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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.

The color of crayfish (Procambarus clarkii) shells not only affects their value, but also has a significant impact on individual size. Astaxanthin is a common carotenoid that has been found in many studies to have different functions, including regulating body color formation. In this study, the levels of different carotenoids were detected using high performance liquid chromatography (HPLC) and found a significant correlation between astaxanthin content and shell color. An astaxanthin gene (PcASTA) was identified from P. clarkii, and it was expressed in tissues of crayfish with dark-red shells and green shells. The highest expression levels of PcASTA were found in the hepatopancreas, followed by the muscle. The expression of PcASTA in all tissues of red shell crayfish was higher than that of green shell crayfish, indicating that PcASTA may be involved in shell color formation in crayfish. Moreover, high water temperature and feeding β-carotene can lead to an increase in tissue expression of PcASTA and astaxanthin content in crayfish shells. The findings indicate that PcASTA may affect shell color in P. clarkii by being involved in astaxanthin synthesis and transformation.

The Chinese soft-shelled turtle (Pelodiscus sinensis) is an important freshwater aquaculture turtle due to its taste and nutritional and medicinal value. More ecological culturing modes, such as rice–turtle co-culture, should be developed to meet the ecological benefit demand. We compared growth, physiological parameters, and transcriptome data to detect the physiological responses and regulatory mechanisms of pond-cultured turtles as compared to co-cultured turtles. The co-cultured turtles grew slower than pond-cultured turtles. The gonadosomatic index of co-cultured male turtles was lower than that of pond-cultured male turtles, and both the mesenteric fat index and limb fat index were lower in co-cultured turtles than in pond-cultured turtles (p < 0.05). The blood GLU of the co-cultured turtles was significantly lower than the GLU of the pond-cultured turtles (p < 0.05), while the values of CRE, UA, BUN, AKP, ACP, GOT, and CAT were higher in the co-cultured turtles than in the pond-cultured turtles (p < 0.05). In total, 246 and 598 differentially expressed genes (DEGs) were identified in the brain and gut from turtles cultured in the two different modes, respectively. More DEGs were related to environmental information processing, metabolism, and human diseases. In the brain, the top enriched pathways of DEGs included the longevity regulating pathway, glycerolipid metabolism, cytokine–cytokine receptor interaction, Toll-like receptor signaling pathway, and PI3K-Akt signaling pathway, while in the gut, the top enriched pathways of DEGs included the cell cycle, DNA replication, cellular senescence, and p53 signaling pathway. The turtles acclimated to the different culturing conditions by adjusting their growth, physiological, and biochemical characteristics and related gene expression during a short culture period.

Abstract Background Protein kinase C (PKC) is a multifunctional serine and PKC can phosphorylate serine residues in the cytoplasmic domain of tyrosinase, thereby regulating the activity of tyrosinase. Activated PKC is bound to the melanosome membrane, and unactivated PKC is free in the cytoplasm of melanocytes. In this study, we study the role of PKC gene in the melanin synthesis pathway and its effect on the color of the nacre of H. cumingii. Results In this study, a HcPKC gene in H. cumingii was cloned and its effects on melanin synthesis and nacre color were studied. HcPKC was expressed in both purple and white mussels, and the level of mRNA expression was higher in the purple mussels than in white mussels. Strong and specific mRNA signals were detected in the dorsal epithelial cells of the mantle pallial layer, indicating that HcPKC may be involved in nacre formation. After SNP association with inner shell color related traits, according to the principle that 0.25

We conducted an 8-week feeding trial to investigate the effect of mixed functional oligosaccharides (chitosan oligosaccharide, fructooligosaccharide, and xylooligosaccharide) extracted from wheat straw on the growth, feeding, physiology, histology, muscle texture, and gut microbiota of Micropterus salmoides. Six diets were formulated by incrementally adding mixed functional oligosaccharides (0.1, 0.5, 1.0, 1.5, and 2.0 mg/kg) to the control diet. 30 individuals with initial body weight of 25.1±3.5 g were randomly allocated to 6 triplicate tanks and fed to apparent satiation twice daily. The fish fed 1.0 mg/kg additives displayed maximum growth, and the feed conversion ratio decreased with the increase in additives from 0 to 1.0 mg/kg (P0.05). The villus height and width were significantly higher in the supplementation groups than in the control group, while the gut and liver structures presented abnormalities with excessive supplementation above 1.5 mg/kg. There were significant differences in muscle texture indices for M. salmoides over the fed additive gradient, and the hardness, gumminess, and chewiness were highest in the 1.0 mg/kg group. High oligosaccharide levels, such as 2.0 mg/kg, decreased the LZM level, while there were no significant differences in the SOD and MDA levels. Gut microbiome analysis revealed no significant differences in richness and diversity for groups fed the functional oligosaccharide gradient; however, the PCoA results showed that the microbial community composition changed markedly in response to different addition levels, and the 0.5 and 1.0 mg/kg supplementation groups were far apart from the lower and higher supplementation groups. The relative abundance of Proteobacteria was lower in the 0.5 and 1.0 mg/kg addition groups, while that of the phyla Fusobacteria and Firmicutes were higher in these two groups. Functional classification showed that microbes related to carbohydrate metabolism were more abundant in the 0.5 and 1.5 mg/kg groups than in the other groups.

Pearl color is an important factor influencing pearl value, and is affected by the nacre color of the shell in Hyriopsis cumingii. Coproporphyrinogen-III oxidase (CPOX) is a key enzyme in porphyrin synthesis, and porphyrins are involved in color formation in different organisms, including in the nacre color of mussels. In this study, a CPOX gene (HcCPOX) was identified from H. cumingii, and its amino acid sequence was found to contain a coprogen-oxidase domain. HcCPOX mRNA was expressed widely in the tissues of white and purple mussels, and the highest expression was found in the gill, followed by the fringe mantle. The expression of HcCPOX in all tissues of purple mussels (except in the middle mantle) was higher than that of white mussels. Strong hybridization signals for HcCPOX were observed in the dorsal epithelial cells of the outer fold of the mantle. The activity of CPOX in the gill, fringe mantle, and foot of purple mussels was significantly higher than that in white mussels. Moreover, the expression of HcCPOX and CPOX activity were decreased in RNA interference experiments. The findings indicate that HcCPOX might contributes to nacre color formation in H. cumingii by being involved in porphyrin synthesis.

Creb (Cyclic AMP response element binding protein) is a nuclear regulatory factor that regulates transcription through autophosphorylation. In melanocytes, cAMP's corresponding elements bind to the Creb protein to autophosphorylation and activate MITF (Microphthalmia-associated transcription factor). MITF stimulates Tyrosine(tyr) to induce melanocytes to differentiate into eumelanin and pheomelanin. In this study, a HcCreb gene in Hyriopsis cumingii was cloned and its effects on melanin synthesis and nacre color were studied. HcCreb was expressed in both purple and white mussels, and there was a significant difference in expression between adductor muscle (p