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.

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.