Effect of dietary protein and energy levels on growth,oxygen consumption,haemolymph and digestive gland carbohydrates,nitrogen excretion and osmotic pressure of Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles (Crustacea,Decapoda; Penaeidae)

The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ⁻¹ were fed at 20% of shrimp body weight of two sizes: < 1 g and > 1 g. Both species showed a optimum P/E ratio of 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate) in juveniles < 1 g. For shrimp > 1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ⁻¹ (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2–3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ⁻¹ diet and lower values (O/N = 73) with a 36-mg kJ⁻¹ diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus < 1 g fed with 36 mg kJ⁻¹ and the lowest in L. vannamei < 1 g fed with 31 mg kJ⁻¹. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles < 1 g of both species are more affected by the P/E ratio than juveniles > 1 g. All results showed that juveniles > 1 g of both species are less dependent of P/E ratio than juveniles < 1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds.     

Genetic diversity in the Indian population of Penaeus monodon (Fabricius, 1798) as revealed by mtDNA sequence analysis

Genetic diversity in the Indian population of the tiger shrimp Penaeus monodon was determined by using partial sequence data of the mitochondrial DNA (mtDNA) control region (D‐loop) and the 16S rRNA gene. Eight populations from different geographical locations (Mumbai, Kochi, Mangalore, Kakinada, Gopalpur, Chilika, Paradeep and Andaman) were collected and analysed. The amplified polymerase chain reaction products of size 577 bp for the control region and 472 bp for 16S rRNA were sequenced in both directions and data were analysed through clustal , arlequin , mega and phylip . A significant genetic structure was found among the Indian populations. The mtDNA control region proved to be a powerful marker in comparison with 16S rRNA for population studies of this species. The east coast population was more genetically diverse than the west coast. The Andaman population was found to be the most diverse among all the populations. The populations on the west coast were found to be genetically more structured and differentiated than the populations on the east coast. The results revealed a high level of genetic diversity and also distinct population structuring of P. monodon, suggesting great possibilities of genetic improvement for growth and other economic traits.     

Studies of the Thermal and Haline Influences on Growth and Survival of Litopenaeus vannamei and Litopenaeus setiferus

A series of experiments were conducted to examine the effects of salinity (1–48 g/L) on the biological performance, as evaluated by growth and survival, of the Pacific white shrimp, Litopenaeus vannamei, and the Atlantic white shrimp, Litopenaeus setiferus, reared at temperatures of 20, 24 or 28 C. Poor growth and survival of L. vannamei was observed after 21–28 d of culture at low salinity (2 and 4 g/L) at 20 C. Raising salinity to 8 and up to 32 g/L significantly increased survival at this temperature, indicating that avoiding low temperatures is critical for survival of this species when reared at low salinity. A major improvement in the growth rate of L. vannamei was observed at 24 C, but it still was sub‐optimal compared to growth observed at 28 C. Irrespective of salinity, high survival rates were observed at both 24 and 28 C, but variable growth rates were recorded. Contrary to L. vannamei, the Atlantic white shrimp, L. setiferus, which was reared for 28 d at 24 C only, had better growth performance at 8 g/L compared to 2, 16 and 32 g/L. Under equal experimental conditions, L. setiferus had considerably lower weight gain and survival than L. vannamei.     

Comparative study of the intracellular superoxide anion production in different penaeid species through the NBT‐reduction assay

The capacity of reactive oxygen intermediates production upon haemocyte stimulation is one of the most important immunoparameter utilized to assess the health status in cultivated shrimps. In the present study, we compared oxidative stress potential, by measuring the superoxide anion production in three penaeid shrimps: two wild Atlantic species, the pink shrimp Farfantepenaeus paulensis and the white shrimp Litopenaeus schmitti and one cultivated Pacific species, the white shrimp, Litopenaeus vannamei, through the nitro‐blue‐tetrazolium‐reduction assay. We also proposed an optimized experimental protocol for this assay, that produces rapid and consistent results with low levels of basal superoxide anion (O₂^?) production by unstimulated haemocytes and high levels of this oxygen radical after cell stimulation. Among the different cell elicitors used (zymosan, laminarin, lipopolysaccharide and phorbol myristate acetate), laminarin (β‐1,3‐glucans – 2 mg mL^?1) was the most potent cell activator for the haemocytes of all three penaeids and we recommend this immunostimulant to routinely evaluate shrimp respiratory burst. In general terms, the most elevated levels of O₂^? production, after cell stimulation with microbial components, were detected in L. schmitti. Interestingly, the stimulation profile of the haemocytes of L. vannamei was more similar to F. paulensis, than to L. schmitti, which is more phylogenetically related.     

Replacement of live food with a microbound diet in feeding Litopenaeus setiferus (Burkenroad) larvae

Microbound feeds have been well accepted by shrimps and farmers in many penaeid shrimp hatcheries. The present study focused on an adequate level of replacement of Artemia nauplii and microalgae by a microbound diet for rearing Litopenaeus setiferus (Burkenroad) larvae. A microbound diet (MBD) consisting of fishmeal, squid meal, shrimp meal, yeast meal and soybean meal was used. The first experiment was designed to obtain the optimum level of MBD to complete the live feeding schedule, from Protozoea (PZ_III) to Mysis (M_III). The experimental levels of the microbound diet tested were 2, 4, 6 and 8 mg MBD L^?1 day^?1. The next step was to determine the Artemia nauplii replacement level from PZ_I to M_III by MBD. These experiments were carried out either in the presence (Experiment 2) or in the absence of algae (Experiment 3). Four replacement levels were tested: 0% (4 mg MBD L^?1 day^?1: 1 Artemia nauplii mL^?1), 40% (5.5 mg MBD L^?1 day^?1: 0.6 Artemia nauplii), 60% (6.5 mg MBD L^?1 day^?1: 0.4 Artemia nauplii) and 100% (8 mg MBD L^?1 day^?1: 0 Artemia nauplii). In all experiments growth, survival, development, quality index (QI) and performance index (PI), were used to determine the optimum concentration of microbound diet. Results showed that 6 mg MBD L^?1 day^?1 can be recommended as a complement to live food for L. setiferus larvae from PZ_III to M_III. In the presence of algae, maximum growth and survival may be obtained in 40–60% (5.5–6.5 mg MBD L^?1 day^?1) of Artemia nauplii replacement levels. In the absence of algae, the Artemia nauplii replacement resulted in slower development, less salinity resistance, lower growth and lower survival than was obtained in larvae fed with algae.     

Preliminary Comparisons of the Native Penaeus setiferus and Pacific P. vannamei White Shrimp for Pond Culture in South Carolina, USA

Two pond experiments were conducted at the Waddell Mariculture Center to compare production characteristics of the native Penaeus setiferus and Pacific P. vannamei white shrimp in South Carolina. In 1985, 7–9 day old postlarval P. setiferus were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1, one 0.25, and one 0.5 ha ponds. Both species were stocked at 12 shrimp/m². The shrimp were fed a 25% protein commercial food and harvested by draining after 147 d. Sarvival in all ponds was > go%, but growth and production of the P. setiferus were considerably lower than values obtained for P. vannamei: 12.8 g and 1,555 kg/ha/crop for P. satiferus versus 19.7 g and 2,477 kg/ha/crop for P. vannamei. In 1989, duplicate 0.1 ha ponds were stocked with P. setiferus and P. vannamei at 60 shrimp/m², and two additional 0.1 ha ponds were stocked with P. setiferus at 40/m². The P. setiferus postlarvae were produced at the Waddell Center from captive-reared and wild South Carolina brood stock. Rearing procedures involved paddlewheel aeration (10 hp/ha), regular water exchange (averaging 16–21%/d in all ponds), and use of a 40% protein feed. Due to the availability of postlarvae, the various treatments were stocked at different times. Both P. setiferus treatments were reared for 145 d, while the P. vannamei were reared for 165 d. P. setiferus at the 40/m² density attained mean size, survival, and standing crop biomass at harvest of 13.5 g, 97.5% and 5,259 kg/ha/crop, respectively. The 60/m²P. setiferus treatment was stocked 2 wk earlier and yielded 15.2 g mean weight, 87.5% survival, and 7,995 kg/ha/crop at harvest. The P. vannamei 60/m² treatment, which was stocked 3 wk earlier than any of the P. setiferus, produced mean size, survival and standing crop biomass at harvest of 17.1 g, 69.5% and 7,187 kg/ha/crop. Both survival and production levels would have been higher had not one replicate experienced a partial mortality due to a feeding accident. The 1989 study yielded what is thought to be the highest production levels yet achieved with P. setiferus in pond culture. These results suggest that P. setiferus may be a viable alternative to P. vannamei for intensive cultivation in the continental U.S. when P. vannamei are unavailable. Further evaluation of this potential is needed.     

Oxygen consumption and ammonia-N excretion related to protein requirements for growth of white shrimp, Penaeus setiferus (L.), juveniles

An experiment was conducted to study the effect of protein level on the growth rate, survival, pre- and postprandial oxygen consumption, and ammonia (N-NH₃) excretion in white shrimp. Penaeus setiferus (L.), juveniles. Diets containing 10%, 20%, 30%, 40% and 50% protein were provided at a proportion of 15% of the dry weight of shrimp weighing 0.19 ± 0.01g. The instantaneous growth rate was recorded for 45 days. The optimum protein level, in terms of the best growth rate, was that of the 30% protein diet (1.1 5g45days^?1). All shrimp fed with the diets had significantly higher respiration rates after feeding because of the apparent heat increment (AHI). A greater postprandial nitrogen excretion (PPNE) excretion was also observed after feeding. Shrimp maintained on the 30% protein diet had the lowest AHI and PPNE coefficients (percentage of ingested energyl. and took the least time to reach the oxygen consumption and nitrogen excretion peak. The 0:N ratios varied according to protein level, with higher values (32 and 44, fasting and Feeding, respectively) with a 30% protein diet, and lower values (10 and 13. fasting and feeding, respectively) with 10% and 50% protein diets. These results indicate that P. setiferus juveniles use protein when fed with high (50%) and low (10%) protein diets, and lipid-protein substrates with a 30% protein diet. Under these conditions, P. setiferus grow better with a 30% protein diet where shrimp use food more efficiently.     

Lambari fish Deuterodon iguape as an alternative to live bait for estuarine recreational fishing

Fishing tourism is growing steadily in Brazil. Artisanal fishers meeting the demand for recreational fishing are capturing live juvenile shrimp in the estuaries and selling them for live bait, preventing the recruitment of a larger contingent into the ocean. This study compares the efficiency of using lambari, Deuterodon iguape Eigenmann, as live bait with the shrimp, Penaeus schmitti Burkenroad, while fishing for common snook (Centropomus spp.), as well as to evaluate the swimming behaviour of D. iguape in different salinities. The results showed that there was no significant difference between the live baits used (P. schmitti vs D. iguape). The month, the period of the day and salinity presented differences. The size of the species did not depend on the type of bait used. There was no statistical difference in swimming behaviour, but there was a trend of increased speed and displacement in the group exposed to a salinity of 10 g/L. In conclusion, D. iguape appears as effective as P. schmitti and can be successfully used as live bait; and from an ecological point of view, it reduces the impact of fishing on juvenile shrimp.     

Phenoloxidase and peroxidase activity in the shrimp Litopenaeus schmitti,Pérez‐Farfante and Kensley (1997) exposed to low salinity

Phenoloxidase and peroxidase activity were analysed in haemolymph of juvenile shrimp, Litopenaeus schmitti, exposed to different salinity levels (35%, 18%, 8%) for 48 h. A significant reduction (P<0.05) in total glucose and phenoloxidase activity in animals exposed to lower salinities (18% and 8%) was recorded, while peroxidase activity and total protein concentration did not vary. Histology revealed the occurrence of oedema in gills in shrimp exposed to 8%. The work demonstrates for the first time that in L. schmitti, low salinities can decrease glucose levels in haemolymph and create an immunosuppressive state by reducing phenoloxidase activity.     

Genotypic diversity among Shewanella spp. collected from freshwater fish

Different Shewanella species are isolated both from healthy and from diseased fish. To date, contemporary methods do not provide sufficient insight to determine species and detail differentiation between tested strains. Bacteria isolated from cultured (n = 33), wild (n = 12) and ornamental (n = 6) fish, as well as several reference strains, were tested by 16S rRNA gene sequencing, ERIC‐PCR and pulsed‐field gel electrophoresis (PFGE) assays. Our study indicates that isolates collected from freshwater fish were genetically diverse. Based on 16S rRNA gene sequences, bacteria were clustered into groups S. putrefaciens, S. xiamenensis and S. oneidensis. Some isolates were classified only to genus Shewanella; thus, 16S rRNA gene analyses were not enough to determine the species. ERIC‐PCR revealed 49 different genotype profiles indicating that the method might be useful for differentiation of Shewanella isolates irrespectively to species identification, contrary to PFGE which is not suitable for Shewanella typing.     

中国对虾线粒体16S rRNA基因序列分析

中国对虾(Fenneropenaeus chinensis)是我国海洋渔业重要的经济虾种之一。本研究以相应引物对野生群体和人工培育第1代、第4代、第5代、第6代群体(CP1、CP4、CP5、CP6)的各2个个体的线粒体16SrRNA基因片段进行了PCR扩增和序列测定分析。分析结果表明，测得的16SrRNA基因片段长为520bp，10个中国对虾个体间无碱基差异，其A、T、G、C含量分别为171bp(32．88％)、176bp(33．85％)、104bp(20．00％)、69bp(13．27％)，AT含量明显高于GC含量。利用其中长度为413bp的同源序列，以环斑鼓虾(Alpheus armillatus)为外群探讨了对虾科(Penaeidae)中的对虾属、美对虾属、明对虾属、囊对虾属和滨对虾属5个属(Penaeus，Farfantepenaeus,Fenneropenaeus,Marsupenaeus,Litopenaeus)12种对虾间的系统关系。以NJ法构建的分子系统树显示可将以上12种虾类分为两个大群：中国对虾和斑节对虾先聚到一起后与日本对虾聚成一大群；美对虾属、滨对虾属个体各聚成1支后聚成一大群，最后与中国对虾等聚到一起。同时可见，小褐美对虾(F．subtilis)与保罗美对虾(F.paulensis)、南方滨对虾(L.schmitti)与白滨对虾(L.setiferus)种间的亲缘关系较近。     

A chimeric recombinant crustacean hyperglycemic hormone from Litopenaeus schmitti (Burkenroad) obtained as C‐terminus fusion protein boost hemolymph glucose concentration in Litopenaeus vannamei (Boone)

To date, no hormonal treatments are available for control of shrimp reproduction and only eyestalk ablation is of practical use. The crustacean hyperglycemic hormone (CHH) is the most abundant neuropeptide of the eyestalk CHH family. It plays an important role in the regulation of hemolymph glucose levels, as its principal function, but it is also implicated in additional physiological processes such as moulting and reproduction. In the present study, the cDNA encoding Litopenaeus schmitti (Burkenroad) mature CHH was cloned into the Escherichia coli pTYB2 expression vector. Using this strategy we have obtained, for the first time, the recombinant CHH from L. schmitti with its C‐terminus fused to an intein tag. The expected fused protein of about 63 KDa was expressed in E. coli forming inclusion bodies. It was purified in a soluble form by electroelution following molecular size fractionation in sodium dodecil sulphate polyacrylamide gel electrophoresis. The ability of the chimeric CHH protein to elevate glucose levels in the hemolymph of the eyestalk‐ablated Litopenaeus vannamei (Boone) shrimps indicates that its biological activity as hyperglycemic protein is preserved. The results provide an alternative tool to obtain soluble recombinant proteins from the CHH family of neuropeptides to get a better understanding of shrimp endocrinology.     

Genetic characteristics of Streptococcus dysgalactiae isolated from cage cultured cobia,Rachycentron canadum (L.)

Disease outbreaks occurred during 2007–2013 in Taiwan with 2.5–10% mortality among the cage cultured cobia, Rachycentron canadum (L.), characterized by the presence of polyserositis, pericarditis and peritonitis. The micro‐organisms isolated from internal organs were Gram‐positive cocci. The isolates were confirmed as Streptococcus dysgalactiae by a polymerase chain reaction assay that yielded the expected specific 259 bp amplicon. Additionally, partial sequence of the 16S–23S rDNA intergenic spacer region of the GCS strain isolates from fish was also compared and produced 100% sequence identity with S. dysgalactiae (GenBank accession number AB252398 ). The genetic characterization was then determined by pulsed‐field gel electrophoresis (PFGE) analysis. Based on PFGE, the Apa I or Sma I digestion patterns of chromosomal DNA of these isolates were grouped into three main clusters. Taiwanese strains were divided into two clusters, and the tet(M) gene was detected in cluster 1 (pulsotypes: A1–A2 and S1–S3), but not in cluster 2 strains (pulsotypes: A3–A4 and S4–S5). Three Japanese strains from amberjack, Seriola dumerili (Risso), were grouped into cluster 3 (pulsotypes: A5–A7 and S6–S8) and displayed no mortality to cobia in the challenge experiment. Conversely, Taiwanese strains from cobia and snubnose pompano, Trachinotus blochii (L.), displayed a mortality rate of 50–87.5% in cobia.     

Denaturing Gradient Gel Electrophoresis (DGGE) as a tool for the characterisation of Brachionus sp. strains

Many zooplanktonic organisms, like the cyclic parthenogenetic rotifer Brachionus plicatilis (Rotifera: Monogononta), are actually a complex of species and biotypes with a high degree of morphological similarity (i.e. cryptic species). Various phylogenetic studies with molecular markers (e.g. ITS1 and COI) on wild Brachionus populations described the presence of at least nine genetically divergent Brachionus species and biotypes. Because different studies found evidence that these cryptic species and biotypes differ significantly in ecological preferences and thus probably behave differently in response to rearing conditions in the hatchery, questions rise on the actual identity of the rotifer strains used in aquaculture, where Brachionus discrimination is still based on morphology. This study is a part of an investigation of the genetic make-up of strains used in hatcheries, aquaculture research institutes and laboratories, and describes the rapid and sensitive PCR-DGGE method for the detection of Brachionus species and biotypes based on nucleotide sequence variation within the mitochondrial 16S rRNA gene. Considerable genetic diversity was found, albeit smaller within hatcheries than within laboratories and aquaculture research institutes. All 16S haplotypes produced an unambiguous DGGE fingerprint out of which a database was constructed.     

基于COI和16S rRNA的库页岛马珂蛤遗传多样性和分子系统进化研究

本研究以库页岛马珂蛤(Pseudocardium sachalinense)为研究对象,讨论COI和16S rRNA两种DNA条形码在贝类的遗传多样性、分子进化和种类鉴定的适用性,并利用两种条形码评估库页岛马珂蛤的遗传多样性。本文在获得库页岛马珂蛤线粒体全基因组的基础上,测序获得库页岛马珂蛤群体的COI和16S rRNA序列,发现COI基因核苷酸多样性为0.00195,高于16S rRNA核苷酸多样性(0.00073)。基于COI基因的单倍型多样性为0.76,大于16S rRNA的单倍型多样性(0.318)。其次,用全线粒体基因组构建8种贝类的系统进化树为参考,发现基于COI和16S rRNA的系统进化树与参考一致,提示这两种条形码片段可用于推断贝类的分子进化关系。最后,分别对马珂蛤科和帘蛤科15属17种贝类的COI基因和16Sr DNA进行序列比较,发现COI基因和16S rRNA的种间遗传距离均是种内距离的62倍。以上结果说明,16S rRNA与COI基因一样,能有效地构建马珂蛤科和帘蛤科的系统发育关系和物种鉴定,但在分析库页岛马珂蛤的遗传多样性时利用COI基因比16S rRNA能发现更多的遗传变异。     

Molecular identification and distribution of mangrove oysters ( Crassostrea) in an estuarine ecosystem in Southeast Brazil: implications for aquaculture and fisheries management

This study investigated the existing species of Crassostrea in the natural environment, farming systems and artificial spat collectors at a protected estuarine area in Brazil, through PCR‐RFLP of mitochondrial 16S rRNA. Among 450 samples collected in the natural environment, 303 were C. brasiliana and 147 C. rhizophorae. Oysters present in the rocky subtidal zone were C. brasiliana. However, both species occurred on mangrove roots in the intertidal zone. Farm‐raised samples included only C. brasiliana. It was observed that attached specimens in commercial collectors had a banding pattern distinct from C. brasiliana and C. rhizophorae, indicating the presence of a third species in the estuary. The 16S rRNA sequence analysis showed that these specimens are clustered with the oysters from Pacific and Indian Oceans, and genetically close to the oysters of Beihai, China (0.3% genetic distance). Oysters obtained from the seed capture showed 17.8% distance of in relation to C. brasiliana, 17.6% for C. rhizophorae and 10.3% for C. gigas, demonstrating high genetic divergence from these species. The occurrence of an exotic species in the Cananéia estuary may have strong ecological and economic implications which require new guidelines for farming, conservation and sustainable fisheries management for the native oyster species.     

4种河蓝蛤线粒体COI和16S rRNA基因序列的种间遗传分析

对光滑河蓝蛤Potamocorbula laevis、黑龙江河蓝蛤P.amurensis、焦河蓝蛤P.ustulata、红肉河蓝蛤P.rubromuscula4个野生种共40个个体的线粒体COI和16SrRNA基因片段进行了扩增和测序,经过筛选和剪切,得到长度为650bp和450bp的片段。序列分析显示,序列的碱基组成中G+C含量较低,16SrRNA基因种间和种内的变异较低,COI基因片段种内和种间的变异较高。以沙海螂Mya arenaria为外群,用MEGA 4.0软件中的NJ法构建了系统进化树,通过遗传距离和系统进化树可以看出,4种河蓝蛤未能达到不同种之间显著的遗传分化。     

中国沿海紫蛤属的系统发育

紫蛤属(Sanguinolaria)贝类具有很高的经济价值,长期以来却存在着物种鉴定错误、种名使用混乱、同物异名等一系列问题,关于其系统分类和演化问题的研究较少。为探究中国沿海紫蛤属的系统发育关系,本研究利用两个线粒体基因(COI和16S rRNA),以及两个核基因(H3和28S rRNA)的部分序列,对采自中国沿海紫蛤属3亚属9种紫蛤61个个体进行系统发育分析。基于4个基因片段联合数据集T12(剔除COI第三位密码子位置)构建系统发育树。结果表明,两个线粒体基因片段GC含量明显低于AT含量,表现出对AT偏斜,两个核基因表现出对GC的偏斜。4个基因片段(COI、16S rRNA、H3和28S rRNA)的颠换与转换比值分别为5.073、3.042、1.564和1.480,均远高于系统分析的临界值0.4,能够提供有效的系统发育信息。基于4个基因片段的遗传多样性分析表明,9种紫蛤均具有较高的核苷酸多样性(Pi0.05)与单倍型多态性(Hd0.5)。基于COI基因片段的紫蛤属种内遗传距离为0~0.016,种间的平均遗传距离为0.087~0.331,其中卵紫蛤(Sanguinolaria ovalis)与中国紫蛤(Sanguinolaria chinensis)遗传距离最小,仅为0.087。利用最大似然法(maximum likelihood,ML)和贝叶斯法(Bayesian inference,BI)构建的系统发生树拓扑结构一致,分化为3大支,与形态学分类的三个亚属分别对应。中国紫蛤和卵紫蛤在系统树上首先聚为一支,表明其亲缘关系最近。本研究结果阐明了中国沿海紫蛤属贝类的遗传多样性及其系统演化关系,为紫蛤属贝类种质资源的保护及可持续利用提供了科学依据。     

基于线粒体D-loop基因的中国海三疣梭子蟹遗传多样性与遗传分化研究

为探明分布于中国四大海区的天然三疣梭子蟹群体遗传多样性与遗传分化状况,实验以大连(DL)、东营(DY)、连云港(LYG)、舟山(ZS)、湛江(ZJ)和漳州(ZZ)6个三疣梭子蟹地理群体为研究对象,采用线粒体控制区D-loop全基因序列为分子标记,对中国海三疣梭子蟹野生群体的遗传多样性及群体遗传结构进行了分析。结果发现,在用于分析的1 141 bp的D-loop全基因序列中共有185个变异位点,129个简约信息位点。60个个体中共计48个单倍型,单倍性多样性指数和核苷酸多样性指数显示中国沿海三疣梭子蟹群体具有较高的遗传多样性,而且三疣梭子蟹在过去没有出现很强的选择效应,群体大小稳定。6群体三疣梭子蟹遗传分化指数(F_ST)为0.189 7,将中国沿海三疣梭子蟹作为一个大群体来讲已产生了中度分化,群体分化时间推断为(19.68～26.05)万年。LYG分别和DY、ZJ、ZZ,以及ZJ和ZZ这4组之间无明显分化,基因流较大(N_em>5),而其他11个群组间已存在一定程度的分化。特别是ZS与其它5群体产生了高度的遗传分化,DL与其他4群体发生了中度分化。遗传距离与地理距离不存在显著的相关性,群体发生与扩散可能有更复杂的原因。     

一株斑点叉尾致病菌的分离鉴定

从斑点叉尾(Ictalurus punctatus)肝脏分离到的一株细菌GD091027,对该菌进行人工感染试验、生理生化特性测定和16S rRNA序列测定并构建系统发育树,同时进行了抗菌药物敏感性试验。结果显示:当人工感染剂量大于1.0×107 CFU/尾时,能引起斑点叉尾100%发病死亡,对斑点叉尾的LD50为6.2×104 CFU/g。分离株GD091027为革兰氏阴性短杆菌,氧化酶阴性,在25℃、35℃均有运动性,能耐3%的NaCl,不发酵葡萄糖、麦芽糖、蔗糖、D-甘露醇及L-阿拉伯糖,不利用西蒙氏柠檬酸盐,不利用丙二酸,赖氨酸脱羧酶和鸟氨酸脱羧酶阳性,产生硫化氢和吲哚,甲基红(MR)试验阴性。在16S rRNA系统发育树中,该菌与迟缓爱德华氏菌(Edwardsiella tarda)聚为一分支。分离株GD091027对氨苄西林、庆大霉素、妥布霉素等16种抗菌药物敏感,利福平、青霉素等3种抗菌药物不敏感。除不产生溶血、不发酵葡萄糖和麦芽糖、甲基红(MR)试验阴性外,病原菌形态及生理生化特征符合迟缓爱德华氏菌,结合16S rRNA序列分析结果将其鉴定为迟缓爱德华氏菌。