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Notothenioidei fishes have evolved under stable cold temperatures; however, ocean conditions are changing globally, with polar regions poised to experience the greatest changes in environmental factors, such as warming. These stressors have the potential to dramatically affect energetic demands, and the persistence of the notothenioids will be dependent on metabolic capacity, or the ability to match energy supply with energy demand, to restore homeostasis in the face of changing climate conditions. In this study we examined aerobic metabolic capacity in three species, Trematomus bernacchii, T. pennellii and T. newnesi, and between two life stages, juvenile and adult, by assessing mitochondrial function of permeabilized cardiac fibers. Respiratory capacity differed among the adult notothenioids in this study, with greater oxidative phosphorylation (OXPHOS) respiration in the pelagic T. newnesi than the benthic T. bernacchii and T. pennellii. The variation in mitochondrial respiratory capacity was likely driven by differences in the mitochondrial content, as measured by citrate synthase activity, which was the highest in T. newnesi. In addition to high OXPHOS, T. newnesi exhibited lower LEAK respiration, resulting in greater mitochondrial efficiency than either T. bernacchii or T. pennellii. Life stage largely had an effect on mitochondrial efficiency and excess complex IV capacity, but there were little differences in OXPHOS respiration and electron transfer capacity, pointing to a lack of significant differences in the metabolic capacity between juveniles and adults. Overall, these results demonstrate species-specific differences in cardiac metabolic capacity, which may influence the acclimation potential of notothenioid fishes to changing environmental conditions.

Trematomus species (suborder Notothenioidei; family Nototheniidae) are widely distributed in the southern oceans near Antarctica. There are 11 recognized species in the genus Trematomus, and notothenioids are known to have high chromosomal diversity (2n = 24–58) because of relatively recent and rapid adaptive radiation. Herein, we report the chromosomal-level genome assembly of T. loennbergii, the first characterized genome representative of the genus Trematomus. The final genome assembly of T. loennbergii was obtained using a Pacific Biosciences long-read sequencing platform and high-throughput chromosome conformation capture technology. Twenty-three chromosomal-level scaffolds were assembled to 940 Mb in total size, with a longest contig size of 48.5 Mb and contig N50 length of 24.7 Mb. The genome contained 42.03% repeat sequences, and a total of 24,525 protein-coding genes were annotated. We produced a high-quality genome assembly of T. loennbergii. Our results provide a first reference genome for the genus Trematomus and will serve as a basis for studying the molecular taxonomy and evolution of Antarctic fish.

Our knowledge on distribution, habitats and behavior of Southern Ocean fishes living at water depths beyond scuba-diving limits is still sparse, as it is difficult to obtain quantitative data on these aspects of their biology. Here, we report the results of an analysis of seabed images to investigate species composition, behavior, spatial distribution and preferred habitats of demersal fish assemblages in the southern Weddell Sea. Our study was based on a total of 2736 high-resolution images, covering a total seabed area of 11,317 m2, which were taken at 13 stations at water depths between 200 and 750 m. Fish were found in 380 images. A total of 379 notothenioid specimens were recorded, representing four families (Nototheniidae, Artedidraconidae, Bathydraconidae, Channichthyidae), 17 genera and 25 species. Nototheniidae was the most speciose fam- ily, including benthic species (Trematomus spp.) and the pelagic species Pleuragramma antarctica, which was occasionally recorded in dense shoals. Bathydraconids ranked second with six species, followed by artedidraconids and channichthyids, both with five species. Most abundant species were Trematomus scotti and T. lepidorhinus among nototheniids, and Dol- loidraco longedorsalis and Pagetopsis maculatus among artedidraconids and channichthyids, respectively. Both T. lepi- dorhinus and P. maculatus preferred seabed habitats characterized by biogenous debris and rich epibenthic fauna, whereas T. scotti and D. longedorsalis were frequently seen resting on fine sediments and scattered gravel. Several fish species were recorded to make use of the three-dimensional structure formed by epibenthic foundation species, like sponges, for perching or hiding inside. Nesting behavior was observed, frequently in association with dropstones, in species from various families, including Channichthyidae (Chaenodraco wilsoni and Pagetopsis macropterus) and Bathydraconidae (Cygnodraco mawsoni).

The Antarctic silverfish (Pleuragramma antarctica) is a keystone species in the continental shelf waters around the Antarctic, performing an essential role of connecting higher and lower trophic levels in the Southern Ocean ecosystem. Its early life history is dependent on the platelet ice layer found below sea ice, thus intimately intertwining its fate with that of sea ice extent. Antarctic silverfish belong to the family Nototheniidae, part of the Notothenioidei suborder whose species radiation in the Southern Ocean 24 million years ago is one of the most expansive among teleost fish. Most notothenioids inhabit a benthic niche as adults, though many experience a pelagic egg and larval phase. Antarctic silverfish are unique among notothenioids in that they are pelagic throughout their life history. Larvae develop in the platelet ice layer near the surface beneath sea ice, descending into deeper waters as they grow in size as juveniles, finally reaching their maximum depth range as adults at 400 – 700 m below the surface. While they lack a swim bladder, Antarctic silverfish manage to remain in the water column as adults by a type of paedomorphy in which they retain lipids from larval and juvenile life stages, allowing them to achieve neutral buoyancy. Despite their presence in the water column as adults, they practice a similar energy-efficient life strategy to their benthic counterparts. Their feeding strategy involves hanging in the water column and passively consuming prey. Remaining in the water column throughout their life history combined with their passive life strategy renders Antarctic silverfish especially susceptible to transport via local and circumpolar current systems. Thus, local and circumpolar current systems form the hydrographic framework in which hypotheses regarding Antarctic silverfish population connectivity must be tested. How populations of fish are defined, and the extent to which separate populations exchange individuals forms the basis of marine fish population biology. The extent to which Antarctic silverfish, which have a circumpolar distribution, represent one fully connected, panmictic population around the Antarctic continent, remains an open question. It is reasonable to presume that, given their pelagic larval phase, many species of notothenioids with a circumpolar distribution represent large, homogeneous populations. This presumption remains the null hypothesis to test when investigating population structure in notothenioids, and it is especially salient when considering the fully pelagic Antarctic silverfish. The first investigation into Antarctic silverfish population structure employed mitochondrial DNA markers on a circumpolar scale and did not find evidence to reject the null hypothesis of panmixia throughout the Southern Ocean. Intriguingly, while comparisons between regions failed to indicate differentiation, comparisons within regions between years hinted at inter-annual variation in patterns of connectivity. Genetic differentiation within the same geographic area that is lost and gained between sampling years due to variations in recruitment, mortality and hydrography is known as chaotic genetic patchiness. The extent to which chaotic genetic patchiness is relevant to understanding Antarctic silverfish population structure was further studied in a more recent investigation, restricting its geographic focus to the Antarctic Peninsula, and employing a set of highly polymorphic EST-linked microsatellite markers to understand population connectivity around the Antarctic Peninsula. Based on both its more focused regional scale and sampling scheme, as well as the use of genetic markers more adept at capturing population differentiation, this study was able to detect genetic structuring on the scale of the Antarctic Peninsula. Building upon these initial studies, this thesis aimed to characterize the circumpolar population structure of Antarctic silverfish, integrating aspects of life history and hydrography in order to describe mechanisms of connectivity between populations. The first aim was to understand the hydrography underlying life history connectivity on the scale of the Ross Sea region in order to better understand what may be occurring on the circumpolar level. Silverfish larvae were collected from areas in the Ross Sea coincident with hydrographic features hypothesized to influence their connectivity. While a microsatellite-based analysis was precluded due to the poor state of preservation of the larvae, it was possible to confirm species identification using mitochondrial sequence analysis. The genetic confirmation of species was especially important given that this study proposed a new spawning ground for silverfish in the Ross Sea based on size at collection and established growth rates from the time of hatching. Importantly, this study provided renewed support for the life history hypothesis in silverfish, emphasizing the impact of trough circulation in transporting early life stage fish from the ice shelf edge to the continental slope, where retention back towards the coast or entrainment in shelf-long currents modulates connectivity between neighboring populations of silverfish. The Ross Sea investigation was then expanded on a circumpolar scale, now carried out using a suite of highly polymorphic EST-linked microsatellite markers developed in a closely related notothenioid species and shown to successfully amplify in silverfish in a previous study. This analysis was carried out on fish collected over 25 years from six different regions: the western Ross Sea, the eastern Weddell Sea, Larsen Bay, the northern Antarctic Peninsula, the South Orkney Islands, and the western Antarctic Peninsula. The data analyzed included samples from the two previous investigations of silverfish population structure described earlier, the first using mitochondrial markers on a circumpolar scale that had not found evidence of population structuring, and the second using the same suite of microsatellite markers employed in this thesis on a regional scale around the Antarctic Peninsula. The integration of these previous datasets into the present analysis allowed for an increase in the resolving power of the previous mitochondrial marker-based study, as well as for the integration of the Antarctic Peninsular work into the greater circumpolar context. The circumpolar investigation of Antarctic silverfish population structure confirmed that the population structure of silverfish on a circumpolar scale is characterized by high levels of gene flow, and suggested that the Antarctic Slope Front and Current System (AFS) plays an integral role in connecting populations in the Southern Ocean. The importance of the AFS was evident in that reductions in gene flow were only observed in the South Orkney Islands and west Antarctic Peninsula, which were the only two areas in the study where the AFS has not been shown to arrive. This result also expanded to a circumpolar scale the earlier Ross Sea study, which had emphasized the importance of the AFS in connecting Ross Sea populations between local trough systems. It remained however, that small scale population differentiation which had been observed in the Ross Sea based on larval distributions, as well as in the eastern Weddell Sea based on the distribution of older and younger cohorts between sampling areas, was unable to be resolved using genetic techniques. Thus, the final aim of the main project of this thesis was carried out in order to resolve population structure on the regional scale, this time in the Weddell Sea, employing otolith chemistry. Analysis of trace element deposition in otolith nuclei, reflective of oceanographic conditions to which fish were exposed in early life, has been shown to delineate population structure in the Southern Ocean, in both silverfish and related notothenioids. Of the stations for which samples were available in the Weddell Sea, five stations were selected based on their locations with respect to hydrographic features hypothesized to influence population structuring in the region, in Atka Bay, Halley Bay, off of Coats Land, and west and east of the Filchner Trough. Previous studies, as well as data on biomass and abundance from the sampling expedition during which the silverfish were collected, emphasized the importance of the Filchner Trough in supporting a local population of silverfish in the eastern Weddell Sea continental shelf area. Furthermore, hydrographic data collected in the Weddell Sea emphasized the importance of warm water mass intrusion onto the continental shelf carried from the east into the Weddell Sea region by the AFS. These warm water intrusions from the AFS not only have the potential to carry fish from other regions into the Weddell Sea area, but regulate circulation patterns and the strength and directionality of coastal currents in the region, modulating local connectivity. The results of the otolith nucleus chemistry analysis revealed significant population structuring along the eastern Weddell Sea, in contrast to the structure revealed using genetics. The population structure revealed by the otolith chemistry analysis supported the importance of warm water intrusions from the AFS in transporting fish between areas, while highlighting the role of the Filchner Trough circulation in supporting a coherent population in the southeast Weddell Sea. These results emphasize the importance of the integration of multidisciplinary techniques in the context of local hydrography in addressing questions of population structure and life history connectivity in Antarctic silverfish in the Southern Ocean, and for that matter, any pelagic species inhabiting a continental shelf ecosystem.

The Tristan klipfish, Bovichtus diacanthus, an endemic species at Tristan da Cunha Island was successfully aged using whole sagittal otoliths. The annulation pattern was clear, resulting in an alternating combination of opaque and translucent zones that form an annulus. Although sampling limitations did not allow direct validation of annual ring deposition, most otoliths showed a translucent edge, perhaps suggesting that the deposition of translucent zones is a synchronous process which takes place in winter coincident with the spawning season. The reliability of ageing methodology was supported by the good agreement between readings. The maximum age was estimated to be five years in females and four years in males. In order to increase the small number of direct readings, the length at age was back-calculated for each fish by fitting growth curves. The resulting growth of B.diacanthus was described by the von Bertalanffy growth model, as summarized by the following parameters: L∞ = 207.1 mm TL, k = 0.49 per year, and t0 = 0.04 years. The size at which 50% of the population spawns for the first time was c. 147 mm, corresponding to 2.5 years of age.

Fish skeletal muscle is an excellent model for studying muscle structure and function, since it has a very well-structured arrangement with different fiber types segregated in the axial and pectoral fin muscles. The morphological and physiological characteristics of the different muscle fiber types have been studied in several teleost species. In fish muscle, fiber number and size varies with the species considered, limiting fish maximum final length due to constraints in metabolites and oxygen diffusion. In this work, we analyze some special characteristics of the skeletal muscle of the suborder Notothenioidei. They experienced an impressive radiation inside Antarctic waters, a stable and cold environment that could account for some of their special characteristics. The number of muscle fibers is very low, 12,700-164,000, in comparison to 550,000-1,200,000 in Salmo salar of similar sizes. The size of the fibers is very large, reaching 600 μm in diameter, while for example Salmo salar of similar sizes have fibers of 220 μm maximum diameter. Evolutionary adjustment in cell cycle length for working at low temperature has been shown in Harpagifer antarcticus (111 h at 0°C), when compared to the closely related sub-Antarctic species Harpagifer bispinis (150 h at 5°C). Maximum muscle fiber number decreases towards the more derived notothenioids, a trend that is more related to phylogeny than to geographical distribution (and hence water temperature), with values as low as 3,600 in Harpagifer bispinis. Mitochondria volume density in slow muscles of notothenioids is very high (reaching 0.56) and since maximal rates of substrate oxidation by mitochondria is not enhanced, at least in demersal notothenioids, volume density is the only means of overcoming thermal constraints on oxidative capacity. In brief, some characteristics of the muscles of notothenioids have an apparent phylogenetic component while others seem to be adaptations to low temperature. Fil: Fernandez, Daniel Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Calvo, Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Made available in DSpace on 2019-09-12T16:53:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Secretariat of the Interministerial Commission for the Resources of the Sea (SeCIRM) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) The well-being, feeding habits and energetic and plasmatic parameters of the notothenioids Notothenia rossii and Notothenia coriiceps were assessed in specimens collected at a depth of up to 25 m in the Admiralty Bay region, King George Island, Antarctic Peninsula. The population structure of N. rossii (n = 221) was composed of juveniles, and that of N. coriiceps (n = 151) was composed of adults. The greatest mean length and weight measurements of N. coriiceps may be related to warming waters in the Antarctic Peninsula region. Salps were the dominant item in the diet of both species responsible for high protein quantity item found in muscle tissues and liver. The krill and amphipods were an important food item and related to lipid reserves. Among the indices evaluated, greater variation was observed in the hepatosomatic index of N. coriiceps and was related to the greater sizes and ages attained by this species. The liver and muscle energetic components showed great variability between different months may be related by the variability in diet. The plasma components did not exhibit seasonal patterns but displayed large monthly variation. Long-term analysis of the biological parameters evaluated in this study should be continued to monitor the species present in Admiralty Bay, a region with great biological diversity. [Raga, Gabriela; Pichler, Helen Audrey; Zaleski, Tania; Vaz da Silva, Flavia Baduy; Machado, Cintia; Rios, Flavia Sant'Anna; Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, Adapt Biol Lab, BR-80060000 Curitiba, Parana, Brazil [Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst, Sao Paulo, Brazil [Kawall, Helena Goncalves] Univ Sao Paulo, Oceanog Inst, Sao Paulo, Brazil

Like the Arctic, the Antarctic region hosts some of the hot spots of climatic change. At the western Antarctic Peninsula, alterations of air and water temperature, pH, salinity and sea-ice regime were reported and associated shifts in species abundance and changes in food web structure have already become evident. In contrast, for most high-Antarctic regions, no climate related changes have yet been found. However, future temperature increases are also projected for these areas. Ocean warming affects marine ectotherms by directly impacting their body temperature and thus physiology. Antarctic marine ectotherms, such as fish, are highly adjusted to the very cold and stable conditions of the Southern Ocean and are suggested to be highly temperature sensitive. Fish constitute an important link in Antarctic food webs by being prey and predator alike. While various studies focused on the impact of elevated temperature on lower organisational levels in Antarctic fish, trade-offs of increased temperature for the whole organism remain unclear, but are highly relevant from an ecological perspective. Thus, this thesis aimed to assess the impact of increasing temperature on Antarctic fish at the whole-organism level from an energy budget perspective. The energy taken up by an organism can be allocated to different vital functions, such as routine metabolism, growth, reproduction and excretion. When routine metabolic costs are covered, energy can be allocated to growth and reproduction, the factors influencing a species abundance and population structure. In the first study of this thesis, energy allocation to routine metabolism as well as response patterns to an acute increase of temperature in the fish species Lepidonotothen squamifrons, Trematomus hansoni and Lepidonotothen nudifrons were analysed using oxygen consumption measurements. While metabolic responses to changing temperature were comparable in all species, metabolic costs of high-Antarctic fish were higher at habitat temperatures. Starting from higher metabolic rates at habitat temperature, it was hypothesised that high-Antarctic species might achieve critical thermal thresholds much earlier than low-latitude species when temperature increases. In the second study, temperature-dependent trade-offs at the whole-organism-level in Antarctic fish were analysed measuring different energy budget parameters. The results indicated a lower thermal tolerance of the high-Antarctic Trematomus bernacchii compared to the low-Antarctic Lepidonotothen nudifrons. After nine weeks of acclimation to elevated temperatures (4 degree Celsius), routine metabolic rates of T. bernacchii returned to baseline levels (0 degree Celsius). However, mass growth was reduced by 84% at 2 degree Celsius, likely due to less efficient food assimilation. In nature, such severe reductions in fish growth could delay sexual maturity and reduce production. In the third study, temperature-dependent growth rates of fish species from different latitudes were assessed. Polar and especially Antarctic species showed low growth and a narrow thermal tolerance window for growth performance compared to temperate species. A further climate induced reduction of already low growth rates could significantly affect population structures and abundances of polar fish. In conclusion, this thesis indicates differences in energy allocation, such as potentially higher routine metabolism, among low- and high-Antarctic fish. These could contribute to a high thermal sensitivity of high-Antarctic species. On the whole-organism level, this thermal sensitivity was displayed by significant reductions of already low growth rates at elevated temperatures. Finally, these results suggest that ocean warming may have far-reaching consequences for Antarctic fish production and population structures with potential extensive implications for entire Antarctic ecosystems and food webs.

The influence of temperature on the aerobic metabolism and the energetic cost of food intake (Specific Dynamic Action; SDA) have been investigated in four species of Sub-Antarctic teleosts. The species were the notothenioids Paranotothenia magellanica, Patagonotothen sima and Harpagifer bispinis and the zoarcid Austrolycus depressiceps. Individuals were captured in the vicinity of Ushuaia Bay. Experimental temperatures were 10, 4 and 2 °C, which correspond to summer, winter and extreme winter respectively. Individual respirometry chambers and calorimetric techniques were used. Different food items were provided: crustaceans (isopods and amphipods) and Argentinean hake muscle. Interspecific analysis was done on species fed with isopods. A rapid increase in oxygen consumption was registered after meals, indicating a typical SDA response. The Duration of the SDA was longer at low temperatures. The extra energy spent during the process itself, and when expressed as a percentage of consumed food energy, decreased with decreasing temperature. The SDA Coefficient was higher for H. bispinis that were fed with isopods. We suggest that decreases in temperature diminish the metabolic cost and extend SDA. Energy-saving mechanisms could be an evolutionary advantage to minimize the energetic cost of living at low sub-Antarctic temperatures. A general model of exponential decay is suggested for the duration of SDA and Temperature, based on the present study and compiled from literature data. Fil: Vanella, Fabián Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Lattuca, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Calvo, Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina