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Abstract Recent studies have confirmed historic atmospheric deposition of uranium in Antarctica, with a steep and significant increase in levels deposited since the 1980s in Antarctic Peninsula ice core samples. To date, however, there has been little or no attention paid to uranium in the Antarctic food web. Here, we present results for uranium content in scales of three common nototheniid species (Trematomus bernacchii , Gobionotothen gibberifrons , Notothenia coriiceps) from coastal waters off James Ross Island (Antarctic Peninsula). While mean total uranium levels (mean ± SD) were low and similar between species (N. coriiceps 0.08 μg g−1 ± 0.01, T. bernacchii 0.17 μg g−1 ± 0.10; G. gibberifrons 0.11 μg g−1 ± 0.04), linear regressions against standard length indicated bioaccumulation in T. bernacchii (ANOVA, F = 7.8349, P = 0.0076). We suggest this may be the result of dietary specialisation on prey with calcareous shells that accumulate uranium. To the best of our knowledge, this paper provides the first quantitative baseline data on uranium levels in coastal Antarctic nototheniids. While the low levels recorded are unlikely to represent a threat within the food chain, we suggest that further long-term trophic studies (including stable isotope analysis) are needed, recognising that the feeding ecology of individual species (and even individuals) can have a strong effect on overall trends. Graphical abstract Image 1 Highlights • First quantitative baseline uranium levels presented for Antarctic nototheniids. • Levels low but emerald rockcod show evidence of bioaccumulation. • Bioaccumulation linked with dietary specialisation on molluscs? • Possible links with atmospheric deposition and climate change. • In depth trophic studies needed on Antarctic food-web dynamics. [ABSTRACT FROM AUTHOR]

It has been suggested that High-Antarctic waters, despite their remoteness from human activities, are impacted by anthropogenic pollution, and that the local biota are accumulating the contaminants. At present, no data exist on persistent organic pollutant (POP) body burdens for notothenioid fish inhabiting the High-Antarctic Weddell Sea. We determined the pollutant load in white muscle tissue of red- and white-blooded notothenoids from the Weddell Sea ( Trematomus loennbergii and Chionodraco hamatus , respectively), and compared them to our previous measurements of POPs in Low-Antarctic notothenioids. Analytes included various organochlorine pesticides (OCPs), polychlorinated biphenyls (indicator (i) PCBs, dioxine-like (dl) PCBs) and polybrominated diphenyl ethers (PBDEs). The analytical concentrations were converted into 2,3,7,8-TCDD toxic equivalents (TEQs). Compared to T. loennbergii, C. hamatus had lower levels of β-HCH (0.45 vs. 4.5 ng g −1 lipid weight), and Σ iPCBs (30 vs. 39 ng g −1 lipid weight), as well as lower levels of Σ PBDEs (131 vs. 261 ng g −1 fresh weight). POP body burdens and TEQs were mostly similar to those of Low-Antarctic notothenioids analysed previously, and not related to the trophic positions of the species. The variations in POP levels between and within High- and Low-Antarctic notothenioids only marginally corresponded to sampling site, ecological differences or trophic levels of the species, and might rather be related to metabolism or age effects. The present findings suggest that fishes of High-Antarctic waters, although this area is more remote and less influenced by local human activities, do not show lower POP body burdens than fishes from Low-Antarctic waters. [ABSTRACT FROM AUTHOR]

Short-term storage of semen is a useful strategy for preservation of fish spermatozoa in reproductive management, however, no information is available on Patagonian blenny ( Eleginops maclovinus ) semen. This study was designed to evaluate the effects of in vitro storage on sperm function parameters in Patagonian blenny. Samples of undiluted (C: control) and diluted semen 1:1 v/v (DS1) and 1:3 v/v (DS2) in Storfish® were stored at 4 °C for 7 days. Motility, viability, mitochondrial membrane potential (ΔΨMit), DNA fragmentation and ATP content were assessed at 0, 3 and 7 days. The results demonstrated that sperm function parameters were affected significantly by the time of storage, and that dilution allows better preservation of sperm motility. On the third day of storage, spermatozoa showed a motility > 56% in DS1 and DS2, nevertheless, in C it significantly decreased as well as its ATP content ( P < 0.05), whereas viability was maintained > 70% and ΔΨMit > 45%. However, a significant decline in the percentage of sperm function parameters ( P < 0.05) was observed at 7 days of storage for all samples of undiluted and diluted semen. DNA fragmentation showed no significant increase in all groups, demonstrating < 5% at day 7. In vitro storage conditions maintain better sperm motility in diluted than undiluted semen, preserving the sperm function in all groups assessed during 3 days. In conclusion, the results provide new data on Patagonian blenny sperm quality with respect to in vitro short-term storage evaluated by flow cytometry, this information must be considered for implementing in aquaculture reproductive strategies for the conservation of this species. [ABSTRACT FROM AUTHOR]

Ferritin is a major iron storage protein essential not only in the infectious process, but also in any circumstance generating oxidative stress. In this study, the cDNA coding sequence of ferritin-H was obtained from the sub-Antarctic Notothenioid fish Eleginops maclovinus through transcriptomic analysis of the head kidney. This sequence contained a 534 bp open reading frame that coded for a 177 amino acid protein with a molecular weight of 20,786.2 Da and a theoretical pI of 5.56. The protein displayed a region of iron putative response elements in the 5′UTR, two putative ferritin iron-binding region signatures, and seven characteristic amino acids with ferroxidase functions. Phylogenetic analysis related this sequence to ferritin-H sequences of other Antarctic Notothenioid fish, sharing 96.61% similarity. Constitutive gene expression analysis in different organs revealed increased ferritin-H gene expression in the gills, spleen, muscle, and liver. After infection with two bacterial strains of Piscirickettsia salmonis (LF-89 and Austral-005), ferritin-H was differentially expressed depending on bacterial strain and tissue. This study provides relevant information towards understanding the iron metabolism of a sub-Antarctic Notothenioid fish. [ABSTRACT FROM AUTHOR]

White-blooded Antarctic crocodile icefish are the only vertebrates known to lack functional hemoglobin genes and red blood cells throughout their lives. We do not yet know, however, whether extinction of hemoglobin genes preceded loss of red blood cells or vice versa, nor whether erythropoiesis regulators disappeared along with hemoglobin genes in this erythrocyte-null clade. Several microRNAs, which we here call erythromiRs, are expressed primarily in developing red blood cells in zebrafish, mouse, and humans. Abrogating some erythromiRs, like mir144 and mir451a , leads to profound anemia, demonstrating a functional role in erythropoiesis. Here, we tested two not mutually exclusive hypotheses: 1) that the loss of one or more erythromiR genes extinguished the erythropoietic program of icefish and/or led to the loss of globin gene expression through pseudogenization; and 2) that some erythromiR genes were secondarily lost after the loss of functional hemoglobin and red blood cells in icefish. We explored small RNA transcriptomes generated from the hematopoietic kidney marrow of four Antarctic notothenioids: two red-blooded species (bullhead notothen Notothenia coriiceps and emerald notothen Trematomus bernacchii ) and two white-blooded icefish (blackfin icefish Chaenocephalus aceratus and hooknose icefish Chionodraco hamatus ). The N. coriiceps genome assembly anchored analyses. Results showed that, like the two red-blooded species, the blackfin icefish genome possessed and the marrow expressed all known erythromiRs. This result indicates that loss of hemoglobin and red blood cells in icefish was not caused by loss of known erythromiR genes. Furthermore, expression of only one erythromiR, mir96 , appears to have been lost after the loss of red blood cells and hemoglobin—expression was not detected in the erythropoietic organ of hooknose icefish but was present in blackfin icefish. All other erythromiRs investigated, including mir144 and mir451a , were expressed by all four species and thus are present in the genomes of at least the two white-blooded icefish. Our results rule out the hypothesis that genomic loss of any known erythromiRs extinguished erythropoiesis in icefish, and suggest that after the loss of red blood cells, few erythromiRs experienced secondary loss. Results suggest that functions independent of erythropoiesis maintained erythromiRs, thereby highlighting the evolutionary resilience of miRNA genes in vertebrate genomes. [ABSTRACT FROM AUTHOR]

Antarctic icefishes (Family Channichthyidae) within the suborder Notothenioidei lack the oxygen-binding protein hemoglobin (Hb), and six of the 16 species of icefishes lack myoglobin (Mb) in heart ventricle. As iron-centered proteins, Hb and Mb can promote the formation of reactive oxygen species (ROS) that damage biological macromolecules. Consistent with this, our previous studies have shown that icefishes have lower levels of oxidized proteins and lipids in oxidative muscle compared to red-blooded notothenioids. Because oxidized proteins are usually degraded by the 20S proteasome and must be resynthesized, we hypothesized that rates of protein synthesis would be lower in icefishes compared to red-blooded notothenioids, thereby reducing the energetic costs of protein synthesis and conferring a benefit to the loss of Hb and Mb. Rates of protein synthesis were quantified in hearts, and the fraction of oxygen consumption devoted to protein synthesis was measured in isolated hepatocytes and cardiomyocytes of notothenioids differing in the expression of Hb and cardiac Mb. Neither rates of protein synthesis nor the energetic costs of protein synthesis differed among species, suggesting that red-blooded species do not degrade and replace oxidatively modified proteins at a higher rate compared to icefishes but rather, persist with higher levels of oxidized proteins. [ABSTRACT FROM AUTHOR]

Notothenioidei are typical Antarctic teleosts evolved to adapt to the very low temperatures of the Antarctic seas. Aim of the present paper is to investigate sequence and structure of C3, the third component of the complement system of the notothenioid Trematomus bernacchii and Chionodraco hamatus . We determined the complete nucleotide sequence of two C3 isoforms of T. bernacchii and a single C3 isoform of C. hamatus . These sequences were aligned against other homologous teleost sequences to check for the presence of diversifying selection. Evidence for positive selection was observed in the evolutionary lineage of Antarctic teleost C3 sequences, especially in that of C. hamatus , the most recently diverged species. Adaptive selection affected numerous amino acid positions including three residues located in the anaphylatoxin domain. In an attempt to evaluate the link between sequence variants and specific structural features, we constructed molecular models of Antarctic teleost C3s, of their proteolytic fragments C3b and C3a, and of the corresponding molecules of the phylogenetically related temperate species Epinephelus coioides , using human crystallographic structures as templates. Subsequently, we compared dynamic features of these models by molecular dynamics simulations and found that the Antarctic C3s models show higher flexibility, which likely allows for more pronounced movements of both the TED domain in C3b and the carboxyl-terminal region of C3a. As such dynamic features are associated to positively selected sites, it appears that Antarctic teleost C3 molecules positively evolved toward an increased flexibility, to cope with low kinetic energy levels of the Antarctic marine environment. [ABSTRACT FROM AUTHOR]

The reproductive biology of three species of icefishes (family Channicthyidae), Champsocephalus gunnari , Pseudochaenichthys georgianus and Chaenocephalus aceratus in South Georgia and Shag Rocks Islands was studied by means of a histological analysis. Parental care, a widespread behaviour among icefishes such as C . aceratus , is not observed in C . gunnari , which has a broadcast spawning strategy. There were large differences in total fecundity mainly due to the different sizes reached by each species (total fecundity range was 2,500–21,300 hydrated oocytes). Nevertheless, when comparing relative fecundity values, the average results were, in general, similar for P . georgianus and C . aceratus (6–9 hydrated oocytes per female gram). However, relative fecundity estimated for C . gunnari was 10–37 hydrated oocytes per ovary-free female gram. The difference may be a consequence of the smaller oocyte size of the species as compared to other icefishes. The small diameter of hydrated oocytes was also associated with low values of dry weight. The high relative fecundity recorded for C . gunnnari may compensate, in part, for a broadcast spawning strategy. [ABSTRACT FROM AUTHOR]

In the present work, persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, polybrominated diphenyl ethers (PBDEs), and hexachlorocyclohexane (HCH) were analyzed in three Antarctic notothenioids fish species: Trematomus newnesi (TRN), Notothenia coriiceps (NOC) and Notothenia rossii (NOR). The contribution of each POP-family to the total load was as follows: ΣPCB (40%) > ΣDDT (27%) > ΣPBDEs (23%) > ΣHCH (10%). Among the 23 PCB congeners analyzed, penta -CBs homologues were the prevalent group, followed by hexa -CBs and hepta -CBs. DDT and its metabolites presented the following trend: p , p ′-DDT > p , p ′-DDE ~ p , p ′-DDD. PBDE profile was dominated by BDE-47 and BDE-99 congeners, followed by BDE-100 > BDE-28 > BDE-154, BDE-153. Among HCHs, the γ-HCH isomer was detected in all samples, constituting 69% total HCH load, while α-HCH and β-HCH contributions were 15% and 16%, respectively. The levels of POPs reported here suggest that NOR and NOC are more susceptible to accumulate the analyzed contaminants than TRN, a species not previously analyzed for POPs. Distribution of POPs among different tissues of the three species (muscle, liver, gonads, and gills) was also investigated. Considering lipid weight, the general pattern of POPs distribution in tissues indicated that while gonads showed higher levels of PCBs, DDTs and HCH, the most significant PBDE concentrations were recorded in gills. Also, a comparative analysis of POPs concentration in fish samples from Antarctic area was included. [ABSTRACT FROM AUTHOR]

Abstract: Genes involved in the calcium signalling pathway have a relationship with cold tolerance in many plants. The primary reaction to many different environmental stresses is an increase in the cytoplasmic Ca2+ concentration. Such variations in the Ca2+ concentration could change the activity of Ca2+-dependent protein functions, further regulating the expression of stress-related genes; therefore, the Ca2+ signalling pathway is involved in the biological stress reaction. The expression of the calcium-modulated protein gene, calmodulin, in Antarctic notothenioid fish (Dissostichus mawsoni) accounts for 0.23% of all transcripts, which is a very high level of expression in this cold-water fish. To elucidate the function of calmodulin (CaM) from Antarctic notothenioid fishes, we introduced the calmodulin (CaM) gene into tobacco plants using a viral vector based on pea early browning virus (PEBV). RT-PCR and Western blot results confirmed that the CaM gene was over-expressed in tobacco. Under low-temperature stress, the CaM transgenic plants exhibited faster growth than wild-type plants. The physiological and biochemical effects of the high-level expression of CaM in tobacco were analysed, and the changes in the electrolyte leakage activity and malondialdehyde content showed that CaM over-expression in tobacco increased the cold tolerance of the plants. These results demonstrate that CaM can possibly be used to enhance the low-temperature tolerance of plants. [Copyright &y& Elsevier]

Abstract: Population genetics patterns of marine fish in general and of Southern Ocean fish in particular range from virtual panmixia over ocean-wide scale to deeply fragmented populations. However the causes underlying these different patterns are not properly understood. In this paper, we tested the hypotheses that population connectivity is positively related to a combination of life history traits, namely duration of pelagic larval period and the tendency towards pelagic life style in the adulthood. To do so, we analysed the variability of six microsatellite and one mitochondrial marker (cytochrome b) in three Southern Ocean fish species (Trematomus newnesi, Trematomus hansoni and Trematomus bernacchii). They share a recent common ancestor but notably differ in their duration of pelagic larval period as well as pelagic versus benthic lifestyle. We sampled over a range of more than 5000km for all three species and used a number of population genetics tools to investigate past and contemporary levels of connectivity. All species experienced population fluctuations, but coalescent simulations suggested that contemporary populations are in migration-drift equilibrium. Although global FST values were rather low, a significant population structure separated the High-Antarctic from the Peninsular regions in all species. The level of genetic differentiation was much lower in the pelagic versus benthic species. Present data suggest that past and present genetic structuring in the Southern Ocean are indeed related with the ecological traits of Antarctic fish, however the relative importance of individual factors remains unclear. [Copyright &y& Elsevier]

Abstract: The Antarctic marine environment is one of the most extreme on Earth due to its stably low temperature and high oxygen content. Here we discuss various aspects of the molecular adaptations evolved by Antarctic fish and marine microorganisms living in this environment. This review will in particular focus on: (i) the genetic/genomic bases of adaptation in Antarctic notothenioid fish; (ii) the role of neuroglobin recently identified in the brain of Antarctic icefish; (iii) the structural and functional features of globins of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125. [Copyright &y& Elsevier]

Abstract: Pelagic fish assemblages and community structure were examined along longitudinal and meridian transects off Adélie and George V Land, East Antarctica, in the austral summer 2008. Fish were sampled with an RMT 8 net principally from six discrete depth layers (0–50–100–200–500–1000–2000 m) in the oceanic zone and from three depth layers (0–50–100–200 m) over the continental shelf zone. A total of 20,281 individuals from 27 species were collected. Pleuragramma antarcticum was the most dominant species by number (18,710 inds), followed by Chionodraco hamatus (768), Trematomus newnesi (375), Cyclothone microdon (101), Electrona antarctica (92), Bathylagus antarcticus (51) and Notolepis coatsi (54). Cluster analysis revealed that the fish community was clearly divided at the Antarctic Slope Front into separate oceanic and shelf assemblages, being dominated by mesopelagic fish and notothenioids, respectively. The Southern Boundary of Antarctic Circumpolar Current likely restricted a more northern distribution of notothenioids in the upper 200 m. Mesopelagic fish dominated the large biomass below 500 m and notothenioids dominated that in the upper 100 m. It is considered that mesopelagic fish in the oceanic zone would unlikely be eaten by seabirds because no distinctive diel vertical migration to the surface layer was observed. In the neritic zone, notothenioids (C. hamatus, T. newnesi and P. antarcticum) possibly play an important role as prey items for flying seabirds, penguins and other notothenioids fish especially in the shallow depth stratum (0–100 m). [Copyright &y& Elsevier]

Abstract: The feeding ecology of the notothenioid fish Pleuragramma antarcticum was studied in the Dumont d’Urville Sea (East Antarctica) near the French Antarctic station. Stable isotopes (δ13C and δ15N) and diet contents were used in order to study dietary shifts between fish larvae and juveniles. All specimens had low δ13C values (<−24‰), a main characteristic of high-Antarctic pelagic species. Fish larvae showed differences in both carbon and nitrogen ratios when compared with juveniles. Muscle δ15N values showed a difference of one trophic level (∼3‰) between larvae (6.7‰) and juveniles (9.7–10.0‰) and a trophic position of tertiary consumers. Diet content analyses (stereomicroscope and scanning electron microscopes) indicated that larvae are omnivorous, feeding on phytoplankton (mainly diatoms) as well as on zooplankton species. A positive relationship between δ15N values and size was found and indicated a carnivorous diet for older specimens. [Copyright &y& Elsevier]

Abstract: The RSV Aurora Australis survey allowed the first comprehensive study of the demersal ichthyofaunal environment and of the diversity of the Dumont d’Urville Sea. We observed a high dominance of the Notothenioidei in both the number of species and in integrated abundances. The Nototheniidae was the most abundant family with 44.7% of the total integrated abundance, followed by Bathydraconidae (18.8%). Trematomus eulepidotus was the dominant species with 19.9% of the total individuals catch. Nevertheless, 43 of the 53 species caught could be considered as very rare. The Bathydraconidae was the most diversified family with 11 species caught. The highest integrated abundances of fish were found from 400 to 800m. Well-structured species communities were observed, with high species richness from 570 to 681m. The richest zones were located along the basins and along their upper-sides. Statistical analyses indicated large-scale spatial patterns in species composition, with clear differences in fish communities from the continental slopes, the basins and on the shelf. At a finer spatial scale, the current in the George V Basin and iceberg scouring on the banks and their sides tended to create locally heterogeneous small-scale habitats. We suggest that the glacial history and the structured habitats allowed successive colonisations of the seabed by demersal fish. [Copyright &y& Elsevier]

Abstract: The Southern Ocean is home to two major types of fishes: the largely endemic suborder Notothenioidei and representatives of oceanic fish families that are widely distributed in the midwater and benthic environments elsewhere (e.g. bathylagids, myctophids, liparids, and zoarcids). In most regions of the coastal Antarctic, e.g. the Ross Sea, there is a distinct separation in the pelagic communities at the shelf break between the oceanics (off-shelf) and the endemics (on-shelf). Coincidentally, in much of the coastal Antarctic, the shelf break also marks the boundary between a water column entirely composed of the very cold (−2°C) Ice Shelf Water and an oceanic profile that includes warmer circumpolar deep water (2°C at 200m) at intermediate depths. The distinct separation in pelagic communities observed in most coastal regions of the Antarctic is not seen on the western Antarctic Peninsula (WAP), where circumpolar deep water intrudes to form a warmer midwater and oceanic species are strongly represented. It was hypothesized that the cold ice-shelf water, lethal to fishes without antifreeze glycoproteins (AFGPs) in their blood, was excluding the oceanic species from most of the Antarctic continental shelf waters. To test the hypothesis, nine species of fish captured in WAP shelf waters were tested for the presence of AFGPs. The oceanic fish families analyzed: Myctophidae (Electrona and Gymnoscopelus), Zoarcidae (Melanostigma), Gempylidae (Paradiplospinus), Paralepididae (Notolepis), and Bathylagidae (Bathylagus) showed no antifreeze activity. Two endemic species captured in the same sampling program did show antifreeze activity: the important pelagic species Pleuragramma antarcticum (Nototheniidae) and the Bathydraconid species Vomeridens infuscipinnus. The absence of AFGPs in the blood of Antarctic oceanic species makes a strong case for temperature exclusion of oceanic fishes in the coastal Antarctic. [Copyright &y& Elsevier]

Abstract: The adaptive radiation of the Antarctic notothenioid ancestral benthic fish stock within the chronic freezing waters of the Southern Ocean gave rise to five highly cold adapted families. Their stenothermy, first observed from several high-latitude McMurdo Sound species, has been of increasing recent interest given the threat of rising polar water temperatures from global climate change. In this study we determined the heat tolerance in a geographically diverse group of 11 Antarctic species as their critical thermal maximum (CTMax). When acclimatized to their natural freezing water temperatures, environmental CTMaxs ranged from 11.95 to 16.17°C, well below those of fishes endemic to warmer waters. There was a significant regional split, with higher CTMaxs in species from the more northerly and thermally variable Seasonal Pack-ice Zone. When eight of the Antarctic species were warm acclimated to 4°C all showed a significant increase over their environmental CTMaxs, with several showing plasticity comparable in magnitude to some far more eurythermal fishes. When the accrual of heat tolerance during acclimation was followed in three high-latitude McMurdo Sound species, it was found to develop slowly in two of them, which was correlated with their low metabolic rates. [Copyright &y& Elsevier]

Abstract: Nitric oxide (NO)-mediated angiogenesis may play a role in establishing dense retinal vasculatures of Antarctic hemoglobinless icefishes (suborder: Notothenioidei). We hypothesized that loss of hemoglobin (Hb) leads to elevation in [NO] due to decreased degradation of the compound when the NO-scavenger Hb is absent, thereby inducing vascular growth. We found that total mass of NO metabolites, nitrite plus nitrate (NO x ), in plasma is greater in icefishes than in red-blooded notothenioids [e.g. C. aceratus (Hb−), 22.7±2.9μM; N. coriiceps (Hb+), 14.7±1.7μM], suggesting a higher NO load in hemoglobinless animals. High NO levels do not appear to be a result of greater NO synthesis; we consistently measured lower activities of the enzyme catalyzing NO production, nitric oxide synthase, in tissues of icefishes than in Hb-expressing notothenioids [e.g. 96±10 and 216±39 pmol(min g wet wt)−1 in brain tissue of C. aceratus (Hb−) and G. gibberifrons (Hb+), respectively]. Levels of mRNA for hypoxia-induced (HIF-1α and PHD2) and angiogenic genes (VEGF) were similar in red- and white-blooded species, indicating that vascular maintenance in adult animals does not require differences in angiogenic tone. This does not preclude a cause-and-effect relationship between absence of Hb and NO-mediated angiogenesis during earlier ontogenetic stages of icefishes. [Copyright &y& Elsevier]

Abstract: The Trematominae are a particularly interesting subfamily within the antarctic suborder Notothenioidei (Teleostei). The 14 closely related species occupy a large range of ecological of niches, extremely useful for evolutionary and biogeography studies in the Antarctic Ocean. But some Trematomus species can be difficult to identify by using morphological criteria, specially young stages and damaged specimens. Molecular identification would therefore be highly useful, however the suitability of the cytochrome oxidase I gene in a barcoding approach needs to be assessed. We evaluated species delineation within the genus Trematomus comparing morphological identification, nuclear markers (the rhodopsin retrogene and a new nuclear marker pkd1: polycystic kidney disease 1) and COI. We show that Trematomus vicarius is not distinguishable from Trematomus bernacchii with the molecular markers used, and neither is Trematomus loennbergii from Trematomus lepidorhinus. We suggest that until this is investigated further, studies including these species list them as T. loennbergii/T. lepidorhinus group, and keep voucher samples and specimens. Generally, COI gives a congruent result with the rhodopsin retrogene, and except for the previously cited species pairs, COI barcoding is efficient for identification in this group. Moreover pkd1 might not be suitable for a phylogenetic study at this scale for this group. [Copyright &y& Elsevier]

Abstract: Fishes of the perciform suborder Notothenioidei provide an excellent opportunity for studying the evolution and functional importance of evolutionary adaptations to temperature. To understand the unique biochemical features of high-Antarctic notothenioids, it is important to improve our knowledge of these highly cold-adapted stenotherms with new information on their sub-Antarctic relatives. This paper focuses on the oxygen-transport system of two non-Antarctic species, Eleginops maclovinus and Bovichtus diacanthus. Unlike most Antarctic notothenioids, the blood of E. maclovinus and B. diacanthus displays high hemoglobin (Hb) multiplicity. E. maclovinus, the sister group of Antarctic notothenioids, has one cathodal (Hb C) and two anodal components (Hb 1, Hb 2). B. diacanthus, one of the most northern notothenioids, has three major Hbs. The multiple Hbs may have been maintained as a response to temperature differences and fluctuations of temperate waters, much larger than in the Antarctic. Although non-Antarctic notothenioids have never developed cold adaptation, the amino-acid sequence reveals high identity with the globins of Antarctic notothenioids. Hbs of sub-Antarctic notothenioids are characterised by high oxygen affinity and Root effect. Phylogenetic analyses are consistent with the hypothesis that Bovichtidae and Eleginopidae diverged after they became established in more temperate waters north of the Antarctic Polar Front. [Copyright &y& Elsevier]

Abstract: Survival of some polar fishes is associated with high levels of circulating antifreeze glycoproteins (AFGPs). AFGP prevent ice growth giving rise to thermal hysteresis. The inhibiting action of AFGPs implies that polar fish contain ice to which AFGPs adsorb. Cryopelagic Pagothenia borchgrevinki, inhabiting the ice-laden waters of McMurdo Sound, Antarctica, were assayed for ice and ice was found on skin, gills, in the intestine, and in the spleen. Two methods used to assess the number of ice crystals in spleens gave comparable results (12.1+/−1.9 and 22+/−3.8 per spleen). Attempts were made to measure the rate of uptake of ice by P. borchgrevinki held in cages immediately beneath the sub-ice platelet layer in McMurdo Sound; uptake was sporadic. Introduction of ice into fish by spray freezing a small patch of the integument resulted in detection of splenic ice after 1h, illustrating that a mechanism exists for ice transport from the periphery to the spleen. Splenic ice did not seem to be eliminated from fish held in ice-free water at −1.6°C for approximately two months. The relatively small number of splenic ice crystals and the slow rate of ice uptake suggest efficient ice barriers exist in P. borchgrevinki. [Copyright &y& Elsevier]

Abstract: This mini-review makes a survey and a summary of some major issues concerning the chromosomal organisation of ribosomal genes in fish genomes, by using Notothenioidei as the model. The increasing body of information, published during the last two decades on the chromosomal mapping of the two ribosomal genes classes (45S rDNA and 5S rDNA) in notothenioids, makes it possible to recognise the main evolutionary trends across the phylogeny of the group. As one of the major features, the rDNA clusters are organised in a single chromosomal locus in most of the species. This locus is located at different positions along the chromosomes in the basal groups (non-Antarctic Clade), whereas it maintains a strongly conserved location in the cold-adapted species (Antarctic Clade). Important structural changes, leading to the co-localisation of the two ribosomal gene classes, occurred early in the notothenioid phylogeny, perhaps in the common ancestor of the Eleginopidae and Nototheniidae. The cytogenetic evidences indicate that an increased amount of ribosomal genes, organised in two large chromosomal loci, is present in the giant Antarctic fish Dissostichus mawsoni. This gain in rRNA genes is an important genomic change, having possible implications for the fitness of this notothenioid fish that combines large size, pelagic lifestyle and cold-adaptation. [Copyright &y& Elsevier]

Abstract: Given the unique thermal history of the Antarctic continent, fishes of dominant suborder Notothenioidei offer a remarkable opportunity to study the physiological and biochemical characters gained and, conversely, lost during their evolutionary history and to map this information on the species phylogenetic trees. The availability of phylogenetically related notothenioid taxa living in a wide range of latitudes (in the Antarctic, sub-Antarctic and temperate regions) allows to look into the molecular bases of environmentally driven gene birth and death. This evolutionary perspective has also been supported by comparison of some features of the hemoprotein devoted to the oxygen transport in fish species living in the other polar region, the Arctic. The Arctic and Antarctic marine ichthyofaunas differ by age and isolation. Fishes of the two polar regions have undergone different regional histories which have engineered the physiological diversities, so that Antarctic fish are much more stenothermal than Arctic ones. Understanding the mechanisms of phenotypic response to cold exposure in species living at different latitudes in polar habitats offers fundamental insights into environmental adaptations. This review aims at surveying the current knowledge of molecular structure, functional features, phylogeny and adaptations of the hemoglobin of fish thriving in the Antarctic, sub-Antarctic and Arctic regions (with some excursions in the temperate latitudes). Investigating the evolutionary adaptations of hemoglobins to these environments can provide new insights into adaptation currently studied merely in temperate organisms, and can shed light into the convergent processes that evolved in response to thermal adaptations. [Copyright &y& Elsevier]

Abstract: With the notable exception of Antarctic icefishes, haemoglobin (Hb) is present in all vertebrates. In polar fish, Hb evolution has included adaptations with implications at the biochemical, physiological and molecular levels. Cold adaptation has been shown to be also linked to small changes in primary structure and post-translational modifications in proteins, including hydrophobic remodelling and increased flexibility. A wealth of knowledge is available on the oxygen-transport system of fish inhabiting Antarctic waters, but very little is known on the structure and function of Hb of non-Antarctic notothenioid fishes. The comparison of the biochemical and physiological adaptations between cold-adapted and non-cold-adapted species is a powerful tool to understand whether (and to what extent) extreme environments require specific adaptations or simply select for phenotypically different life styles. This study focuses on structure, function and molecular phylogeny of Hb in Antarctic and non-Antarctic notothenioid fishes. The rationale is to use the primary structure of Hb as tool of choice to gain insight into the pathways of the evolution history of α and β globins of notothenioids and also as a basis for reconstructing the phylogenetic relationships among Antarctic and non-Antarctic species. [Copyright &y& Elsevier]

Abstract: Previous research on Antarctic notothenioids has demonstrated that cells of cold-adapted Antarctic notothenioids lack a common cellular defense mechanism called the heat shock response (HSR), the induction of a family of heat shock proteins (Hsps) in response to elevated temperatures. The goal of this study was to address how widespread the loss of the HSR is within the Notothenioidei suborder and, specifically, to ask whether cold temperate non-Antarctic notothenioids possess the HSR. In general, Antarctic fish have provided an important opportunity for physiologists to examine responses to selection in the environment and to ask whether traits of the notothenioids represent cold adaptation, or whether the traits are related to history and are characteristics of the notothenioid lineage. Using in vivo metabolic labeling, results indicate that one of the two New Zealand notothenioids possess an HSR. The thornfish, Bovichtus variegatus Richardson, 1846, expressed heat shock proteins (Hsp) in response to heat stress, whereas the black cod, Notothenia angustata Hutton, 1875, did not display robust stress-inducible Hsp synthesis at the protein-level. However, further analysis using Northern blotting clearly demonstrated that mRNA for a common Hsp gene, hsp70, was present in cells of both New Zealand species following exposure to elevated temperatures. Overall, combined evidence on the HSR in notothenioid fishes from temperate New Zealand waters indicate that the loss of the HSR in Antarctic notothenioid fishes occurred after the separation of Bovichtidae from the other Antarctic notothenioid families, and that the HSR was most likely lost during evolution at cold and constant environmental temperatures. [Copyright &y& Elsevier]

The radiation of notothenioid fishes (order Perciformes) in the Southern Ocean provides a model system for investigating evolution and adaptation to a low temperature environment. The Notothenioid fishes comprising eight families, 43 genera and 122 species dominate the fish fauna in Antarctica. The diversification of the clade probably began 15–20 million years ago after the formation of the Antarctic Polar Front. The radiation was, therefore, associated with climatic cooling down to the present day temperature of −1.86 °C. Origins and Evolution of the Antarctic Biota Geological Society Special Publication No. 47, Geological Society of London. pp. 253–268). The success of the group has been closely linked with the evolution of glycopeptide and peptide antifreezes, which are amongst the most abundant proteins in blood and interstitial fluid. The radiation of the clade has been associated with disaptation (evolutionary loss of function) and recovery. For example, it is thought that the icefishes (Channichyidae) lost haemoglobin through a single mutational event leading to the deletion of the entire β-globin gene and the 5′ end of the linked α-globin gene, resulting in compensatory adaptations of the cardiovascular system. Phylogenetically based statistical methods also indicate a progressive and dramatic reduction in the number of skeletal muscle fibres (FNmax) at the end of the recruitment phase of growth in basal compared to derived families. The reduction in FNmax is associated with a compensatory increase in the maximum fibre diameter, which can reach 100 μm in slow and 600 μm in fast muscle fibres. At −1 to 0 °C, the oxygen consumption of isolated mitochondria per mg mitochondrial protein shows no evidence of up-regulation relative to mitochondria from temperate and tropical Perciform fishes. The mitochondria content of slow muscle fibres in Antarctic notothenioids is towards the upper end of the range reported for teleosts with similar lifestyles, reaching 50% in Channichthyids. High mitochondrial densities facilitate ATP production and oxygen diffusion through the membrane lipid compartment of the fibre. Modelling studies suggest that adequate oxygen flux in the large diameter muscle fibres of notothenioids is possible because of the reduced metabolic demand and enhanced solubility of oxygen associated with low temperature. At the whole animal level size-corrected resting metabolic rate fits on the same temperature relationship as for Perciformes from warmer climates. It seems likely that the additional energetic costs associated with antifreeze synthesis and high mitochondrial densities are compensated for by reductions in other energy requiring processes: a hypothesis that could be tested with detailed energy budget studies. One plausible candidate is a reduction in membrane leak pathways linked to the loss of muscle fibres, which would serve to minimise the cost of maintaining ionic gradients. [Copyright &y& Elsevier]

The involvement of nitric oxide (NO) in the branchial circulation and cardiac performance of the Antarctic hemoglobinless icefish Chionodraco hamatus was investigated using isolated and perfused head and working heart preparations. In the branchial vasculature under basal (i.e. unstimulated conditions), the nitric oxide synthase (NOS) inhibitor l-NIO (l-N5-(1-iminoethyl) ornithine, 10−5 and 10−4 M), caused a marked vasoconstriction (20%), indicating a basal nitrergic vasodilator tone, while the dose–response curve of the NO donor SIN-1 (3-morpholinosydnonimine) showed a dose-dependent vasodilator effect. Acetylcholine induced a dose-dependent branchial vasoconstriction mediated by muscarinic receptors, since the effects were abolished by pre-treatment with atropine (10−4 M). Serotonin (5-HT) induced a dose-dependent branchial methysergide-sensitive vasoconstriction which was abolished by pre-treatment with l-NIO, indicating a NO-dependent mechanism. On the isolated heart, the NOS inhibitor l-NMMA (NG-monomethyl-l-arginine) 10−4 M produced a small, but significant decrease of heart rate and, as a consequence, a decrease of power output, while the NO donor sodium nitroprusside (SNP) 10−4 M elicited increases of stroke volume, stroke work and power output, suggesting an exogenous NO-dependent positive inotropism. Exposure of the bulbus arteriosus to l-NMMA was without any appreciable effect. In contrast, SNP produced a notable relaxation of the bulbus wall with a marked increase of its stiffness, as indicated by the increase of systolic and diastolic dP/dt max (23 and 104%, respectively). [Copyright &y& Elsevier]

Concentrations of polybrominated diphenyl ethers (PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs); are reported in specimens of fish notothenioids Chaenocephalus aceratus (SSI), Trematomus bernacchii (ERN), and Nototheniops nudifrons (NOD) from the South Shetland Islands, Antarctica. Significant differences in the accumulation of 2′-MeO-BDE-68 and 6-MeO-BDE-47 were detected among the analysed species. MeO-BDEs were significantly higher in SSI (11.7, 8.6, and 14.1 ng g−1 lw) than in NOD (1.63, 1.63, and 3.0 ng g−1 lw) in muscle, liver, and gill, respectively. Feeding ecology traits explain the accumulation patterns of MeO-PBDEs. SSI has a higher feeding activity with a broader diet, followed by ERN, whereas NOD is a benthic/sedentary fish with a narrower diet. The accumulation of PBDEs was neither species-, nor tissue-specific. The current study expands the knowledge concerning the accumulation of PBDEs and MeO-PBDEs in Antarctic marine fish and supports the importance of species-specificity in the accumulation of MeO-PBDEs. [Display omitted] • Marked interspecific differences for notothenioid fish in MeO-PBDE accumulation • BDE-47 and 6-MeO-BDE-47 contributed 53 and 90% to the total load, respectively. • C. aceratus and N. nudifrons showed the highest and lowest MeO-PBDE levels, respectively. • C. aceratus and N. nudifrons had a broader and narrower diet, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the cytogenetic features of the Antarctic silverfish Pleuragramma antarctica (Boulenger 1902), a keystone species of the Antarctic coastal marine ecosystem. Conventional cytogenetic analyses and physical mapping of repetitive DNA sequences were performed on metaphase plates obtained through direct chromosome preparation from P. antarctica early larvae. The Antarctic silverfish have a diploid number (2n) = 48, and a karyotype made up of a majority of two-armed chromosomes (karyotype formula36m/sm + 10st + 2a, fundamental number = 94). Major ribosomal gene repeats were detected on three chromosome pairs (20, 21, and 23), in correspondence of dim DAPI stained regions. Long Interspersed Nuclear Elements (LINEs) were abundant and wide spread over all chromosomes. Overall, the cytogenetic data presented herein are consistent with a long independent cytogenetic and evolutionary history for the species. The large number of two-armed chromosomes, indicative of highly-rearranged karyotype, coupled with a diploid number of 48, a presumed primitive character for this fish group, and the spread of the major ribosomal genes on three chromosome pairs, make the Antarctic silverfish distinct from all other notothenioid species. [ABSTRACT FROM AUTHOR]