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Simple Summary: Great temperature variations increase the risk of illness or death in the Chinese soft-shelled turtle, potentially leading to significant economic losses in the farming industry. Therefore, it is crucial to find effective strategies to overcome temperature stress-induced damage in the farming industry. Herein, we evaluated the roles of dietary tannic acid in regulating liver health under temperature fluctuations. The results found that 2 g/kg dietary tannic acid improved the activities of antioxidant enzymes and alleviated histological injuries in the liver. Furthermore, it affected the metabolic profiles and regulated energy-related signaling pathways in the liver to deal with cold stress, such as adipocytokine signaling pathway, steroid biosynthesis, and α-linolenic acid metabolism. Generally, this research indicated that 2 g/kg TA could protect hepatic health from temperature fluctuations by enhancing the antioxidant capacity, reducing histological injuries, and regulating lipid-related signaling pathways. To assess the impact of tannic acid (TA) on the hepatic health of the Chinese soft-shelled turtle, the individuals were fed diets containing 0 (CG), 0.5, 1, 2, and 4 g/kg TA diets for 60 days (0 hps). Afterwards, the turtles were challenged with 15 °C cold stress for 24 h (24 hps) and then recovered to 28 °C for 24 h (48 hps). The results indicated that 4 g/kg TA has a significant toxic effect on the turtles after 60-day administration. The hepatic T-SOD, CAT, GSH-Px, and T-AOC activities in the TA2 were increased at 0 hps and 24 hps (p < 0.05) compared with CG. Similarly, Sod1, Sod2, Cat, Gsh-px3, and Gsh-px4 mRNA levels in the TA2 were higher than in the other four groups at 0 hps and 24 hps (p < 0.05). The histology data showed that 4 g/kg TA induced injuries in liver at 0 hps and after temperature fluctuation, whereas the 2 g/kg TA effectively attenuated the hepatic injuries. A total of 202 differentially expressed metabolites (DEMs) in the CG vs. TA2 and 115 DEMs in the LTCG vs. LTTA2 were separately detected by the metabolome. The cephalosporin C, protoporphyrin, bis(2-ethylhexyl) phthalate, 2-acetamidoethylphosphonat, verbasosid, and norcocain, were obvious DEMs in the CG vs. TA2. Furthermore, valienone 7-phosphate, 5-HETE, pregnanetriolone, 4-keto-anhydrotetracyclin, dephospho-CoA, and lysoPC(18:4(6Z,9Z,12Z,15Z)/0:0) were top DEMs in the LTCG vs. LTTA2. The "adipocytokine signaling pathway" and "AMPK signaling pathway" were the key pathways enriched in the CG vs. TA2, while "fatty acid biosynthesis", "steroid biosynthesis", and "linoleic acid metabolism" were most abundant in the LTCG vs. LTTA2. Generally, this research indicated that 2 g/kg TA could protect hepatic health from temperature fluctuations by improving antioxidant capacity, reducing histological injuries, and regulating lipid-related signaling pathways. [ABSTRACT FROM AUTHOR]

The Chinese soft-shelled turtle (Pelodiscus sinensis), as a type of warm-water reptile, could be induced to massive death by sharp temperature decline. Hence, the mechanism of spleen tissue responding to cold stress in the P. sinensis was investigated. The present results showed that the superoxide dismutase (SOD) activity declined from 4 to 16 days post-cold-stress (dps), while the catalase (CAT) and glutathione peroxidase (GSH-Px) activities increased, from 4 to 8 dps in the 14 °C (T14) and 7 °C (T7) stress groups. The spleen transcriptome in the T7 group and the control group (CG) at 4 dps obtained 2625 differentially expressed genes (DEGs), including 1462 upregulated and 1663 downregulated genes. The DEGs were enriched mainly in the pathways "intestinal immune network for IgA production" (Pigr, Il15ra, Tnfrsf17, Aicda, and Cd28), "toll-like receptor signaling pathway" (Mapk10, Tlr2, Tlr5, Tlr7, and Tlr8), and "cytokine–cytokine receptor interaction" (Cx3cl1, Cx3cr1, Cxcl14, Cxcr3, and Cxcr4). The metabolomic data showed that esculentic acid, tyrosol, diosgenin, heptadecanoic acid, and 7-ketodeoxycholic acid were obviously increased, while baccatin III, taurohyocholate, parthenolide, enterolactone, and tricin were decreased, in the CG vs. T7 comparison. Integrated analysis of the two omics revealed that "glycine, serine and threonine metabolism", "FoxO signaling pathway", and "neuroactive ligand–receptor interaction" were the main pathways responding to the cold stress. Overall, this work found that low temperature remarkably influenced the antioxidant enzyme activities, gene expression pattern, and metabolite profile in the spleen, indicating that immunity might be weakened by cold stress in P. sinensis. [ABSTRACT FROM AUTHOR]

To investigate the effect of tannic acid (TA) on the growth, disease resistance, and intestinal health of Chinese soft-shelled turtles, individual turtles were fed with 0 g/kg (CG), 0.5 g/kg, 1 g/kg, 2 g/kg, and 4 g/kg TA diets for 98 days. Afterwards, the turtles' disease resistance was tested using Aeromonas hydrophila. The results showed that 0.5–4 g/kg of dietary TA increased the growth performance and feed utilization (p < 0.05), with 2.38 g/kg being the optimal level for the specific growth rate (SGR). The addition of 0.5–4 g/kg of TA in diets increased the mucosal fold height and submucosa thickness of the small intestine, which reached a maximum of 2 g/kg. The addition of 0.5–2 g/kg of TA effectively reduced the cumulative mortality that had been induced by A. hydrophila, with the 2 g/kg dosage leading to the lowest mortality. Additionally, 1–4 g/kg of TA improved the T-SOD, CAT, and GSH-Px activities during infection, while 2 g/kg of dietary TA enhanced the richness and diversity of the microbiota, for example, by increasing Actinobacteria but inhibiting Firmicutes. The transcriptome demonstrated that the predominant differentially expressed genes (DEGs) in TA2 were mainly enriched in the PPAR signaling pathway (Acsl5, Apoa2, Apoa5, Fabp1, Fabp2, and Fabp6); in glycine, serine, and threonine metabolism (Chdh, Gatm, and Shmt1); and in steroid biosynthesis (Cel, Hsd17b7, Soat2, and Sqle). The main differentially expressed metabolites (DEMs) that were discovered by means of metabolome analysis included cholylhistidine, calcipotriol, 13-O-tetradecanoylphorbol 12-acetate, and hexahomomethionine in CG vs. TA2. Integrative analyses of two omics revealed that 2 g/kg of TA mitigated inflammation by activating the PPAR signaling pathway and regulating the lipid metabolism via multiple pathways, such as steroid biosynthesis and α-linolenic acid metabolism. In general, the inclusion of 2 g/kg of TA in turtle diets can optimally promote growth and bacterial resistance by maintaining intestinal health and improving antioxidant capacity. [ABSTRACT FROM AUTHOR]

Simple Summary: As a warm-water species, The Chinese soft-shelled turtle is fragile to external cold stress. It has been reported that the sudden temperature decline can lead to massive turtle death, which brings about huge economic loss in the farming industry. Our study can help us to understand how cold stress can damage turtles. In addition, it can promote knowing about the responding mechanism of turtles to low temperatures with molecular, metabolic, and pathway analyses. The Chinese soft-shelled turtle (Pelodiscus sinensis), a type of warm-water reptile, is frequently chosen as the model animal to understand how organisms respond to environmental stressors. However, the responsive mechanism of P. sinensis to natural cold stress is unclear, especially in terms of metabolic pattern and molecular pathways. Herein, plasma biochemical, hepatic morphological, apoptotic, transcriptomic, and metabolomic detection methods were performed to investigate the response of P. sinensis to acute cold stress. A consistent increase in plasma AST and ALT activities with a decline in ALP activity was found following 14 °C and 7 °C cold stress compared with the control group. Plasma GLU, TG, CHO, and HDL contents, reflecting energy metabolism, were decreased to lower levels from 2 to 16 days post cold stress (dps). Histological and TUNEL detection in the liver demonstrated that the 14 °C and 7 °C cold stress caused severe morphological damage and cell apoptosis in a time-dependent manner. DEGs in the biosynthesis of fatty acids (Acsbg2, Acsl3, Acsl4, Acsl5, Mcat, and Acacb), as well as unsaturated fatty acids (Hsd17b12, Elovl7, Scd, and Baat), starch and sucrose metabolism (Pgm1, Pgm2, and Treh), and apoptosis (Ddit3, Gadd45a, Lmnb1, Tuba1c, Tnf, Tnfsf10, Fos, Itpr1, and Ctso) were discovered in the transcriptome under cold stress. The metabolomic data showed that metabolites, including chenodeoxycholic acid, oleoylethanolamide, uric acid, fructose 1,6-bisphosphate, CMP, and S-(Hydroxymethyl)-glutathione, were remarkably altered in the cold stress groups. Combined transcriptomic and metabolomic data revealed that pyrimidine metabolism, amino acid metabolism, and pyruvate metabolism were the most significant pathways regulated by the low-temperature exposure. Overall, this work suggests that 14 °C and 7 °C cold stress could induce obvious morphological damage and apoptosis in the liver at 4 dps. Moreover, energy metabolism and amino acid metabolism were the main signaling pathways in response to cold stress for P. sinensis. [ABSTRACT FROM AUTHOR]

Simple Summary: The growth pattern of the Chinese soft-shelled turtle (Pelodiscus sinensis) is remarkably sexually dimorphic. However, the molecular mechanism of this phenomenon has been studied mainly in the gonadal tissues of P. sinensis, and no article has been published on the study of sex differentiation in the brain of P. sinensis. Here, we performed a whole transcriptome analysis of the brains of adult female and male P. sinensis. We obtained a set of differentially expressed genes and transcription factors, which we annotated with GO and KEGG, and screened some genes and pathways related to growth. In addition, through GESA analysis, we screened out two genes, LHX1 and FGF7, which are related to both growth and sex differentiation, and through protein interaction analysis of these genes, we screened out eight genes and verified the expression levels of these eight genes in the brain of P. sinensis by qRT-PCR, which supported the reliability and accuracy of our transcriptome analysis. This study provides a solid foundation for analyzing the growth mechanism of sexual dimorphism in P. sinensis and even other turtles. The Chinese soft-shelled turtle (Pelodiscus sinensis) is an economically important species in aquaculture, and its growth pattern is characterized by significant sexual dimorphism. However, the underlying molecular mechanisms of this phenomenon have mostly been investigated in the gonadal tissues of P. sinensis, and there are no articles on sex differentiation from the brain of P. sinensis. Here, we analyzed transcriptomes of the brains of adult male and female P. sinensis using high-throughput Illumina sequencing technology, establishing a set of differential genes and differential transcription factors. The data showed that there were 908 genes with significant differences in expression, of which 357 genes were up-regulated and 551 genes were down-regulated. We annotated using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and screened some genes and pathways related to growth. There were 282 growth-related differential genes and 181 sex-related differential genes. We screened the genes' growth hormone receptor (GHR) and vascular endothelial growth factor A (VEGFA), which may be related to the growth of P. sinensis. The pathways related to the growth and development of P. sinensis are the growth hormone synthesis, secretion, and action pathway; the MAPK (mitogen-activated protein kinase) pathway; and the calcium signaling pathway. In addition, through gene set enrichment analysis (GSEA), we screened out two genes, LIM homeobox protein 1 (LHX1) and fibroblast growth factor 7 (FGF7), which are related to both growth and sex differentiation, and through protein interaction analysis of these genes, we screened out eight genes, including LHX1, FGF7, GHR, fibroblast growth factor 4 (FGF4), EGFR, BMP3, GLI family zinc finger 2 (GLI2), and neuronal differentiation 1 (NEUROD1), and verified the expression levels of these eight genes in the brain of the P. sinensis by real-time quantitative PCR (qRT-PCR), which supported the reliability and accuracy of our transcriptome analysis. Our study provides a solid foundation for analyzing the mechanisms of sexual-dimorphic growth of P. sinensis and even other turtles. [ABSTRACT FROM AUTHOR]

Narrow-headed softshell turtles constitute a group of critically endangered freshwater turtles that belong to the family Trionychidae. Here, we determine the complete mitogenome of the Burmese narrow-headed softshell turtle Chitra vandijki. The length of the mitochondrial genome was 16,614 bp, composed of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and twelve noncoding regions. The phylogenetic analysis strongly indicated that C. vandijki is closely related to C. indica. The mitochondrial genome will contribute to the genetic research and conservation of C. vandijki in the future.

Simple Summary: Hibernation in turtle species is an adaptive survival strategy to colder winter conditions or food restrictions. However, the mechanisms underlying seasonal adaptions remain unclear. In this study, we isolated and performed scRNA-seq analysis on P. cantorii hemocytes in the active state and during hibernation to classify the hemocyte types and obtain the relevant cell maps. We identified the marker genes of each cell population and the differentiation pathways associated with their maturation. We also discovered different immune-related genes that might play crucial roles in hemocyte differentiation before and after hibernation. Our study aims to provide a reference dataset for the unified classification of P. cantorii hemocytes and improve our understanding of the immune system of P. cantorii. Hibernation in turtle species is an adaptive survival strategy to colder winter conditions or food restrictions. However, the mechanisms underlying seasonal adaptions remain unclear. In the present study, we collected hemocytes from Pelochelys cantorii and compared the molecular signature of these cells between the active state and hibernation period based on single-cell RNA sequencing (scRNA-seq) analysis. We found six cell types and identified a list of new marker genes for each cell subpopulation. Moreover, several heat shock genes, including the Hsp40 family chaperone gene (DNAJ) and HSP temperature-responsive genes (HSPs), were upregulated during the hibernation period, which predicted these genes may play crucial roles in the stress response during hibernation. Additionally, compared to hemocytes in the active state, several upregulated differentially expressed immune-related genes, such as stat1, traf3, and socs6, were identified in hemocytes during the hibernation period, thus indicating the important immune function of hemocytes. Therefore, our findings provide a unified classification of P. cantorii hemocytes and identify the genes related to the stress response, thereby providing a better understanding of the adaptive mechanisms of hibernation. [ABSTRACT FROM AUTHOR]