Polar Biology最新文献

The nesting site of Magellanic penguins (Spheniscus magellanicus) at Tucker islets (54°09'S; 70°17'W), Chile, is documented and information from the first population abundance estimate on the largest islet during the beginning of chick rearing is provided. Ground-based counts yielded an estimate of 8883 (95% Confidence Intervals: 6653–11,802) burrows; however, counts of active burrows resulted in a total estimate of 2218 (95% Confidence Intervals: 1593–2840) breeding pairs. Based on the estimated total of burrows, this suggests a population decline consistent with trends for other colonies in the Magellan Strait and adjacent waters in Chile. An annual monitoring program to track population changes, breeding success, and chick and egg survival rates is required to assess the species' conservation status of the colony.

Abstract

The fish community of the Scotia Sea is diverse and plays key roles in Antarctic food webs and biogeochemical cycling. However, knowledge of the spatial and community structure of their early life stages is limited, particularly in the region surrounding the South Orkney Islands. Here we examine the structure of the early life stage fish community in the epipelagic using data from a basin-scale survey conducted in early 2019, which sampled the top 200 m of the water column. 347 early life stage fish from 19 genera were caught in 58 hauls. A third of all specimens belonged to the genus Notolepis and the nine most common genera comprised over 90% of specimens. Cluster analysis revealed five distinct groupings, the most common were a group dominated by pelagic and shelf slope genera (Notolepis, Muraenolepis and Electrona) found mainly in oceanic waters (depth ≥ 1000 m), and a group dominated by species with demersal or benthopelagic adults (Chionodraco, Chaenocephalus and Nototheniops) found mainly in shelf waters. Bottom depth was the main environmental determinant of community structure, separating the diverse on-shelf assemblage at the South Orkneys from the less species-rich community of widespread oceanic taxa. Our results indicate the highest diversities of early life stages of endemic fish occur on the shelf and near-shelf areas. Dedicated monitoring is recommended to understand the seasonal differences in larval community assemblages and the implications of early life stages fish bycatch within the krill fishery.

Pink salmon, Oncorhynchus gorbuscha (Walbaum, 1792), a native of the North Pacific Ocean, is an invasive fish species rapidly expanding in the North Atlantic, the adjacent waters of the Arctic Ocean, and rivers in their watersheds. We investigated the species composition of parasites and the structure of parasite communities of the introduced pink salmon in Kandalaksha Bay of the White Sea in 2021. The parasites were identified using morphological and genetic methods. A total of 14 parasite species were recorded. The core species of the parasitic fauna of the introduced pink salmon in the Kandalaksha Bay were Clistobothrium sp., ʽDiphyllobothriumʼ spp., Scolex polymorphus Rudolphi, 1819 (plerocercoids), Brachyphallus crenatus (Rudolphi, 1802), Derogenes varicus (Müller, 1784), Lecithaster salmonis Yamaguti, 1934 (adults), Anisakis simplex (Rudolphi, 1809) sensu stricto (juvenile III), and Hysterothylacium aduncum (Rudolphi, 1802) (juveniles III and IV). We provided the first evidence that the Pacific genetic lineage of A. simplex sensu stricto occurs in European marine waters. In 2021, there was a noticeable increase in the mean abundance of the third-stage juveniles of Anisakis in the White Sea pink salmon compared to the period of 1990s-early 2000s. We conclude that the pink salmon occupies the same trophic niche in the new region of its introduction as in the native range.

The Antarctic continent hosts life forms specially adapted to the extreme climatic challenges. Among these organisms are nematodes, key organisms in the cycling of nutrients in soil food webs. These organisms are bioindicators of environmental disturbances, making their study essential for assessing the impact of human activity in this unique ecosystem. The Carlini Station and the Antarctic Specially Protected Area 132 on the 25 de Mayo/King George Island, Antarctica, has seen limited investigation of free-living soil nematodes. This study aimed to analyze free-living nematode communities in pristine soils and anthropic-intervened soils in the Carlini Station area. Nematodes were extracted from soil samples and morphologically identified at the genus and family levels to calculated ecological indices to assess nematode community structure. Ecological indices (abundance, maturity, enrichment, and soil food structure) were calculated and their values were compared between anthropic and pristine sites using the ANOSIM, SIMPER, and ANOVA statistical tests. Additionally, using molecular analysis, a phylogenetic study was conducted. The study identified four nematode genera, including Plectus spp., Calcaridorylaimus spp., Eudorylaimus spp., and Coomansus spp., with Plectus spp. being the most abundant and widely distributed. Anthropic sites had lower maturity and higher enrichment values, indicative of disturbance, while pristine sites exhibited higher maturity and structure values, suggesting a healthier soil food web. These results suggest that anthropic intervention disrupts nematode communities and represent a significant contribution to the understanding of free-living nematode communities in Antarctica.

This study presents the pattern of occurrence of sub-Antarctic fur seals (SAFS), Arctocephalus tropicalis, in the southern Brazilian coast and evaluate its association with climatic variability and anomalies in the concentration of chlorophytes and sea surface temperature in the reproductive colonies of Gough and Tristan da Cunha Islands. Date, sex, and age class of 254 stranded SAFS recorded between 1992 and 2013 were analyzed. Representative indexes of the patterns of climatic variability and environmental variables were obtained between four and five months before the records, the assumed interval of displacement for species between their closest breeding colonies and the southern Brazilian coast. The species was observed in southern Brazil between May and November each year, and most individuals were adult males. The records of SAFS on the southern Brazilian coast were associated with low concentration of chlorophytes interacting with negative sea surface temperature anomalies, and positive events of South Annular Mode, South Atlantic Ocean Dipole and Indian Ocean Dipole. Climatic variability is influencing the ecology SAFS, because it affects the environmental factors, that act as a driver of dispersion of the species. These variables had been interacting together in the region of the breeding colonies, and possibly during the fur seals’ journey towards the Brazilian coast. Considering the current scenario of global climate change, we expect that SAFS will continue to disperse to areas beyond their regular distribution, not only in the direction of the coasts of southern continents, but also further south, towards higher latitudes.

Carrion decomposition contributes to the soil microbial community structure. This research aimed to identify the soil arthropod, nematode, bacterial, and fungal communities associated with penguin carrion on King George Island, Antarctica. Soil samples were collected around and beneath fresh (freshly killed penguins by the predators) and dried (decomposed more than a year) penguin carrion. Soil bacterial and fungal communities associated with the penguin carrion were analyzed using the 16S rRNA and internal transcribed spacer (ITS) gene sequencing, respectively. Arthropod identification was using Sanger sequencing and nematodes were determined using morphological identification. This study demonstrated no significant differences in arthropod and nematode, bacteria, and fungi communities between decomposition stages, soil location, and species of penguin carrion. This is the first study to identify soil arthropods, nematodes, bacterial, and fungal communities associated with penguin carrion, offering important insights into the initial documentation of the necrobiome communities in the polar region.

Understanding the energy requirement and prey consumption of Arctic predators is crucial to assess their vulnerability to climate change. The bowhead whale (Balaena mysticetus) is the largest predator of the Arctic, with Disko Bay in Greenland constituting a major feeding ground for a segment (predominantly larger juveniles and adult non-lactating females) of the Eastern Canada-West Greenland population. We used unmanned aerial vehicle photogrammetry to measure the body size and condition of bowhead whales in Disko Bay during the spring (March 26–June 1, 2022), from which we quantified their energy requirements and prey consumption. Measurements of body length, width and height were used to estimate the body volume and condition of juveniles (50 measurements from 39 individuals) and adults (232 measurements from 154 individuals). The body condition of adults increased at a rate of 0.112 percentage points day⁻¹, or 44.1–87.8 L of blubber day⁻¹ (for lengths 13.0–17.0 m). Using published data from harvested whales, the estimated blubber mass gain was 37.1–73.9 kg day⁻¹, which equals an energy deposition rate of 1.01–2.01 GJ day⁻¹. Body maintenance costs were predicted from allometric models, while activity costs and the heat increment of feeding were derived from published archival tag data. Reported length-at-age curves were used to estimate somatic growth costs. The energy requirements for juveniles and adults were 0.621–0.778 GJ day⁻¹ (for lengths 11.0–12.9 m) and 3.662–7.826 GJ day⁻¹ (for lengths 13.0–17.0 m), respectively, which equals a prey consumption rate of 17–22 kg of prey day⁻¹ (0.1% of body mass) and 102–218 kg day⁻¹ (0.3% of body mass).

Introduction: Diabetic neuropathy is a well-known complication of diabetes. Recently, hyperglycemia-induced toxicity has been confirmed to participates in multiple cellular pathways typical for neural deterioration. Nicotinamide phosphoribosyltransferase/pre-b cell colony-enhancing factor (Nampt/PBEF)/visfatin is a novel endogenous ligand that some studies have shown its neuroprotective effects on neurodegenerative disease. Therefore, we hypothesized that visfatin may prevent high glucose (HG)-induced neurotoxicity by inhibiting apoptosis, autophagy, and reactive oxygen species (ROS) responses properly.

Methods: In this study, pheochromocytoma cell line 12 (PC12) cells were exposed to both HG concentrations (50, 75, 100, 125, 150 mM) and visfatin (50, 100, 150 ng/mL) at different time -points to determine the optimum time and dose of glucose and visfatin. To investigate the effects of visfatin on HG-induced damage in the PC12 diabetic neuropathy model, we examined ROS response, apoptosis, and autophagy using ROS detection kit, flow cytometry, and real-time PCR/Western blot, respectively.

Results: We determined that HG concentration significantly increased the ROS level and apoptosis of diabetic PC12 cells. However, visfatin treatment significantly decreased the ROS production (P<0.05) and apoptosis of diabetic PC12 cells (P<0.0001). Beclin-1 messenger ribonucleic acid (mRNA) level (P<0.05) and light chain 3 (Lc3)-II protein level (P<0.05) showed that the autophagy pathway is impaired by HG concentrations.

Conclusion: We concluded that visfatin can sufficiently decrease neural damage caused by ROS production and apoptosis under HG-induced toxicity.

Highlights: High glucose significantly increased the ROS level and apoptosis of diabetic PC12 cells;The autophagy pathway is impaired by high glucose;Nampt/PBEF/visfatin can significantly reduce neural damage caused by ROS production and apoptosis of diabetic PC12 cells.

Plain language summary: Diabetes mellitus is a metabolic disorder characterized by hyperglycemia resulting from a failure in insulin secretion, insulin action, or both. Visfatin (Nampt/PBEF) has insulin-mimetic effects. So far, no study has assessed its effects on diabetic neuropathy. Therefore, we examined the neuroprotective effects of visfatin on cell line 12 (PC12) against glucose-induced neurotoxicity. Based on the results, it was concluded that the Nampt/PBEF/visfatin can significantly reduce neural damage caused by production of reactive oxygen species and apoptosis of diabetic PC12 cell.