Acute Single and Joint Toxicity Effects of Deltamethrin and Lambda-cyhalothrin on Zebrafish(Danio rerio)

In this research,the single and combined toxicity effects of two commonly used pesticides,lambda-cyhalothrin and deltamethrin,were investigated on zebrafish at 20℃,with a weight of(1±0.1)g and a length of(3.5±0.35)cm.The study revealed that lambda-cyhalothrin exhibited higher toxicity compared to deltamethrin.Additionally,when used together,these pesticides showed significantly increased toxic effects on zebrafish.The 96-h LC 50 values were determined to be 3.059μg/L(confidence limits 0.077-0.351μg/L)for lambda-cyhalothrin and 1.304μg/L(confidence limits;0.046-0.228μg/L)for deltamethrin,both demonstrating a significant positive correlation(P<0.05).These results underscore the importance of regulating and managing pesticide use to safeguard aquatic organisms and uphold environmental sustainability.

Chromosome-level genome assembly of the freshwater snail Bellamya purificata(Caenogastropoda)

DEAR EDITOR,Bellamya purificata(Gastropoda:Caenogastropoda;Architaenioglossa;Viviparidae:Bellamyinae;Sinotaia),a homotypic synonym of S.purificata,is widely distributed in freshwater habitats in Asia.It is an economically important edible snail and plays a vital function in freshwater wetland ecology.However,genomic resources for this snail are lacking and no reference genome has been released.In this study,we constructed the first chromosome-level genome of B.purificata using PacBio long-read sequencing and high-throughput chromosome conformation capture(Hi-C)technology.

Research Progress of Rice-Fish Integrated Farming

Rice-fish integrated farming （RFIF） can change the agricultural production pattern from mono-farming model to the co-farming model, and the stereoscopic and integrated farming system established by RFIF can change the flat production to the stereoscopic production. Therefore, RFIF is the important development direction for agriculture to change pattern and adjust structure. In order to further promote development of the research and application of RFIF, the general development situation of RFIF in China was reviewed; the effects of RFIF on increasing farmer income and enhancing agricultural efficiency were clarified. The technologies matched with RFIF, such as rice paddy engineering technology, safe plant protection technology, security fertilization technology, fish disease prevention and control technology and water quality management technology, were summarized, and the supporting role of RFIF for agriculture was pointed out. In addition, the development prospect of RFIF was proposed, as well as the key research direction of RFIF.

Otolith microchemical evidence revealing multiple spawning site origination of the anadromous tapertail anchovy(Coilia nasus)in the Changjiang(Yangtze)River Estuary

The estuarine tapertail anchovy(Coilia nasus)is a high-value commercial fish.Estimating the spawning site or hatchery origin and habitat is essential for its conservation.This study aimed to determine the habitat use and life history characteristics of C.nasus from the Changjiang River Estuary.We investigated the environmental signatures of strontium(Sr)and calcium(Ca)in the otoliths of the collected specimens using electron probe microanalysis;additionally,we examined their gonadal maturity stage.Our results indicate that the 31 adult C.nasus specimens used in this study could be classified into two types based on their otolith Sr:Ca concentration ratios and their gonadal maturity stage.The long freshwater early life history type(Type LF)had wider central region in the otolith with low Sr:Ca concentration ratios ranging from 1.24±0.62 to 1.92±0.78 and a bluish pattern of low Sr content level.These fish are of riverine origin and had a relatively long early life history in freshwater and low gonadal maturation when captured.The short freshwater early life history type(Type SF)had a shorter central region in the otolith with low Sr:Ca concentration ratios ranging from 1.35±0.5 to 2.82±0.97 and a correspondingly bluish pattern.These fish also had a relatively short-term early life history in freshwater and high gonadal maturation when captured.The results of the otolith microchemical analysis indicated that Type LF and Type SF originated in spawning/hatching sites far from and close to the estuary,respectively.The mature gonads of Type SF fish indicated that they may breed in areas close to the estuary,whereas the immature gonads of Type LF fish indicated that they may breed in areas far from the estuary.This study is the first to reveal that the Changjiang River Estuary contains stocks of anadromous C.nasus originating in different spawning sites during the same season.The estuarine habitat plays a critical role in the connectivity between freshwater recruitment and the marine resources available to adult spawners of this commercially valued species.From a conservation perspective,this study provides important information for identifying anadromous C.nasus stocks originating in different spawning sites in the Changjiang River Basin.

The Research Progress of Polyploid Induction to Eriocheir sinensis

Polyploidy induction to aquatic animals is a kind of biological technology with important economic value,its induction methods include physical method,chemical method and biological method. There have been mroe reports about aquatic animals polyploid induction in fish and shellfish,by contrast,in decapod crustaceans,researches about polyploid induction are relatively little,currently only in Eriocheir japonicus,Fenneropenaeus chinensis and Macrobrachium rosenbergii. Through heat shock to induce polyploid of crabs,50% of triploid and 52% of tetraploid can be obtained,and through cytochalasin B（ CB） solution treatment to induce fertilized eggs of crabs,it can also get 58. 18% of triploid and 57. 89% of triploid. By adding KCl solution to a certain salinity of seawater to induce crab triploid,100% of triploid induction rate was obtained after exploring the optimum time and concentration of induction. In this paper,the author summarized the principle,methods and development process of polyploidy induction,and compared each induction method and their inducing effects,aimed at providing the reference for researchment of polyploidy induction of crabs.

Unravelling habitat use of Coilia nasus from the Rokkaku River and Chikugo River estuaries of Japan by otolith strontium and calcium

The migratory history of the engraulid fish Coilia nasus in the Rokkaku and Chikugo River estuaries of the Ariake Sea, Japan was assessed using otolith strontium（Sr） X-ray intensity maps and strontium：calcium（Sr：Ca） ratio life history transects by an electron probe microanalyzer（EPMA）. The results showed that seven of the ten specimens from the Rokkaku River Estuary（LJC） and all 15 specimens collected in the Chikugo River Estuary（ZHC） had low Sr：Ca ratios（≤3） at the central otolith area, indicating their riverine origin and initial freshwater residence. After the first regime shift adjacent to natal regions, the Sr level mapping displayed a wide variety of color patterns, and the Sr：Ca ratios obtained by the line transect analysis could be divided into one to six significantly different phases indicative of gradual life history transition. The other three specimens from the Rokkaku River Estuary had high Sr：Ca ratios（3–6.7） at the central otolith area but showed alternating changes between low and high values outside the natal region, suggesting that estuarine-origin individuals occurred in the Rokkaku River Estuary. The two-dimensional maps of the Sr level and average of the otolith Sr：Ca ratios along the life-history transects could be used as effective tools for reconstruction of past habitat use of the tapertail anchovy in estuaries of the Ariake Sea, Japan.

Migration and population structure characteristics of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics（especially body length and sex ratio） in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0＋ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios（female to male） were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that ＂the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds＂ but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.

Migration patterns and habitat use of the tapertail anchovy Coilia mystus in the Oujiang River Estuary and the Zhujiang River Estuary, China

Habitat use of the tapertail anchovy(Coilia mystus Linnaeus, 1758) from the Oujiang River Estuary and the Zhujiang(Pearl) River Estuary was studied by examining the environmental signatures of Sr and Ca in otoliths using electron probe microanalysis. Individuals from the Oujiang River had higher and varied Sr:Ca ratios(expressed as(Sr:Ca)×1 000, 3.83–13.0 average) in the otolith core regions, suggesting that they were born in brackish or sea waters, and that a freshwater habitat might not be necessary for egg hatching and larval growth.While, individuals from the Zhujiang River had lower Sr:Ca ratios(0.39–2.51 average) in the core regions,suggesting a freshwater origin. After hatching, anchovies from the Zhujiang River migrate downstream to the river estuary close to brackish water. Our results demonstrated varied habitat use for spawning during stages of early life history between the two populations, and suggested that such variations are promoting diversity of life history strategies of this species.

Isolation and characterization of AHL-degrading bacteria from fish and pond sediment

Quorum sensing (QS) disruption is considered as a potential alternative strategy to combat bacterial diseases in aquaculture. In this study, we isolated and identified bacteria degrading QS molecules from pond sediment and fish intestine. A total of 132 strains were obtained in the enrichment culture, of which two strains were identified as Enterobacter sp. f003 and Staphylococcus sp. sw120, being isolated from the fish intestine and pond sediment, respectively. We found that strains f003 and sw120 could degrade acyl-homoserine lactones (AHLs) and cause no hemolysis of sheep red blood cells. The AHL lactonase (aiiA) homologous gene in the two strains was detected in PCR amplification and the high-degrading activity to N-hexanoyl-L-homoserine lactone (C6-HSL) and AHLs secreted from pathogenic Aeromonas hydrophila was assessed. Meanwhile, the artificial infection of cyprinid Carassius auratus gibelio with intraperitoneal injection showed that the two strains were avirulent. Therefore, the obtained indigenous bacteria are candidate probiotics against pathogenic A. hydrophila in aquaculture.

Molecular cloning,tissue expression of gene Muc2 in blunt snout bream Megalobrama amblycephala and regulation after re-feeding

Mucins are important components of mucus, which form a natural, physical, biochemical and semipermeable mucosal layer on the epidermis offish gills, skin, and the gastrointestinal tract. As the first step towards characterizing the function of Muc2, we cloned a partial Megalobrama amblycephala Muc2 cDNA of 2 175 bp, and analyzed its tissue-specific expression pattern by quantitative real-time PCR （qPCR）. The obtained sequence comprised 41 bp 5＇-untranslated region （5＇-UTR）, 2 134 bp open reading frame encoding a protein of 711 amino acids. BLAST searching and phylogenetic analysis showed that the predicted protein contained several common secreted mucin-module domains （VWD-C8-TIL-VWD-C8） and had high homology with mucins from other vertebrates. Among four candidate reference genes （β-Actin, RP113a, RPII, 18S） for the qPCR, RPII was chosen as an appropriate reference gene because of its lowest variation in different tissues. M. amblycephala Muc2 was mainly expressed in the intestine, in the order （highest to lowest） middle-intestine 〉 fore-intestine 〉 hind-intestine. Muc2 was expressed relatively poorly in other organs （brain, liver, kidney, spleen, skin and gill）. Furthermore, after 20-days of starvation, M. amblycephala Muc2 expressions after refeeding for 0 h, 3 h, 16 h, 3 d, and 10 d were significantly decreased in the three intestinal segments （P〈0.05） at 16 h, and were then upregulated to near the initial level at 10 d.

Early life migration and population discrimination of the small yellow croaker Larimichthys polyactis from the Yellow Sea: inferences from otolith Sr/Ca ratios

The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacifi c Ocean,especially in the Chinese coastal waters of the Bohai,Yellow,and East China Seas.As a highly migratory species,the whole life migration of L.polyactis has been intensively studied.However,knowledge about its early life migration is scarce,and population divisions are inconsistent,limiting the ability of fishery scientists and administrators to evaluate the design and potential benefits of thorough conservation and resource-management strategies.In the present study,otolith Sr/Ca was analyzed to investigate the early migratory patterns and discriminate the populations of L.polyactis in the Yellow Sea,including two spawning groups and one overwintering group.The variation in Sr/Ca ratios of ontogenetic growth zones,including the nucleus(N),larval(L),metamorphosis(M),juvenile(J),and edge(E)zones,was measured by electron probe microanalysis.The variation in Sr/Ca ratios in early developmental growth zones was generally characterized by an evident downward trend from the N to J zone,which suggests that the early migratory pattern of L.polyactis might be from inshore to nearshore water.Canonical discriminant analysis,based on the otolith Sr/Ca ratios of the N,L,M,and J zones,allowed the successful discrimination of the two populations,namely,the northern and southern Yellow Sea groups,whose diff erences were mainly reflected in the L and J zones.Compared with previous studies,the traditional geographic boundaries(34°N)separating these two populations might be moving northward.The application of otolith Sr/Ca ratios based on ontogenetic stage could improve our understanding of the migration and population discrimination of L.polyactis from the Yellow Sea.

16S rRNA gene sequencing analysis on changes in the intestinal flora of Procambarus clarkii with“Black May”disease

The morbidity and mortality peak of farmed Procambarus clarkii occurs around May every year,a phenomenon known as"Black May"disease(BMD).Increasing evidence shows that the intestinal flora is closely related to host health.We analyzed and compared the microbiota of healthy and BMDaffected P.clarkii intestines.The results show that there was no significant difference in bacterial a-diversity(richness P=0.59;evenness P=0.43;and diversity P=0.052)between the diseased group and the control group.Four dominant phyla in the intestines of crayfish in the control group,namely Tenericutes(30.86%),Bacteroidetes(29.99%),Firmicutes(22.23%),and Proteobacteria(15.23%),were identified.However,a striking shift in the microbial compo sition were found in the intestines of P.clarkii with BMD.Bacteroidetes was a dominant phylum in healthy P.clarkii,whereas the prevalence was low in diseased P.clarkii(1.87%).By contrast,the prevalence of Proteobacteria was significantly higher(P<0.05)in P.clarkii with BMD than in P.clarkii without BMD.Candidatus Bacilloplasma,Bacteroides,Vibrio,and Aeromonas showed significant differences(P<0.05)at the genus level.Tax4 Fun function prediction indicated that the relative abundance of genes involved in energy metabolism in the intestinal flora of P.clarkii with BMD was significantly reduced(P<0.05).Therefore,BMD can change the composition of the intestinal microbiota of P.clarkii.This study contributes to the understanding of the relationship between intestinal flora and host especially in aquatic animals.

Occurrence of Bothriocephalus acheilognathi (Cestoda, Bothriocephallidea) in grass carp Ctenopharyngodon idella in the Changjiang River drainage

Bothriocephalus acheilognathi is a potentially serious pathogen in wild or cultured fish in worldwide distribution. We examined 58-farmed grass carp from Nanchang in the Changjiang (Yangtze) River drainage, from which 20.7% were found to harbor the parasite with an infection intensity of 36.9 ± 54.7. The parasites were identified based on morphology and rDNA ITS sequence analysis. The present report represents the first record of the parasite in grass carp Ctenopharyngodon idella in the river drainage.

Evidence of return of chum salmon released from Tangwang River by strontium marking method

In order to assess the effect of enhancement release of chum salmon(Oncorhynchus keta),otolith strontium(Sr)marking method was used to tag chum salmon released in Tangwang River in 2016.The homing chum salmon were detected and the samples were collected in Tangwang River,Ussuri River and Suifen River in the autumn of2018.The samples were analyzed by examining Sr and calcium(Ca)fingerprints in the otolith using electron probe microanalysis.The results suggested that two samples collected in Tangwang River had the marking ring near the core of otolith where the Sr concentration and Sr/Ca ratio were significantly higher than comparative samples.Proving that the two fish belonged to the released population in Tangwang River in 2016.This article indicated the success of the enhancement release of chum salmon from the Tangwang River for the first time and also confirmed the validity of Sr marking in enhancement release of fishes.

Combining otolith elemental signatures with multivariate analytical models to verify the migratory pattern of Japanese Spanish mackerel(Scomberomorus niphonius) in the southern Yellow Sea

Japanese Spanish mackerel,Scomberomorus niphonius,is a commercially important,highly migratory species that is widely distributed throughout the northwestern Pacific region.However,its life history and migratory patterns are only partially understood.This study used otolith chemistry to investigate the migratory pattern of S.niphonius in the southern Yellow Sea,an important fishing ground.Transverse sections of otoliths from 15 age-1 spawning or spent individuals,comprising up to one complete migration cycle,were analyzed from the core to the margin by using laser ablation inductively coupled plasma mass spectrometry.The ratios of the element to Ca were integrated with microstructural analysis to produce age-related elemental profiles.Combining multielemental analysis of otolith composition with multivariate analytical models,we quantified structural changes in otolith chemistry profiles.Results revealed there were diverse changing patterns of otolith chemistry profiles for detected elements and the elements of Na,Mg,Sr and Ba were important for the chronological signal.Five clusters were identified through chronological clustering,representing the five life stages from the early stage to the spawning stage.Variation of Ba:Ca ratio was most informative,showing a step-decreasing pattern in the first four stages and a rebound in the spawning stage.These results support the hypothesized migratory pattern of S.niphonius:hatching and spending their early life in the coastal sandy ridges system of the southern Yellow Sea,migrating northeastward and offshore for feeding during juvenile stage,aggregating in early October and migrating outward to the Jeju Island for wintering,and returning to the coastal waters for spawning.This study demonstrated the value of life-history related otolith chemistry profiles combined with multivariate analytical models was a means to verify the migration patterns of S.niphonius at regional scales with potential application in fisheries assessment and management.

Isolation of Nile Tilapia (Oreochromis niloticus) β-actin Promoter and Assay of Its Transcription Activity

Through PCR amplification, 5’ flanking region and partial open reading frame（ORF） of gene of Nile tilapia（Oreochromis niloticus） was cloned by PCR amplification. Sequence analysis showed that no difference was found in known functional regions. This study was to construct and identify the mammalian expression vector of pEGFP-β-actin and to detect whether it could express in HEK 293T cell line. pEGFP-β-actin was transfected into HEK 293T cells with Lipofectamine 2000. The results showed that correct construction of recombinant pEGFP-β-actin has been shown by restriction enzyme digestion. The expression of gene in HEK 293T cells could be observed under microfluoroscope. pEGFP-β-actin could repress EGFP protein in HEK 293T cells. The results showed that β-actin gene promoter possessed effective transcription activities in eukaryotic cells. The work laid foundations for further study on the gene engineering and autotransgenic tilapia.

Construction of Suppression Subtractive Hybridization Library for Testis of Male Tilapia Under the Stress of Methomyl

[Objectives]This study was conducted to construct forward and reserve libraries of suppression subtractive hybridization (SSH) in the testis of male tilapia under the stress of methomyl by using SSH technology.[Methods]Using male tilapia as the test animal,the forward and reserve libraries of SSH in the testis of tilapia under the stress of methomyl were constructed by using the SSH technology.[Results]45 expressed sequence tags (ESTs) were obtained,and 25 expressed sequence tags were successfully noted,including 13 forward libraries and 12 reverse libraries.The genes with confirmed functions were classified into five types.Genes related to catalytic activity and cell characteristics were up-regulated,while genes related to structural molecule's activity and biological process were down-regulated.The expression amount of integrin β1 was up-regulated,while serine/threonine protein kinase pim-3,Ca^2+-ATPase,Na^+-K^+-ATPase and ribosomal protein L22 were down-regulated.[Conclusions]The research results could lay a foundation for revealing the molecular mechanism of methomyl's reproductive toxicity to tilapia.

Overview on Genetic Diversity of Coilia nasus

Coilia nasus is an important economic migratory fish in China, and it is known as ＂Three Delicious Fish of the Yangtze River＂ with puffer fishes and reeves shad. However, because of water pollution, blocked migration and overfishing, wild resources of C. nasus have suffered severe damage. This article gives an overview on genetic diversity of C. nasus from morphology, protein and DNA levels, to supply a theoretical foundation for protection of C. nasus resources.

Investigation and Study on the Alien Species in Aquaculture in the Lower Reaches of the Yangtze River

The lower reaches of the Yangze River is one of the central areas of freshwater shallow lakes in China and has the diverse climates with both warm temperate zone and sub-tropical zone,which makes it become one of the best areas for aquaculture,so nearly all of the aquaculture species from the world can live in the area.It is important for perfecting alien aquaculture species information data-base and environmental risk assessment system to investigate and study the aquaculture alien species in the lower reaches of the Yangze River.The results showed that the number of aquaculture alien species in the lower reaches of the Yangze River is 45 species,including 33 species of fishes,4 species of shellfish,7 species of crustaceans and 1 species of amphibian.Most of alien species are from America and the main transmitting way is intentional introducing.

Effect of Organic Fertilizer on Aquaculture Water Quality and Tilapia Production

A two-month trial was carried out in China to evaluate the possibility of recycling animal manure through pond tilapia production.And the effects of chicken manure,cattle manure and chicken-cattle mixture together on the water quality and tilapia production were investigated.The results showed that the yield of tilapia was 3.46,3.89,2.49 and 3.20 kg in the control,chicken M,cattle M,and chicken-cattle M,respectively,and the tilapia yields following the order of chicken M>control>chicken-cattle M>cattle M.The tilapia yield in chicken M group increased by 12.43% compared with the control.Chicken manure could increase the tilapia production,but cattle manure has no the effect.And the effect of animal manure on water quality showed that adding chicken manure into tilapia pond could make water quality decreased at the beginning 20 d,but could increase water quality after 20 d and stabilize the phytoplankton structure.