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openother-openDec 2019View details →

Data from: Assembly ASM291031v2 (Genbank: GCA_002910315.2) identified as assembly of the Northern Dolly Varden (Salvelinus malma malma) genome, and not the Arctic char (S. alpinus) genome

Here is the data that is a supplementary to the preprint: Shedko S.V. 2019. Assembly ASM291031v2 (Genbank: GCA_002910315.2) identified as assembly of the Northern Dolly Varden (Salvelinus malma malma) genome, and not the Arctic char (S. alpinus) genome // arXiv:1912.02474 <a href="https://arxiv.org/abs/1912.02474">https://arxiv.org/abs/1912.02474</a>

Fig. 3 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 3. Normal aspect of the retina in Arctic charr with different layers. From the eye exterior to the eye interior: (RP): Retinal pigment epithelium. (RC) Cones and rods layer. (ON) Outer nuclear layer. (OP) Outer plexiform layer. (IN) Inner nuclear layer (IP) Inner plexiform layer. (GC) Ganglion cell layer. (GA) Axons of the ganglion layer. Scale bar = 300 μm.

Fig. 6 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 6. Edge of one of the vesicles produced by the accumulation of parasites. Retinal pigment layer and rods and cones layer display a progressive alteration in their structure and finally both layers become detached. Notice the reduction of the thickness of the RPE (arrow) in the vesicle. Scale bar = 300 μm.

Fig. 12 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 12. PP-morphs. Diffuse changes in the posterior retina affecting mainly the RPE layer suggesting potential healing. Scale bar = 200 μm.

Fig. 4 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 4. Diplostomum sp. metacercaria within the retinal structures. This specimen is clearly placed between the retinal pigmented epithelium (RP) and rod and cones layer (RC) creating a small space between them and the parasite. Damaged retinal pigment epithelium is clearly observed and also rod and cone layer display morphological alterations. Scale bar = 200 μm.

Fig. 11. A in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 11. A single Diplostomum sp. metacercaria within the posterior retina with scarce development of surrounding vesicle and mechanical compression against the RPE and the cones and rods layers. Scale bar = 200 μm.

Fig. 7 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 7. Early lesions in RPE and RC in the retina closer to the edge of the vesicles. Cones and rods display a disorganized pattern between the pigmented processes of the RPE. Scale bar = 100 μm.

Fig. 2 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 2. Vesicle with several Diplostomum specimens in a histological section. Vesicles are typically located near the ciliary body/retina contact area. C: cornea. I: iris. H/E. Scale bar = 1 mm.

Fig. 5 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 5. Large vesicle with sections of many Diplostomum specimens. The vesicle clearly creates a large space between RP and RC. Scale bar = 400 μm.

opencc-zeroSep 2020View details →

Limited genetic parallelism underlies recent, repeated incipient speciation in geographically proximate populations of an Arctic fish (Salvelinus alpinus)

The genetic underpinnings of incipient speciation, including the genomic mechanisms which contribute to morphological and ecological differentiation and reproductive isolation, remain poorly understood. The repeated evolution of consistently, phenotypically distinct morphs of Arctic Charr (Salvelinus alpinus) within the Quaternary period offer an ideal model to study the repeatability of evolution at the genomic level. Sympatric morphs of Arctic Charr are found across this species' circumpolar distribution. However, the specific genetic mechanisms driving this morph differentiation are largely unknown despite the cultural and economic importance of the anadromous morph. We used a newly designed 87k SNP chip to investigate the character and consistency of the genomic differences among sympatric morphs within three recently deglaciated and geographically proximate lakes in Labrador, Canada. We found genetically distinct small and large morph Arctic Charr in all three lakes consistent with resident and anadromous morphs, respectively. A degree of reproductive isolation among sympatric morphs is likely given genome-wide distributions of outlier SNPs and high genome-wide FSTs. Across all lakes, outlier SNPs were largely non-overlapping suggesting a lack of genetic parallelism driving morph differentiation. Alternatively, several genes and paralogous copies of the same gene consistently differentiated morphs across multiple lakes suggesting their importance to the manifestation of morphs. Our results confirm the utility of Arctic Charr as a model for investigating the predictability of evolution and support the importance of both genetic parallelism and non-parallelism to the incipient speciation of Arctic Charr morphs.

opencc-zeroDec 2021View details →

Investigating the morphological and genetic divergence of arctic char (Salvelinus alpinus) populations in lakes of arctic Alaska

Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char (Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length-frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus were likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present-day char populations. Although some lakes exhibit bimodal size distributions, using model-based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping-by-sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha-1), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food-limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.

opencc-zeroFeb 2022View details →

Genomic basis of deep‐water adaptation in Arctic Charr (Salvelinus alpinus) morphs

Colonization of extreme habitats requires extensive adaptation to novel environmental challenges. Deep-water environments (>50 m) have high hydrostatic pressure, low temperature, and low light, requiring physiological and visual system adaptation, but genomic mechanisms underlying evolution in these environments are rarely known. Post-glacial colonization of Gander Lake in Newfoundland, Canada, by Arctic Charr (Salvelinus alpinus) provides the opportunity to study the genomic basis of adaptation to extreme deep-water environments. Here, we compare genomic and morphometric divergence between a phenotypically divergent deep-water, demersal morph adapted to depths of up to 288m and a larger, piscivorous morph occupying shallower depths. Using a SNP array and resequencing of nuclear and mitochondrial genomes, we find moderate genetic divergence (FST = 0.15 - 0.11) between morphs, consistent with divergence in body shape and size, despite absence of mitochondrial genome divergence. Outlier analyses identified three key genes with very high divergence against a genome-wide distribution of diverged genomic islands containing genes with functions related to deep-water adaptation such as sensory processes, ligand binding and regulation of transcription. Quantification of SNP array signal intensity variation associated with complex polymorphisms (e.g. copy number variants), similarly uncovered genetic separation of morphs and coincided with several islands of genomic divergence, but also revealed additional genomic regions and molecular mechanisms associated with depth adaptation. Together, these results show that adaptation to an extreme deep-water environment has been facilitated by multiple polymorphism types with roles in cellular and physiological processes, providing insight into the genomic basis of adaptation in extreme environments.

opencc-zeroApr 2022View details →

The genomic consistency of the loss of anadromy in an Arctic fish (Salvelinus alpinus)

The potentially significant genetic consequences associated with the loss of migratory capacity of diadromous fishes which have become landlocked in freshwater are poorly understood. Consistent selective pressures associated with freshwater residency may drive repeated differentiation both between allopatric landlocked and anadromous populations and within landlocked populations (resulting in sympatric morphs). Alternatively, the strong genetic drift anticipated in isolated landlocked populations could hinder consistent adaptation, limiting genetic parallelism. Understanding the degree of genetic parallelism underlying differentiation has implications for both the predictability of evolution and management practices. We employed an 87k SNP array to examine the genetic characteristics of landlocked and anadromous Arctic Charr (Salvelinus alpinus) populations from five drainages within Labrador, Canada. One gene was detected as an outlier between sympatric, size-differentiated morphs in each of two landlocked lakes. While no single locus differentiated all replicate pairs of landlocked and anadromous populations, several SNPs, genes, and paralogs, were consistently detected as outliers in at least 70% of these pairwise comparisons. A significant C-score suggested the amount of shared outlier SNPs across all paired landlocked and anadromous populations was greater than expected by chance. Our results indicate that despite their isolation, selection due to the loss of diadromy may drive consistent genetic responses in landlocked populations.

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Fig. 13 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 13. Diplostomum sp. metacercaria in a choroidal vessel. Scale bar = 200 μm.

opencc-by-4.0Nov 2024View details →

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Supplementary data for: "Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago after the End of the Little Ice Age"

Supplementary data for: “Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago after the End of the Little Ice Age” <a href="https://doi.org/10.1029/2024JG008367">https://doi.org/10.1029/2024JG008367</a>   Abstract: Glaciers in the Svalbard Archipelago are retreating rapidly in response to climate change. The retreat of glaciers leads to alteration of the hydrological and thermal regimes of the freshwater ecosystems. In this delicate context, existing anadromous Arctic charr (Salvelinus alpinus) populations are at severe risk and might disappear from the archipelago. However, the retreat of glaciers also promotes the formation of new lake systems that might be suitable for colonization by anadromous Arctic charr. These systems may provide a substantial opportunity for the establishment of new populations of anadromous charr, potentially buffering the decline in existing systems. To date, there is a lack of information on the number of recently deglaciated lake systems that have emerged since the end of the Little Ice Age (ca. 1920) that might be suitable for charr colonization. Therefore, the goal of this paper is to provide an initial assessment of the number of these lakes. To this end, and in accordance with previously published research, this study assesses whether a recently deglaciated lake system is potentially open to colonization based on gradient, river length, and lake surface area. Depending on the applied threshold (four in total), up to 24 lake systems are classified as potentially open to colonization by anadromous Arctic charr, with Spitsbergen emerging as a colonization hotspot. The findings of this paper might serve as basis for new studies and for implementing proactive management and conservation strategies to protect anadromous charr populations.   Data description:   Recently_Deglaciated_Systems [EPGS: 25833] - Shapefile containing the information of 168 lake systems that emerged between 1936/1938 and 2020 in the Svalbard Archipelago ID: Identification number X: Easting Y: Northing Fall?: Presence of the lake system in fall (with dates when the lake was visible in satellite images) Spring?: Presence of the lake system in spring (with dates when the lake was visible in satellite images) Info: information regarding the type of system (i.e., larger lake surrounded by lakes and ponds or system of multiple lakes and ponds). If blank, lake is considered single.   Analysis [EPGS: 25833] - Shapefile containing the analysis of 125 lake systems with connection to the ocean. ID: Identification number X: Easting Y: Northing Surface (km2): Surface of the connected recently deglaciated lake system (km2) Elevation (m): Elevation of the outlet (m) Length (m): River length (m) Slope (%): Slope of the river (%) SV1: Result of the classification with SV1 SV2: Result of the classification with SV2 HY: Result of the classification with HY NO: Result of the classification with NO

opencc-zeroNov 2022View details →

Relationships between egg size and maternal size, life-history forms, and habitats of Greenlandic Arctic charr (Salvelinus alpinus)

Arctic charr (Salvelinus alpinus [L.] complex) has been widely used as a model system for studies in evolutionary ecology because of its diversity in feeding ecology, habitat use, life-history forms, and associated morphologies observed in matured individuals. However, we still know relatively little about traits exhibited early in life of the species, although the trait diversity of matured individuals may largely be shaped during development. Egg size is a key determinant ofvarious traits exhibited early in life. Therefore, describing egg size variation within- and between-individuals as well as the link between egg size and adult traits will be a useful step in understanding the early life trait diversity of Arctic charr. Here, using Greenlandic Arctic charr, which includes alternative life-history forms (i.e., anadromous and resident) and spawning habitat use (i.e., lake- and river- spawner), we described egg size variation (i.e., clutch-mean egg diameter and within-clutch variation) and explored the link between egg size variation and female body length, life-history form, and spawning habitats. As in many other fishes, clutch-mean egg diameter increased with female body length. No significant effect of other female traits on clutch mean-egg diameter was detected, suggesting that female body size variation could be a direct cause of early life history trait variation. On the other hand, we found that the degree of within-clutch variation of the anadromous life-history form was higher than that of the resident life-history form. The pattern could be interpreted in an adaptive context. For instance, given that the anadromous life-history form tends to be semelparous, anadromous females could decrease the likelihood of complete reproductive failure by producing variable-sized offspring within a clutch since at least some offspring are expected to be matched to the prevailing environment.

publicDec 2021View details →

Investigating the morphological and genetic divergence of arctic char (Salvelinus alpinus) populations in lakes of arctic Alaska

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publicSep 2020View details →

Limited genetic parallelism underlies recent, repeated incipient speciation in geographically proximate populations of an Arctic fish (Salvelinus alpinus)

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publicApr 2022View details →

The genomic consistency of the loss of anadromy in an Arctic fish (Salvelinus alpinus)

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