Morphological characteristics and genetic differentiation of Lutraria maxima in coast waters off southeast China

To explore genetic diversity and estimate the genetic differences among populations of Lutraria maxima in the coastal waters off south to southeast China,the morphology of the species of five different geographical populations(Beihai,Weizhou Island,Zhanjiang,Xiamen,and Fuzhou)in Guangxi,Guangdong,and Fujian provinces was studied statistically in combination with the microsatellite markers.As revealed by morphological principal component analysis(PCA),the cumulative contribution rate of the first three principal components was 72.596%.The discrimination accuracy ranged from 47.5%to 80.0%,and the scatter plots of principal component and discriminant analysis were consistent in overall,showing that the Xiamen and Fuzhou populations were overlapped obviously.For microsatellite markers,10 pairs of polymorphic primers were obtained by high-throughput transcriptome sequencing,and used for genetic diversity analysis.It was showed that the average number of alleles and eff ective alleles observed in each population ranged from 8.100 to 10.900,and from 3.497 to 4.228,respectively.The average observed heterozygosity(H_(o))and expected heterozygosity(H_(e))in the five populations ranged from 0.541 to 0.615,and from 0.642 to 0.733,respectively.The genetic distance(DA)ranged from 0.078 to 0.523,and the population genetic differentiation index(F_(ST))ranged from 0.027 to 0.139.The unweighted pair-population method with arithmetic means(UPGMA)and structure analysis showed that the five populations could be divided into two main clusters,the Beibu Gulf group(Beihai and Weizhou Island)and the Southeast China Sea group(Zhanjiang,Xiamen,and Fuzhou),suggesting that L.maxima has been separated geographically by the barrier of the Leizhou Peninsula into two groups in evolution,which provided us with a scientific clue to better protect the bioresource and establish an appropriate fishery management stocks for L.maxima populations in south China.

Study on Fishery Ecological Environment and Fish Species Diversity in Yantan Water Area

Through analysis on water quality,planktonic organism,fish resources,and fish species diversity in Yantan water area,this paper evaluated current situation of quality of fishery ecological environment in Yantan water area. The survey recorded all 52365 fishes and 1410. 2kg catches obtained by fishermen in half a year,and more than 98% catches are small fishes. The Shannon-Weiner diversity index of Yantan water area is 0. 162,Wilhm improvement index is 1. 814,DG- Findex is 0. 083,and the index of fish species diversity is far lower than other water areas. The average quantity per unit of phytoplankton is 1. 0134 million ind. / L,and the average quantity per unit of organisms is 1. 1151 mg / L. The average quantity per unit of zooplankton is 459. 6 ind. / L,and the average quantity per unit of organisms is 0. 6422 mg / L. Evaluation results indicate that water quality and planktonic organism in Yantan water area are basically normal,but fish resources are increasingly exhausted,fish resource composition is not reasonable,and fish species diversity is extremely low. From the perspective of biomanipulation,it is required to restore fishery ecological environment of reservoir area through restoring normal composition of aquatic organisms.

Early Embryo and Larval Development of Inviable Intergeneric Hybrids Derived from Crassostrea angulata and Saccostrea cucullata

To detect the intergeneric hybridization between the oyster Crassostrea angulata and Saccostrea cucullata coexisting along the southern coast of China, reciprocal crosses were conducted between the two species. Barriers for sperm recognizing, binding, penetrating the egg, and forming the pronucleus were detected by fluorescence staining. From the results, although fertilization success was observed in hybrid crosses, the overall fertilization rate was lower than that of intraspecific crosses. A large number of hybrid larvae died at 6–8 d after hatching, and those survived could not complete metamorphosis. C. angulata ♀× S. cucullata ♂ larvae had a growth rate similar to that of the maternal species, whereas S. cucullata ♀× C. angulata ♂ larvae grew the slowest among all crosses. Molecular genetics analysis revealed that hybrid progeny were amphimixis hybrids. This study demonstrated that hybrid embryos generated by crossing C. angulata and S. cucullata could develop normally to the larval state, but could not complete metamorphosis and then develop to the spat stage. Thus, there is a post-reproductive isolation between C. angulata and S. cucullata.

Comparison of fungal community composition within different intestinal segments of tilapia and bighead carp

Although intestinal fungi play important roles in host health and disease,the composition and diversity of fungal communities remain poorly reported in fish.In this study,fungi in the fore-,mid-,and hindintestine of tilapia(Oreochromis mossambicus)and bighead carp(Aristichthys nobilis)from Hongchaojiang Reservoir in Guangxi,China were investigated by ITS sequencing.Based on this,we obtained 1763478 high-quality tags,which clustered into 1089 operational taxonomic units(OTUs).In total,404 OTUs were annotated,of which 310,68,and 26 belonged to Ascomycota,Basidiomycota,and other,respectively.Results show significant differences in the community composition of intestinal fungi between tilapia and bighead carp but not within their different intestinal segments.Furthermore,154 of the 404 annotated OTUs were considered reliable and were classified into three trophic modes and nine guilds.The three trophic modes consisted of 108 OTUs of saprotrophic fungi,41 OTUs of pathotrophic fungi,and five OTUs of symbiotrophic fungi.The top three most abundant OTUs overall(i.e.,Otu000002,Scopulariopsis acremonium;Otu000018,Alternaria palandui;Otu000034,Aureobasidium pullulans)showed lower abundance in the hind-intestinal segments of bighead carp,suggesting uneven distribution of these fungi in this species.In addition,saprotrophic and pathotrophic fungi were markedly decreased in the hindintestine.It is indicated that the fungal community was not only related to host species specificity but also to the respective physiological functions of different intestinal segments.These findings provide valuable information on the composition,structure,and potential function of the intestinal fungi community associated with different intestinal segments in tilapia and bighead carp under natural conditions,thus highlighting the importance of fungi as an integral part of the inte stinal microbiota in maintaining host health.

Novel evolutionary insights into nemacheilid cavefi sh: evidence from comparative analysis of mitochondrial genomes

Cavefi sh can be important models for understanding the relationships among evolution,adaptation,and development in extreme environments.However,cavefi sh remain poorly studied,particularly at the genome level.Here,we sequenced the complete mitogenome of three cavefi sh in the family Nemacheilidae(Paranemachilus pingguoensis,Oreonectes polystigmus,and Heminoemacheilus longibarbatus),which were collected from karst caves in South China.The mitogenomes each contained 37 genes(13 protein coding,22 tRNA,and two rRNA genes)and a single control region,with the same genetic arrangement and distribution as those found in vertebrates.The non-synonymous/synonymous mutation ratios(Ka/Ks)of the mitogenomes indicated that the protein-coding genes(PCGs)of the three cavefi sh evolved under purifying selection.The mitogenomes of the three cavefi sh exhibit nucleotide composition biases for PCGs,tRNAs,rRNAs,and the whole genome,indicating that the mitochondrial DNA might have been subjected to evolutionary selection in response to extreme cave environments.Divergence time and evolutionary history analyses suggested that the speciation and diversifi cation of the cavefi sh coincided with the Miocene uplift of the southern Qinghai-Tibet Plateau,which greatly changed cave habitats.Overall,our study sheds light on the mitogenomes,phylogeny,and evolutionary history of nemacheilid cavefi sh.

Crystal Structure and Luminescent Properties of a Zn(Ⅱ) Coordination Polymer Assembled by Mixed-ligand

A Zn（Ⅱ） coordination polymer [Zn（NIP）（3,3＇-bpt）].H20 （1, NIP = 5-nitroisophtha- late, 3,3＂-bpt = 1H-3,5-bis（3-pyridyl）-l,2,4-triazolate） has been synthesized by the hydrothermal reaction at 140 ℃ and structurally characterized by IR spectroscopy, X-ray diffraction, thermal analysis, single-crystal X-ray diffraction and luminescent properties. In complex 1, the zinc atom is five-coordinated with three carboxylate oxygen atoms from three H2NIP and two nitrogen atoms from two 3,3＇-bpt, respectively, forming a distorted trigonal bipyramidal geometry and showing a 1D chain structure, which is further bridged by NIP to form a 3D supramolecular network via self-assembly of hydrogen bonds.

A Pathological Study of GIFT Strain of Nile Tilapia(Oreochromis niloticus)Infected by Streptococcus agalactiae

[Objectives] This study aimed to determine the infection pathway and target organs of Streptococcus agalactiae in GIFT strain of Nile tilapia, thus providing theoretical basis for the breeding of disease-resistant tilapia and development of S. agalactiae vaccines.[Methods] GIFT strain of Nile tilapia was inoculated by S. agalactiae through intraperitoneal injection, oral gavage and in vitro immersion. The gill, spleen, liver and small intestine tissues of infected tilapia were collected for pathomorphological observation. Immunohistochemical localization was conducted using rabbit anti- S. agalactiae serum to identify the distribution pattern of S. agalactiae in various tissues of tilapia and its target organs via different infection pathways.[Results] GIFT strain of Nile tilapia could be infected by S. agalactiae via three artificial inoculation modes. Specifically, pathological changes occurred at 2 h post-inoculation in intraperitoneal injection and oral gavage groups, whereas tilapia in in vitro immersion group showed pathological changes at 5 h post-inoculation, and the lesion intensity in in vitro immersion group was slighter than that in intraperitoneal injection and oral gavage groups. Immunohistochemical localization indicated that the appearance time of positive signals in intraperitoneal injection group demonstrated an order of spleen→liver and gill→small intestine; positive signals in oral gavage group appeared in the order of small intestine→gill and spleen→liver; the appearance time of positive signals in in vitro immersion group showed an order of gill→spleen→liver and small intestine.[Conclusions] GIFT strain of Nile tilapia could be infected by S. agalactiae via intraperitoneal injection, oral gavage and in vitro immersion. The corresponding positive signals for pathogen infection were preferentially present in the spleen, intestine and gill tissues. Thus, preventing S. agalactiae contamination in aquaculture water and food sources is an effective measure to control the outbreak of S. agalactiae infections in tilapia under natural aquaculture conditions.

Morphometric analysis and fluorescent microsatellite markers to evaluate the genetic diversity of five populations of Penaeus japonicus in China

To understand the current status of germplasm resources of Penaeus japonicus,in this study,genetic diversity was analyzed based on morphometric analysis and fluorescent microsatellite markers.For morphometric analysis,the cumulative ratios of the PC1 and PC2(85.90%)were greater than 75%,which can explain the morphological variation among populations.For microsatellite analysis,the allele number in 10 microsatellite loci ranged from 27 to 53,and the effective allele number ranged from 21 to 42.The observed heterozygosity ranged from 0.463 to 0.983,whereas expected heterozygosity ranged from 0.932 to 0.966,and the average polymorphism information content was 0.947,which indicated a high level of genetic diversity.The unbiased genetic distance among populations ranged from 0.230 to 0.431,and the genetic similarity coefficient ranged from 0.654 to 0.782.Analysis of molecular variance(AMOVA)showed that the genetic variation within individuals was the main source of variation,accounting for 88.55%,and only 1.49%of the genetic variation came from among populations.