ngzhi Li

The Gut Microbial Community of Antarctic Fish Detected by 16S rRNA Gene Sequence Analysis

Intestinal bacterial communities are highly relevant to the digestion, nutrition, growth, reproduction, and a range of fitness in fish, but little is known about the gut microbial community in Antarctic fish. In this study, the composition of intestinal microbial community in four species of Antarctic fish was detected based on 16S rRNA gene sequencing. As a result, 1 004 639 sequences were obtained from 13 samples identified into 36 phyla and 804 genera, in which Proteobacteria, Actinobacteria, Firmicutes, Thermi, and Bacteroidetes were the dominant phyla, and Rhodococcus, Thermus, Acinetobacter, Propionibacterium, Streptococcus, and Mycoplasma were the dominant genera. The number of common OTUs (operational taxonomic units) varied from 346 to 768, while unique OTUs varied from 84 to 694 in the four species of Antarctic fish. Moreover, intestinal bacterial communities in individuals of each species were not really similar, and those in the four species were not absolutely different, suggesting that bacterial communities might influence the physiological characteristics of Antarctic fish, and the common bacterial communities might contribute to the fish survival ability in extreme Antarctic environment, while the different ones were related to the living habits. All of these results could offer certain information for the future study of Antarctic fish physiological characteristics.

The complete mitochondrial genome of Chionodraco hamatus (Notothenioidei: Channichthyidae) with phylogenetic consideration

Abstract The complete mitochondrial genome of Chionodraco hamatus was obtained, which was 17 457 bp in length. This genome consists of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and a putative control region. Of the 37 genes, 28 were encoded by heavy strand, while 9 were encoded by light strand. Overall base composition of mitogenome is estimated to be 26.38% for A, 17.44% for G, 26.00% for T, 30.18% for C, respectively, with a slight A + T bias (52.38%). The phylogenetic analysis based on 13 concatenated protein-coding genes suggested that C. hamatus as a sister species to Chionodraco myersi was clustered in family Chionodraco. The complete mitochondrial genome sequence of C. hamatus could provide a basic data for the studies on evolution for low temperature adaptability, population structure, molecular systematic, stock evaluation and conservation genetics.

Geographical distribution and age composition of Euphausia superba larvae (Crustacea: Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions

Spatial distribution patterns of the different life stages of Euphausia superba in the region of the South Shetland Islands and southern Scotia Sea (Antarctica) were assessed based on scientific survey data collected in January and February of 2010. Adults, eggs, nauplii, metanauplii, calyptopis I-III, and furcilia I-II were found in the investigation. The abundance of larvae averaged 1 172.8 ind./m2, with calyptopis I and II as the dominant stages. Habitat occupancy patterns varied among Euphausia superba at different stages, and three sub-regionswere identified by cluster analysis. The degree of larval development increased fromwest to east. Larvae were not observed north of the South Shetland Islands. Calyptopis I was predominant in the water between Elephant Island and the South Orkney Islands, which featured no thermocline. Older stages, including calyptopis II and III and furcilia I and II, were common in north and northeast of the South Orkney Islands, which were characterized by high temperature and high chlorophyll concentration. Distribution and abundance of the early life stages of E. superba were associated with specific environmental conditions. According to Biota-Environment matching (BIOENV), the distributions of E. superba larvae were correlated with a combination of temperature at the surface and 200m, and 0–100 mintegrated chlorophyll a concentration.

A metabolomic study of Antarctic krill ( Euphausia superba ) raises a warning about Antarctic pollution

Antarctic krill ( Euphausia superba ) is one of the most successful species on Earth and serves as the largest potential protein bank for both Antarctic animals and humans. Research on this species is of great value for exploitation of Antarctic biotic resources. In this study, the metabolomics of E. superba were investigated using the GC-MS method. A total of 293 compounds were initially identified; these compounds could be divided into several classes, including amino acids, sugars and polyols, metabolic intermediates, small molecules and other metabolites. However, a serious problem was that both 2-hydroxybiphenyl and dioctyl phthalate were also detected in these krill tissues. Moreover, some intermediates of pesticides and medicinal or chemical compound products were found in krill tissue as well. This is the first survey to investigate the occurrence of chemical contamination in metabolites of Antarctic krill. These findings suggest that international contracts or policies should be developed to protect the pristine ocean.

Isolation and characterization of the mitochondrial genome of Gymnodraco acuticeps (Perciformes: Bathydraconidae) with phylogenetic consideration

Abstract Gymnodraco acuticepsis is an Antarctic fish living in the Southern Ocean. Until now, studies on G. acuticeps are still limited. As an Antarctic fish, obtaining and characterization of the mitochondrial genome of G. acuticeps will be important for elucidation of the mechanism of cold-adapting evolution in mitochondrion. In this study, we first isolated and characterized the mitochondrial genome sequence of G. acuticeps with 15,987 bp in length. It contained of 34 genes (12 protein-coding genes, 20 transfer RNA genes, 2 ribosomal RNA genes) and a partial putative control region. Gene organization and nucleotide composition of obtained mito-genome were similar to those of other Antarctic fish. Twenty-eight genes were encoded by heavy strand, while six genes were encoded by light strand. Further, the phylogenetic tree, which based on 12 protein-coding genes, revealed that the G. acuticeps was genetically closest to species Parachaenichthys charcoti among 18 species. We hope this work would be helpful for the population genetics and molecular evolution studies.

Hydrodynamic characteristics of the oval cambered double slotted otter board in bottom trawl fisheries

The otter board is one of the main components of single boat trawl fisheries. An oval cambered double slotted otter board was developed for improving the expansion performance of trawl net in bottom trawl fisheries. A flume model experiment was conducted to measure the lift coefficient (C L), drag coefficient (C D), and lift to drag ratio (K) in different angles of attack (α). The experimental results are as follows : (1) The C L and K value show a trend of increasing at the beginning and then decreasing with the increase of angle of attack, the C D value reflects an upward trend as the angle of attack increases; (2) The D3 otter board (front flow deflector angle at 29°) showed a better hydrodynamic performance. When α=30°, the max lift coefficient (C Lmax) was 1.464, in this case C D = 0.554 and K=2.643. When α=15°, the max lift to drag ratio (K max) was 4.165, C L =0.633, and C D = 0.152. This suggests that the best working scope for the angle of attack is between 15°~30°, in which case, C L>0.633 and K>2.643. The mean value of the lift coefficient was 1.071 and the mean of the lift to drag ratio was 3.482. Comparative analysis of the hydrodynamic performance of different types of otter boards showed that the D3 otter board both had good expansion performance and efficiency, which can provide a reference basis for further optimization of the bottom trawl otter board.

Effects of Cold Storage Environment Change on Antarctic Krill (Euphausia superba) Quality Center

In order to deal with the quality of Antarctic krill during the storage and transportation process caused by the failure of the supply system and the freezing equipment in the process of storage and circulation in the form of frozen products, the project team changed the refrigerated environment to the Antarctic The effect of krill quality was studied. When the ambient temperature increased from -20 °C to -12 °C, -7 °C, -3 °C, -1.5 °C, 0 °C, 1 °C, 2.5 °C, 4 °C, 6 °C , 8 °C, 12.5 °C, 16 °C, the Antarctic krill samples for sensory evaluation, pH value, the meat rate and soup turbidity and other quality indicators of the determination. The results show that when the ambient temperature from -20 °C up to -1.5 °C process, the Antarctic krill soup after cooking is more clear, little change in turbidity, pH quickly increased from 7.60 to 7.85 Antarctic krill muscle elasticity began to change Poor, the sensory quality has begun to change from good to change; when the temperature from -1.5 °C to 4 °C, the pH value slowly increased, there is a certain fluctuation, may be due to differences in the composition of the various components of the decision, Antarctic krill soup after the soup turbidity quickly increased from 0.5 to 0.7Brix maximum, sensory quality is still at a moderate level; when the temperature rose to 16 °C, the pH has risen to 8.05, Antarctic krill Sensory quality from the change into a bad, this time the Antarctic krill has been unable to eat, only as a feed or other use.

The complete mitochondrial genome sequence and gene organization of Trematomus bernacchii (Perciformes: Nototheniidae) with phylogenetic consideration

Abstract In this study, the complete mitochondrial DNA sequence was obtained from Trematomus bernacchii. The full length of mitogenome was 16 018 bp, including 20 transfer RNA genes, a 16S ribosomal RNA genes and an incomplete 12S rRNA, 12 protein-coding genes and an incomplete ND6 protein-coding gene, and 2 non-coding regions: control region (D-loop) and origin of light-strand (L-strand) replication (OL). Most genes were located on the heavy-strand (H-strand), while ND6 and seven tRNA genes were located on the L-strand. T. bernacchii’s mitogenome was comprised of 24.52% for A, 25.44% for C, 20.38% for G and 29.66% for T, with a higher A + T content (54.18%). From the NJ phylogenetic tree, it revealed that T. bernacchii’s was genetically closest to species Dissostichus eleginoides among seven species within suborder Notothenioidei. This study could lay the foundation for the future studies in species identification, taxonomic status, molecular systematics, stock evaluation and conservation genetics for T. bernacchii’s.