Keep numbers in view: red-eared sliders (Trachemys scripta elegans) learn to discriminate relative quantities.

The ability to discriminate relative quantities, one of the numerical competences, is considered an adaptive trait in uncertain environments. Besides humans, previous studies have reported this capacity in several non-human primates and birds. Here, we test whether red-eared sliders (Trachemys scripta elegans) can discriminate different relative quantities. Subjects were first trained to distinguish different stimuli with food reward. Then, they were tested with novel stimulus pairs to demonstrate how they distinguished the stimuli. The results show that most subjects can complete the initial training and use relative quantity rather than absolute quantity to make choices during the testing phase. This study provides behavioural evidence of relative quantity discrimination in a reptile species and suggests that such capacity may be widespread among vertebrates.

Metabolomic changes of blood plasma associated with two phases of rat OIR.

Although acute hyperoxia/hypoxia alternation can shift sharply physiological processes of vessel development, e.g. oxygen induced retinopathy (OIR), very little is known of metabolic products resulted from the neovascularization disorder. In this study, the influence of abnormal oxygen exposures on the plasma metabolomic profiles of rats with OIR was investigated by the gas chromatography mass spectrometry (GC-MS). Rat pups were divided into four groups, each with 12 individuals: (i) reared in room air and sampled at P12 (CT1); (ii) exposed to high oxygen for 5 days and sampled at P12 (HO1, simulating the vaso-obeliteration process (phase I)); (iii) reared in room air and sampled at P17 (CT2); (iv) exposed to high oxygen for 5 days then followed by room air for 5 days and sampled at P17 (HO2, simulating the neovasculization one (phase II)). Plasma samples were analyzed with GC-MS, resulted in 122 metabolite species. Distinct differences in the plasma metabolome were found between groups of CT1 vs. HO1, and HO1 vs. HO2, by using univariate and multivariate analyses. Alternating hyperoxia/hypoxia conditions induced significant changes of richness of proline, ornithine and glutamine, that were important components of 'arginine and proline metabolism' pathway. These metabolites contributed largely to plasma sample classification, determined with receiver operating characteristic curve analysis and were involved profoundly in the proline-dependent production of reactive oxygen species (ROS) related to the cellular redox reactions. Our results from the rat OIR model suggest proline and 'arginine and proline metabolism' pathway as the potential biomarkers for human retinopathy of prematurity (ROP) diagnosis.

Do pit vipers assess their venom? Defensive tactics of Deinagkistrodon acutus shift with changed venom reserve.

To maximize survival probability, animals must assess predation risks and adopt flexible defensive strategies based on specific conditions. Pit vipers utilize venom for predation and self-defense, and venom status significantly influences its effectiveness. Thus, pit vipers may evaluate their venom reserve and adopt corresponding defensive tactics. Twenty-three sharp-snouted pit vipers (Deinagkistrodon acutus) were grouped by different venom status and were subjected to eight behavior trials. Subjects' defensive behaviors were recorded and analyzed. Results showed that the normal venom group displayed stable responses across the trials. The low venom group showed fewer strikes and more fleeing behaviors at the end of experiments. After given prolonged intervals for replenishing the venom, significant increases of strike behaviors were observed in the replenishing venom group. These results demonstrated the capability of adopting flexible defensive tactics based on varied venom reserve and provided new evidence for venom-status-recognition.