Search Results (16)

The environmental drivers of fin whale (Balaenoptera physalus) acoustic presence in Eastern Antarctic waters were investigated based on passive acoustic recordings from four sites, 2013–2019. Fin whale 20 Hz pulses were detected from late austral summer to early winter. Daily values of sea-ice concentration (SIC) were compared with the number of days with fin whale 20 Hz acoustic presence using a generalized additive model approach. At the Southern Kerguelen Plateau, Casey, and Dumont d’Urville sites, SIC correlated with fin whale calling activity, but less so at the Prydz site. Changes in SIC between sites resulted in variation in acoustic presence: Earlier sea-ice formation at Dumont d’Urville resulted in less acoustic presence in comparison to the Southern Kerguelen Plateau, where sea ice formed later in the season. Interannual variability in SIC impacted yearly acoustic presence, with a later onset of high SIC resulting in greater acoustic presence and later departure (migration timing) of the animals. Identifying the environmental drivers of fin whale presence is key to informing how this migratory species may be affected by environmental variability resulting from climate change. Full article

The Southern Ocean, located between Antarctica and the southern tips of South America, Africa and Australia, encompasses an immense area across the southern Atlantic, Pacific and Indian oceans with no clearly defined limits. For the purposes of studying marine heterobranch sea slugs, we consider the Southern Ocean to include all ocean areas located south of latitude 41° S. South of this latitude, we consider different areas and zones: the area of South America (the Patagonia/Magellanic area), the island of Tasmania, the southern island of New Zealand, the Subantarctic area (the Falkland Islands, South Georgia Island, the South Orkney Islands, South Sandwich Island, Bouvet Island, the islands of Crozet and Prince Edward, the Kerguelen Islands, and Macquarie Island) and the area of Antarctica, in which we consider four zones (Weddell Sea, West Antarctica, Ross Sea and East Antarctica). Reviewing all available references and unpublished data from the authors, in total, 394 species of heterobranch sea slugs have been recorded to date in the Southern Ocean > 41° S, with Nudibranchia standing out with 209 species and Cephalaspidea with 90 species. The marine heterobranchs of Tasmania (154 species) and southern New Zealand (120 species) have been well studied. Sea slug fauna of the Antarctic and Subantarctic regions have been the subject of several partial studies; however, there are still many gaps in knowledge across both areas. Eighty-nine different species of sea slug have been recorded so far in strictly Antarctic waters (West Antarctica, 45 species; Weddell Sea, 48 species; Ross Sea, 51 species; East Antarctica, 42 species), while in the various Subantarctic regions, there are 93 species (36 species from South Georgia, 17 species from the South Orkneys, 12 species from south Sandwich, 6 species from Bouvet, 10 species from Prince Edward and Crozet Islands, 15 species from Kerguelen, 3 species from Macquarie Island, 29 species from the Falkland Islands and 71 species from the coast of South America). In the taxonomic section, for each of the species, the location and the authors of the records are indicated, and for many of the species, interesting biological, taxonomic or biogeographic observations are also provided. The importance of sampling in underexplored areas is discussed, as well as greater-depth sampling for a better understanding of the sea slugs of the Southern Ocean. Full article

The widespread occurrence of Mesozoic ocean island basalt (OIB)-like igneous rocks in the Southern Tibetan Himalayan Belt provides important constraints on the rifting of East Gondwana. This study undertook a petrological, geochronological, and geochemical investigation of mafic intrusive rocks in the Cuona area of the eastern Tethyan Himalayan Belt. The mafic intrusions have OIB-type geochemical signatures, including diabase porphyrite, gabbro, and diabase. Zircon U–Pb dating indicates that the diabase porphyrite formed at 135.0 ± 1.6 Ma. The diabase porphyrite and gabbro are enriched in high-field-strength elements (Nb and Ti) and large-ion lithophile elements (Sr and Pb) and experienced negligible lithospheric mantle or crustal contamination. The diabase is enriched in large-ion lithophile elements (LILEs, e.g., La and Ce) and depleted in high-field-strength elements (HFSEs, e.g., Ru, Zr and Ti). In general, the mafic intrusions exhibit significant light REE enrichment and heavy REE depletion and have no Eu anomalies. Whole-rock neodymium (ε_Nd(t) = 1.55) and zircon Hf (ε_Hf(t) = 0.60–3.73) isotopic compositions indicate derivation of the magma from enriched type I mantle. We propose that the diabase porphyrite and diabase formed in a continental margin rift setting, influenced by the Kerguelen mantle plume, and represent magmatism related to the breakup of East Gondwana. However, the gabbro formed in a relatively stable continental intraplate environment, likely derived from deep magmatic processes associated with the Kerguelen mantle plume. Our results provide new constraints on the early activity of the Kerguelen mantle plume and offer insights into the breakup and tectonic evolution of East Gondwana. Full article

The Zhegu area in southern Tibet is situated in the central and eastern part of the Tethys Himalayan tectonic belt, with the Kangbuzhenri area being abundant in gneissic granites. This study examines the petrology, chronology, and geochemistry of the Kangbuzhenri gneissic granite, providing insights into its Pan-African and Early Paleozoic geological evolution. The zircon U-Pb chronology indicates an upper intercept age of ~539 Ma, reflecting Pan-African orogenic events in the eastern part of the Tethys Himalayan tectonic belt, and a lower intercept age of ~144 Ma, representing a late tectonic–thermal event. Geochemically, the gneissic granites are calc-alkaline peraluminous rocks with high SiO₂ and Al₂O₃ contents and low TiO₂, P₂O₅, MgO, and FeO^T contents. The gneissic granites are enriched in LREE and LILEs (Rb, Pb, Th, U, etc.), but relatively depleted in HREE and HFSEs (Nb, Ti, P, etc.). Most of them show a weak negative δEu anomaly, except for two samples which show a significant negative δEu anomaly due to the crystallization of plagioclase. Based on the above study, most of the gneissic granites exhibited the characteristics of an I-type granite, while two of the samples were a highly differentiated I-type granite with S-type affinities. All the above characteristics indicate that the gneissic granite likely originated from the partial melting of crustal materials and sediments with a minor involvement of mantle-derived materials. Combined with the previous chronological studies, the Kangbuzhenri gneissic granites were formed in an extensional tectonic environment during post-collision orogeny and then they were influenced by the Kerguelen mantle plume tectonic–thermal event around ~144 Ma and the subsequent Southern Tibet Detachment System (STDS). Full article

Abatus is a genus of irregular brooding sea urchins to the Southern Ocean. Among the 11 described species, three shared morphological traits and present an infaunal lifestyle in the infralittoral from the Subantarctic province; A. cavernosus in Patagonia, A. cordatus in Kerguelen, and A. agassizii in Tierra del Fuego and South Shetlands. The systematic of Abatus, based on morphological characters and incomplete phylogenies, is complex and largely unresolved. This study evaluates the shape variation among these species using geometric morphometrics analysis (GM). For this, 72 individuals from four locations; South Shetlands, Kerguelen, Patagonia, and Falklands/Malvinas were photographed, and 37 landmarks were digitized. To evaluate the shape differences among species, a principal component analysis and a Procrustes ANOVA were performed. Our results showed a marked difference between the Falklands/Malvinas and the other localities, characterized by a narrower and more elongated shape and a significant influence of location in shape but not sex. Additionally, the effect of allometry was evaluated using a permutation test and a regression between shape and size, showing significant shape changes during growth in all groups. The possibility that the Falklands/Malvinas group shows phenotypic plasticity or represents a distinct evolutionary unit is discussed. Finally, GM proved to be a powerful tool to differentiate these species, highlighting its utility in systematic studies. Full article

Atherosclerosis is the primary cause of cardiovascular disease. The development of plaque complications, such as calcification and neo-angiogenesis, strongly impacts plaque stability and is a good predictor of mortality in patients with atherosclerosis. Despite well-known risk factors of plaque complications, such as diabetes mellitus and chronic kidney disease, the mechanisms involved are not fully understood. We and others have identified that the concentration of circulating leucine-rich α-2 glycoprotein 1 (LRG1) was increased in diabetic and chronic kidney disease patients. Using apolipoprotein E knockout mice (ApoE−/−) (fed with Western diet) that developed advanced atherosclerosis and using human carotid endarterectomy, we showed that LRG1 accumulated into an atherosclerotic plaque, preferentially in calcified areas. We then investigated the possible origin of LRG1 and its functions on vascular cells and found that LRG1 expression was specifically enhanced in endothelial cells via inflammatory mediators and not in vascular smooth muscle cells (VSMC). Moreover, we identified that LRG1 was able to induce calcification and SMAD1/5-signaling pathways in VSMC. In conclusion, our results identified for the first time that LRG1 is a direct contributor to vascular calcification and suggest a role of this molecule in the development of plaque complications in patients with atherosclerosis. Full article

The volcanic Kerguelen Islands are formed on one of the world’s largest submarine plateaus. Located in the remote segment of the southern Indian Ocean close to Antarctica, the Kerguelen Plateau is notable for a complex tectonic origin and geologic formation related to the Cretaceous history of the continents. This is reflected in the varying age of the oceanic crust adjacent to the plateau and the highly heterogeneous bathymetry of the Kerguelen Plateau, with seafloor structure differing for the southern and northern segments. Remote sensing data derived from marine gravity and satellite radar altimetry surveys serve as an important source of information for mapping complex seafloor features. This study incorporates geospatial information from NOAA, EMAG2, WDMAM, ETOPO1, and EGM96 datasets to refine the extent and distribution of the extracted seafloor features. The cartographic joint analysis of topography, magnetic anomalies, tectonic and gravity grids is based on the integrated mapping performed using the Generic Mapping Tools (GMT) programming suite. Mapping of the submerged features (Broken Ridge, Crozet Islands, seafloor fabric, orientation, and frequency of magnetic anomalies) enables analysis of their correspondence with free-air gravity and magnetic anomalies, geodynamic setting, and seabed structure in the southwest Indian Ocean. The results show that integrating the datasets using advanced cartographic scripting language improves identification and visualization of the seabed objects. The results include 11 new maps of the region covering the Kerguelen Plateau and southwest Indian Ocean. This study contributes to increasing the knowledge of the seafloor structure in the French Southern and Antarctic Lands. Full article

The linear Ninetyeast Ridge (NER) is the longest oceanic intraplate volcanic edifice and main feature in the Eastern Indian Ocean. Many seamounts are located on the ridge, whose origin and age remain unclear due to the lack of samples of the bedrock of which they are composed. Carbonate sedimentary caps on these seamounts prevent their direct geological sampling by dredging, therefore indirect geophysical methods are an alternative. Such integrated geophysical studies (the main methods are multibeam bathymetry and magnetic surveys) were carried out in cruise #42 of the R/V Akademik Boris Petrov in 2017 on a large seamount at the base of the NER’s western slope near 0.5° S. The collected data also includes seismic reflection data that reveal morphology, fault tectonics, depth structure, and an assumed origin of this volcanic feature. The Ninetyeast Ridge was formed by the Kerguelen plume magmatism at 50° S in the giant N-S fault. The seamount studied in cruise #42 of the R/V Akademik Boris Petrov was formed mainly to the north as a result of two-stage magmatism in a transverse strike-slip fault. The first stage (47 Ma) formed the main western part of the seamount at 20° S. The second stage (23 Ma) formed its eastern part at 8° S. The time intervals between the formation of the main massif of the Ninetyeast Ridge and the stages of subsequent magmatism that formed the western and eastern parts of the seamount are approximately 31 and 55 Ma, respectively. Full article

Our understanding of how microbiome signatures are modulated in wild fish populations remains poorly developed and has, until now, mostly been inferred from studies in commercial and farmed fish populations. Here, for the first time, we have studied changes in the skin and blood microbiomes of the Salmo trutta population of the volcanic Kerguelen archipelago located at the northern limit of the Antarctic Ocean. The Kerguelen Islands present a natural framework of population expansion and reveal a likely situation representing further climate change in distribution areas. Our results showed that S. trutta of the Kerguelen Islands has a microbiome signature distinct from those of salmonids of the Northern Hemisphere. Our study also revealed that the skin and blood microbiomes differ between sedentary and migratory S. trutta. While 18 phyla were shared between both groups of trout, independent of the compartment, 6 phyla were unique to migratory trout. Further analyses showed that microbiome signatures undergo significant site-specific variations that correlate, in some cases, with the peculiarity of specific ecosystems. Our study also revealed the presence of potential pathogens at particular sites and the impact of abiotic factors on the microbiome, most notably due to the volcanic nature of the environment. This study contributes to a better understanding of the factors that modulate the microbiome signatures of migratory and sedentary fish populations. It will also help to better monitor the impacts of climate change on the colonization process in the sub-Antarctic region. Full article

The Late Aptian Rajmahal Traps originated through Kerguelen-Plume-related volcanism at the eastern margin of the Indian Shield. Clinopyroxene and whole-rock thermobarometry reveals that the Rajmahal magmas crystallized at P-T conditions of ≤~5 kbar/~1100–1200 °C. These pressures correspond to upper crustal depths (≤~19 km). Modeling shows that the Rajmahal primary magmas were last in equilibrium with mantle at P-T conditions of ~9 kbar/~1280 °C. The corresponding depths (~33 km) are consistent with gravity data that indicate a high-density layer at lower crustal depths below an upwarped Moho. Thus, the high-density layer probably represents anomalous mantle. It is likely that the mantle-derived magmas accumulated below the upwarped Moho and were subsequently transported via trans-crustal faults/fractures to the upper crust where they evolved by fractional crystallization in small staging chambers before eruption. In the lower part of the Rajmahal plumbing system, buoyant melts from the Kerguelen Plume may have moved laterally and upward along the base of the lithosphere to accumulate and erode the eastern Indian lithospheric root. The Rajmahal plumbing system was probably shaped by tectonic forces related to the breakup of Gondwana. Full article

The isolated sub-Antarctic islands are of major ecological interest because of their unique species diversity and long history of limited human disturbance. However, since the presence of Europeans, these islands and their sensitive biota have been under increasing pressure due to human activity and associated biological invasions. In such delicate ecosystems, biological invasions are an exceptional threat that may be further amplified by climate change. We examined the invasion trajectory of the blowfly Calliphora vicina (Robineau-Desvoidy 1830). First introduced in the sub-Antarctic Kerguelen Islands in the 1970s, it is thought to have persisted only in sheltered microclimates for several decades. Here, we show that, in recent decades, C. vicina has been able to establish itself more widely. We combine experimental thermal developmental data with long-term ecological and meteorological monitoring to address whether warming conditions help explain its current success and dynamics in the eastern Kerguelen Islands. We found that warming temperatures and accumulated degree days could explain the species’ phenological and long-term invasion dynamics, indicating that climate change has likely assisted its establishment. This study represents a unique long-term view of a polar invader and stresses the rapidly increasing susceptibility of cold regions to invasion under climate change. Full article

Age and growth of blue antimora Antimora rostrata were examined in the waters off New Zealand and Macquarie Island (southwestern Pacific). Samples off Macquarie Island were collected from bycatch in the Patagonian toothfish longline fishery. Individuals between 20 and 44 years in age measured between 37.6–71.1 cm in total length. Bottom trawl catches from New Zealand waters consisted of smaller and younger fish (11 to 38 years), measuring 22.5–52.5 cm long. The age classes with the greatest numbers in the former area were represented by fish aged 33–34 years (25.7%). In the latter area, the most numerous age classes were 21–23 years (12.1%), 28–29 years (17.6%), and 32 years (6.6%). The blue antimora from off the Macquarie Island show similar growth rates to those of individual fish from the Ross, Lazarev and Weddell Seas, waters off the Kerguelen and Crozet Islands, and southeastern Greenland. Individuals from New Zealand waters demonstrate the slowest growth rates compared to other parts of the species’ range but are quite similar to individuals from the Flemish Cap area. Further research to identify the stock structure of this broadly distributed species is warranted to provide context to differences in growth rates observed between populations. Full article

Latin America is the center of domestication and diversity of maize, the second most cultivated crop worldwide. In this region, maize landraces are fundamental for food security, livelihoods, and culture. Nevertheless, genetic erosion (i.e., the loss of genetic diversity and variation in a crop) threatens the continued cultivation and in situ conservation of landrace diversity that is crucial to climate change adaptation and diverse uses of maize. We provide an overview of maize diversity in Latin America before discussing factors associated with persistence of large in situ maize diversity, causes for maize landrace abandonment by farmers, and strategies to enhance the cultivation of landraces. Among other factors, maize diversity is linked with: (1) small-holder farming, (2) the production of traditional food products, (3) traditional cropping systems, (4) cultivation in marginal areas, and (5) retention of control over the production system by the farmers. On the other hand, genetic erosion is associated with substitution of landraces with hybrid varieties or cash crops, and partial (off-farm labor) or complete migration to urban areas. Continued cultivation, and therefore on-farm conservation of genetic diversity held in maize landraces, can be encouraged by creating or strengthening market opportunities that make the cultivation of landraces and open pollinated varieties (OPVs) more profitable for farmers, supporting breeding programs that prioritize improvement of landraces and their special traits, and increasing the access to quality germplasm of landraces and landrace-derived OPVs. Full article

Small populations establishing on colonization fronts have to adapt to novel environments with limited genetic variation. The pace at which they can adapt, and the influence of genetic variation on their success, are key questions for understanding intraspecific diversity. To investigate these topics, we performed a reciprocal transplant experiment between two recently founded populations of brown trout in the sub-Antarctic Kerguelen Islands. Using individual tagging and genetic assignment methods, we tracked the fitness of local and foreign individuals, as well as the fitness of their offspring over two generations. In both populations, although not to the same extent, gene flow occurred between local and foreign gene pools. In both cases, however, we failed to detect obvious footprints of local adaptation (which should limit gene flow) and only weak support for genetic rescue (which should enhance gene flow). In the population where gene flow from foreign individuals was low, no clear differences were observed between the fitness of local, foreign, and F1 hybrid individuals. In the population where gene flow was high, foreign individuals were successful due to high mating success rather than high survival, and F1 hybrids had the same fitness as pure local offspring. These results suggest the importance of considering sexual selection, rather than just local adaptation and genetic rescue, when evaluating the determinants of success in small and recently founded populations. Full article

Plants produce a high diversity of metabolites which help them sustain environmental stresses and are involved in local adaptation. However, shaped by both the genome and the environment, the patterns of variation of the metabolome in nature are difficult to decipher. Few studies have explored the relative parts of geographical region versus environment or phenotype in metabolomic variability within species and none have discussed a possible effect of the region on the correlations between metabolites and environments or phenotypes. In three sub-Antarctic Ranunculus species, we examined the role of region in metabolite differences and in the relationship between individual compounds and environmental conditions or phenotypic traits. Populations of three Ranunculus species were sampled across similar environmental gradients in two distinct geographical regions in îles Kerguelen. Two metabolite classes were studied, amines (quantified by high-performance liquid chromatography and fluorescence spectrophotometry) and flavonols (quantified by ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry). Depending on regions, the same environment or the same trait may be related to different metabolites, suggesting metabolite redundancy within species. In several cases, a given metabolite showed different or even opposite relations with the same environmental condition or the same trait across the two regions, suggesting metabolite versatility within species. Our results suggest that metabolites may be functionally redundant and versatile within species, both in their response to environments and in their relation with the phenotype. These findings open new perspectives for understanding evolutionary responses of plants to environmental changes. Full article