Responding of zooplankton to environmental factor changes in the Changjiang River estuarine regions in spring-summer from 2016 to 2020

The estuarine areas are under frequent influence from freshwater intrusion and ocean currents,in which zooplankton species are diversified and variable as they are sensitive to physio-chemical variations in water.Therefore,understanding the relationships between zooplankton and environmental factors help us know the water quality.To achieve co-existence with species in similar ecological group or habit,they could inevitably alter themselves to fit the ecology and adjust the function according to the competitive exclusion in ecological theory.However,information of the co-existence of dominant species in the Changjiang(Yangtze)River estuary(CRE)and adjacent waters remains scarce.We explored the relationships between dominant zooplankton and environmental factors in the study region in spring-summer from 2016 to 2020,involving particularly the composition of dominant species,ecological groups,their relationships with environmental factors,and co-existence of important species,using the non-multidimensional scale analysis(nMDS)method and redundancy analysis.Results show that Labidocera euchaeta and Tortanus vermiculus were dominant species in the study scope.The turnover rate of dominant zooplankton was greater(>50%)in spring while the species number was higher in summer.The dominant species were estuarine,offshore,and eurytopic based on the adaptation to salinity.In spring,the ecological groups were dominated by estuarine species,while in summer by estuarine and offshore species.In addition,the nMDS showed that the dominant species in the same ecological group were more dispersed and not prominently clustered;the dominant species were staggered among different ecological groups.The temperature,salinity,pH,dissolved oxygen,and chlorophyll a were the main environmental factors on the distribution of the dominant species in spring,while in summer were dissolved oxygen,temperature,salinity,and pH.The domination of medusae of Nemopsis bachei and Pleurobrachia globosa in zooplankton community in spring,and the continuous decrease in abundance of L.euchaeta reflected the effects of local climate change.The temperature and salinity changes in different years and the subsequent response of zooplankton reflected the influence of freshwater intrusion and/or ocean currents.Zooplankton in similar ecological habits exhibited the competitive exclusion in terms of co-existence.

An Effective Extract Method of Phospholipids from Antarctic Krill <em>Euphausea superba</em>

Phospholipids are one of the major bioactive ingredients of Antarctic krill Euphausea superba. A feasible and effective extraction method of Antarctic krill oil was investigated and modified by orthogonal test which the ratio of solid to liquid was 1:2.5, extraction time was 5 min, ratio of ethyl acetate (EA) and n-butanol (BuOH) was 1:1. With this method, the extract of krill oil has a higher phospholipids content of 27.7% - 42.3%, together with total oil yields of 4.15% - 6.18%.

Histological Characterization of Peppermint Shrimp (Lysmata wurdemanni) Androgenic Gland

The androgenic gland(AG) is an important endocrine gland for male reproductive function in crustaceans. In the present study, we investigated the histological characteristics of the androgenic gland of peppermint shrimp, Lysmata wurdemanni. The peppermint shrimp matures as male first, then some individuals may become euhermaphrodite after several moltings(transitional phase). Euhermaphrodite-phase shrimp acts as male at intermolts. However, it can be fertilized as a female immediately after molting. Considering the male reproductive function acts in its lifespan except for at larval stages, and female reproductive system starts to develop at transitional phase, we hypothesized that AG activity might be reduced to allow and promote vitellogenesis onset in early transitional phase and the following euhermaphrodite phase. So AG cell structure might be different in three phases in L. wurdemanni. The results showed that AG exists in the male in transitional and euhermaphrodite phases. The gland cell clusters surrounding the ejaculatory ducts locate at the roots of the fifth pereopods. The nucleus diameters are similar in the three phases while the nucleus-to-cell ratio is the lowest in euhermaphrodite phase. Our results indicated that for the individuals that will become euhermaphrodite, the cellular structure of AG changes since transitional phase. Male reproductive function which is still available in euhermaphrodite-phase shrimp should be due to the existence of the gland.

Identification and profiling of microRNAs of Euphausia superba using Illumina deep sequencing

MicroRNAs(miRNAs) are an abundant class of conserved, non-coding small RNAs that play important role in gene regulation at post translational level. There have been no reports on the miRNAs of the Antarctic krill E uphausia superba despite the species' crucial position in Antarctic food webs. Two small RNA libraries were constructed from eyestalk and muscle, subsequently, and deep sequencing analysis was performed to investigate and profile E. superba miRNAs. A total of 19 304 586 and 23 005 104 unique sequences were obtained from the eyestalk and muscle, respectively. After compared the small RNA sequences with the Rfam database, 12 342 039 and 7 907 477 reads in eyestalk and muscle were matched to the transcriptome sequence of E. superba. A total of 236 distinct miRNAs were identified after annotation to known animal miRNAs registered in miRBase 21. In both libraries, the most abundant known miRNA were miR-750 with 92 583 reads in muscle and miR-1304-3 p with 56 386 reads in eyestalk while the average value was less than 106, revealing a wide range of different expression levels. In addition, miR-277 a enriched in both libraries and may be involved in modulating Krebs cycle by targeting to Vimar. Differential expression analysis showed that 56 mature miRNAs were significantly up/down regulated according to expression fold change. It appeared that the expression of several abundant miRNAs maybe tissue-specific or tissue-bias. Notably, the expression pattern of miR-750 and miR-1 family, which was suggested as the crucial candidates, involved in muscle development. Taken together, this study provides the first miRNA profile of E. superba and some of these miRNAs were expected to play important role in immune response, reproduction, energy metabolism, and muscle development and so on. Thus, the results provides a reference for functional studies of miRNAs in E. superba.

Gene expression during different periods of the handling-stress response in Pampus argenteus

Common aquaculture practices subject fish to a variety of acute and chronic stressors. Such stressors are inherent in aquaculture production but can adversely affect survival, growth, immune response, reproductive capacity, and behavior. Understanding the biological mechanisms underlying stress responses helps with methods to alleviate the negative effects through better aquaculture practices, resulting in improved animal welfare and production efficiency. In the present study, transcriptome sequencing of liver and kidney was performed in silver pomfret( Pampus argenteus) subjected to handling stress versus controls. A total of 162.19 million clean reads were assembled to 30 339 unigenes. The quality of the assembly was high, with an N50 length of 2 472 bases. For function classification and pathway assignment, the unigenes were categorized into three GO(gene ontology) categories, twenty-six clusters of egg NOG(evolutionary genealogy of genes: non-supervised orthologous groups) function categories, and thirty-eight KEGG(Kyoto Encyclopedia of Genes and Genomes) pathways. Stress affected different functional groups of genes in the tissues studied. Differentially expressed genes were mainly involved in metabolic pathways(carbohydrate metabolism, lipid metabolism, amino-acid metabolism, uptake of cofactors and vitamins, and biosynthesis of other secondary metabolites), environmental information processing(signaling molecules and their interactions), organismal systems(endocrine system, digestive system), and disease(immune, neurodegenerative, endocrine and metabolic diseases). This is the first reported analysis of genome-wide transcriptome in P. argenteus, and the findings expand our understanding of the silver pomfret genome and gene expression in association with stress. The results will be useful to future analyses of functional genes and studies of healthy artificial breeding in P. argenteus and other related fish species.

Comparison of Nutritional Components in the Muscle of Juvenile Siganus guttatus Fed with Enteromorpha prolifera and Artificial Feed

[ Objective] This experiment was conducted to analyze and compare the nutritional components in the muscle of juvenile Siganus guttatus fed with Enteromorpha prolifera and artificial feed. [ Method] A total of 180 healthy S. guttatus juveniles with similar body size were assigned into two groups： one fed with E. prolifera, and the other fed with artificial feed, respectively. There were three replicates in each group, and 30 fish in each replicate. And the experiment lasted for 90 d. [ Result] The results showed that the weight gain rate, specific growth rate and relative growth rate of E. prolifera-fed group were significantly lower than those of artificial feed-fed group （P 〈0.05） ; the contents of crude protein and crude ash of E. prolifera-fed group were significantly higher than those of artificial feed-fed group （P 〈 0.05 ）. However, the content of crude fat of E. prolifera-fed group was significantly lower than that of artificial feed-fed group （P 〈 0.05 ）. The moisture content had no significant difference between the two groups （P 〉 0.05 ）. The amino acid composition was similar between the two groups. Seventeen amino acids were found in both groups, and the essential amino acid index （EAAI） was 76.71 in E. prolifera-fed group and 70.05 in artificial feed-fed group, both of which met the criteria set by the Food and Agriculture Organization of the United Nations （FAO）/World Health Organization （WHO）. The content of eicosapentaenoic acid （EPA） ＋ docosahexaenoic acid （DHA） and the content of to-3 polyunsaturated fatty acids （ to-3 PUFAs） of E. prolifera-fed group were significantly higher than those of artificial feed-fed group （ P 〈 0.05 ）. [ Conclusion ] In conclusion, the juvenile S. guttatus in both groups contains a variety of nutritional components. S. guttatus fed with E. prolifera has higher levels of essential amino acids, more balanced composition of polyunsaturated fatty acids, higher nutritive val- ue and better taste than that fed with artificial feed.

Facile Synthesis Route of Au-Ag Nanostructures Soaked in PEG

A nanostructured gold-silver soaked in polyethylene glycol 400 (Au-Ag@PEG) is designed using gold(I) chloride and silver nitrate (AgNO3) as precursors and, polyethylene glycol 400 (PEG) as capping agent. The result of the structure characterization using Selected Area Electron Diffraction (SAED) has showed that the synthesized nanomaterial has a good crystallinity while Transmission Electron Microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and Dynamic Light Scattering (DLS) measurements suggest mixed Au-Ag nanoparticles with an average diameter size of around 7 nm and 30 nm for Au and Ag respectively.

Extensive parental care experience of male seahorses increases their future mating attractiveness

Male-only parental care,where the male is the sole carer of his offspring,is a rare strategy in most animals.In mammals,the majority of families(about 90%)show femaleonly care and male-only care is absent.In birds,biparental care is the norm(about 90%of families)and male-only care is present in fewer than 2%of families.In reptiles,about 85%of families show no care,but of those that do,femaleonly care is dominant and there is also no male-only care(Reynolds et al.2002).

Intelligent droplet tracking with correlation filters for digital microfluidics

Tracking the movement of droplets in digital microfluidics is essential to improve its control stability and obtain dynamic information for its applications such as point-of-care testing,environment monitoring and chemical synthesis.Herein,an intelligent,accurate and fast droplet tracking method based on machine vision is developed for applications of digital microfluidics.To continuously recognize the transparent droplets in real-time and avoid the interferes from background patterns or inhomogeneous illumination,we introduced the correlation filter tracker,enabling online learning of the multi-features of the droplets in Fourier domain.Results show the proposed droplet tracking method could accurately locate the droplets.We also demonstrated the capacity of the proposed method for estimation of the droplet velocity as faster as 20 mm/s,and its application in online monitoring the Griess reaction for both colorimetric assay of nitrite and study of reaction kinetics.