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1.
Four successive mass selection lines of the Pacific oyster, Crassostrea gigas, selected for faster growth in breeding programs in China were examined at ten polymorphic microsatellite loci to assess the level of allelic diversity and estimate the effective population size. These data were compared with those of their base population. The results showed that the genetic variation of the four generations were maintained at high levels with an average allelic richness of 18.8–20.6, and a mean expected heterozygosity of 0.902–0.921. They were not reduced compared with those of their base population. Estimated effective population sizes based on temporal variances in microsatellite frequencies were smaller to that of sex ratio-corrected broodstock count estimates. Using a relatively large number of broodstock and keeping an equal sex ratio in the broodstock each generation may have contributed to retaining the original genetic diversity and maintaining relatively large effective population size. The results obtained in this study showed that the genetic variation was not affected greatly by mass selection progress and high genetic variation still existed in the mass selection lines, suggesting that there is still potential for increasing the gains in future generations of C. gigas. The present study provided important information for future genetic improvement by selective breeding, and for the design of suitable management guidelines for genetic breeding of C. gigas.  相似文献   

2.
Manila clam （Ruditapes philippinarum） was monthly sampled from its benthic aquaculture area in Jiaozhou Bay from May 2009 to June 2010.The annual variations of major elemental composition,organic content,fatness and element ratio of Manila clam were examined.The element removal effect of clam farming in Jiaozhou Bay was analyzed based on natural mortality and clam harvest.The results indicated that the variation trend of carbon content in shell （Cshell） was similar to that in clam （Cclam）.Such a variation was higher in summer and autumn than in other seasons,which ranged from 9.10±0.13 to 10.38 ± 0.09 mmol g^-1 and from 11.28 ±0.29 to 12.36±0.06 mmol g 1,respectively.Carbon content of flesh （Cflnesh） showed an opposite variation trend to that of shell in most months,varying from 29.42 ± 0.05 to 33.64 ± 0.62 mmol g^-1.Nitrogen content of shell （Nshell） and flesh （Nflesh） changed seasonally,which was relatively low in spring and summer.Nshell and Nflesh varied from 0.07 ±0.009 to 0.14±0.009 mmol g^-1 and from 5.46 ± 0.12 to 7.39 ± 0.43 mmol g^-1,respectively.Total nitrogen content of clam ranged from 0.50 ± 0.003 to 0.76 ± 0.10 mmol g^-1 with a falling tend except for a high value in March 2010.Phosphorus content of clam （Nclam） fluctuated largely,while phosphorus content of shell （Pshell） was less varied than that of flesh （Pflesh）.Pshell varied from 0.006±0.001 to 0.016±0.001 mmol g^-1; while Pflesh fluctuated between 0.058±0.017 and 0.293±0.029mmolg^-1.Pclam ranged from 0.015±0.002 to 0.041 ±0.006mmolg^-1.Carbon and nitrogen content were slightly affected by shell length,width or height.Elemental contents were closely related to the reproduction cycle.The removal amounts of carbon,nitrogen and phosphorus from clam harvest and natural death in Jiaozhou Bay were 2.92× 10^4t,1420t and 145 t,respectively.The nutrient removal may aid to reduce the concentrations of nitrogen and phosphorus,the main causes of eutrophication,and to maintain the ecosystem health of J  相似文献   

3.
To investigate the genetic components of growth in the brine shrimp Artemia sinica, we estimated the genetic parameters of body length and the response to selection using a fully pedigreed population of A. sinica. The base population was generated from four wild founder populations. We tested 4160 offspring in 360 families over four generations for growth and survival performance. Across four generations, we produced full-and half-sib families with nested mating, where two dams were mated to the same sire. Individual body length was measured for each nauplius at day 20 post-hatching. Heritability of body length was estimated across four generations with the restricted maximum likelihood method. The heritability of body length in A. sinica was low(0.14 ± 0.05), and the common environmental effect was 0.14 ± 0.02. We estimated the response to selection for body length by calculating the difference in the mean breeding values between different generations. The accumulated genetic gain in body length was 278.94 μm after three generations of selection. This low response to selection was probably caused by the low heritability of body length, small sample size, and the low selection intensity(50%). The results suggest that A. sinica selective breeding programs must be changed to generate any substantial, sustainable genetic increases in body length. We suggest that optimal genetic gains could be achieved by introducing wild strains into the nuclear breeding population to increase genetic variation, and by increasing the size of the breeding population to allow for increased selection intensity.  相似文献   

4.
In order to determine whether growth performance could be improved by hybridizing full-sib families of Manila clam(Ruditapes philippinarum), crosses between two full-sib families including self and reciprocal crosses were carried out. The effects of heterosis, combining ability and interaction on the growth of shell length were estimated. The results showed that the growth of hybrid larvae was intermediate between parents on days 6 and 9. Heterosis on shell length was observed, which varied at juvenile stage. The cross of ♂A×♀B(Hp varied between 10.41% and 68.27%) displayed larger heterosis than ♂B×♀A(Hp varied between 1.89% and 32.33%) did, suggesting that ♂A×♀B was an ideal hatchery method of improving the growth performance of Manila clam. The variances of general combining ability(GCA), special combining ability(SCA) and interaction(I) were significant in shell length(P 0.05), indicating that both additive and non-additive genetic factors were important contributors to the growth of larvae and juveniles. The GCA for shell length of ♂A×♀B was higher than that of ♂B×♀A at both larval and juvenile stages. This confirmed that the cross between ♂A and ♀B showed great growth in shell length. In summary, the growth of Manila clam seeds could be improved by hybridizing selected parents from large numbers of full-sib families.  相似文献   

5.
Fishery biology of jumbo flying squid Dosidicus gigas off Costa Rica Dome   总被引：1，自引：0，他引：1  
The jumbo flying squid(Dosidicus gigas) population was surveyed with the help of Chinese squid jigging vessels off the Costa Rica Dome(4°–11°N, 90°–100°W) in 2009 and 2010. The daily catch of D. gigas in the two survey cruises ranged from 0 to 5.5 t and was mostly obtained from the areas bounded by 6°–9°N and 91°–94°W and by 6°30′–7°30′N and 96°–97°W. The sea surface temperature in the areas yielding the most catch ranged from 27.5 to 29℃. The sex ratio of the total catch was 3.75:1(female: male). The mantle length of the squid ranged from 211 to 355 mm(male) and from 204 to 429 mm(female) with an average of 297.9 and 306.7 mm, respectively. In the relationship of the mantle length(mm) and body weight(g) of the squid, there was no significant difference between sexes. The female and male were at a similar maturity, and most individuals are maturing or have matured with a few females being spent. The size(mantle length) and age at the first sexual maturity were 297 mm and 195 d in females, and less than 211 mm and 130 d in males, respectively. Most of the sampled stomachs(70.6%) had no food remains. The major preys of the squids were fish, cephalopods and crustaceans, with the most abundant Myctophum orientale and D. gigas. The preys in more than 65% of the non-empty sampled stomachs evidenced the cannibalism of D. gigas. The results improved current understanding of the fishery biology of D. gigas off the Costa Rica Dome, which may facilitate the assessment and management of relative fishery resources.  相似文献   

6.
Iwagaki oyster,Crassostrea nippona,widely distributes along the seashore of Eastern Asia,and has been considered to be a potential breeding species due to its delicious taste and high commercial value.In order to study its genetic background and population structure,we developed 46 novel polymorphic microsatellite markers using next-generation sequencing technique and characterized them in 30 individuals.The number of alleles ranged from 3 to 22,while the observed and expected heterozygosities varied from 0.133 to 1.000 and 0.455 to 0.949,respectively.Fifteen microsatellite markers were selected and grouped into five highly informative multiplex PCRs for C.nippona.We evaluated and validated these multiplex PCRs in a cultured population including 173 candidate parents and 486 offspring.In actual parentage analysis,80%of the offspring were correctly assigned to their parental pairs using three multiplex PCRs.Furthermore,the success rate of parentage assignment reached 96%when the other two multiplex PCRs were added.These 46 microsatellite loci with high variability and the five multiplex PCRs described here provide a powerful tool for pedigree reconstruction,resource conservation and selective breeding program of C.nippona.  相似文献   

7.
The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas.  相似文献   

8.
We estimated the reproductive success of adult brood fish and the heritability of growth-related traits for large yellow croaker (Larimichthys crocea). We created two independent full-factorial cross groups (1 and 2) by crossing 4 males×4 females and 4 males×3 females, respectively. We measured the body weight (BW), body length (BL), and body height (BH) of 281 individuals from group 1 and 318 individuals from group 2 at 20 months post hatch (harvest age). We also collected a tissue sample from each individual. The parents and offspring were genotyped using six polymorphic microsatellites. Of the 599 offspring, 99.2% were assigned to a single pair of parents. In both groups, some parent pairs produced a large number of offsprings while other pairs did not produce any offspring. The genetic diversity and putative Ne were lower in the offsprings than in the parents in both groups. The heritability estimates at 20-month age were 0.13±0.10 for BW, 0.19±0.13 for BL, and 0.09±0.06 for BH. The genetic and phenotype correlation between BW, BL, and BH was close to 1. The results provide basic information for selective breeding and further genetic characterization of large yellow croaker.  相似文献   

9.
Interspecific hybridization can generate heterosis, which is proven to be a useful tool in selective breeding programs for oyster culture. Crassostrea angulata and C. ariakensis are two important economic shellfish species in China. We conducted 2 × 2 reciprocal crosses to determine whether these two species can cross-fertilize and their hybrids can hatch, survive and perform heterosis. Fertilization was found symmetrical without delay. The rate of fertilization success of C. angulata ♀× C. ariakensis ♂ was lower than that of C. ariakensis ♀× C. angulata ♂, and the success rate of both hybridizations was lower than that of two intraspecific crosses each. During the planktonic period, survival rate of the progeny was lower in the hybrid crosses than in the intraspecific crosses. On day 360, mean shell height of the progeny of C. angulata ♀× C. angulata ♂ was highest, which was followed by that of C. angulata ♀× C. ariakensis ♂, C. ariakensis ♀× C. ariakensis ♂ and C. ariakensis ♀× C. angulata ♂ in a descending order. Morphology of adults produced by the hybrid crosses was similar to that of C. angulata. Both hybrids underwent normal gonad development and produced mature gametes in the mating season. This study provided new insights into the quantitative traits in interspecific crosses of Crassostrea species, thus being of guidance value for selective breeding of oyster.  相似文献   

10.
Monthly investigatiom were made on the population of Chinese freshwater crab, Sinopotamon yangteskiense Bott, 1967 from April, 1984 to Match, 1985. The data on 4413 specimens show that the growth was affected mainly by temperature. During the April to November growth period, the crabs' major development occured from June through October. One year was required for a fine white oocyte to develop into a mature egg. The reproduction period was June-October. Females bearing eggs were taken from June-August, and crabs with young were found from July-October. The females reproduced once a year but could for more than one year. The number of eggs carried by a female varied greatly according to the size of the crab, ranging from 30 to 100 eggs. New-bom crabs become mature after 1-2 yeats. The sex ratio was approximately 1:1 in the overall population. However, the larger crabs are predominantly male. The age distribution of S. yangtsekinese was estimated from size frequency histograms. There were more adult crabs  相似文献   

11.
Wang  Huanshan  Wang  Teng  Li  Wenjing  Liu  Huanzhang 《中国海洋湖沼学报》2019,37(3):1042-1050
Megalobrama pellegrini is a cyprinid fish endemic to upper reaches of the Changjiang(Yangtze) River, China, which is also an important economic species in the local area. In recent years,resources of this species have decreased sharply and its conservation has drawn great attention. In the present study, we collected 120 individuals from the Longxi River, a tributary isolated from the main channel of the Changjiang River, where M. pellegrini is still relatively abundant. Using two different molecular markers, mitochondrial cytochrome b(cyt b) gene, and nuclear microsatellite(simple sequence repeat,SSR), we analyzed the genetic diversity of this isolated population. The results show that sequence genetic diversity was low(H_d:0.290 and P_i: 0.000 77 for cyt b gene),while the SSR genetic diversity was high(H_o:0.824 4±0.147 2,H_e: 0.823 510.145 1). Analysis indicated that this population had experienced a bottleneck,with inbreeding and small effective population size(around 50). Based on SSR data, relatedness analyzing revealed that the 120 samples were grouped into 10 completely independent clusters. It was inferred that the mating system of M. pellegrini was polygamy. We suggested that the low genetic diversity could be induced by the overfishing and inbreeding depression. Therefore, we suggested that the urgent conservation measures should be taken to control the overfishing and give better conditions for the fish to grow and spawn, then to restore population size.  相似文献   

12.
From June 2003 to June 2004, an investigation on the life cycle, production and trophic basis of dominant species of macrozoobenthos community in a second-order river of the Hanjiang River basin, Hubei, China was carded out. The results showed that the dominant species Leptophlebia sp. and Ephemera sp. appeared to develop two generations per year, and there was a small overlap in the two generations of both species. The pupation of Leptophlebia sp. mainly occurred in autumn and winter, while pupation of Ephemera sp. mainly took place in summer and winter. The standing stocks of the Leptophlebia sp. population and Ephemera sp. population had two peaks in a year. The cohort production and cohort P/B ratio of the Leptophlebia sp. population estimated by size frequency method were 19.018 1 g/m^2.a and 5.7 respectively, while its annual production and P/B ratio were 38.036 2 g/m^2.a and 11.4. The cohort production and cohort P/B ratio of the Ephemera sp. population were 38.015 9 g/m^2.a and 5.9, while its annual production and P/B ratio were 76.031 8 g/m^2.a and 11.8.  相似文献   

13.
Pyropia yezoensis is an important macroalga because of its extensive global distribution and economic importance. Color is an important trait in the thalli of P. yezoensis, it is also an effective marker to identify the hybridization in genetic breeding. In this study, a high-density genetic linkage map was constructed based on high-throughput single nucleotide polymorphism(SNP) markers, and used for analyzing the quantitative trait loci(QTLs) of red color trait in the thalli of P. yezoensis. The conchospore undergoes meiosis to develop into an ordered tetrad, and each cell has a haploid phenotype and can grow into a single individual. Based on this theory, F1 haploid population was used as the mapping population. The map included 531 SNP markers, 394.57 cM long on average distance of 0.74 cM. Collinear analysis of the genetic linkage map and the physical map indicated that the coverage between the two maps was 79.42%. Furthermore, QTL mapping identified six QTLs for the chromosomal regions associated with the red color trait of the thalli. The value of phenotypic variance explained(PVE) by an individual QTL ranged from 4.71%–63.11%. And QTL qRed-1-1, with a PVE of 63.11%, was considered the major QTL. Thus, these data may provide a platform for gene and QTL fine mapping, and marker-assisted breeding in P. yezoensis in the future.  相似文献   

14.
Nutrient limitation is known to inhibit growth and metabolism and to alter elemental stoichiometric ratios in phytoplankton. In this study, physiological changes in Thalassirosira weissflogii were measured under different dissolved inorganic phosphate (DIP) regimes in semi-continuous cultures to revisit the utility of the Redfield ratio for assessing nutrient limitation. The results showed that cell size increased with decreasing DIP availability. In the P-depleted treatment (f/2-P) the cell size was 1.48 times larger than that in the P-limited (f/100) treatment and 2.67 times larger than that in the P-saturated treatment (f/2 and f/10). The fucoxanthin to chlorophyll a ratio (Fuco/chl a) was relatively stable (about 0.3) in P-saturated cultures and was 10 times higher than that in P-limited and P-depleted cultures. During the experimental period, the photosynthetic efficiency index, ?F/Fm′, was relatively stable at ~0.50 in the P-saturated cultures, but quickly declined with decreasing DIP availability. Although cellular P content showed a significant difference between the P-saturated culture (1.6 pg/cell) and the P-limited culture (0.7 pg/cell), the N/P ratio in T. weissflogii did not show a trend with DIP availability and fluctuated slightly around 25. Our results suggest that cell division in T. weissflogii is not strictly size-gated but is probably regulated by a biochemical, and hence, an elemental stoichiometric ratio threshold, and that deviation of the cellular N/P ratio from the Redfield ratio is not a reliable indicator of algal nutrient stress.  相似文献   

15.
Heritability estimates may be severely biased when a large common environmental effect on a family arises from a longlasting separate rearing at early stages(SRES) in traditional selective breeding programs, especially when bred populations have weak genetic ties. Communal rearing at early stages(CRES) may reduce common environmental effect since all families are reared in the same environment immediately after hatching. Here, we compared the effects of CRES and SRES strategies on genetic parameter estimation for harvest body weight in a selective breeding population of Litopenaeus vannamei with a small number of half-sib families. Genetic parameters of each strategy were estimated by using animal models excluding and including the common environmental effect(Model 1 and Model 2, respectively). Heritability estimates for body weight were 0.21 ± 0.06(P 0.05) and 0.69 ± 0.09(P 0.05) for CRES and SRES, respectively, in Model 1, and 0.21 ± 0.06(P 0.05) and 0.52 ± 0.27(P 0.05) in Model 2. The ratio of common environmental variance to phenotypic variance was 0.002 ± 0.000 and 0.071 ± 0.112 for CRES and SRES, respectively. Neither strategy precisely partitioned the common environmental variance according to likelihood ratio test. Lower heritability for body weight in CRES than in SRES implied that a large common environmental variance was confounded with additive genetic variance and was not effectively partitioned in SRES. Moreover, genetic correlation of body weight between the two strategies was 0.75 ± 0.15, indicating that family rankings truly changed. The CRES should be followed in the selective breeding program of shrimp, especially in a population with a shallow pedigree and weak genetic ties between families.  相似文献   

16.
We studied the waterbird population at Lashihai Lake, Yunnan Province, China, which is a Ramsar Site(Wetland of International Importance), to determine seasonal variation in the species composition and size of the waterbird population. The study was conducted at five selected spots along Lashihai Lake at the same time each week from August 2011 to September 2013. In total, 62 waterbird species were recorded, of which 38.71%, 35.48%, 16.13%, and 9.68% were winter migrants, passage visitors, residents, and summer migrants, respectively. We found important seasonal changes in waterbird species composition and population size. Waterbird species richness was highest from September to the following April, with the total species numbers peaking in December. Total individual numbers peaked twice from late November to early December and mid-to-late February. However, waterbird species and individual numbers were comparatively lower from May to August. The change in species composition was determined by the arrival and departure dynamics of winter migrants and passage visitors. Winter migrants primarily caused the periodic changes in population size. Of concern,species and overall waterbird numbers seemed to be lower than the numbers in historical records. The decline of waterbird numbers implies that environmental changes caused by the implementation of the dam upstream of Lashihai Lake may have had adverse effects on this waterbird population. This study confirms the existence of major seasonal changes in species composition and size of the waterbird population at Lashihai Lake. Furthermore, the findings demonstrate that this wetland is of high conservation importance for waterbirds using the Central Asian–Indian and Asian–Pacific migratory routes.  相似文献   

17.
This study documents the horizontal distribution and demography of Antarctic krill （Euphausia superba Dana）, col- lected using trawls, from the Prydz Bay region during January 2002. Euphausia superba （E. superba） was distributed primarily south of 64S. The average density and biomass were estimated as 68.85 ind.（1 000 m3） and 24.16 g wet weight-（1 000 m3）, re- spectively. Highest values were located in the open sea （depth 〉 3 000 m）. Body length ofE. superba ranged from 30 to 55 mm （N=1 758）, with a mean length of 38.45~3.68 mm （SD）. The overall sex ratio was approximately 1 ： 1, 47.6% females （41.9% sub-adults and 5.7% adults）, 46.6% males （42.7% sub-adults and 3.9% adults）, while 5.8% were juveniles. The population struc- ture of E. superba exhibited geographical variation. At stations in the western part of the survey area populations had a high pro- portion of juveniles, a lower sexual maturity stage for males and small body size, while the opposite was found at stations in the eastern part. A latitudinal difference was found at stations along 70.5°E and 73°E transects： body length was small and the sex ratio was high in regions of high latitude, while the opposite occurred in areas of low latitude.  相似文献   

18.
Population genetics of the left-eyed flounder, Paralichthys olivaceus, including natural and cultured stocks distributed in the coastal waters near Qingdao of eastern maritime China, was analyzed in allozyme and RAPD. The results showed that among total 29 gene loci of 15 isozymes, 9 and 7 were po- lymorphic in natural and cultured stocks, respectively. The status of genetic diversity in P. olivaceus is low in terms of polymorphic loci in chi-square test and genetic departure index of Hardy-Weinberg equi- librium. More alleles in IDHP, CAT, GDH and Ldh-C allozymes were found in the fish, which could be used as markers in assortive breeding and distinguishing stock, population or species evolution. Total 88 and 86 RAPD bands ranging from 200 to 2 500 bp were recognized individually in average of 7.8–8.0 bands per primer. The genetic diversity in cultured stock is lower than that in natural ones showing an ob- viously decreasing genetic divergence. Therefore, effective countermeasures must be taken to protect ge- netic resources of marine cultured fishes. The 2 markers have their own pros and cons. Combining the 2 markers to investigate the genetic variation of populations is suggested. The results provide basic data of this flounder and they are useful for studying genetic improvement and genetic resources of the fish.  相似文献   

19.
The Yellow Sea Cold Water Mass （YSCWM） was suggested as an over-summering site of the dominant copepod species Calanus sinicus in coastal Chinese seas. Population abundance and structure were investigated by monthly sampling along three transects across the northern boundary of the YSCWM during 2009-2010. Results show that thermal stratification existed from June to October and that the vertical thermal difference increased with depth. Generally, total abundance was lowest in October and highest in June, and the female/male sex ratio was highest in February and lowest in August. Evident spatial differences in abundance were observed during the existence of the YSCWM. In June, total abundance averaged 158.8 ind/m~ at well-stratified stations, and 532.1 ind/m3 at other stations. Similarly, high abundances of 322.0 and 324.4 ind/m3 were recorded from July to August inside the YSCWM, while the abundance decreased from 50.4 to 1.9 ind/m3 outside the water mass. C. sinicus distribution tended to even out over the study area in September when the YSCWM disappeared. We believe that the YSCWM may retard population recruitment in spring and preserve abundant cohorts in summer. The summer population was transported to neritic waters in autumn. In addition to low temperatures, stable vertical structure was also an essential condition for preservation of the summer population. C. sinicus can survive the summer in marginal areas in high abundance, but the population structure is completely different in terms of C5 proportion and sex ratio.  相似文献   

20.
The Bohai Sea is a semi-enclosed marginal sea in the North West Pacific. Meiofauna samples were collected from 22 stations in the Bohai Sea to document the spatial distribution, structure, and diversity of the meiofaunal community and investigate the major factors influencing the community features. A total of 20 higher taxa of meiofauna were identified. The dominant group was Nematoda, accounting for 90.8% of the total meiofaunal abundance on average, followed by Copepoda, Bivalvia, Polychaeta, Kinorhyncha, and Ostracoda. Meiofaunal abundance ranged from 121 ± 89 ind(10 cm2)-1 to 3042 ± 1054 ind(10 cm2)-1. Diversity indices also varied among different stations, with a Margalef's richness index(d) of 1.1–3.1, Shannon-Wiener diversity index(H′) of 0.7–1.8, and Pielou's evenness index(J′) of 0.4– 0.8. Meiofaunal abundance and diversity indices were significantly lower in the areas of Bohai Bay and adjacent to Laizhou Bay. The correlation analysis showed that meiofaunal abundance and diversity indices are closely linked to variations in sediment silt-clay content, medium grain size(MDΦ), and chlorophyll-a concentrations. The ecological quality status of most stations can be ranked from poor to moderate based on meiofaunal richness. According to the value of nematode to copepod ratio(Ne:Co ratio), most stations are uncontaminated, except seven stations are slightly or moderately contaminated. Both meiofaunal richness and Ne:Co ratio indicate the poor ecological quality of three stations adjacent to Laizhou Bay. The efficiency of the meiofauna communities as environmental indicators will be tested in a greater area in the future studies.  相似文献   

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