurotransmitter, and maintein postsynaptic membrane properties, was measured in vivo and in vitro in claw closer muscles in stone crabsMenippe mercenaria (Say) and blues crabsCallinectes sapidus (Rathbun).In vivo muscle stress (defined as force generated per unit of muscle cross-sectional area) was measured in crabs of both species collected from northern populations (annual temperature range 2–30°C) and southern populations (annual temperature range 15–30°C). Muscle stress was compared between (1) crabs of both species maintained in the laboratory at 30°C (laboratory warmed); (2) crabs given a brief acclimation period (4 weeks for blue crabs; 7 weeks for stone crabs) at 8°C in the laboratory (laboratory colled), and (3) stone crabs that had been naturally acclimated from summer (30°C) to winter (8°C) temperatures over a 6 month period in the field (naturally cooled). No differences were found in the abilities of the northern and southern populations of either species to generate muscle stress when tested at summer temperatures (30°C) common to both populations. Northern and southern blue crabs produced similar levels of muscle stress whether laboratory warmed (30°C) or laboratory cooled (8°C). Conversely, northern and southern stone crabs showed significantly reduced muscle stress in laboratory cooled crabs compared with laboratory warmed crabs. Stone crabs from both populations generated the same amount of muscle stress after having been naturally cooled to 8°C as they had generated the previous summer (30°C).In vitro neuromuscular properties (i.e. (1) muscle stress as a measure of contractile ability; (2) excitatory junction potential (EJP) amplitude as a measure of neurotransmitter release; (3) specific membrane resistance (R_m) as a measure of postsynaptic membrane properties) were compared at 8, 20, and 30°C between northern cold acclimated (naturally cooled stone crabs and laboratory cooled blue crabs) and non-cold acclimated (laboratory cooled stone crabs. Muscle fibers in claws of stone crabs and blue crabs showing cold acclimation had higher R_m at 8°C than non-cold acclimated crabs. This higher R_m resulted in a broadening of EJP's which enhanced EJP summation, muscle fiber depolarization, and muscle stress.Abbreviations EJP excitatory junction potential - E _r resting membrane potential - F _e lacilitation - R _m specific membrane resistance     

The geography of crushing: Variation in claw performance of the invasive crab Carcinus maenas

The major claws of predatory, durophagous decapods are specialized structures that are routinely used to crush the armor of their prey. This task requires the generation of extremely strong forces, among the strongest forces measured for any animal in any activity. Laboratory studies have shown that claw strength in crabs can respond plastically to, and thereby potentially match, the strength of their prey's defensive armor. These results suggest that claw strength may be variable among natural populations of crabs. However, very few studies have investigated spatial variation in claw strength and related morphometric traits in crabs. Using three geographically separate populations of the invasive green crab in the Gulf of Maine, we demonstrate, for the first time, geographic variation in directly measured claw crushing forces in a brachyuran. Despite variation in mean claw strength however, the scaling of claw crushing force with claw size was consistent among populations. We found that measurements of crushing force were obtained with low error and were highly repeatable for individual crabs. We also show that claw mass, independent of a linear measure of claw size, and carapace color, which is an indicator of time spent in the intermoult, were important predictors of claw crushing force.     

Molecular genetic structure and evolution in native and colonized populations of the Chinese mitten crab, Eriocheir sinensis

Chinese mitten crab (Eriocheir sinensis), a native species in China, has populated Continental Europe and North America since 1912. In this paper, the nucleotide variation in the fragments of mitochondrial COII (693 bp), Cytb (766 bp), and nucleotide ITS (706 bp) was analyzed in native (Yantgze, Yellow, and Liaohe Rivers in China) and colonized (Elbe, Rhine, and Thames Rivers in Europe, and San Francisco Bay in North America) populations of the Chinese mitten crab. The major findings are as follows. First, the genetic variability in the native populations is higher than that in the colonized European and North American populations, with the exception of the Elbe River population, which possesses a similar level of variability with the native populations. Second, a remarkable loss of singletons has been associated with the colonization of Chinese mitten crabs. Third, the AMOVA and F _ST results demonstrate that there are no significant genetic differentiations among the populations from the three continents, but there is a significant differentiation between pairwise populations within and among continents. Fourth, it is found that expansion-drift and gene flow pattern are involved in the European populations. The neutrality test and R ₂ statistics suggest that a moderate founder population exists in the colonized populations, and only the Yangtze River population has undergone a recent population expansion. Finally, the results demonstrate that the European populations originate from multiple rivers in China on multiple occasions. The San Francisco population originates from both the native Chinese populations and the colonized European populations, most likely the Thames population.     

Effect of natural disturbance on migrations and population dynamics of a catadromous species, Eriocheir japonicus, along the Lo-Mei stream in northern Taiwan

Japanese mitten crab, Eriocheir japonicus (de Haan), migrates between stream and sea and breeds in shallow coastal areas, exhibiting a catadromous life cycle. This study investigated how the crabs adjust reproductive strategy and migratory behavior to climate fluctuation and what kind of life history strategy individual crabs adopt in a disturbed environment. We conducted a 14-year monitoring study from 1998 to 2011 in Lo-Mei Stream in northern Taiwan. Streamflow and flood timing are controlled by precipitation and typhoons. Abundance of crabs was lower after disturbances by several typhoons and by lower temperatures associated with cold winters in 2006 and 2007. Samples from 2003 showed a reversal in reproductive trends, with increasing size in the same pattern of oocytes, compared to reproductive biology from 1999 to 2005. The life history of E. japonicus can be divided into three stages: spawning migration, growth period, and upstream migration of juveniles to compensate for downstream migration of mature crabs. Reproductively, in E. japonicus the combination of semelparity and synchronous breeding can increase reproductive potential and increase survival in a less disturbed environment at the optimum time. Environmental cues play an important role as major triggers in the persistence of populations.     

Mitochondrial DNA analysis of Tunisians reveals a mosaic genetic structure with recent population expansion

Tunisia is a country of great interest for human population genetics due to its strategic geographic position and rich human settlement history. These factors significantly contributed to the genetic makeup of present-day Tunisians harbouring components of diverse geographic origins. Here, we investigated the genetic structure of Tunisians by performing a mitochondrial DNA (mtDNA) comparison of 15 Tunisian population groups, in order to explore their complex genetic landscape. All Tunisian data were also analysed against 40 worldwide populations. Statistical results (Tajima's D and Fu's F_S tests) suggested recent population expansion for the majority of studied populations, as well as showed (AMOVA test) that all populations were significantly different from each other, which is evidence of population structure even if it is not guided by geographic and ethnic effects. Gene flow analysis revealed the assignment of Tunisians to multiple ancestries, which agrees with their genetic heterogeneity. The resulting picture for the mtDNA pool confirms the evidence of a recent expansion of the Tunisian population and is in accordance with a mosaic structure, composed by North African, Middle Easterner, European and Sub-Saharan lineages, resulting from a complex settlement history.     

长江口中华绒螯蟹放流亲蟹对环境的生理适应

按回捕日期取样测定长江口中华绒螯蟹亲蟹标志放流前后血清与肝胰腺的生理指标, 初步研究了放流亲蟹对长江口环境的生理适应过程。结果表明, 在放流后6d, 亲蟹肝胰腺超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性以及血清甘油三酯(TG)和血蓝蛋白含量均降低, SOD、CAT和TG在放流后9d达到较低水平, 其中SOD活性和TG含量较放流前显著降低(P<0.05); 肝胰腺酸性磷酸酶(ACP)以及血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、碱性磷酸酶(ALP)、总蛋白质(TP)、白蛋白(ALB)、总胆固醇(TC)和肌酐(CREA)水平在放流后总体呈现先升高后降低的趋势; 在放流后79d, 肝胰腺SOD、CAT、ACP与血清ALP、ALT、AST活性均恢复至放流前水平(P>0.05), 而血清TP、血蓝蛋白、ALB、TC、TG、CREA含量较放流前均显著降低(P<0.05)。综合各项指标表明, 中华绒螯蟹亲蟹在放流后6d内出现免疫力下降、代谢增强等反应, 放流22d后亲蟹各项机能逐步恢复, 并在70d后接近或达到放流前水平。建议今后放流前对亲蟹进行环境适应性驯化, 以便提高亲蟹增殖放流效果。     

Stimulation of feeding behavior in three species of fiddler crabs by hexose sugars

Feeding responses to five hexoses were examined in three closelyrelated species of fiddler crabs, Uca minax, U.pugnax and U.pugilator.Hexoses tested were glucose, galactose, sorbose, fructose andmannose. Intact crabs and eyestalk-ablated crabs were tested.Responses to sugars were species specific. Eyestalks are directlyinvolved in vision and overall neural integration as well aswith chemosensory and metabolic pathways associated with feeding.Overall, eyestalk-ablated crabs were more sensitive uian intactcrabs. Studies of responses of individuals within a populationto hexoses showed tiiere are individual U.pugnax that respondto galactose and others that do not. Similarly, there were U.pugilatorindividuals that were mannose responsive and others that didnot respond to mannose. An additional study of differences inpopulation responses to hexoses would provide valuable toolsin studying geographic relationships between fiddler crab populations.