Supplementation of alanine improves biomass accumulation and lipid production of Chlorella pyrenoidosa by increasing the respiratory and metabolic processes

The function of exogenous alanine(Ala)in regulating biomass accumulation,lipid production,photosynthesis,and respiration in Chlorella pyrenoidosa was studied.Result shows that the supplementation of Ala increased C.pyrenoidosa biomass and lipid production in an 8-d batch culture.The concentration of 10 mmol/L of Ala was optimum and increased the microalgal cell biomass and lipid content by 39.3%and 21.4%,respectively,compared with that in the control(0-mmol/L Ala).Ala supplementation reduced photosynthetic activity while boosting respiratory activity and pyruvate levels,indicating that C.pyrenoidosa used exogenous Ala for biomass accumulation through the respiratory metabolic process.The accelerated respiratory metabolism due to Ala supplementation elevated the substrate pool and improved the lipogenic gene expression,promoting lipid production at last.This study provided a novel method for increasing biomass accumulation and lipid production and elucidated the role of Ala in regulating lipid production.

CMIP 6 models simulation of the connection between North/South Pacific Meridional Mode and ENSO

The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.

Contrasting vertical distribution between prokaryotes and fungi in different water masses on the Ninety-East Ridge, Southern Indian Ocean

Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean.In the present study,we divided 60 water column samples on the Ninety-East Ridge(NER)into fi ve water masses according to the temperature-salinity curves.We presented,for the fi rst time,a full description of the microbial biodiversity on NER through high-throughput amplicon sequencing approach,including bacteria,archaea,and fungi.We found that bacteria exhibited higher richness and diversity than archaea and fungi across the water masses on NER.More importantly,each water mass on NER featured distinct prokaryotic microbial communities,as indicated by the results of non-metric multidimensional scaling.In contrast,fungi were eurybathic across the water masses.Redundancy analysis results demonstrated that environmental factors might play a pivotal role in the formation and stability of prokaryotic communities in each water mass,especially that of archaea.In addition,indicator species might be used as fi ngerprints to identify corresponding water masses on NER.These results provide new insights into the vertical distribution,structure,and diversity of microorganisms on NER from the perspective of water mass.

Determination of the heating efficiency of magnetotactic bacteria in alternating magnetic field

Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.

Distribution pattern and geochemical analysis of rare earth elements in deep-ocean sediments

The content and distribution pattern of rare earth elements(REEs)in surface sediments from the Eastern and Western Pacifi c Ocean,the Northern and Southern Atlantic Ocean,and the Southwestern Indian Ocean were explored and the resources and geochemical characteristics of REEs in deep-ocean sediments from diff erent oceans were studied.The total REE abundances(ΣREE)in the diff erent oceans ranged as follows:Eastern Pacifi c,56.88–500.02μg/g;Western Pacifi c,290.68–439.94μg/g;Northern Atlantic,55.33–154.90μg/g;Southern Atlantic,40.83–69.30μg/g;and Southwestern Indian Ocean,20.24–64.76μg/g.Their corresponding LREE(La-Eu)/HREE(Gd-Lu)average values were 5.18,5.86,9.01,5.21,and 4.59,which indicated that the light REEs were all evidently enriched.δEu andδCe showed slight Eu-negative anomalies and signifi cant Ce-positive anomalies in all sediments.Although the contents of REEs in the sediments varied among the diff erent oceans,the distribution patterns of REEs were similar,and the correlation coeffi cient was greater than 0.9290.In the Eastern Pacifi c sediments,ΣREE showed a signifi cantly positive correlation with Co,Cu,Zn,Mn,Mo and a weak correlation with Fe.In the Western Pacifi c and Southern Atlantic sediments,ΣREE presented no obvious correlation and a weakly negative correlation with Co,Cu,Zn,Mn,Mo and Fe,respectively.ΣREE in the Southwestern Indian Ocean sediments positively correlated with Cu,Zn,Mn,Mo,Fe,and had a weakly negative correlation with Co.

Removal of phenol by Isochrysis galbana in seawater under varying temperature and light intensity

Phenol is a common industrial chemical produced and transported worldwide largely.Therefore,accidental spillage of phenol in the ocean causes an increasing concern.Microalgae are promising to remove phenol from marine waters.However,temperature and light intensity are two main factors that markedly influence biodegradation in marine environments.In this study,a marine golden alga Isochrysis galbana is selected to research the removal of phenol under different temperatures(10-30℃)and light intensities(0-240μmol/(m^2·s)).The results show that the most suitable temperature and light intensity for phenol removal are 20℃and 180μmol/(m2·s),respectively,and 100 mg/L of phenol can be completely removed by microalga in 24 h at these conditions.I.galbana can also remove phenol under dark and low-temperature conditions.The removal of phenol by I.galbana at diverse temperatures and light intensities conform to first-order kinetics,and the process under dark conditions conform to zero-order kinetics.Thus,I.galbana can be used in the in-situ bioremediation of polluted seawater by phenol.

Spatiotemporal shoreline change in Boushehr Province coasts,Iran

Since coastal areas have highly dynamic nature and are one of the most beneficial regions of civilizations,it is of great significance to understand their characteristics and behavior.Changes in shorelines in the form of accretion and erosion can leave devastating effects on businesses and cities located along the shore.In this study,we statistically calculated the tendency of shoreline changes by processing and analyzing historical satellite images of Boushehr Province,Iran.Results show that these shores have experienced both sedimentation and erosion in the past 30 years.Net shoreline movement presents more than 350 m of erosion and 650 m of accretion,which are corresponded to change rates of almost 12 and 22 m/a,respectively.Statistics of shoreline changes are calculated from regression methods including end point rate,linear regression rate,weighted linear regression,and least median of squares.The best-performed method is applied to predict the shoreline position in 2050 and 2100.Potential locations of excessive changes are identified for the predicted shorelines,which should be dealt with properly.

Sediment transport in the Luanhe River delta:grain size trend analysis

Sediment grain size in the deltaic environment of the Luanhe River(LR),Liaoning,China,contains sediment transport pathway information useful in elucidating the shoreline change and fluvialmarine interaction.In this study,we utilized numerical partitioning of the sedimentary components and geostatistical grain size trend analysis(GSTA)to define the sediment transport pattern in the Luanhe River delta(LRD)and interpolated the sediment transport pattern using content changes of end numbers(EM).EM1(the mean grain size 7.12Ф,fine silt),EM2(2.37Ф,fine sand),and EM3(1.27Ф,medium sand)components were identified by the numerical partitioning by GSTA.Kriging interpolation method was used to interpolate the parameters of the grain size for the regular grid,and the interpolation radius was 0.015 decimal degree.We chose 0.09 decimal degree as the characteristic distance for GSTA in the semivariogram model using the geostatistical method.The FB(-)case(finer,better sorted and more negatively skewed)was adopted in GSTA for its satisfaction in the Global Moran’s I test.The result of the GSTA shows that the sediments in the south barriers(SBs)were transported to the southwest of the study area.The sediments in the north,in the SE direction of sediment transport trend from the river mouth,indicated that the sediments in the north of the study area were transported from the LR to the northern beaches,and to the south and east of the study area.The sediment transport trend that simplified by GSTA as the FB(-)case was approved by the content changes of sedimentary components(i.e.EM1,EM2,and EM3).In addition,the turbulent jet diffusion pattern indicated that the coarse sediments(EM3)were delivered by LR during the flood season,and the EM2 and EM1 were from wave and tide,respectively.

The characteristic pattern of multiple colored layers in coastal stratified lakes in the process of separation from the White Sea

An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located.

Computational identification and characterization of microRNAs and their targets in Penaeus monodon

Study on shrimp miRNAs was limited and just 7 mature miRNA sequences of Marsupenaeus japonicus are deposited in mir Base database. In this study, miRNAs and their target gene candidates were computationally identified from shrimp Penaeu s monodon and then experimentally validated. Using 39 908 expressed sequence tags(ESTs) and 21 124 genome survey sequences(GSSs) of P. monodon(pmo) as reference dataset, a comprehensive approach based on inter-species homolog search was employed to investigate the candidate miRNAs(i.e. pmo-miRNA). A total of eight miRNAs belonging to 7 families were computationally identified and five out of them were subsequently validated by PCR and sequencing. Of these, pmo-miR-4961a, pmo-miR-4961b, pmo-miR-4979 and pmo-miR-3819 were first identified from shrimps. Both the mature pmo-miRNAs and the corresponding precursors were conserved among different species. Based on perfect or near-perfect match to the target region, the target gene candidates of pmomiRNAs were predicted from 10 331 mRNA sequences of P. monodon. A total of 20 genes were predicted as the targets of pmo-miR-4961a, pmo-miR-4961b, pmo-miR-4979 and pmo-miR-6492. Experimental validation by dual luciferase reporter assay confi rmed the targeting between 3 pmo-miRNAs and one or two of their target genes, especially the pmo-miR-4979 which could significantly down-regulate the expression of target gene(JR226772). This study updates the miRNAs and their targets in P. monodon and lays a solid foundation for future RNAi study.

Formation of an anticyclonic eddy and the mechanism involved: a case study using cruise data from the northern South China Sea

Data from satellite altimetry and in situ observations together with the Hybrid Coordinate Ocean Model (HYCOM) reanalysis data were used to investigate the mechanism and formation of an anticyclonic eddy in the northeastern South China Sea (SCS). Analysis of water mass using cruise data indicated that the water captured in the eddy diff ers from those in the SCS, the Kuroshio intrusion, and the eddy-forming region. Data from sea surface height (SSH) and sea level anomaly (SLA) indicate that the eddy formed due both to the Kuroshio intrusion and the local circulation in the SCS. The Kuroshio intrusion is present at the start of the eddy growth (March 5-9) before Kuroshio leaps the Luzon Strait. The eddy then becomes larger and stronger in the absence of the Kuroshio intrusion. From the eddy budget of the HYCOM reanalysis data, the formation of the eddy goes in three steps. By the third step, the eddy had become aff ected by variations of local SCS circulation, which is more strongly than in the fi rst step in which it is aff ected more by the Kuroshio intrusion. The variability of the temperature and salinity inside the eddy provide a support to this conclusion. The water in the SCS intruded into the eddy from the southeast, which decrease the salinity gradually in the southern part of the eddy during the growth period.

Coastline changes and tidal current responses due to the large-scale reclamations in the Bohai Bay

China’s Bohai Bay has experienced large-scale land reclamation since 2000.These reclamation projects create a nearshore ecological imbalance and shift sediment transport by changing the tidal current.However,these tidal current changes are not comprehensively understood.In this paper,the coastline changes in Bohai Bay due to reclamation are investigated and the responses of the tidal current are calculated through numerical methods.The results show that the coastline length of the bay increases by more than 500 km from 2000 to 2015 with the largest reclamation rate of 150.9 km^(2)/a.Consequently,the current velocity changes with an uneven distribution near the reclamation due to construction masking and dike protrusion.The tidal symmetry also changes in most nearshore areas,with opposite variations in the current velocity at peak flood and ebb tide.In addition,the tide direction deflects to bypass the reclamation and is usually consistent with the coastline.Harmonic analysis of the dominant M2 tidal constituent shows that the range of the reciprocating current is widely extended.The total influence of the reclamation can reach the-8-m isobaths in Bohai Bay.Changes in the tidal current are the main causes of water environment deterioration.Therefore,the arrangement and structural optimization of reclamation projects should be considered in the future.

Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China

Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.

Morphological and molecular analyses of a Philine kinglipini outbreak in summer of 2022 in Jiaozhou Bay,China

A sudden and unprecedented outbreak of molluscan Philine kinglipini occurred in summer 2022 in Jiaozhou Bay,Shandong,China,causing substantial damage to local mariculture industry of the Manila clam Ruditapes philippinarum.Although P.kinglipini has been found in many coastal regions of China,the molecular research of P.kinglipini has not been extensively studied,making it difficult to accurately identify and track P.kinglipini samples in field using molecular methods.Samples were collected during the outbreak and their morphological features and molecular sequences were analyzed.Results show that the causative species of the outbreak was P.kinglipini.The mitochondrial genome(mt DNA)of P.kinglipini was constructed for the first time,based on which phylogenetic analysis of the mt DNAs of P.kinglipini and related species in the order Cephalaspidea was carried out.As revealed by metabarcoding analysis of 18S rDNA V4,the seasonal change of P.kinglipini and closely related Philine species was striking with peaks between April and August.Therefore,metabarcoding analysis is applicable tool for monitoring the bloom development of P.kinglipini and related species.This study generated for the first time essential molecular marker sequences and mtDNA of P.kinglipini,which provided a reference for future characterization and monitoring of its outbreaks and for phylogenetic analysis of Philine species.

Effect of ChREBP on carbohydrate feeding regulation in mandarin fish Siniperca chuatsi

Carnivorous fish have poor tolerance to carbohydrate in feed and low utilization rate of carbohydrate.Therefore,the balance of carbohydrate and lipids in the nutrient metabolism of carnivorous fish,the ef fective conversion and utilization of carbohydrate and lipids,and the feedback regulation of feeding are the key links for the e fficient utilization of carnivorous fish feed.Carbohydrate response element binding protein(ChREBP)is a new transcription factor found in recent years in the glucose signaling pathway,and can also participate in feeding regulation.We performed in-vivo and in-vitro experiments to reveal the role of ChREBP in the glucose metabolism and feeding in mandarin fish.The mRNA expression of ChREBP and appetite regulatory factors were measured after intraperitoneal injection of glucose in mandarin fish Siniperca chuatsi and cotransfection with glucose and glucose+siRNA in the hypothalamic cells in mandarin fish.The results reveal that at hour 2 and 4 post intraperitoneal injection with 1 mg/g BW glucose,the blood glucose level of the mandarin fish increased significantly,but food intake decreased significantly,and it also displayed a significantly increased ChREBP mRNA expression levels in liver.At hour 4 post injection,hypothalamic ChREBP mRNA level was significantly increased,whereas the mRNA expression levels of appetite genes neuropeptide Y(npy)and agouti-related peptide(AgRP)were decreased significantly.When the glucose concentration was 40 mmol/L,the expression level of ChREBP mRNA in mandarin fish hypothalamic cells was significantly up-regulated,but the expression level of appetite gene npy mRNA was down-regulated.When siRNA and glucose were co-transfected into mandarin fish brain cells,the expression level of chrebp mRNA was significantly decreased,and the appetite gene npy mRNA was significantly increased.The results indicated that glucose regulated food intake through the modulation of appetite gene npy by ChREBP.

Do alternative stable states exist in large shallow Taihu Lake,China?

Regime shifts from submersed macrophyte dominance to phytoplankton dominance have been widely reported in small-to medium-sized shallow lakes.However,alternative stable states in large shallow lakes(surface area>500 km^(2))remain unconfirmed.To understand the alternative stable states and the main influencing factors of submersed macrophytes in large lakes,the ecosystem states from monitoring data from 1959 to 2019 in large shallow Taihu Lake(2338 km^(2)in average depth of 2.12 m)in China were examined.Changes in submersed macrophyte coverage(C_(Mac))and phytoplankton chlorophyll a(Chl a)in the time series and their relationships with environmental factors were analyzed.During the field investigation from August 2018 to May 2019,nutrients and Chl a showed obvious heterogeneity across the lake,being generally higher in the western and northern areas and lower in the southeast area,while C_(Mac)was only observed in the eastern areas,e.g.,East Taihu Lake,Xukou Bay,and Gonghu Bay.During the long-term monitoring from 1959 to 2019 in the Central Region,Meiliang Bay,and East Taihu Lake,Chl a increased significantly in the time series.C_(Mac)varied slightly among different subareas,always at low levels(<10%)in the Central Region and Meiliang Bay but at relatively high levels in East Taihu Lake(10%–90%).Frequency distributions of response variables had no multimodality except for C_(Mac)in East Taihu Lake,with two peaks between 15%and 20%and between 55%and 60%.A dual relationship was found between Chl a and total phosphorus(TP)in the areas with and without macrophytes,while C_(Mac)showed no relationship with TP,and submersed macrophytes did not flourish in the Central Region and Meiliang Bay even when TP was at very low levels(≈10 mg/m3).Taihu Lake had similar algal turbidity(TurbAlg)as small-to mediumsized lakes but generally presented with higher values of nonalgal turbidity(TurbNonAlg),as did their contribution to total turbidity as a percentage.This study suggested that large shallow Taihu Lake may have no alternative stable states,but more evidence is needed for East Taihu Lake,which was dominated by macrophytes,as it remains unknown whether hysteresis occurs between the processes of eutrophication and oligotrophication.Unfavorable conditions caused by wind might be the main reason due to the absence of submersed macrophytes in Taihu Lake.These results demonstrate that stricter nutrient control is needed to maintain a healthy state or to recover from a decayed state for large lakes.

Effects of iron and humic acid on competition between Microcystis aeruginosa and Scenedesmus obliquus revealed by HPLC analysis of pigments

Iron is a vital micronutrient for growth of bloom-forming Microcystis aeruginosa and competition with other algae,and its availability is affected by humic acid.The effect of iron and humic acid on growth and competition between M.aeruginosa and Scenedesmus obliquus was assessed.The results showed the growth of M.aeruginosa and S.obliquus in mono-cultures was inhibited by humic acid at low iron concentrations(0.01 mg/L);the maximum inhibition ratios were 67.84%and 38.31%,respectively.The inhibition of humic acid on the two species was significantly alleviated when iron concentrations were 1.00 mg/L,with the maximum inhibition rate reduced to 5.82%for M.aeruginosa and to 23.06%for S.obliquus.S.obliquus was the dominant species in mixed cultures,and the mutual inhibition between M.aeruginosa and S.obliquus at low iron concentration was greater than that at high iron concentration.The inhibition of S.obliquus on M.aeruginosa was reduced at low iron concentrations;it increased at high iron concentrations,as concentrations of humic acid rose.

Seasonal and spatial variations of macrobenthic community in intertidal Sargassum field off Naozhou Island, South China Sea

Seasonal and spatial variations in the macrobenthic community in an intertidal gulfweed field off Naozhou Island were investigated from April 2011 to January 2012.We identified 407 macrobenthic organism species:64 macroalgae(15.72%of total species);123 Arthropoda(30.22%);107 Mollusca(26.29%);67 Annelida(16.46%);15 Cnidaria(3.69%);14 Echinodermata(3.44%);8 Porifera(1.97%);4 Chordata(0.98%);2 Urochorda(0.49%);and 1 each of Echiura,Sipunculida and Angiospermae(0.25%).Arthropods,mollusks,annelids,and macroalgae were four main groups in the benthic organism community and accounted for 88.70%of the total species.In terms of abundance of biomass,there were 15 dominant species,including 8 macroalgal,5 mollusk and 2 arthropod species.The species diversity indices ranged from 1.21 to 4.42 with an average of 2.80;the annual average of evenness was 0.47.Species richness indices varied from 2.97 to 7.24(average 4.97);and Simpson dominance indices varied from 0.20 to 0.92 in annual average of 0.75.Macroalgal distribution showed clear vertical zonation and seasonal changes.The number of macroalgal species found in the high tide zone,upper middle tide zone,middle tide zone,lower middle tide zone,low tide zone,and below low tide zone were 1,8,10,16,22,and 32,respectively.Biomass among the benthic organisms,macroalgae and crustaceans had significant positive correlation(P<0.05)with the coefficients of 0.802,0.894,and 0.592,respectively.Macroalgal biomass showed a clearly negative correlation with the concentration of dissolved inorganic nitrogen(DIN)(R=0.486,P<0.05).During the winter and spring,when macroalgae were growing vigorously,DIN reached the lowest level in seawater and displayed a clear weak correlation between macroalgal growth and the nutrient concentration.

Identification and characterization of endosymbiosis-related immune genes in deep-sea mussels Gigantidas platifrons

Deep-sea mussels of the subfamily Bathymodiolinae are common and numerically dominant species widely distributed in cold seeps and hydrothermal vents.During long-time evolution,deep-sea mussels have evolved to be well adapted to the local environment of cold seeps and hydrothermal vents by various ways,especially by establishing endosymbiosis with chemotrophic bacteria.However,biological processes underlying the establishment and maintenance of symbiosis between host mussels and symbionts are largely unclear.In the present study,Gigantidas platifrons genes possibly involved in the symbiosis with methane oxidation symbionts were identified and characterized by Lipopolysaccharide(LPS)pull-down and in situ hybridization.Five immune related proteins including Toll-like receptor 2(TLR2),integrin,vacuolar sorting protein(VSP),matrix metalloproteinase 1(MMP1),and leucine-rich repeat(LRR-1)were identified by LPS pull-down assay.These five proteins were all conserved in either molecular sequences or functional domains and known to be key molecules in host immune recognition,phagocytosis,and lysosome-mediated digestion.Furthermore,in situ hybridization of LRR-1,TLR2 and VSP genes was conducted to investigate their expression patterns in gill tissues of G.platifrons.Consequently,LRR-1,TLR2,and VSP genes were found expressed exclusively in the bacteriocytes of G.platifrons.Therefore,it was suggested that TLR2,integrin,VSP,MMP1,and LRR-1 might be crucial molecules in the symbiosis between G.platifrons and methane oxidation bacteria by participating in symbiosis-related immune processes.

Molecular cytogenetic of the Amoy croaker, A rgyrosomus amoyensis(Teleostei, Sciaenidae)

The family Sciaenidae is remarkable for its species richness and economic importance. However, the cytogenetic data available in this fish group are still limited, especially those obtained using fl uorescence in situ hybridization(FISH). In the present study, the chromosome characteristics of a sciaenid species, Argyrosomus amoyensis, were examined with several cytogenetic methods, including dual-FISH with 18 S and 5 S rDNA probes, and a self-genomic in situ hybridization procedure(Self-GISH). The karyotype of A. amoyensis comprised 2 n=48 acrocentric chromosomes. A single pair of nucleolar organizer regions(NORs) was located at the proximal position of chromosome 1, which was positive for silver nitrate impregnation(AgNO_3) staining and denaturation-propidium iodide(DPI) staining but negative for Giemsa staining and 4',6-diamidino-2-phenylindole(DAPI) staining, and was confi rmed by FISH with 18 S rDNA probes. The 5 S rDNA sites were located at the centromeric region of chromosome 3. Telomeric FISH signals were detected at all chromosome ends with dif ferent intensities, but internal telomeric sequences(ITSs) were not found. Self-GISH resulted in strong signals distributed at the centromeric regions of all chromosomes. C-banding revealed not only centromeric heterochromatin, but also heterochromatin that located on NORs, in interstitial and distal telomeric regions of specifi c chromosomes. These results suggest that the karyotype of Amoy croaker was relatively conserved and primitive. By comparison with the reported cytogenetic data of other sciaenids, it can be deduced that although the karyotypic macrostructure and chromosomal localization of 18 S rDNA are conserved, the distribution of 5 S rDNA varies dynamically among sciaenid species. Thus, the 5 S rDNA sites may have different evolutionary dynamics in relation to other chromosomal regions, and have the potential to be ef fective cytotaxonomic markers in Sciaenidae.