The enormous repetitive Antarctic krill genome reveals environmental adaptations and population insights.

Antarctic krill (Euphausia superba) is Earth's most abundant wild animal, and its enormous biomass is vital to the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene families associated with molting and energy metabolism, providing insights into adaptations to the cold and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical sites around the Antarctic continent reveals no clear population structure but highlights natural selection associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for future Antarctic research.

Effect of trace elements in the toxicity of copper to Chlamydomonas reinhardtii.

Copper sulfate (CuSO4) is widely used in the control of algal blooms. Cu can promote or inhibit algal growth, while also affecting trace element uptake, therefore, the response mechanisms of algae cells under Cu2+ interference should be studied. In this study, wild-type Chlamydomonas reinhardtii (C. reinhardtii) and wall-less mutant C. reinhardtii were selected as the research objects. Except for the cell wall, these two algae were physiologically the same. While manipulating the concentration of Cu, the accumulation of Cu, Fe, Zn, and Mn by the two algal cell types was studied. The cell wall hindered the accumulation of Cu by cells and alleviated the toxicity of Cu to C. reinhardtii. The addition of Cu increased the accumulation of Fe by both cell types. In an environment with excess Cu, the total amount of Zn and Mn accumulated by cells also increased. On the one hand, this may be due to the synergistic and antagonistic effects of trace elements in the adsorption and uptake process, and on the other hand, it may be due to the changes in metal speciation in the culture medium. In addition, the difference in the total accumulation of various trace elements between wild-type and wall-less-type C. reinhardtii may be due to the structure and function differences between cell wall and cell membrane. At the same time, by measuring the changes in the levels of glutathione (GSH) in algal cells, the relevant mechanisms underlying the algae's uptake of trace elements by algae were further explored.

[Shrimp community structure and its relationships with environmental factors in the Yellow Sea in summer].

Based on the data collected from the bottom trawl survey in Yellow Sea, August, 2014, the community structure of shrimp assemblage and its relationships with environmental factors in summer was examined by using index of relative importance, ecological diversity indices and multivariate statistical analysis. A total of 20 shrimp species were captured, belonging to 3 orders, 10 families, 16 genera. The relative abundance of shrimp of all stations ranged from 13 to 45047 g · h(-1) and its mean value was 6838 g · h(-1). The dominant species was Crangon affinis, and the common species was Eualus sinensis. The rare species were Metapenaeopsis dalei, Palaemon gravieri and Oratosquilla oratoria. The ranges of Shannon diversity index (H) , Pielou' s evenness index (J) and the Margalef' s species richness index (D) of all stations of the shrimp community structure were 0.007-1.538, 0.101-1.138 and 0.006-0.947, respectively, and the mean values of H, Jand D were 0.391, 0.374 and 0.298, respectively. MDS and Cluster analyses revealed that two clusters of Group I named cold water mass group and Group II named coastal group, which were bounded by the 45 m isobaths, were identified for all the sampling stations. Significant difference was detected by ANOSIM analysis between Group I and Group II. BIOENV analysis indicated that bottom temperature and bottom salinity were the most important environmental factors for structuring the spatial distribution of the shrimp assemblage. Cold water mass group accounted for absolute advantage and Yellow Sea cold mass had a decisive influence on the distribution pattern of the shrimp community in the Yellow Sea in summer.