| 1. |
- Arnason, T., et al.
(författare)
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Impact of temperature and growth hormone on growth physiology of juvenile Atlantic wolffish (Anarhichas lupus)
- 2019
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 504, s. 404-413
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Tidskriftsartikel (refereegranskat)abstract
- The effects of temperature and growth hormone (GH) implantation on growth of juvenile Atlantic wolffish (Anarhichas lupus) were investigated. The year-long study had three sequential experimental phases (EP) termed EP1, EP2 and EP3, lasting for 6, 9 and 37 weeks, respectively. The experimental fish were divided into four groups and reared at different target temperatures (3, 7, 11 and 15 degrees C) during EP1 and EP2, but at a constant temperature of 7 degrees C during EP3. At the beginning of EP2, half of the fish from each group was implanted with formulation of recombinant bovine GH (Posilac (R)), while the other half was sham-implanted with vehicle. The optimal temperature for growth (T-opt.G) of early juveniles (geometric mean weight 7.5 g) was determined as 12.1 degrees C during EP1, while the upper critical temperature (Tc) was concluded to be very close to 15 degrees C, as fish at that temperature had stunted growth, increased mortality and showed external signs of skeletal deformities. Thus, the species was found to be relatively stenothermic during the early juvenile stages and therefore vulnerable to relatively modest increases in environmental temperature above T-opt.G At 15 degrees C, GH implantation had no effects on growth rate. This indicates that the high allostatic load at this temperature leaves no scope for increased growth. In contrast, at lower rearing temperatures, the GH implantation had substantial, long-term effects on growth rate and induced remarkably similar relative growth stimulation at 3, 7 and 11 degrees C, suggesting a temperature-independent mechanism for the growth-promoting effects of GH.
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| 2. |
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| 3. |
- Tetarenko, B. E., et al.
(författare)
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The First Low-Mass Black Hole X-Ray Binary Identified in Quiscence Outside of a Globular Cluster
- 2016
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 825:1
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Tidskriftsartikel (refereegranskat)abstract
- The observed relation between the X-ray and radio properties of low-luminosity accreting black holes (BHs) has enabled the identification of multiple candidate black hole X-ray binaries (BHXBs) in globular clusters (GCs). Here, we report an identification of the radio source VLA J213002.08+120904 (aka M15 S2), recently reported in Kirsten et al., as a BHXB candidate. They showed that the parallax of this flat-spectrum variable radio source indicates a - + 2.2 0.30.5 kpc distance, which identifies it as lying in the foreground of the GC M15. We determine the radio characteristics of this source and place a deep limit on the X-ray luminosity of ∼4 × 1029 erg s.1. Furthermore, we astrometrically identify a faint red stellar counterpart in archival Hubble images with colors consistent with a foreground star; at 2.2 kpc, its inferred mass is 0.1-0.2Me. We rule out that this object is a pulsar, neutron star X-ray binary, cataclysmic variable, or planetary nebula, concluding that VLA J213002.08+120904 is the first accreting BHXB candidate discovered in quiescence outside of a GC. Given the relatively small area over which parallax studies of radio sources have been performed, this discovery suggests a much larger population of quiescent BHXBs in our Galaxy, 2.6 ± 104-1.7 × 108 BHXBs at 3× confidence, than has been previously estimated (∼102-104) through population synthesis.The observed relation between the X-ray and radio properties of low-luminosity accreting black holes (BHs) has enabled the identification of multiple candidate black hole X-ray binaries (BHXBs) in globular clusters (GCs). Here, we report an identification of the radio source VLA J213002.08+120904 (aka M15 S2), recently reported in Kirsten et al., as a BHXB candidate. They showed that the parallax of this flat-spectrum variable radio source indicates a - + 2.2 0.30.5 kpc distance, which identifies it as lying in the foreground of the GC M15. We determine the radio characteristics of this source and place a deep limit on the X-ray luminosity of ∼4 × 1029 erg s.1. Furthermore, we astrometrically identify a faint red stellar counterpart in archival Hubble images with colors consistent with a foreground star; at 2.2 kpc, its inferred mass is 0.1-0.2Me. We rule out that this object is a pulsar, neutron star X-ray binary, cataclysmic variable, or planetary nebula, concluding that VLA J213002.08+120904 is the first accreting BHXB candidate discovered in quiescence outside of a GC. Given the relatively small area over which parallax studies of radio sources have been performed, this discovery suggests a much larger population of quiescent BHXBs in our Galaxy, 2.6 ± 104-1.7 × 108 BHXBs at 3× confidence, than has been previously estimated (∼102-104) through population synthesis.
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| 4. |
- Árnason, Úlfur, et al.
(författare)
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Whole-genome sequencing of the blue whale and other rorquals finds signatures for introgressive gene flow
- 2018
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Reconstructing the evolution of baleen whales (Mysticeti) has been problematic because morphological and genetic analyses have produced different scenarios. This might be caused by genomic admixture that May have taken place among some rorquals. We present the genomes of six whales, including the blue whale (Balaenoptera musculus), to reconstruct a species tree of baleen whales and to identify phylogenetic conflicts. Evolutionary multilocus analyses of 34,192 genome fragments reveal a fast radiation of rorquals at 10.5 to 7.5 million years ago coinciding with oceanic circulation shifts. The evolutionarily enigmatic gray whale (Eschrichtius robustus) is placed among rorquals, and the blue whale genome shows a high degree of heterozygosity. The nearly equal frequency of conflicting gene trees suggests that speciation of rorqual evolution occurred under gene flow, which is best depicted by evolutionary networks. Especially in marine environments, sympatric speciation might be common; our results raise questions about how genetic divergence can be established.
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| 5. |
- Kutschera, Verena E., et al.
(författare)
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High genetic variability of vagrant polar bears illustrates importance of population connectivity in fragmented sea ice habitats
- 2016
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Ingår i: Animal Conservation. - : Wiley. - 1367-9430 .- 1469-1795. ; 19:4, s. 337-349
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Tidskriftsartikel (refereegranskat)abstract
- Projections by the Intergovernmental Panel on Climate Change (IPCC) and sea ice forecasts suggest that Arctic sea ice will decline markedly in coming decades. Expected effects on the entire ecosystem include a contraction of suitable polar bear habitat into one or few refugia. Such large-scale habitat decline and fragmentation could lead to reduced genetic diversity. Here we compare genetic variability of four vagrant polar bears that reached Iceland with that in recognized subpopulations from across the range, examining 23 autosomal microsatellites, mitochondrial control region sequences and Y-chromosomal markers. The vagrants' genotypes grouped with different genetic clusters and showed similar genetic variability at autosomal microsatellites (expected heterozygosity, allelic richness, and individual heterozygosity) as individuals in recognized subpopulations. Each vagrant carried a different mitochondrial haplotype. A likely route for polar bears to reach Iceland is via Fram Strait, a major gateway for the physical exportation of sea ice from the Arctic basin. Vagrant polar bears on Iceland likely originated from more than one recognized subpopulation, and may have been caught in sea ice export during long-distance movements to the East Greenland area. Although their potentially diverse geographic origins might suggest that these vagrants encompass much higher genetic variability than vagrants or dispersers in other regions, the four Icelandic vagrants encompassed similar genetic variability as any four randomly picked individuals from a single subpopulation or from the entire sample. We suggest that this is a consequence of the low overall genetic variability and weak range-wide genetic structuring of polar bears - few dispersers can represent a large portion of the species' gene pool. As predicted by theory and our demographic simulations, continued gene flow will be necessary to counteract loss of genetic variability in increasingly fragmented Arctic habitats. Similar considerations will be important in the management of other taxa that utilize sea ice habitats.
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