Coping with extremes: High-altitude sparrows enhance metabolic and thermogenic capacities in the pectoralis muscle and suppress in the liver relative to their lowland counterparts.

Animals living at high altitudes are challenged by the extreme environmental conditions of cold temperature and hypobaric hypoxia. It is not well understood how high-altitude birds enhance the capacity of metabolic thermogenesis and allocate metabolic capacity in different organs to maximize survival in extreme conditions of a cold winter. The Qinghai-Tibet Plateau (QTP) is the largest and highest plateau globally, offering a natural laboratory for investigating coping mechanisms of organisms inhabiting extreme environments. To understand the adaptive strategies in the morphology and physiology of small songbirds on the QTP, we compared plasma triiodothyronine (T3), pectoralis muscle mitochondrial cytochrome c oxidase (COX) and state IV capacities, the expression of peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), adenine nucleotide translocase (ANT), uncoupling protein (UCP), and adenosine monophosphate-dependent kinase (AMPK) α1 mRNA in the pectoralis and liver of Eurasian tree sparrows (Passer montanus) from high-altitude (3,230 m), medium-altitude (1400 m), and low-altitude (80 m) regions. Our results showed that high-altitude sparrows had greater body masses, longer wings and tarsometatarsi, but comparable bill lengths relative to medium- and low-altitude individuals. High-altitude sparrows had higher plasma T3 levels and pectoralis muscle mitochondrial COX capacities than their lowland counterparts. They also upregulated the pectoralis muscle mRNA expression of UCP, PGC-1α, and ANT proteins relative to low-altitude sparrows. Unlike pectoralis, high-altitude sparrows significantly down-regulated hepatic AMPKα1 and ANT protein expression as compared with their lowland counterparts. Our results contribute to understanding the morphological, biochemical, and molecular adaptations in free-living birds to cope with the cold seasons in the extreme environment of the QTP.

Global face mask pollution: threats to the environment and wildlife, and potential solutions.

Face masks are an indispensable low-cost public healthcare necessity for containing viral transmission. After the coronavirus disease (COVID-19) became a pandemic, there was an unprecedented demand for, and subsequent increase in face mask production and use, leading to global ecological challenges, including excessive resource consumption and significant environmental pollution. Here, we review the global demand volume for face masks and the associated energy consumption and pollution potential throughout their life cycle. First, the production and distribution processes consume petroleum-based raw materials and other energy sources and release greenhouse gases. Second, most methods of mask waste disposal result in secondary microplastic pollution and the release of toxic gases and organic substances. Third, face masks discarded in outdoor environments represent a new plastic pollutant and pose significant challenges to the environment and wildlife in various ecosystems. Therefore, the long-term impacts on environmental and wildlife health aspects related to the production, use, and disposal of face masks should be considered and urgently investigated. Here, we propose five reasonable countermeasures to alleviate these global-scale ecological crises induced by mask use during and following the COVID-19 pandemic era: increasing public awareness; improving mask waste management; innovating waste disposal methods; developing biodegradable masks; and formulating relevant policies and regulations. Implementation of these measures will help address the pollution caused by face masks.

Physiological but not morphological adjustments along latitudinal gradients in a human commensal species, the Eurasian tree sparrow.

Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments. Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics. Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms. Here, we studied morphological traits in breeding Eurasian tree sparrows (ETSs; Passer montanus) among low-latitude (Yunnan and Hunan) and middle-latitude (Hebei) localities in China. We then compared body mass; lengths of bill, tarsometatarsus, wing, total body, and tail feather; and baseline and capture stress-induced levels of plasma corticosterone (CORT) and the metabolites including glucose (Glu), total triglyceride (TG), free fatty acid (FFA), total protein, and uric acid (UA). None of the measured morphological parameters varied with latitude except in the Hunan population, which demonstrated longer bills than those in other populations. Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude, but total integrated CORT levels did not vary with latitude. Capture stress-induced significantly increased Glu levels and decreased TG levels, independent of site. However, the Hunan population had significantly higher baseline CORT, baseline and stress-induced FFA levels, but lower UA levels, which differed from other populations. Our results suggest that rather than morphological adjustments, physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs. It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.

Hibernation with Rhythmicity in the Retina, Brain, and Plasma but Not in the Liver of Hibernating Giant Spiny Frogs (Quasipaa spinosa).

Hibernation in ectotherms is well known, however, it is unclear how the circadian clock regulates endocrine and antioxidative defense systems of aquatic hibernators. Using the giant spiny frog (Quasipaa spinosa), we studied mRNA expression levels of (1) circadian core clock (Bmal1, Clock, Cry1 and Per2), clock-controlled (Ror-α, Mel-1c and AANAT), and antioxidant enzyme (AOE) (SOD1, SOD2, CAT and GPx) genes in retina, brain, and liver; and (2) plasma melatonin (MT) and corticosterone (CORT) levels, over a 24-hour period at six intervals pre-hibernation and during hibernation. Our results showed that brain Bmal1, Cry1, Per2 and Mel-1c were rhythmic pre-hibernation and Clock and Ror-α during hibernation. However, the retina Bmal1, Clock and Mel-1c, and plasma MT became rhythmic during hibernation. All brain AOEs (SOD1, SOD2, CAT and GPx) were rhythmic pre-hibernation and became non-rhythmic but upregulated, except SOD1, during hibernation. However, plasma CORT and liver clocks and AOEs were non-rhythmic in both periods. The mRNA expression levels of AOEs closely resembled those of Ror-α but not plasma MT oscillations. In the hibernating aquatic frogs, these modulations of melatonin, as well as clock and clock-controlled genes and AOEs might be fundamental for them to remain relatively inactive, increase tolerance, and escape hypoxia, and to prepare for arousal.

Hibernation with rhythmicity: the circadian clock and hormonal adaptations of the hibernating Asiatic toads (Bufo gargarizans).

Hibernation is one of the fundamental strategies in response to cold environmental temperatures. During hibernation, the endocrine and circadian systems ensure minimal expenditure of energy for survival. The circadian rhythms of key hormones, melatonin (MT), corticosterone (CORT), triiodothyronine (T3 ), and thyroxine (T4 ), and the underlying molecular regulatory mechanisms of hibernation have been well determined in mammals but not in ectotherms. Here, a terrestrial hibernating species, Asiatic toad (Bufo gargarizans), was employed to investigate the plasma CORT, MT, T3 , and T4 ; and the retina, brain, and liver mRNA expression of the core clock genes, including circadian locomotor output cycles kaput (Clock), brain and muscle ARNT-like 1 (Bmal1), cryptochrome (Cry) 1 and 2, and period (Per) 1 and 2, at 7-time points over a 24-h period under acute cold (1 day at 4°C), and hibernation (45 days at 4°C). Our results showed that the circadian rhythms of the core clock genes were rather unaffected by acute cold exposure in the retina, unlike the brain and liver. In contrast, during hibernation, the liver clock genes displayed significant circadian oscillations, while those in the retina and brain stopped ticking. Furthermore, plasma CORT expressed circadian oscillations in both groups, and T3 in acute cold exposure group, whereas T4 and MT did not. Our results reveal that the plasma CORT and the liver sustain rhythmicity when the brain was not, indicating that the liver clock along with the adrenal clock synergistically maintains the metabolic requirements to ensure basic survival in hibernating Asiatic toads.