Elevated antioxidant defence in the brain of deep-diving pinnipeds

While foraging, marine mammals undertake repetitive diving bouts. When the animal surfaces, reperfusion makes oxygen readily available for the electron transport chain, which leads to increased production of reactive oxygen species and risk of oxidative damage. In blood and several tissues, such as heart, lung, muscle and kidney, marine mammals generally exhibit an elevated antioxidant defence. However, the brain, whose functional integrity is critical to survival, has received little attention. We previously observed an enhanced expression of several antioxidant genes in cortical neurons of hooded seals (Cystophora cristata). Here, we studied antioxidant gene expression and enzymatic activity in the visual cortex, cerebellum and hippocampus of harp seals (Pagophilus groenlandicus) and hooded seals. Moreover, we tested several genes for positive selection. We found that antioxidants in the first line of defence, such as superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione (GSH) were constitutively enhanced in the seal brain compared to mice (Mus musculus), whereas the glutaredoxin and thioredoxin systems were not. Possibly, the activity of the latter systems is stress-induced rather than constitutively elevated. Further, some, but not all members, of the glutathione-s-transferase (GST) family appear more highly expressed. We found no signatures of positive selection, indicating that sequence and function of the studied antioxidants are conserved in pinnipeds

Environmental drivers of population-level variation in the migratory and diving ontogeny of an Arctic top predator

This work is an output of the ARISE project (NE/P006035/1 and NE/P00623X/1), part of the Changing Arctic Ocean programme jointly funded by the UKRI Natural Environment Research Council (NERC) and the German Federal Ministry of Education and Research (BMBF). Fieldwork in Canada was carried out under a Canadian Council on Animal Care permit no. NAFC2017–2 and funded by Fisheries and Oceans Canada and a bursary from Department for Business, Energy and Industrial Strategy (BEIS) administered by the NERC Arctic Office. Fieldwork in the Greenland Sea was approved by the Greenland Ministry of Fisheries, Hunting and Agriculture and the Norwegian Food Safety Authority (permit no. 11546) as part of the Northeast Greenland Environmental Study Program 2017–2018 (by the Danish Centre for Environment and Energy at Aarhus University, The Greenland Institute of Natural Resources and the Environmental Agency for Mineral Resource Activities of the Government of Greenland) and financed by oil licence holders in the area.The development of migratory strategies that enable juveniles to survive to sexual maturity is critical for species that exploit seasonal niches. For animals that forage via breath-hold diving, this requires a combination of both physiological and foraging skill development. Here, we assess how migratory and dive behaviour develop over the first year of life for a migratory Arctic top predator, the harp seal Pagophilus groenlandicus, tracked using animal-borne satellite relay data loggers. We reveal similarities in migratory movements and differences in diving behaviour between 38 juveniles tracked from the Greenland Sea and Northwest Atlantic breeding populations. In both regions, periods of resident and transitory behaviour during migration were associated with proxies for food availability: sea ice concentration and bathymetric depth. However, while ontogenetic development of dive behaviour was similar for both populations of juveniles over the first 25 days, after this time Greenland Sea animals performed shorter and shallower dives and were more closely associated with sea ice than Northwest Atlantic animals. Together, these results highlight the role of both intrinsic and extrinsic factors in shaping early life behaviour. Variation in the environmental conditions experienced during early life may shape how different populations respond to the rapid changes occurring in the Arctic ocean ecosystem.Publisher PDFPeer reviewe

Why Rudolph's nose is red: Observational study

Objective: To characterise the functional morphology of the nasal microcirculation in humans in comparison with reindeer as a means of testing the hypothesis that the luminous red nose of Rudolph, one of the most well known reindeer pulling Santa Claus's sleigh, is due to the presence of a highly dense and rich nasal microcirculation. Design: Observational study. Setting: Tromsø, Norway (near the North Pole), and Amsterdam, the Netherlands. Participants: Five healthy human volunteers, two adult reindeer, and a patient with grade 3 nasal polyposis. Main outcome measures: Architecture of the microvasculature of the nasal septal mucosa and head of the inferior turbinates, kinetics of red blood cells, and real time reactivity of the microcirculation to topical medicines. Results: Similarities between human and reindeer nasal microcirculation were uncovered. Hairpin-like capillaries in the reindeers' nasal septal mucosa were rich in red blood cells, with a perfused vessel density of 20 (SD 0.7) mm/mm2. Scattered crypt or gland-like structures surrounded by capillaries containing flowing red blood cells were found in human and reindeer noses. In a healthy volunteer, nasal microvascular reactivity was demonstrated by the application of a local anaesthetic with vasoconstrictor activity, which resulted in direct cessation of capillary blood flow. Abnormal microvasculature was observed in the patient with nasal polyposis. Conclusions: The nasal microcirculation of reindeer is richly vascularised, with a vascular density 25% higher than that in humans. These results highlight the intrinsic physiological properties of Rudolph's legendary luminous red nose, which help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer's brain, factors essential for flying reindeer pulling Santa Claus's sleigh under extreme temperatures

Tissue distribution of angiotensin-converting enzyme 2 (ACE2) receptor in wild animals with a focus on artiodactyls, mustelids and phocids

Natural cases of zooanthroponotic transmission of SARS-CoV-2 to animals have been reported during the COVID-19 pandemic, including to free-ranging white-tailed deer (Odocoileus virginianus) in North America and farmed American mink (Neovison vison) on multiple continents. To understand the potential for angiotensin-converting enzyme 2 (ACE2)-mediated viral tropism we characterised the distribution of ACE2 receptors in the respiratory and intestinal tissues of a selection of wild and semi-domesticated mammals including artiodactyls (cervids, bovids, camelids, suids and hippopotamus), mustelid and phocid species using immunohistochemistry. Expression of the ACE2 receptor was detected in the bronchial or bronchiolar epithelium of several European and Asiatic deer species, Bactrian camel (Camelus bactrianus), European badger (Meles meles), stoat (Mustela erminea), hippopotamus (Hippopotamus amphibious), harbor seal (Phoca vitulina), and hooded seal (Cystophora cristata). Further receptor mapping in the nasal turbinates and trachea revealed sparse ACE2 receptor expression in the mucosal epithelial cells and occasional occurrence in the submucosal glandular epithelium of Western roe deer (Capreolus capreolus), moose (Alces alces alces), and alpaca (Vicunga pacos). Only the European badger and stoat expressed high levels of ACE2 receptor in the nasal mucosal epithelium, which could suggest high susceptibility to ACE2-mediated respiratory infection. Expression of ACE2 receptor in the intestinal cells was ubiquitous across multiple taxa examined. Our results demonstrate the potential for ACE2-mediated viral infection in a selection of wild mammals and highlight the intra-taxon variability of ACE2 receptor expression, which might influence host susceptibility and infection

Seasonal variation in the thermal responses to changing environmental temperature in the world's northernmost land bird

Arctic homeotherms counter challenges at high latitudes using a combination of seasonal adjustments in pelage/plumage, fat deposition and intricate thermoregulatory adaptations. However, there are still gaps in our understanding of their thermal responses to cold, particularly in Arctic birds. Here, we have studied the potential use of local heterothermy (i.e. tissue cooling that can contribute to significantly lower heat loss rate) in Svalbard ptarmigan (Lagopus muta hyperborea) °C the world's northernmost land bird. We exposed birds kept under simulated Svalbard photoperiod to low ambient temperatures (Ta; between 0 and -30°C) during three seasons (early winter, late winter, summer), whilst recording resting metabolic rate (RMR), core temperature (Tc) and several cutaneous temperatures. Leg skin temperature varied the most, but still only by up to 15°C, whereas body trunk skin temperature changed 1°C when Ta decreased from 0 to -30°C. At the same time, Tc increased by 0.9°C, concomitant with increased RMR. This was probably driven by the triggering of cerebral thermosensors in response to cooling of the poorly insulated head, the skin of which was 5.4°C colder at -30°C than at 0°C. Thermal conductance in winter was higher in yearlings, probably because they were time/resource constrained from acquiring a high-quality plumage and sufficient fat reserves as a result of concomitant body growth. In conclusion, Svalbard ptarmigan do not employ extensive local heterothermy for cold protection but instead rely on efficient thermogenesis combined with excellent body insulation. Hence, cold defence in the world's northernmost land bird is not mechanistically much different from that of its lower latitude relatives

Ambient temperature effects on stress-induced hyperthermia in Svalbard ptarmigan

Stress-induced hyperthermia (SIH) is commonly observed during handling in homeotherms. However, in birds, handling in cold environments typically elicits hypothermia. It is unclear whether this indicates that SIH is differently regulated in this taxon or if it is due to size, because body temperatures changes during handling in low temperature have only been measured in small birds ≤0.03 kg (that are more likely to suffer high heat loss when handled). We have, therefore, studied thermal responses to handling stress in the intermediate-sized (0.5-1.0 kg) Svalbard ptarmigan (Lagopus muta hyperborea) in 0°C and −20°C, in winter and spring. Handling caused elevated core body temperature, and peripheral vasoconstriction that reduced back skin temperature. Core temperature increased less and back skin temperature decreased more in −20°C than in 0°C, probably because of higher heat loss rate at the lower temperature. Responses were qualitatively consistent between seasons, despite higher body condition/insulation in winter and dramatic seasonal changes in photoperiod, possibly affecting stress responsiveness. Our study supports the notion that SIH is a general thermoregulatory reaction to acute stressors in endotherms, but also suggests that body size and thermal environment should be taken into account when evaluating this response in birds