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Fig. 6 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 6. Icefish (Salanx ariakensis) collected from the Yangtze River estuary show diverse otolith Sr/Ca profiles that represent whole-life residence in the sea (a), the movement from the river to the sea at during juvenile stage (b) and the movement from the sea to the river at adult stage (c).

Fig. 5 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 5. Icefish (Neosalanx anderssoni) collected from Qinhuangdao (Bohai Sea) display variably high otolith Sr/Ca ratios, indicating marine residence for the fish.

Fig. 4 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 4. Icefish (Neosalanx tangkahkeii) collected from the Pearl River estuary display consistently high otolith Sr/Ca ratios, indicating brackish and marine residence for these 10 fish.

Fig. 2 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 2. Otolith of the icefish (Neosalanx anderssoni) collected in Qinhuangdao (Bohai Sea) showing the daily growth increments and electron microprobe transect from the core to the edge for measuring Sr/Ca ratios. Arrows point out the rectangular beam marks after the analysis by the eletron microprobe.

Fig. 1 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 1. Approximate sampling locations (indicated by the arrows) of the icefish in the Bohai Sea, the Yangtze River estuary, Taihu Lake and the Pearl River estuary.

Fig. 3 in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 3. Consistently low otolith Sr/Ca ratios of the icefish, Neosalanx tangkahkeii (a) and, Protosalanx chinensis (b) collected from Taihu Lake and Protosalanx chinensis (c) collected from the Yangtze River estuary.

Fig. 7. A in Habitat Use and Migratory Life History of Salangid Icefish (Salangidae) Revealed by Otolith Sr/Ca Ratios

Fig. 7. A diagram shows the habitat use and migratory life history of the icefish species reconstructed from their otolith Sr/ Ca profiles.

opencc-zeroFeb 2023View details →

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Supplementary data for: Genomics of secondarily temperate adaptation in the only non-Antarctic icefish

White-blooded Antarctic icefishes are an example of extreme biological specialization both to the chronic cold of the Southern Ocean and to life without hemoglobin. As a result, icefishes display derived physiology that limits them to the cold and highly oxygenated Antarctic waters. Despite these constraints, a single icefish species, the pike icefish Champsocephalus esox, is presently found in temperate South American waters. To study the genetic mechanisms underlying temperate adaptation in this species, we generated chromosome-level genome assemblies of both C. esox and its Antarctic sister species, Champsocephalus gunnari. The C. esox genome is similar in structure and organization to that of Antarctic icefishes. However, we observe evidence of chromosomal rearrangements, some of which coincide with regions of elevated genetic divergence in pike icefish populations. Our results show several key biological pathways under selection, including genes related to the mitochondria, iron transport, and light sensing, highlighting candidates behind temperate adaptation in this species. The C. esox genome also shows antifreeze glycoprotein pseudogenization, likely due to relaxed selection following ancestral escape from Antarctica. While the organization of the canonical antifreeze glycoprotein locus is conserved in both C. esox and C. gunnari, both species show a translocation of antifreeze genes, previously unobserved in notothenioids. Our results present the first genomic characterization of a secondarily temperate notothenioid to date and serve as a basis for understanding the group's adaptive potential against a rapidly changing Antarctic environment.

opencc-by-4.0Mar 2018View details →

Figure 1 in Some histological data on bone and teeth in the grey notothen (Lepidonotothen squamifrons) and in the mackerel icefish (Champsocephalus gunnari) (Notothenioidei; Perciformes; Teleostei)

Figure 1. – Lepidonotothen squamifrons (227 mm SL). Cross section of the dental (APS-Groat-PIC). A: Bony tissue is deprived of osteocytes. Arrows point to vascular cavities. B: Detail of an erosive cavity showing active osteoclasts (arrowheads). The arrows point to osteoblastic canaliculi. C: Champsocephalus gunnari (150 mm SL) (AZAN). Bony tissue is deprived of osteocytes and osteoblastic canaliculi are seen (arrowheads). Scale bars: A = 250 μm; B, C = 25 μm.

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Cranial modularity drives phenotypic diversification and adaptive radiation of Antarctic icefishes

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publicSep 2025View details →

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Supplementary data for: Genomics of secondarily temperate adaptation in the only non-Antarctic icefish

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publicFeb 2023View details →

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Data from: The loss of hemoglobin and myoglobin does not minimize oxidative stress in Antarctic icefishes

The unusual pattern of expression of hemoglobin (Hb) and myoglobin (Mb) among Antarctic notothenioid fishes provides an exceptional model system for assessing the impact of these proteins on oxidative stress. We tested the hypothesis that the lack of oxygen-binding proteins may reduce oxidative stress. Levels and activity of pro-oxidants, small-molecule and enzymatic antioxidants, and levels of oxidized lipids and proteins in liver, oxidative skeletal muscle, and heart ventricle were quantified in five species of notothenioid fishes differing in the expression of Hb and Mb. Levels of ubiquitinated proteins and rates of protein degradation by the 20S proteasome were also quantified. Although levels of oxidized proteins and lipids, ubiquitinated proteins, and antioxidants are higher in red-blooded fishes than in Hb-less icefishes in some tissues, this pattern does not persist across all tissues. Expression of Mb is not associated with oxidative damage in heart ventricle, whereas the activity of citrate synthase and contents of heme are positively correlated with oxidative damage in most tissues. Despite some tissue differences in levels of protein carbonyls among species, rates of degradation by the 20S proteasome are not markedly different, suggesting either alternative pathways for eliminating oxidized proteins or redox tone varies among species. Together, our data indicate that the loss of Hb and Mb does not correspond with a clear pattern of either reduced oxidative defense or oxidative damage.

opencc-zeroDec 2016View details →

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Data from: The loss of hemoglobin and myoglobin does not minimize oxidative stress in Antarctic icefishes

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publicDec 2017View details →

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Species distribution, hybridization and connectivity in the genus Chionodraco: unveiling unknown icefish diversity in Antarctica

Aim The species of the genus Chionodraco (Notothenioidei) are the most abundant icefish on the continental shelf of the Weddell Sea. While previous studies indicated that only Chionodraco hamatus and Chionodraco myersi inhabit the Weddell Sea, the third Chionodraco species, Chionodraco rastrospinosus, was recently sampled in the area. Since C. rastrospinosus is supposed to be found only at the Antarctic Peninsula and Scotia Arc, this study aimed at confirming the species classification of C. rastrospinosus by molecular methods and identifying its putative source population. Given the documented evidence of introgression among the three species, we tested whether the newly found C. rastrospinosus shared any genetic variability with the other Chionodraco species. To explain the pattern of distribution of the Chionodraco species, we aimed at estimating the hydrodynamic connectivity between the Antarctic Peninsula and the Weddell Sea. Location Antarctic Peninsula, southern Scotia Arc and the south-eastern Weddell Sea Methods We genotyped 19 microsatellites and sequenced the mitochondrial D-loop for 560 Chionodraco individuals. We simulated the dispersal of more than 3 million drifters (Lagrangian model). Results The molecular analyses support the presence of C. rastrospinosus in the Weddell Sea and its homogeneity with C. rastrospinosus from the Antarctic Peninsula. Bayesian clustering identifies three putative hybrids among C. rastrospinosus and the other congenerics. Lagrangian simulations do not support connectivity driven by the oceanographic features of the Antarctic Peninsula and Weddell Sea via passive larval dispersal only. Main conclusions This study documents, for the first time, the presence of C. rastrospinosus in the Weddell Sea unveiling more biodiversity than previously known in this region. The sympatry of the three Chionodraco species explains the occurrence of occasional, ongoing events of hybridization in the genus. Alternative possible hypotheses need to be tested in future studies about the mechanisms maintaining the interspecific connectivity in Chionodraco spp.

opencc-zeroFeb 2021View details →

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Data from: Evidence for past and present hybridization in three Antarctic icefish species provides new perspectives on an evolutionary radiation

Determining the timing, extent, and underlying causes of inter-specific gene exchange during or following speciation is central to understanding species' evolution. Antarctic notothenioid fish, thanks to the acquisition of antifreeze glycoproteins during Oligocene transition to polar conditions, experienced a spectacular radiation to >100 species during Late Miocene cooling events. The impact of recent glacial cycles on this group is poorly known, but alternating warming and cooling periods may have affected species' distributions, promoted ecological divergence into recurrently opening niches, and/or possibly brought allopatric species into contact. Using microsatellite markers and statistical methods including Approximate Bayesian Computation, we investigated genetic differentiation, hybridization and the possible influence of the last glaciation/deglaciation events in three icefish species of the genus Chionodraco. Our results provide strong evidence of contemporary and past introgression by showing that: i) a substantial fraction of contemporary individuals in each species has mixed ancestry; ii) evolutionary scenarios excluding hybridization or including it only in ancient times have small or zero posterior probabilities; iii) the data support a scenario of interspecific gene flow associated with the two most recent interglacial periods. Glacial cycles might therefore have had a profound impact on the genetic composition of Antarctic fauna, as newly available shelf areas during the warmer intervals might have favoured secondary contacts and hybridization between diversified groups. If our findings are confirmed in other notothenioids, they offer new perspectives for understanding evolutionary dynamics of Antarctic fish, and suggest a need for new predictions on the effects of global warming in this group.

opencc-zeroDec 2012View details →

Figure 5 in The complete mitochondrial genome of the mackerel icefish, Champsocephalus gunnari (Actinopterygii: Channichthyidae), with reference to the evolution of mitochondrial genomes in Antarctic notothenioids

Figure 5. Phylogenetic relationships of control regions inferred by the maximum likelihood (ML) method. Statistical support is shown on the branches: bootstrap values (above) and posterior probability (below). BI, Bayesian inference; CR, control region.

Figure 1 in The complete mitochondrial genome of the mackerel icefish, Champsocephalus gunnari (Actinopterygii: Channichthyidae), with reference to the evolution of mitochondrial genomes in Antarctic notothenioids

Figure 1. Evolution of mitochondrial genomes in Antarctic notothenioids modified from Zhuang & Cheng (2010). Abbreviations: 12S, 12S ribosomal RNA; CR, control region; Cyt b, cytochrome b; E, tRNAGlu; F, tRNAPhe; ND, nicotinamide adenine dinucleotide (reduced form) dehydrogenase; P, tRNAPro; T, tRNAThr.

Figure 4. A in The complete mitochondrial genome of the mackerel icefish, Champsocephalus gunnari (Actinopterygii: Channichthyidae), with reference to the evolution of mitochondrial genomes in Antarctic notothenioids

Figure 4. A, linear representation of three types of gene content from the partial cytochrome b (Cyt b) to 12S rRNA in the mitochondrial (mt) genome of the mackerel icefish. Black and dark grey arrows respectively represent the first and the second duplicates. The first duplicate of the type-1 genome contains full-length nicotinamide adenine dinucleotide (reduced form) dehydrogenase subunit 6 (ND6) and tRNAGlu. Type-2 contains a half-sized ND6 only. Type-3 does not contain ND6 or tRNAGlu. B, PCR amplifications for detecting ND6 and tRNAGlu in the three types of mt genome of the mackerel icefish. PCR fragments between Cyt b and control region (CR) 2 (Cyt b-CR2) and between CR2 and CR3 (CR2-CR3) contain the first and second copies of ND6, respectively. The PCR fragment between ND5 and Cyt b (ND5-Cyt b) did not contain ND6 or tRNAGlu. M, size marker. Lanes 1, 2, 7, and 10 are type-1 individuals. Lanes 3, 4, 8 and 11 are type-2 individuals. Lanes 5, 6, 9, and 12 are type-3 individuals. Abbreviations: E, tRNAGlu; F, tRNAPhe; P, tRNAPro; T, tRNAThr.

Figure 3 in The complete mitochondrial genome of the mackerel icefish, Champsocephalus gunnari (Actinopterygii: Channichthyidae), with reference to the evolution of mitochondrial genomes in Antarctic notothenioids

Figure 3. Map of the mackerel icefish mitochondrial (mt) genome as a circular diagram. The map represents the mt genome of a type-1 individual in which ND6 and tRNAGlu were transposed to a position between tRNAThr and tRNAPro flanked by intergenic spacers (UN3 and UN4), and the ND6- to -CR segment was duplicated once. Fourteen protein-coding genes, two rRNA genes, and noncoding regions are labelled with abbreviations. Twenty-four tRNA genes are shown by a one-letter amino acid code. Different codons used by each of tRNALeu and tRNASer are shown in parentheses. Genes transcribed from the heavy strand and light strand are respectively presented outside and inside the circle. Heavy- and light-strand replication origins are represented by OH and OL, respectively. Abbreviations: 12S, 12S ribosomal RNA; 16S, 16S ribosomal RNA; A, tRNAAla; ATP, ATP synthase; C, tRNACys; CO, cytochrome oxidase; Cyt b, cytochrome b; D, tRNAAsp; E, tRNAGlu; F, tRNAPhe; G, tRNAGly; H, tRNAHis; I, tRNAIle; K, tRNALys; L, tRNALeu; M, tRNAMet; N, tRNAAsn; ND, nicotiamide adenine dinucleotide (reduced form) dehydrogenase; P, tRNAPro; Q, tRNAGln; R, tRNAArg; S, tRNASer; T, tRNAThr; V, tRNAVal; W, tRNATrp; Y, tRNATyr.