Pelodiscus Sinensis Research Articles

Replacing sea fish with black soldier fly fermentation homogenate in diet for Pelodiscus sinensis: growth, intestinal development and hepatic health

Abstract Black soldier fly larvae (BSFL) meal has the potential to partially replace fish meal in the diet of various aquatic animals. The fermentation treatment of BSFL can retain more nutrients and reduce processing and transportation costs. This study investigated the effects of partially replacing fish meal with Black Soldier Fly Fermentation Homogenate (BSFFH) on the growth performance and health of Chinese soft-shelled (Pelodiscus sinensis) turtle. The experiment was divided into 4 different groups of juvenile P. sinensis diets. The control diet included 60% compound feed and 40% sea fish. The 34%, 61%, and 82% substitution groups were fed mixtures, and varying percentages of sea fish were replaced with BSFFH. The results indicate that replacing 34% and 61% sea fish with BSFFH significantly improved growth (P < 0.05). The 61% substitution significantly decreased the muscle fiber size while the 82% substitution significantly upregulated the expression of myogenic genes MYF5 and MRF4 (P < 0.05). Furthermore, replacing sea fish with BSFFH significantly increased hepatic TG content (P < 0.05) and induced mild liver fibrosis, while it reduced the TG content in skeletal (P < 0.05). However, BSFFH did not affect subcutaneous fat weight (P > 0.05). Lastly, the 34% substitution significantly increased the intestine villus height and the ratio of villus height/crypt depth, while higher substitution reduced both values. In addition, the 61% substitution increased the mucus secreted by the intestine goblet cells. In conclusion, partially replacing sea fish with BSFFH improves the growth performance and intestine structure of Chinese soft-shelled turtles. However, a high level of BSFFH could negatively affect growth performance, intestinal structure, and hepatic health.

Transcriptomic and Proteomic Analyses of the Immune Mechanism in Pathogenetic and Resistant Chinese Soft-Shelled Turtle (Pelodiscus sinensis) Infected with Aeromonas hydrophila

Background: As intensive aquaculture practices have progressed, the prevalence of bacterial diseases in the Chinese soft-shell turtle (Pelodiscus sinensis) has escalated, particularly infections caused by Aeromonas hydrophila, such as ulcerative dermatitis and abscess disease. Despite this, little is known about their immune defenses against this pathogen. Methods: Our study pioneers an integrated analysis of transcriptomics and proteomics to investigate the immune responses of Chinese soft-shelled turtles to A. hydrophila infection. Results: The investigation revealed significant differences in immune-related pathways between groups susceptible and resistant to A. hydrophila infection after 4 days. A total of 4667 and 3417 differentially expressed genes (DEGs), 763 and 568 differentially expressed proteins (DEPs), and 13 and 5 correlated differentially expressed genes and proteins (cor-DEGs-DEPs) were identified in susceptible and resistant Chinese soft-shelled turtles, respectively. In the resistant group, upregulation of immune-related genes, such as CD3ε and CD45, enhanced T-cell activation and the immune response. The proteomic analysis indicated that immune proteins, such as NF-κB1, were significantly upregulated in the resistant group. The correlation analysis between transcriptomics and proteomics demonstrated that the CD40 gene and protein, differentially expressed in the resistant group compared to the control group, were commonly upregulated within the Toll-like receptor signaling pathway. Conclusions: The transcriptomic and proteomic data obtained from this study provide a scientific foundation for understanding the immune mechanisms that enable the Chinese soft-shelled turtle to resist A. hydrophila infection.

Toll-like Receptor Expression in Pelodiscus sinensis Reveals Differential Responses after Aeromonas hydrophila Infection.

Background: Toll-like receptor (TLR), as an important pattern recognition receptor, is a bridge between non-specific immunity and specific immunity, and plays a vital role in the disease resistance of aquatic animals. However, the function of TLR in Pelodiscus sinensis is still unclear. Methods and Results: The sequence characteristics and homology of three TLRs (PsTLR2, PsTLR3 and PsTLR5) were determined in this investigation. Their annotation and orthologies were supported by phylogenetic analysis, functional domain prediction, and sequence similarity analysis. qPCR showed that the identified TLRs were expressed in all tissues, among the high expression of PsTLR5 in the brain and liver and the high expression of PsTLR2 and PsTLR3 in the liver. PsTLR2 mRNA expression increased 6.7-fold in the liver 12 h after Aeromonas hydrophila infection, while the mRNA expression of PsTLR3 was down-regulated by 0.29 times in liver and 0.31 times in spleen. The mRNA expression of PsTLR5 was significantly up-regulated in four immune tissues, and it was up-regulated by 122.8 times in the spleen after 72 h infection. Finally, the recombinant proteins of extracellular LRR domains of these three TLRs were obtained by prokaryotic expression technology, and the binding tests were performed to discover their ability of binding pathogenic microorganisms. Microbial binding test showed that rPsTLR2, rPsTLR3 and rPsTLR5 can combine A. hydrophila, Edwardsiella tarda, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus agalactiae and Candida albicans, while rPsTLR3 can bind A. hydrophila, E. tarda, V. parahaemolyticus and C. albicans. Conclusions: Our findings suggested that TLRs may be crucial to turtles' innate immune response against microbes.

Establishment and population genetic analysis of SNP fingerprinting of Chinese soft-shelled turtle (Pelodiscus sinensis)

Chinese soft-shelled turtle (Pelodiscus sinensis) is an important aquaculture species in China. However, with the continuous development of P. sinensis cultures, problems related to germplasm degradation and population mixing have become increasingly prominent. This has seriously affected the protection and utilization of germplasm resources by P. sinensis. To broaden the understanding of the germplasm resources of P. sinensis and improve the efficiency of germplasm identification, Super-GBS sequencing technology was used to conduct population genetic analysis of P. sinensis samples from six different populations distributed in five provinces. As a result, 1464,488 SNPs were identified. Genetic structure analysis revealed that the six P. sinensis populations could be divided into three sub-populations. The genetic differentiation coefficient of the DT and CY populations was very low (Fst=0.0088), indicating that differentiation had not yet occurred. Additionally, 15 KASP core markers for the identification of P. sinensis populations were developed using KASP typing technique for the first time. Genetic information can lay a foundation for the protection and utilization of germplasm resources by P. sinensis, and the fingerprinting database developed in this study provides a practical tool for authenticating P. sinensis.

Present and future distribution of the European pond turtle versus seven exotic freshwater turtles, with a focus on Eastern Europe

Freshwater turtles are often used as terrarium pets, especially juveniles of exotic species. At the adult stage they are often released by their owners into the wild despite their high invasion potential. In Europe these thermophilic potentially invasive alien species occupy the habitats of the native European pond turtle Emys orbicularis (Linnaeus, 1758), with new records from the wild being made specifically in Eastern Europe (Latvia and Ukraine) during recent decades. Assessing the potential of alien freshwater turtles to establish in new territories is of great concern for preventing invasion risks while preserving native biodiversity in the present context of climate change. We explored this issue by identifying the present and future (by 2050) suitable habitats of the European pond turtle and several potentially invasive alien species of freshwater turtle already settled in Europe, using a geographic information system (GIS) modelling approach based on datasets from CliMond for climate, Near-global environmental information (NGEI) for freshwater ecosystems (EarthEnv) and Maxent modelling using open-access databases, data from the literature and original field data. Modelling was performed for seven species of alien freshwater turtles occurring from the extreme northern to southern borders of the European range of E. orbicularis: the pond slider Trachemys scripta (Thunberg and Schoepff, 1792), the river cooter Pseudemys concinna (Le Conte, 1830), the Florida red-bellied cooter Pseudemys nelsoni (Carr, 1938), the false map turtle Graptemys pseudogeographica (Gray, 1831), the Chinese softshell turtle Pelodiscus sinensis (Wiegmann, 1835), the Caspian turtle Mauremys caspica (Gmelin, 1774) and the Balkan terrapin Mauremys rivulata (Valenciennes, 1833). In Ukraine, the most Eastern limit of E. orbicularis distribution, were previously reported northern American originated T. scripta, M. rivulata, M. caspica, whereas in Latvia, Emys’ most northern limit, were additionally reported P. concinna, P. nelsoni, G. pseudogeographica and Asia originated P. sinensis. The resulting Species Distribution Models (SDM) were of excellent performance (AUC > 0.8). Of these alien species, the most potentially successful in terms of range expansion throughout Europe were T. scripta (34.3% of potential range expansion), G. pseudogeographica (24.1%), and M. caspica (8.9%) and M. rivulata (4.3%) mainly in Eastern Europe, especially in the south of Ukraine (Odesa, Kherson, Zaporizhzhia regions, and Crimean Peninsula). Correlation between the built SDMs for the native E. orbicularis and the invasive alien T. scripta was reliably high, confirming the highly likely competition between these two species in places they cooccur. Moreover, a Multiple Regression Analysis revealed that by 2050, in most of Europe (from the western countries to Ukraine), the territory overlap between E. orbicularis and potentially invasive alien species of freshwater turtles will increase by 1.2 times, confirming higher competition in the future. Importantly, by 2050, Eastern Europe and Ukraine are predicted to be the areas with most suitable habitats for the European pond turtle yet with most limited overlap with the invasive alien species. We conclude that Eastern Europe and Ukraine are the most relevant priority conservation areas for the European pond turtle where it is now necessary to take protective measures to ensure safe habitat for this native species on the long-term.

Identification and expression analysis of NOD-like receptor gene family in response to Aeromonas hydrophila and poly I:C challenge in Chinese soft-shelled turtle (Pelodiscus sinensis)

Nucleotide-binding domain (NOD)-like receptors (NLRs), a type of pattern recognition receptor (PRR), specifically recognize pathogen-associated molecular patterns and damage-associated molecular patterns, playing crucial roles in the immune system. Herein, the composition, expression pattern, and co-expressed pathways of NLRs in Pelodiscus sinensis (PsNLRs) were analyzed. Eight PsNLRs, located on seven chromosomes, were first identified from the genome. Phylogenetic analysis revealed that PsNLRs were most closely related to the NLRs of the western painted turtle and the green sea turtle, and could be clustered into four subfamilies. Besides, the expression profile of PsNLRs exhibited tissue-specificity after infection with Aeromonas hydrophila or poly I:C. Nonetheless, PsCIITA and PsNLRP3.2 displayed infection-specific expression patterns, whereas other PsNLRs showed similar expression patterns during A. hydrophila and poly I:C infections. Weighted gene co-expression network analysis found that six PsNLRs were generated in the turquoise module, in which several immune-related signaling pathways were enriched, including “NOD-like receptor signaling pathway”, “NF-κB signaling pathway”, “PI3K-Akt signaling pathway”, “Chemokine signaling pathway”, “Antigen processing and presentation”, and ”Toll-like receptor signaling pathway”. Additionally, three immune-related genes, NF-κB1, TRAF3, and PIK3CG, were identified as hub genes. These results indicated that PsNLRs may play key roles in regulating immune responses in P. sinensis. Overall, an in-depth study of the NLR gene family in P. sinensis would yield insights into developing strategies to combat bacterial and viral infections.

Identification and expression analysis of dmc1 in Chinese soft-shell turtle (Pelodiscus sinensis) during gametogenesis

DNA meiotic recombinase 1 (disrupted meiotic cDNA, Dmc1) protein is homologous to the Escherichia coli RecA protein, was first identified in Saccharomyces cerevisiae. This gene has been well studied as an essential role in meiosis in many species. However, studies on the dmc1 gene in reptiles are limited. In this study, a cDNA fragment of 1,111 bp was obtained from the gonadal tissues of the Chinese soft-shell turtle via RT-PCR, containing a 60 bp 3′ UTR, a 22 bp 5′ UTR, and an ORF of 1,029 bp encoding 342 amino acids, named Psdmc1. Multiple sequence alignments showed that the deduced protein has high similarity (>95 %) to tetrapod Dmc1 proteins, while being slightly lower (86–88 %) to fish species.Phylogenetic tree analysis showed that PsDmc1 was clustered with the other turtles’ Dmc1 and close to the reptiles’, but far away from the teleost’s. RT-PCR and RT-qPCR analyses showed that the Psdmc1 gene was specifically expressed in the gonads, and much higher in testis than the ovary, especially highest in one year-old testis. In situ hybridization results showed that the Psdmc1 was mainly expressed in the perinuclear cytoplasm of primary and secondary spermatocytes, weakly in spermatogonia of the testes. These results indicated that dmc1 would be majorly involved in the developing testis, and play an essential role in the germ cells’ meiosis. The findings of this study will provide a basis for further investigations on the mechanisms behind the germ cells’ development and differentiation in Chinese soft-shell turtles, even in the reptiles.

Effects of a Chinese herbal medicine mixture on growth performance, immune response, and gene expression in Chinese soft-shelled turtles (Pelodiscus sinensis)

Chinese herbal medicines (CHMs), known for their safety, low toxicity, and minimal impact on the environment, are often used as a natural feed additive in aquaculture to prevent or control diseases of aquatic animals. However, their effect on cell responses of Chinese soft-shelled turtle (Pelodiscus sinensis) remains unexplored. In this study, the extract mixed with four Chinese herbs of Astragalus membranaceus, Lycium barbarum, Rhizoma polygonati and Codonopsis pilosula in proportions (7:8:3:2) was used as a feed additive for 60 days to study their effects on the growth performance and immune response of P. sinensis in greenhouse mode. Results showed that the weight gain rate and the specific growth rate in the CHMs group were 46.63 % and 0.64 %, which were 1.13- and 1.15-fold of that in the control group, respectively. Besides, CHMs could significantly improve the survival rate by 76.94 % after artificial infection of Aeromonas hydrophila. The CHMs group also exhibited significant increases in the activities of total superoxide dismutase (27.76 %), catalase (41.28 %), glutathione peroxidase (14.62 %), and glutathione sulfur transferase (36.75 %) compared to the control group. Conversely, malondialdehyde concentration was reduced to 67.82 % of that in the control group. Moreover, the concentration of lysozyme and complement C3, as well as the activity of acid phosphatase, rose by 16.43 %, 24.30 %, and 27.68 %, respectively. Comparative transcriptome analysis revealed that growth, immunity, and lipid metabolism-related pathways are involved in the response to CHMs. Among these, the two pathways of the cell cycle and the cytokine-cytokine receptor interaction may play important roles in the growth and immunity of P. sinensis. SMOX, STAT3, and HMGCS1 may serve as key genes in CHMs-stimulated immune response in P. sinensis; GADD45B, ARG1, ACVR1C, and BMP7 may be crucial genes in promoting the growth of P. sinensis. This study provides a theoretical and practical basis for the green and efficient culture of P. sinensis.

Transcriptome and pathophysiological analysis during Bacillus cereus group infection in Pelodiscus sinensis uncovered the importance of iron and toll like receptor pathway

The Chinese softshell turtle (CST; Pelodiscus sinensis) is an important freshwater aquaculture species with high economic value. CST is farmed throughout Asia, especially in China and Taiwan. However, the presence of diseases, particularly those caused by the Bacillus cereus group, poses significant threats to commercial CST farming. A recent study has unveiled new genospecies within the B. cereus group, Bacillus shihchuchen. Within this group, strain QF108–045 stands out for its high virulence, notably leading to severe septicemia in CST. This study aimed to explore the transcriptome and pathophysiological changes in CSTs infected with QF108–045. Upon infection with QF108–045, turtles exhibited upregulation of Toll-like receptor (TLR) 2, 4, and 5, among which, TLR5 was significantly upregulated. Activation of TLR signaling leading to elevated levels of IL-1β, TNFα, and Th17 cytokines, which subsequently activate nuclear factor kappa B (NF-κB). CSTs challenged with QF108–045 exhibited a substantial decrease packed cell volume, indicating severe hemolysis. The notable upregulation of transferrin, ZIP8/14, and HO-1 indicates an active transfer of iron or heme into cells, and melanomacrophages in the spleen showed a positive signal in Perl's Prussian blue staining, implying their importance as essential iron storage cells. However, despite the hemolysis, ferroptosis was inhibited by the upregulation of system Xc− related genes. Additionally, our study revealed a notable increase in TLR5 expression following immunization with recombinant flagellin from QF108–045, coupled with analysis of protein tertiary docking modules. These findings advance our understanding of defense mechanisms in CSTs during QF108–045 infection, providing valuable insights for future vaccine development efforts.

Adaptation and feeding preference of Chinese soft-shelled turtle (Pelodiscus sinensis) to different feeding levels in rice–turtle co-culture system

Rice–turtle co-culture is an ecological method involving a low exogenous input of chemicals and excessive feeding might increase the cost and reduce the mutual beneficial effect. To determine the optimal feeding level for co-cultured P. sinensis and for its adaptation, the turtles (878.0±10.3 g) were fed at feeding levels of 0.7 %, 1.4 % and 2.1 % for 90 days. The observation of feeding behavior showed that a low feeding level prompted the turtles to move into field paddies and prolonged their stay. The specific growth rate increased with increasing feeding level, but did not further increase when it exceeded 1.4 %, and the feed conversion ratio increased with increasing feeding level from 0.7 % to 2.1 %. The activities of digestive enzymes were higher in the group with a low feeding level. The plasma triglyceride and total cholesterol levels increased with increasing feeding level, while the creatinine level was significantly lower at a high feeding level of 2.1 %. The trend analysis of gene expression showed that the expression of most of differentially expressed genes (DEGs) in the brain decreased with increasing feeding levels from 0.7 % to 1.4 % and did not further decrease at a feeding level of 2.1 %, while in the gut, most of the genes were significantly downregulated or upregulated at a feeding level of 1.4 %. In the brain, the pathways associated with the DEGs were involved in the relaxin signaling pathway, melanogenesis and the age–rage signaling pathway in diabetic complications. In the gut, the DEGs were most associated with pancreatic secretion, protein digestion and absorption. The related genes expression was consistent with feeding behavior, growth and physiological metabolism. These findings suggest that co-cultured turtles can adapt to different feeding levels, that the optimal feeding level for co-cultured turtles is 1.4 %, and that additional feeding reduced the economic and ecological benefits of co-culture.

Peripheral hearing sensitivity is similar between the sexes in a benthic turtle species despite the larger body size of males.

Sexually dimorphic hearing sensitivity has evolved in many vertebrate species, and the sex with a larger body size typically shows more sensitive hearing. However, generalizing this association is controversial. Research on sexually dimorphic hearing sensitivity contributes to an understanding of auditory sense functions, adaptations, and evolution among species. Therefore, the hypothesized association between body size and hearing needs further validation, especially in specific animal groups. In this study, we assessed hearing sensitivity by measuring auditory brainstem responses (ABRs) in both sexes of 3-year-old Chinese softshell turtles (Pelodiscus sinensis). In this species, male bodies are larger than those of female, and individuals spend most of their lives in the mud at the bottom of freshwater habitats. We found that for both sexes, the hearing sensitivity bandwidth was 0.2-0.9 kHz. Although males were significantly larger than females, no significant differences in ABR thresholds or latencies were found between males and females at the same stimulus frequency. These results indicate that P. sinensis hearing is only sensitive to low-frequency (typically <0.9 kHz) sound signals and that sexually dimorphic hearing sensitivity is not a trait that has evolved in P. sinensis. Physiological and environmental reasons may account for P. sinensis acoustic communication via low-frequency sound signals and the lack of sexually dimorphic hearing sensitivity in these benthic turtles. The results of this study refine our understanding of the adaptation and evolution of the vertebrate auditory system.

Integrative transcriptomics and metabolomics analysis provide insight into the formation of skin pigmentation diversity in Chinese soft-shelled turtle (Pelodiscus sinensis)

Chinese soft-shelled turtle (Pelodiscus sinensis) is an important freshwater breeding species in East and Southeast Asia. The most external differences among different strains are skin pigmentation and blotches, but the mechanism of their formation is unknown. To investigate the mechanism of skin pigmentation diversity in Chinese soft-shelled turtle, three unique phenotypes (Golden strain, Japanese strain and Qingxi black strain) were selected to observe the chromatophores, and the transcriptome and metabolome were compared. The results showed the presence of melanophores, xanthophores and iridophores in the skin of all three strains. However, there were differences in the composition and organelles of chromatophores. The upregulation of gene asip and elevated accumulation of glutathione and cysteine in Golden strain resulted in the production of pheomelanin, leading to yellow pigmentation in the skin. The upregulation of gene dct and elevated accumulation of indole-5, 6-quinone in Qingxi black strain resulted in the production of eumelanin, which made the skin appear black-brown. Japanese strain produced eumelanin and pheomelanin, however, the presence of melanosomes resulted in skin darkening and appeared dark green pigmentation. The white blotches of Gloden strain and Japanese strains were formed through increased production of iridophores, while the black blotches of Qingxi black strain were formed by inducing migration and apoptosis of melanophores within iridophores. In conclusion, the distinctive characteristics of the skin in three strains resulted from combination of melanin type, abundance of melanosomes and interaction between melanophores and iridophores. These results provided valuable reference for investigating the mechanisms underlying skin pigmentation diversity in Chinese soft-shelled turtle and other vertebrates.

Comparative transcriptome sequencing and weighted coexpression network analysis reveal growth-related hub genes and key pathways in the Chinese soft-shelled turtle (Pelodiscus sinensis)

The Chinese soft-shelled turtle (Pelodiscus sinensis) exhibits sexual dimorphism. Compared with females, males are considered to have higher economic value due to their accelerated growth, greater body mass, and longer skirt width. Studies focused on these sex disparities have largely neglected potential sex differences in growth. Here, we performed RNA sequencing of muscle tissue components from 1-year-old specimens to reveal gene expression patterns in P. sinensis. In our male and female cohorts, our analysis revealed, respectively, 388 and 526 upregulated differentially expressed genes (DEGs) and 1129 and 635 downregulated DEGs. Through weighted coexpression network analysis (WGCNA) and integration with phenotype data, we established two main gene modules: a light yellow module encompassing 191 genes (e.g., ACACB, CTH, HADHA, and CTNNB) that demonstrated a positive correlation with population traits, and a black module comprising 298 genes (e.g., CAV3, PIK3CD, SMAD3, and VEGFA) that demonstrated a negative correlation with population traits. We also performed a DEG evaluation and gene set enrichment analysis across individuals of different sizes and noted that pathways such as protein digestion and assimilation (ko04974), were substantially augmented in larger specimens. In these pathways, the collagen (COL) and solute carrier (SLC) gene families were noted to be crucial for sustaining body structure and facilitating nutrient and metabolite transportation. In conclusion, we elucidated the essential modules, pivotal genes, and pathways involved in gene expression differences among various P. sinensis size groupings. Our results provide novel insights for future studies on growth discrepancies in P. sinensis.

Chondrocranial anatomy of Testudo hermanni (Testudinidae, Testudines) with a comparison to other turtles.

Using histological cross-sections, the chondrocranium anatomy was reconstructed for two developmental stages of Hermann's tortoise (Testudo hermanni). The morphology differs from the chondrocrania of most other turtles by a process above the ectochoanal cartilage with Pelodiscus sinensis being the only other known species with such a structure. The anterior and posterior processes of the tectum synoticum are better developed than in most other turtles and an ascending process of the palatoquadrate is missing, which is otherwise only the case in pleurodiran turtles. The nasal region gets proportionally larger during development. We interpret the enlargement of the nasal capsules as an adaption to increase the surface area of the olfactory epithelium for better perception of volant odors. Elongation of the nasal capsules in trionychids, in contrast, is unlikely to be related to olfaction, while it is ambiguous in the case of Sternotherus odoratus. However, we have to conclude that research on chondrocranium anatomy is still at its beginning and more comprehensive detailed descriptions in relation to other parts of the anatomy are needed before providing broad-scale ecological and phylogenetic interpretations.

Aeromonas dhakensis, a pathogen associated with red abdominal shell disease in Chinese soft-shelled turtle Pelodiscus sinensis

Red abdominal shell disease is a major disease that has caused significant economic losses in Chinese soft-shelled turtle Pelodiscus sinensis aquaculture. Yet scarce information is available on Aeromonas dhakensis as a causal agent of red abdominal shell disease in P. sinensis. In the present study, a haemolytic and proteolytic A. dhakensis isolate (F04) was demonstrated as a causative agent of red abdominal shell disease in cultured P. sinensis. It carried virulent aerolysin, heat-labile cytotoxic enterotoxin, polar flagella, and lipase-encoding genes aer, alt, flaA, and lip, exhibited the mean lethal dose (LD50) value of 4.27×105 CFU/ml in P. sinensis, and developed multiple resistances against aminoglycosides, chloramphenicols, cephalosporins, lincosamides, macrolides, penicillins, peptides, sulfonamides, and tetracyclines antimicrobials. To our knowledge, this is the first study to identify a multiply resistant A. dhakensis strain as a pathogen of red abdominal shell disease in P. sinensis, and the findings of this study can also provide valuable insights into the virulence and antimicrobial resistance in Chinese soft-shelled turtle-pathogenic A. dhakensis.

Comparative Analysis of Physiological Responses and Intestinal Microbiota in Juvenile Soft-Shelled Turtle (Pelodiscus sinensis) Fed Four Types of Dietary Carbohydrates.

A 60 day feeding trial was conducted to evaluate the impacts of dietary carbohydrates with different complexities and configurations on the growth, plasma parameters, apparent digestibility, intestinal microbiota, glucose, and lipid metabolism of soft-shelled turtles (Pelodiscus sinensis). Four experimental diets were formulated by adding 170 g/kg glucose, fructose, α-starch, or cellulose, respectively. A total of 280 turtles (initial body weight 5.11 ± 0.21 g) were distributed into 28 tanks and were fed twice daily. The results showed that the best growth performance and apparent digestibility was observed in the α-starch group, followed by the glucose, fructose, and cellulose groups (p < 0.05). Monosaccharides (glucose and fructose) significantly enhanced the postprandial plasma glucose levels and hepatosomatic index compared to polysaccharides, due to the un-inhibited gluconeogenesis (p < 0.05). Starch significantly up-regulated the expression of the genes involved in glycolysis, pentose phosphate pathway, lipid anabolism and catabolism, and the transcriptional regulation factors of glycolipid metabolism (srebp and chrebp) (p < 0.05), resulting in higher plasma triglyceride levels and lipid contents in the liver and the whole body. The fructose group exhibited a lower lipid deposition compared with the glucose group, mainly by inhibiting the expression of srebp and chrebp. Cellulose enhanced the proportion of opportunistic pathogenic bacteria. In conclusion, P. sinensis utilized α-starch better than glucose, fructose, and cellulose.

A novel ACE inhibitory peptide from Pelodiscus sinensis Wiegmann meat water-soluble protein hydrolysate

Pelodiscus sinensis meat is a nutritional food and tonic with angiotensin-converting enzyme (ACE) inhibitory activities. To identify the bioactive substances responsible, several bioinformatics methods were integrated to enable a virtual screening for bioactive peptides in proteins identified within a water-soluble protein fraction of Pelodiscus sinensis meat by Shotgun proteomics. The peptides were generated from the identified proteins by in silico proteolysis using six proteases. A comparison of the numbers of proteins suitable for digestion with each enzyme and the iBAQ (intensity-based absolute quantification) values for these proteins revealed that bromelain and papain were the most suitable proteases for this sample. Next, the water solubility, toxicity, and ADMET (absorption/distribution/metabolism/excretion/toxicity) properties of these peptides were evaluated in silico. Finally, a novel ACE inhibitory peptide IEWEF with an IC50 value of 41.33 µM was identified. The activity of the synthesized peptide was verified in vitro, and it was shown to be a non-competitive ACE inhibitor. Molecular docking revealed that IEWEF could tightly bind to C-ACE, and N-ACE with energies less than 0 kJ mol−1, and the peptide IEWEF can form hydrogen bonds with C-ACE and N-ACE respectively. These results provide evidence that bioactive peptides in the water-soluble protein fraction account for (at least) some of the ACE inhibitory activities observed in Pelodiscus sinensis meat. Furthermore, our research provides a workflow for the efficient identification of novel ACE inhibitory peptides from complex protein mixtures.

Comparative analysis for nutrients, flavor compounds, and lipidome revealed the edible value of pond-cultured male Pelodiscus sinensis with different ages

Pelodiscus sinensis is an aquatic product with a long growth cycle in pond culture and high nutritional value meat. The flavor compounds, nutrients, and lipidome were investigated to explore the edible value changes of turtle meat aged 3 to 6 years (Y3 to Y6). Typically, P. sinensis meat is rich in high-quality protein (EAAI ≥81.22, AAS ≥86.47). Y6 has the highest level of Se, protein, amino acids, and high unsaturated fatty acids, including EPA + DHA. Y5 has the most delicious amino acids, polyunsaturated fatty acids, and key odorant content. The stronger flavor of Y5 may be mainly related to C18:2n6t and C18:2n6c. Further, triacylglycerols (TAG) and phosphatidylcholine (PC) were significant changes in Y5. Additionally, PI (16:0/18:1) was identified as the potential biomarker. These results provided available information on P. sinensis marketing age and revealed the potential impact of nutrients on the formation of VOCs.

Nanoplastic pollution changes the intestinal microbiome but not the morphology or behavior of a freshwater turtle

Humans produce 350 million metric tons of plastic waste per year, leading to microplastic pollution and widespread environmental contamination, particularly in aquatic environments. This subsequently impacts aquatic organisms in myriad ways, yet the vast majority of research is conducted in marine, rather than freshwater systems. In this study, we exposed eggs and hatchlings of the Chinese soft-shelled turtle (Pelodiscus sinensis) to 80-nm polystyrene nanoplastics (PS-NPs) and monitored the impacts on development, behavior and the gut microbiome. We demonstrate that 80-nm PS-NPs can penetrate the eggshell and move into developing embryos. This led to metabolic impairments, as evidenced by bradycardia (a decreased heart rate), which persisted until hatching. We found no evidence that nanoplastic exposure affected hatchling morphology, growth rates, or levels of boldness and exploration, yet we discuss some potential caveats here. Exposure to nanoplastics reduced the diversity and homogeneity of gut microbiota in P. sinensis, with the level of disruption correlating to the length of environmental exposure (during incubation only or post-hatching also). Thirteen core genera (with an initial abundance >1 %) shifted after nanoplastic treatment: pathogenic bacteria increased, beneficial probiotic bacteria decreased, and there was an increase in the proportion of negative correlations between bacterial genera. These changes could have profound impacts on the viability of turtles throughout their lives. Our study highlights the toxicity of environmental NPs to the embryonic development and survival of freshwater turtles. We provide insights about population trends of P. sinensis in the wild, and future directions for research.

Intramuscular and oral single-dose pharmacokinetic profiles and multi-tissue distribution of thiamphenicol in Chinese soft-shelled turtle (Trionyx sinensis)

The aim of this investigation was to reveal the pattern of disposal process of thiamphenicol (TAP) in Chinese soft-shelled turtle after oral (PO) and intramuscular (IM) administration routes. TAP concentration levels in Chinese soft-shelled turtle plasma and multi-tissues were measured by HPLC-MS/MS. Pharmacokinetic (PK) parameters of TAP were estimated using WinNolin software based on the non-compartmental analysis. Compared with IM route, higher absorption, longer elimination time and greater AUC0-∞ value for TAP in plasma were observed after PO treatment. It indicated that Chinese soft-shelled turtle has a higher bioavailability for TAP following PO administration than IM medication. For tissue distribution, higher TAP concentrations were also found following PO medication than IM administration. The prescribed medication dosage of TAP (17.5 mg/kg bw) against susceptible strains with MIC should be below 0.22 mg/L (PO) and 0.13 mg/L (IM) based on the values of Cmax/MIC >10 and AUC0–24 h/MIC >125. TAP elimination pattern was investigated, and skirt was suggested as residual target tissue. Withdrawal time (WT) of TAP was calculated using WT 1.4 software, and the recommended WT was 17 d (391 ℃-day). The present investigation can serve as reference data for TAP use in Chinese soft-shelled turtle.