Leopard predation on wild Sichuan snub-nosed monkeys.

Predation is widely recognized as a powerful selective pressure on primate behavior and ecology, although knowledge of predator-prey relationships remains limited partly due to the rarity of directly observed attacks on primates. Here, we describe four confirmed or suspected instances of leopard (Panthera pardus) predation on free-ranging Sichuan (golden) snub-nosed monkeys (Rhinopithecus roxellana), a highly endangered colobine species endemic to China. We recorded predation events and the reactions of monkey group members. We suggest that the evolution of a multilevel society may be an adaptive response by Sichuan snub-nosed monkeys to the risk from leopards as well as other potential predators, one that balances the pressures of predation and intra-species competition and conflict.

Effects of Starvation and Refeeding on Growth, Digestion, Nonspecific Immunity and Lipid-Metabolism-Related Genes in Onychostoma macrolepis.

The present research was conducted to assess the influences of starvation and refeeding on growth, nonspecific immunity and lipid metabolic adaptation in Onychostoma macrolepis. To date, there have been no similar reports in O. macrolepis. The fish were randomly assigned into two groups: control group (continuous feeding for six weeks) and starved-refed group (starvation for three weeks and then refeeding for three weeks). After three weeks of starvation, the results showed that the body weight (BW, 1.44 g), condition factor (CF, 1.17%), visceral index (VSI, 3.96%), hepatopancreas index (HSI, 0.93%) and intraperitoneal fat index (IPFI, 0.70%) of fish were significantly lower compared to the control group (BW, 5.72 g; CF, 1.85%; VSI, 6.35%; HSI, 2.04%; IPFI, 1.92%) (p < 0.05). After starvation, the serum triglyceride (TG, 0.83 mmol/L), total cholesterol (T-GHOL, 1.15 mmol/L), high-density lipoprotein (HDL, 1.13 mmol/L) and low-density lipoprotein (LDL, 0.46 mmol/L) concentrations were significantly lower than those in the control group (TG, 1.69 mmol/L; T-GHOL, 1.86 mmol/L; HDL, 1.62 mmol/L; LDL, 0.63 mmol/L) (p < 0.05). The activities of intestinal digestive enzymes (amylase, lipase and protease) in the starved-refed group were significantly lower than those in the control group after three weeks of starvation (p < 0.05). The highest activities of immune enzymes such as lysozyme (LZM), acid phosphate (ACP), alkaline phosphate (ALP), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) in the hepatopancreas were presented in the starved-refed group at second week, and significantly higher than those in the control group (p < 0.05). Meanwhile, starvation significantly improved intestinal immune enzymes activities (p < 0.05). the lowest TG contents and the highest expression levels of lipolysis genes including hormone-sensitive lipase (HSL) and carnitine palmitoyl transferase 1 isoform A (CPT-1A) appeared in the hepatopancreas, muscle and intraperitoneal fat after starvation, indicating the mobilization of fat reserves in these tissues (p < 0.05). After refeeding, the recovery of TG content might be mediated by the upregulation of the expression levels of lipogenesis genes such as sterol regulatory element binding protein 1 (SREBP1) and fatty acid synthase (FAS). Understanding the duration of physiological and metabolic changes in O. macrolepis and their reversibility or irreversibility to supplementary feeding response could provide valuable reference for the adaptability of O. macrolepis in large-scale culturing, proliferation and release.

First Insights on the Administration of Insect Oil (Black Soldier Fly Larvae) in the Diet of Juvenile Onychostoma macrolepis.

The use of insect products in aquatic feed is the focus of the aquaculture industry. Black soldier fly larvae oil (BSFLO) has been examined as a potential lipid source for diets for some fish species, but its utilization on Onychostoma macrolepis has not been explored. The influences of substituting fish oil (FO) with BSFLO in the diet on growth, biological indicators, approximate composition, serum biochemistry, antioxidant capacity and expression of lipid metabolism genes in juvenile O. macrolepis were investigated in an eight-week feeding experiment. Four experimental diets were prepared by replacing 0 (control), 25% (BSFLO-25), 50% (BSFLO-50) and 100% (BSFLO-100) FO with BSFLO, and then randomly assigned to twelve aquariums with ten fish (1.75 ± 0.05 g) in each aquarium. The findings showed that the growth indicators, body composition and serum biochemistry in the BSFLO-25 and BSFLO-50 groups had no statistical differences from those of the control group. The activities of superoxide dismutase (SOD) (91.22-94.96 U/mgprot) and the contents of malondialdehyde (MDA) (1.12-1.16 nmol/mgprot) in the liver appeared to be significantly the highest and the lowest in the BSFLO-25, BSFLO-50 and BSFLO-100 groups (p < 0.05). The adipocyte size and intraperitoneal fat index value of fish fed on the BSFLO-100 diet were significantly decreased compared to the control group (p < 0.05). The expression levels of lipid catabolism genes pparα, (peroxisome proliferators-activated receptor alpha) and cpt1a (carnitine palmitoyltransferase 1 isoform a) in the BSFLO-100 group were significantly higher than those of the control group (p < 0.05). The above results indicated that it was feasible to replace 25-50% dietary FO with BSFLO in juvenile O. macrolepis. Dietary BSFLO supplementation could enhance the antioxidant capacity of the liver and suppress intraperitoneal fat accumulation in O. macrolepis. The use of other insect oils in the diets of this species will be evaluated in future research.

Transcriptional response to cold and fasting acclimation in Onychostoma macrolepis during the overwintering stage.

In this study, we investigated the transcriptome responses of the liver of Onychostoma macrolepis in by RNA sequencing. The sampling process involved three groups: 1G (0 week, 10 °C), 2G (12 weeks, 0 °C) and 3G (24 weeks, 10 °C). The body weight, viscera index, hepatopancreas index and intraperitoneal fat index of O. macrolepis showed a decreasing trend with the prolonging of overwintering time. The crude fat contents of whole fish, muscle and liver in O. macrolepis after overwintering were significantly lower than those of the fish before overwintering (p < 0.05). In 1G versus 2G group, 2G versus 3G group and 1G versus 3G group, the differently expressed genes (DEGs) were 4630, 3976 and 2311, respectively. These results indicated that different stages of overwintering period had significant effects on gene expression of O. macrolepis, and the influence degree gradually decreased with the extension of overwintering period. The results of Gene ontology (GO) enrichment showed that these DEGs were mainly related to metabolism and immunity, and most of them were down-regulated. In this study, the KEGG pathway classification results showed that signal transduction was the most representative. In addition, KOG enrichment results showed that many DEGs associated with lipid transport and metabolism were down-regulated during the overwintering period. These observations suggested that slowing metabolism and delaying immunity may be the strategies for overwintering adaptation of O. macrolepis.

Energy response and fatty acid metabolism in Onychostoma macrolepis exposed to low-temperature stress.

Temperature is a key environmental factor, and understanding how its fluctuations affect physiological and metabolic processes is critical for fish. The present study characterizes the energy response and fatty acid metabolism in Onychostoma macrolepis exposed to low temperature (10 °C). The results demonstrated that cold stress remarkably disrupted the energy homeostasis of O. macrolepis, then the AMP-activated protein kinase (AMPK) could strategically mobilize carbohydrates and lipids. In particular, when the O. macrolepis were faced with cold stress, the lipolysis was stimulated along with the enhanced fatty acid ß-oxidation for energy, while the fatty acid synthesis was supressed in the early stage. Additionally, the fatty acid composition analysis suggested that saturated fatty acid (SFA) might accumulate while monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) in storage lipids (mainly containing non-polar lipid, NPL) could be utilized to supply energy during cold acclimation. Altogether, this study may provide some meritorious for understanding the cold-tolerant mechanism of fish in the viewpoint of energy balance combined with fatty acid metabolism, and thus to contribute to this species rearing in fish farms in the future.

CIDEA and CIDEC are regulated by CREB and are not induced during fasting in grass carp Ctenopharyngodon idella adipocytes.

Cell death-inducing DNA fragmentation factor 45-like effector family proteins, including CIDEA, CIDEB and CIDEC, play an important role in energy metabolism. In the present study, CIDEA, CIDEB and CIDEC cDNAs were firstly isolated and characterized from grass carp Ctenopharyngodon idella, encoding peptides of 205, 208 and 238 amino acids, respectively. Analysis of the exon-intron structures clarified that grass carp CIDEA, CIDEB and CIDEC consisted of 5 coding exons, 5 coding exons and 6 coding exons, respectively, which is similar with human and mouse. Both CIDE family genes mRNAs were expressed in a wide range of tissues, but the abundance of each CIDE family gene mRNA showed the tissue-dependent expression patterns. Time-course analysis of CIDE family expressions indicated that their expression were enhanced significantly from day 0 to day 8 after differentiation. Forskolin caused an increase in CIDEA and CIDEC expression, and the effects were attenuated by treatment with CREB inhibitor, revealing that CIDEA and CIDEC are regulated by CREB. Further study found that CIDEA and CIDEC mRNA levels did not show significant changes during fasting. These results provide the groundwork to elucidate the gene structure and physiological function of CIDE family in fish.

Molecular characterization and tissue distribution of SREBP-1 and PPARα in Onychostoma macrolepis and their mRNA expressions in response to thermal exposure.

Fatty acid metabolism is crucial for maintaining energy homeostasis in aquatic vertebrates experiencing environmental stress. Both sterol regulatory element-binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor α (PPARα) are the key regulators of fatty acid metabolism. In this study, the coding sequences (CDS) of SREBP-1 and PPARα were firstly identified and characterized from Onychostoma macrolepis, encoding peptides of 1136 and 470 amino acids, respectively. The functional domains in O. macrolepis SREBP-1 and PPARα proteins retained the high similarity with those of other animals, at 74.69% and 77.29%, respectively. The mRNA encoding SREBP-1 was primarily expressed in the muscle and PPARα was highly expressed in the liver and intestine. Under thermal exposure, the content of non-esterified fatty acid (NEFA) decreased gradually after 1 h in the liver and muscle of O. macrolepis, which might be due to that the organism meet more energy expenditure via fatty acid ß-oxidation. Furthermore, the mRNA expression level of SREBP-1 decreased, while the mRNA expression level of PPARα increased from 0 h to 6 h in the liver. And we found that the mRNA expression levels of both SREBP-1 and PPARα decreased significantly at 48 h (P < .05) in the muscle, which was in accordance with the significant decrease of target gene FAS and CPT1A mRNA expression levels, respectively. It might be the physiological adjustment that the fish adapted to thermal exposure at the end of experiment. These results illustrate that O. macrolepis SREBP-1 and PPARα-mediated fatty acid metabolism is a fundamental requirement for thermal adaptation.

Effect of nitrite on immunity of the white shrimp Litopenaeus vannamei at low temperture and low salinity.

White shrimp Litopenaeus vannamei Boone (6-7 cm) were individually exposed during 8 h to 0 (control), 0.5, 1.0, and 10.0 mg/l NO(2)(-)-N at 22 °C and 10 ‰ salinity. Nitrite concentration was measured, and hemolymph and hepatopancreas were sampled at 0, 4 and 8 h. Superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) in haemolymph and hepatopancreas of L. vannamei Boone, and hemocyanin were examined. The results indicated significant relationships among hemocyanin concentration (Hc), nitrite concentration (nt), and exposure time (t) was as following: Hc = 1.250 + 0.0360 nt + 0.0636t, (R(2) = 0.702, P < 0.01), and Gompertz models with 3-parameters was used to describe well the increase trend of Hc with increase of nitrite concentration at 4, 8 h, respectively (R(2) > 0.99, P ≤ 0.05). MDA level and CAT activity in hemolymph decreased significantly at 8 h, and MDA level and CAT activity in hepatopancreas increased markedly. The SOD activity in hepatopancreas remained almost stably in the range of 0.22-0.24 U/g Hb within 8 h. The results showed there existed a immune difference between in hemolymph and hepatopancreas after white shrimp exposed to ambient nitrite within 8 h, and further experiments should be designed to answer the reason.