Cr (VI), the pathogenicity factor, is widely known to cause toxic effects in living organisms. Given the economic importance of the mantis shrimp (Oratosquilla oratoria), the understanding of impacts by Cr (VI) is considered important. In this study, transcriptome of mantis shrimp was characterized by a comparison between control and Cr (VI)-treated samples using RNA-seq approach. Totally, 88 234 826 bp and 13.24G clean reads were obtained. The total length and number of unigenes were 68 411 206 bp and 100 918, respectively. The maximal and average length of unigenes was 24 906 bp and 678 bp, respectively (N50, 798 bp). 7115 of these unigenes accounted for 7.05% of the total that were annotated in all databases. After annotation of assembled unigenes, 35 619 of them were assigned into 3 functional categories and 56 subcategories using Gene Ontology; 18 580 of them were assigned into 26 functional categories using Clusters of Orthologous Groups of proteins; 16 864 of them were assigned into 5 major categories and 32 subclasses using KEGG. Finally, 1730 genes were differentially expressed (DGEs), 9 up-regulated pathways (protein digestion and absorption, neuroactive ligand–receptor interaction, pancreatic secretion, tyrosine metabolism, amoebiasis, ECM-receptor interaction, riboflavin metabolism, amino sugar and nucleotide sugar metabolism and AGE-RAGE signaling pathway in diabetic complications) were significantly enriched (q < 0.05), and one down-regulated pathway (Staphylococcus aureus infection) was significantly enriched (q < 0.05). Up-regulation of genes in pathways of protein digestion/absorption (PepT1/SLC15A and ATP1B) and environment information processing (COL1AS, COL4A; LAMA3_5, LAMB3; FN1 and TN) may imply the potentially positive toxicity resistance mechanisms.

Chinese mitten crabs (Eriocheir japonica sinensis) are catadromous, spending most of their lives in fresh water, but moving to a mixed salt-fresh water environment for reproduction. The characteristics of this life history might imply a rapidly evolutionary transition model for adaptation to marine from freshwater habitats. In this study, transcriptome-wide identification and differential expression on Chinese mitten crab groups were analysed. Results showed: clean reads that were obtained totalled 93,833,096 (47,440,998 in Group EF, the reference, and 46,392,098 in Group ES, the experimental) and 14.08G (7.12G in Group EF 6.96G in Group ES); there were 11,667 unigenes (15.29%) annotated, and they were located to 230 known KEGG pathways in five major categories; in differential expression analysis, most of the top 20 up-regulated pathways were connected to the immune system, disease, and signal transduction, while most of the top 20 down-regulated pathways were related to the metabolism system; meanwhile, 8 representative osmoregulation-related genes (14-3-3 epsilon, Cu²⁺ transport ATPase, Na⁺/K⁺ ATPase, Ca²⁺ transporting ATPase, V-ATPase subunit A, Putative arsenite-translocating ATPase, and Cation transport ATPase, Na⁺/K⁺ symporter) showed up-regulation, and 1 osmoregulation-related gene (V-ATPase subunit H) showed down-regulation. V-ATPase subunit H was very sensitive to the transition of habitats. These results were consistent with the tests of qRT-PCR. The present study has provided a foundation to further understand the molecular mechanism in response to salinity changing in water.

Excessive rainfall changes salinity in shrimp farming ponds in short period and exerts low salinity stress on the outdoor breeding shrimp under global warming. Fenneropenaeus chinensis can have different performance on vitality in low salinity environments. To reveal mechanisms of vitality difference in shrimp living in low saline environments. This study based on the normal and moribund F. chinensis in 10 ppt salinity environment using high-throughput sequencing identifies 1,429 differentially expressed genes (DEGs), 586 of which are upregulated, while 843 of which are downregulated in the normal group (FCN10) as compared to the moribund group (FCM10). Meanwhile, another transcriptomic analysis is conducted on the normal and moribund shrimp from 25 ppt (FCN25 vs. FCM25) salinity environment as the control, in which 1,311 DEGs (upregulated: 327 genes, downregulated: 984 genes) are identified. In this study, intersective pathways, GO (Gene Ontology) categories and DEGs from the two groups of comparative transcriptome are investigated. The two intersective pathways (Metabolism of xenobiotics by cytochrome P450, Pentose, and glucuronate interconversions) significantly enriched by DEGs are related to detoxification. In these two pathways, there is one vitality regulation-related gene (VRRG), the Dhdh (dihydrodiol dehydrogenase), which is upregulated in both the groups of FCN10 and FCN25 as compared to the groups of FCM10 and FCM25, respectively. Similarly, in the 25 top intersective GO categories, four VRRGs are revealed. Three of them are upregulated (Itgbl, kielin/chordin-like protein, Slc2a8, solute carrier family 2, facilitated glucose transporter member 8-like protein and Cyp3a30, cytochrome P450 3A30-like protein); one of them is downregulated (Slc6a9, sodium-dependent nutrient amino acid transporter 1-like protein isoform X2). These GO categories are related to transmembrane transporter activity of substance, enzyme inhibitor activity, monooxygenase activity. RT-qPCR analysis further verifies the VRRGs. The study gives new insight into understanding the vitality differences for F. chinensis, in low salinity environment. The pathways and DEGs in response to low salinity stress in modulating the vitality of F. chinensis that could serve as tools in future genetic studies and molecular breeding.

The impact of islanding on the genetics of the dominant species, Niviventer confucianus, was analysed using 13 microsatellite markers. All 16 populations are of high genetic diversity with a total of 134 alleles. The average number of effective alleles (Ne) is 6; the average expected heterozygosity (H_E) and polymorphic information content (PIC) are 0.823 and 0.763, respectively. Landscape fragmentation might contribute to weak genetic differentiation among 13 island populations. Values of F_ST simulated by Structure 2.3.4 implied that the 16 populations could be assigned into three clusters, from which we postulated the possible dispersion history. Pairwise F_ST tests showed that genetic differences mainly occurred between small island populations and others. Currently, habitat area appears to be the main factor affecting the genetics of Niviventer confucianus, and not the distances between islands. Hence we suggest that more attention should be paid to habitat area in the future.