Remarkably little information is available about the interaction between the gut microbiota and intestinal immunity in fish and crustaceans. In our study, we used Illumina MiSeq sequencing and real-time quantitative PCR to compare the microbial community and immunity genes expression in the foregut, midgut and hindgut of Chinese mitten crab (Eriocheir sinensis). Our results indicated that the community richness of the midgut is higher than in the foregut or the hindgut, although the bacterial diversity in the hindgut is higher. The predominant phyla were Tenericutes and Firmicutes in the foregut, Tenericutes and Proteobacteria in the midgut and Proteobacteria, Tenericutes and Bacteroidetes in the hindgut. When compared with the midgut, the expression of antimicrobial peptides (AMPs) were significantly elevated in the hindgut (P < 0.05), and the gene expression of EsRelish (IMD pathway) was higher than the Toll signaling pathway genes. Actinobacteria and Lactobacillus had negative correlationship with the expression of AMPs, although Acinetobacter, Bacteroides, Flavobacterium can up-regulate the expression of AMP genes. Collectively, our data indicate that microbiota are site-specific within the digestive tracts of crabs and the bacterial community and intestinal immunity have a close relationship in E. sinensis.

Background: The Chinese grass shrimp,Palaemonetes sinensis, is an economically important freshwater shrimp in China, and the study of genetic diversity and structure can positively contribute to the exploration of germplasm resources and assist in the understanding ofP. sinensisaquaculture. Microsatellite markers are widely used in research of genetic backgrounds since it is considered an important molecular marker for the analyses of genetic diversity and structure. Hence, the aim of this study was to evaluate the genetic diversity and structure of wildP. sinensispopulations in China using the polymorphic microsatellite makers from the transcriptome.Results: Sixteen polymorphic microsatellite markers were developed forP. sinensisfrom transcriptome, and analyzed for differences in genetic diversity and structure in multiple wildP. sinensispopulations in China. Totally of 319 individual shrimps from seven different populations were genotyped to find that allelic polymorphisms varied in two to thirteen alleles seen in the entire loci. Compared to other populations analyzed, the two populations including LD and SJ showed lower genetic diversity. Both the genetic distance (D) and Wrights fixation index (F_ST) comparing any two populations also indicated that LD and SJ populations differed from the other five populations. An UPGMA tree analysis showed three main clusters containing SJ, LD and other populations which were also confirmed using STRUCTURE analysis.Conclusion: This is the first study where polymorphic microsatellite markers from the transcriptome were used to analyze genetic diversity and structures of different wildP. sinensispopulations. All the polymorphic microsatellite makers are believed useful for evaluating the extent of the genetic diversity and population structure ofP. sinensis. Compared to the other five populations, the LD and SJ populations exhibited lower genetic diversity, and the genetic structure was differed from the other five populations. Therefore, they needed to be protected against further declines in genetic diversity. The other five populations, LP, LA, LSL, LSY and LSH, are all belonging to Liaohe River Drainage with a relatively high genetic diversity, and hence can be considered as hot spots for in-situ conservation ofP. sinensisas well as sources of desirable alleles for breeding values.

The aquaculture industry of red swamp crayfish (RSC), Procambarus clarkii, has grown significantly in recent decades due to increasing market demand. In China, low water temperatures, particularly during overwintering, pose a challenge, hindering the development of the RSC aquaculture industry in northern regions. Understanding the molecular mechanism of RSCs’ responses to cold stress could be beneficial for its aquaculture practices. In this study, we exposed RSCs to 4 °C (T4) and 22 °C (T22: control) for 96 h. Transcriptomic and metabolomic analyses of hepatopancreas tissues were performed to identify key genes and metabolites that participate in cold stress response. A total of 787 differentially expressed genes (DEGs) and 198 differentially expressed metabolites (DEMs) were identified between T4 and T22. DEGs were significantly enriched in KEGG pathways related to carbohydrate, lipid, amino acid, and nucleotide metabolism, immunity, and signaling, while DEMs were significantly enriched in pathways associated with lipid and amino acid metabolism and membrane transport. The results indicated that cold stress altered RSCs’ metabolism and their innate immune system. This study provides valuable information to increase our understanding of cold stress responses in RSCs.

Nowadays, a particular focus is using microalgae to get high-valued health beneficiary lipids. The precise localisation of the lipid droplets (LDs) and biochemical changes are crucial to portray the lipid production strategy in algae, but it requires an in vivo tool to rapidly visualise LD distribution. As a novel strategy, this study focuses on detecting lipid bioaccumulation in a green microalga, Chlamydomonas reinhardtii using the aggregation-induced emission (AIE) based probe, 2-DPAN (C₂₄H₁₈N₂O). As the messenger molecule and stress biomarker, hydrogen peroxide (H₂O₂) activity was detected in lipid synthesis with the AIE probe, TPE-BO (C₃₈H₄₂B₂O₄). Distinctive LDs labelled with 2-DPAN have elucidated the lipid inducing conditions, where more health beneficiary α-linolenic acid has been produced. TPE-BO labelled H₂O₂ have clarified the involvement of H₂O₂ during lipid biogenesis. The co-staining procedure with traditional green BODIPY dye and red chlorophyll indicates that 2-DPAN is suitable for multicolour LD imaging. Compared with BODIPY, 2-DPAN was an efficient sample preparation technique without the washing procedure. Thus, 2-DPAN could improve traditional fluorescent probes currently used for lipid imaging. In addition, the rapid, wash-free, multicolour AIE-based in vivo probe in the study of LDs with 2-DPAN could advance the research of lipid production in microalgae.

High mortalities and highly variable results during the subsequent development of post-thaw larvae have been widely considered as key issues restricting the application of cryopreservation techniques to support genetic improvement programs and hatchery production in farmed marine bivalve species. To date, few studies have been undertaken to investigate the effects of cryodamage at the molecular level in bivalves. This study is the first to evaluate the effect of larval cryopreservation on the epigenetics of the resultant progenies of the Pacific oyster Crassostrea gigas. The results show that the level of DNA methylation was significantly (p < 0.05) higher and lower than that of the control when the trochophore larvae were revived and when they developed to D-stage larvae (day 1 post-fertilization), respectively, but the level returned to the control level from day 8 post-fertilization onwards. The expression of the epigenetic regulator genes DNMT3b, MeCP2, JmjCA, KDM2 and OSA changed significantly (p < 0.05) when the trochophore larvae were thawed, and then they reverted to the control levels at the D- and later larval developmental stages. However, the expression of other epigenetic regulator genes, namely, MBD2, DNMT1, CXXC1 and JmjD6, did not change at any post-thaw larval developmental stage. For the newly thawed trochophore larvae, the amount of methylated H3K4Me1 and H3K27Me1 significantly changed, and the expression of all Jumonji orthologs, except that of Jumonji5, significantly (p < 0.05) decreased. These epigenetic results agree with the data collected on larval performances (e.g., survival rate), suggesting that the effect period of the published cryopreservation technique on post-thaw larvae is short in C. gigas.

Torix tukubana is a poorly understood proboscidate leech species, generally an ectoparasite on amphibian species. In this study, the complete mitochondrial genome (mitogenome) of T. tukubana was sequenced using next-generation sequencing (NGS), and the essential characteristics, gene arrangement, and phylogenetic relationship were analyzed. The results showed that the T. tukubana mitogenome was 14,814 bp in length, consisting of 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and 1 control region (CR). The mitogenome composition presented a strong A + T bias (73.6%). All tRNAs had the typical clover structure except the trnS1 (TCT), whose dihydrouridine (DHU) arm was short, having only one complementary base pair. Additionally, 8 gene order patterns were identified among 25 known Hirudinea species, and T. tukubana was identical to the Hirudinea ground pattern. A phylogenetic analysis based on 13 PCGs indicated that all the studied species clustered into three main clades. The relationships among Hirudinea species were basically consistent with their gene arrangement results, but different from their morphological taxonomy. T. tukubana was in the monophyletic group of Glossiphoniidae, a finding consistent with previous research. Our results provided the essential characteristics of the T. tukubana mitogenome. As the first complete mitogenome of Torix, it could offer valuable information for a systematic understanding of the Hirudinea species.