East Antarctic coastal polynyas—semi-permanent areas of ice-free ocean—are vital for sea ice production, Antarctic Bottom Water formation, and global heat redistribution. The Dibble Polynya has pronounced sea-ice production, yet the shelf water properties there and its offshore influence have been unclear. Here we show Dense Shelf Water outflow from the polynya that ventilates a lighter variety of local bottom water. Hydrographic records suggest Dense Shelf Water formation has persisted for 50 years, consistent with satellite-derived sea-ice production since the 1990s. Since the 2010s, the downstream cross-slope salinity gradient within bottom water has weakened and the Antarctic Slope Front has been modified, following a sharp decline in sea-ice production in the neighbouring Mertz Polynya after 2010 icescape changes. We infer that reduced denser Antarctic Bottom Water formation upstream weakens the slope current barrier, promoting outflow of not-so-dense shelf water from the Dibble Polynya that efficiently ventilates the abyssal basin. Recent Dense Shelf Water outflow from the Dibble Polynya in East Antarctica followed a reduction of Antarctic Bottom Water upstream, according to hydrographic observations.
The skin microbiome of humpback whales harbours diverse microbial communities that play a crucial role in host skin protection and environmental interaction. However, studies on cetacean skin microbiomes in the Southern Hemisphere focus on feeding grounds, with limited information on microbiome dynamics at breeding grounds and during migration across contrasting habitats. We characterised the skin microbiome of 46 humpback whales from two seasonal habitats: the Magellan Strait feeding ground and the Ecuadorian coast breeding ground, comparing age, sex, environmental conditions, and seawater. Amplicon sequencing of the 16S rRNA gene revealed no differences in alpha diversity, but habitat-specific compositional shifts were found. Psychrobacter was detected in both regions, with higher abundance in the feeding ground, while Tenacibaculum remained abundant across sites. Additional taxa exhibited habitat-specific patterns, including bacteria associated with thermal sensitivity and ultraviolet radiation-tolerance in the Magellan Strait, and lactic acid bacteria in Ecuador. Skin microbiomes were similar between age classes and sexes, but distinct from seawater. Our findings show that geographic and environmental factors, such as superficial seawater temperature and maximum ultraviolet B radiation, shape the skin microbiome of humpback whales, with certain taxa reflecting migratory behaviour across seasonal habitats.
Blue whales ( Balaenoptera musculus ) experienced substantial population declines in the 19th and 20th centuries due to commercial whaling and are currently listed as endangered species. As a result, they have attracted considerable scientific interest, not least the species' population structure. While the population structure of blue whales has been intensively studied in the Antarctic and South Pacific, the population structure within the North Pacific remains poorly understood. Acoustic and movement data suggest the presence of at least two distinct populations, but genetic evidence has been lacking due to limited sample availability. This study provides the first comprehensive genetic analysis of blue whales across the North Pacific (NP), using the eastern South Pacific (ESP) as an outgroup. We analysed 12,951 SNPs in 50 specimens (NP: n = 35, ESP: n = 15) and a population-informative subset of 96 SNPs in 60 specimens across the North Pacific (ENP: n = 23, WNP: n = 37), along with 480bp of the mitochondrial control region, to investigate population structure. ADMIXTURE analyses, supported by PCA and DAPC, identified three distinct genetic clusters: one separating the eastern South from the North Pacific and two additional dominant clusters within the North Pacific. These North Pacific clusters exhibited trends of site fidelity, with one primarily associated with the eastern North Pacific and the other with the western North Pacific. Our findings provide strong genetic support for the presence of at least two distinct populations in the North Pacific, highlighting the need for a shift in management perspectives - from a single to a two-stock framework.
Carnosine, an imidazole dipeptide, has potential for treating neurodegenerative diseases, including Parkinson's disease. However, carnosine-degrading enzymes limit its bioavailability. In this study, we established a mouse model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-induced Parkinson's disease and intranasally administered balenine, a carnosine analog featuring a methylated imidazole that is resistant to degradation enzymes, to target the brain via the olfactory epithelium. MPTP + balenine-treated mice demonstrated improved recognition scores in the object location test. They also exhibited a significantly increased tyrosine hydroxylase-positive cells and reduced expression of glial fibrillary acidic protein, an inflammatory marker, indicating that balenine mitigated neurodegenerative damage and inflammation in mice with MPTP-induced Parkinson's disease. Proteomic analysis revealed that activation of the KEAP1-NFE2L2 pathway, neddylation, and GSK3B and BTRC:CUL1-mediated degradation of NFE2L2. Collectively, these results highlight the efficacy of intranasal drops of balenine in Parkinson's disease and their potential to improve neurodegenerative disease prognosis.
Abstract The antlers of male deer function as visual displays of power, and as physical weapons to stag opponents, thereby functioning as determinants of social rank. Thus, stags with long and “magnificent” antlers would have more chances for reproductive success. Cervid antlers are shed every year and are costly. Therefore, stags living in resource-poor habitats face a conflict to invest materials into antlers or to maintain good condition. We compared the antlers of sika deer ( Cervus nippon ) living on a small, over-populated island with limited food resources (“Island deer”) and those of a well-nourished populations on the mainland (“Mainland deer”). The antlers of the Island deer were narrower than those of the Mainland deer, and weight per unit length was lighter. The cortex bone was thinner and the density was lower. The cross section was more biased along the anteroposterior axis presumably to provide mechanical strength to cope with stresses imposed when stags lock antlers and push against one another. Numbers of tines were not different between the populations. The Island stags invested limited resources to antlers to maintain its function through maintaining length by increasing porosity, and maintaining numbers and weights of tines.
