Fatty acid composition and lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis, fed different dietary lipid sources

Gut microbiota of homologous Chinese soft-shell turtles (Pelodiscus sinensis) in different habitats

Background

Chinese soft-shell turtle (Pelodiscus sinensis) is an important commercial species for their high nutritional value and unique taste, but it has been a vulnerable species due to habitat loss. In this study, homologous juvenile turtles were allocated to lake, pond and paddy field to investigate the habitat effects on turtles.

Results

The growth, morphology and gut microbial communities were monitored during the 4 months cultural period. It showed higher growth rate of turtles in paddy field and pond. The appearance, visceral coefficients, gut morphology and microbial communities in turtles were distinct among different habitats. The microbial community richness on Chao1 was obviously lower in initial turtle guts from greenhouses, whereas it was relative higher in turtle guts sampled from paddy fields than ponds and lake. Significant differences on dominant microbes were found among initial and subsequent samples from different habitats. Firmicutes was the most abundant phylum in the guts of turtles sampled from the greenhouse initially, while Proteobacteria was the most abundant phylum after cultivation in different habitats, followed by Bacteroidetes. The microbial composition were distinct in different habitats at 60d, and the appearance of dominant phyla and genera was more driven by sampling time than habitats at 120d. Both the sampling time and habitats affected the appearance of dominant phyla and genera during the cultivation. The functional predictions indicated that both habitat type and sampling time had significant effects on metabolic pathways, especially amino acid and carbohydrate metabolism.

Conclusions

The turtles could adapt to natural lakes, artificial ponds and paddy fields. The gut microbial abundance was different among the habitats and sampling time. The species of microbes were significantly more diverse in paddy field specimens than in those from ponds and lakes. Rice-turtle coculture is a potential ecological and economic farming mode that plays important roles in wild turtle protection and food security.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02209-y.

ANALYSIS OF FATTY ACID PROFILES FOR EASTERN BOX (TERRAPENE CAROLINA CAROLINA) AND COMMON SNAPPING (CHELYDRA SERPENTINE) TURTLES IN WILD AND MANAGED CARE ENVIRONMENTS

The housing of wild animals in managed care facilities requires attention to all aspects of husbandry. Diets of wild animals often differ in composition, consistency, and quantity when compared with those in managed care settings including zoos, rehabilitation facilities, and aquaria. It was hypothesized that dietary differences from wild versus managed care would be reflected in data of circulating fatty acids based on previous studies. The current study examined the effect of species and environment on fatty acid concentrations in two omnivorous species of chelonians: Eastern box turtles, Terrapene carolina carolina, and common snapping turtles, Chelydra serpentina, located in the wild and managed care. Whole blood was collected and placed on spot cards for analysis of 26 fatty acids in a total lipid fatty acid profile. The present research indicated that Eastern box turtles have significantly (P < 0.05) higher percentages of linoleic acid (18:2n6), eicosadienoic acid (20:2n6), and mead acid (20:3n9). Common snapping turtles have significantly (P < 0.05) higher percentages of myristic acid (14:0), dihomo-γ-linolenic acid (20:3n6), erucic acid (22:1n9), and n-6 docosapentaenoic acid (22:5n6). Environmental effects also were noted; wild turtles had higher percentages of α-linolenic acid (18:3n3), arachidic acid (20:0), eicosadienoic acid (20:2n6), and eicosatrienoic acid (20:3n3) (P < 0.05), whereas n-6 docosapentaenoic acid (22:5n6) was higher for the managed care group. Eicosadienoic acid (20:2n6), behenic acid; 22:0), adrenic acid (22:4n6), n-6 docosapentaenoic acid (22:5n6), and nervonic acid (24:1) were significantly different (P < 0.05) in species-environment interactions without any noted species or environment patterns. Fatty acids are useful for many important biological functions including proper immune system regulation, and therefore, the present research provides medically relevant data for reptile diagnostics. This research may help further improve diets of all chelonians kept in managed care, regardless of species.

Impact of Dietary Cornstarch Levels on Growth Performance, Body Composition and Digestive Enzyme Activities of Juvenile Soft-Shelled Turtle (Pelodiscus sinensis)

We conducted an 8-week feeding trial to determine the effects of dietary starch levels on growth performance, body composition, and digestive enzyme activities of juvenile soft-shelled turtles. Six fish meal-based diets containing 120, 180, 240, 300, 360 and 420 g kg−1 cornstarch were formulated. Body weight gain (BWG), crude protein concentration in whole body, as well as protease activity increased with increasing dietary starch levels until the highest at 240–300 g kg−1, but it was decreased at higher dietary starch content. In contrast, the feed conversion ratio, moisture content and hepatosomatic index were the lowest at 240–300 g kg−1 of cornstarch. The weight gain correlated significantly with the survival rate, the crude protein composition and the protease activity, but correlated negatively to the moisture content and the hepatosomatic index. The optimal dietary starch levels for the maximum BWG and maximum protease activity were 267.25 g kg−1 and 266.79 g kg−1, respectively. The α-amylase activity was the lowest at 120 g · kg−1 of cornstarch, and increased with increasing cornstrach content. The lipase activity and the amount of crude lipid in the turtles were not influenced by dietary cornstarch. Our results suggest that around 300 g kg−1 of cornstarch in diets is optimal for juvenile soft-shelled turtles.

Division of Chinese soft-shelled turtle intestine with molecular markers is slightly different from the morphological and histological observation

The Chinese soft-shelled turtle (Pelodiscus sinensis) is a commercially important species in Asian countries. Knowledge of its nutritional requirements and physiology is essential for determining the appropriate content of the feed for this animal. However, the lack of functional characterization of the intestine of this turtle limits the understanding of its absorption and utilization of nutritional materials. To solve this problem, this work utilized anatomical and histological methods to characterize 9 segments sampled along the anterior-posterior axis of the intestine. Furthermore, 9 genes, which have been well documented in the intestine division of mammals and fish, were employed to functionally characterize the 9 sampled segments. Our results suggest that regions covering from the starting site to S3 (position at 29.9% of the total length from the starting of the intestine) are the equivalent of mammalian dedumonen, and those covering S4 (40.2%) and S5 (65.4%), posterior to S8 (92.7%), are the equivalent of the mammalian ileum and the large intestine, respectively. As to the region spaning S6 (81.3%) and S7 (87.3%), its functional equivalent (small intestine or large intestine) may be variable and depends on the functional genes. This molecular characterization in relation to the division of the intestine of Chinese soft-shelled turtle may contribute to the understanding of the nutritional physiology of the turtle, and promote Chinese soft-shelled turtle production.

Non-alcoholic fatty liver disease: an emerging liver disease in Taiwan

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder in Western countries, and has become increasingly recognized as a public health problem in Taiwan. Patients with non-alcoholic steatohepatitis, a more severe form of NAFLD, may progress to cirrhosis and its related complications, including hepatocellular carcinoma. Since NAFLD is highly linked to metabolic syndrome, such patients may have increased risks of complications related to both liver disease and metabolic syndrome. Therefore, if we fail to cope with this growing health problem, NAFLD may gradually replace viral hepatitis as the major etiology of liver disease in Taiwan.

The cold but not hard fats in ectotherms: consequences of lipid restructuring on susceptibility of biological membranes to peroxidation, a review

The production of reactive oxygen species is a regular feature of life in the presence of oxygen. Some reactive oxygen species possess sufficient energy to initiate lipid peroxidation in biological membranes, self-propagating reactions with the potential to damage membranes by altering their physical properties and ultimately their function. Two of the most prominent patterns of lipid restructuring in membranes of ectotherms involve contents of polyunsaturated fatty acids and ratios of the abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine. Since polyunsaturated fatty acids and phosphatidylethanolamine are particularly vulnerable to oxidation, it is likely that higher contents of these lipids at low body temperature elevate the inherent susceptibility of membranes to lipid peroxidation. Although membranes from animals living at low body temperatures may be more prone to oxidation, the generation of reactive oxygen species and lipid peroxidation are sensitive to temperature. These scenarios raise the possibility that membrane susceptibility to lipid peroxidation is conserved at physiological temperatures. Reduced levels of polyunsaturated fatty acids and phosphatidylethanolamine may protect membranes at warm temperatures from deleterious oxidations when rates of reactive oxygen species production and lipid peroxidation are relatively high. At low temperatures, enhanced susceptibility may ensure sufficient lipid peroxidation for cellular processes that require lipid oxidation products.