Abele, Doris
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Abele, Doris
Official Name
Abele, Doris
Alternative Name
Abele-Oeschger, D.
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Item-typ:Veröffentlichung, Adaptation and stress defence in intertidal and subtidal Antarctic limpets (Nacella concinna):A study of the plasticity of molecular and biochemical stress response in Antarctic invertebrates(2010-01-19); ; ; In the summer months, a subpopulation of the Antarctic limpet Nacella concinna migrates into the intertidal zone, which becomes increasingly ice-free and expands by glacier retreat due to global warming. Animals inhabiting intertidal zones are air exposed twice a day during low tide while sub-littoral animals are always covered by water. Intertidal and permanently sub-littoral N. concinna can easily be distinguished by their shell morphology. To test whether these morphological differences are accompanied by a physiological adaptation to the intertidal environment, I investigated the biochemical and molecular response of both limpet subpopulations to air exposure and hypoxia, a possible result of desiccation, if the limpets clamp down their shell to the substratum to avoid water loss. The results obtained within my thesis clearly indicate a physiological and molecular adaptation of the intertidal N. concinna to desiccation stress which the sub-littoral limpets do not show. These adaptations enable the limpets to survive in this extreme environment and will potentially allow the repopulation of emerging areas due to glacier retreat.Dissertation468 307 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Tolerance mechanisms and responses of krill species of different latitudes to oxygen minimum zones(2014-07-02); ; ; Euphausiids (krill) constitute a major part of the macrozooplankton community in terms of total biomass and play a key role in the food webs of the most productive marine ecosystems of the world. The physiological strategies and OMZ tolerance mechanisms of euphausiids on a global-scale were investigated to explain the current zoogeographical pattern of major species and project it in the future. A global euphausiid respiration ANN (Artificial Neural Network) model was built with 2479 data sets enclosing 23 of the total 86 species. The model included the effect of latitude (LAT), the day of the year (DoY), and the number of daylight hours (DLh), in addition to the basal variables that determine ectothermal oxygen consumption (temperature, body mass and depth). The ANN model indicated a decrease in respiration with increasing LAT and decreasing DLh. Respiratory measurements and experiments combining hypoxia/reoxygenation exposure coupled with warming were conducted to understand adaptation of species to OMZs. Euphausia mucronata from the Humboldt Current system (HCS) starts metabolic suppression below 80% oxygen (O2) saturation (18 kPa) showing adaptation to OMZ conditions. Euphausia pacifica and the Antarctic krill, Euphausia superba, were characterized as oxyregulators and maintain respiration rates constant down to 30% (6 kPa) and 55% O2 (10 kPa) saturation, respectively. E. mucronata and E. pacifica had higher SOD (superoxide dismutase) values in winter than in summer, which relate to higher winter metabolic rate (in E. pacifica). Normoxic subsurface oxygenation in the HCS during winter already poses a high oxygen stress for E. mucronata. In winter, when temperature is homogenous and the OMZ absent, a 4°C warming combined with hypoxia represents a lethal condition for E. pacifica. Climate change scenario combining warming and hypoxia thus represents a serious threat to E. pacifica and, as a consequence, to its habitat food webs. Antarctic krill had the lowest antioxidant enzyme activities, but the highest concentrations of the molecular antioxidant glutathione (GSH) and was not lethally affected by 6 h exposure to moderate hypoxia. Gene expression related to aerobic metabolism, antioxidant defence, and heat- shock response under severe (2.5% O2 saturation or 0.6 kPa) and threshold (20% O2 saturation or 4 kPa) hypoxia exposure was investigated to detect aspects of the molecular stress response. Expression levels of the genes citrate synthase (CS), mitochondrial manganese superoxide dismutase (SODMn-m) and the heat-shock protein isoform (E) were higher in euphausiids incubated 6 h at 20% O2 saturation than in animals exposed to normoxic conditions. The transcription is likely to prepare the krill for eventual reoxygenation, which connects with the swarming behaviour of this species. This cold-adapted species thus possesses the cellular tools from its sub-polar ancestor to tolerate levels of hypoxia severer than the oxygen concentration of its habitat.Dissertation333 138 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, A molecular view on adaptation on local and continental scales in the Sub-Antarctic and Antarctic bivalve Aequiyoldia(2021-09-28); ; ; Marine species and populations have three potential responses to climate change: shift their distribution, adapt to the new environmental conditions or go extinct. The persistence of species unable to shift their ranges in response to changing conditions will be determined by their standing phenotypic plasticity or their ability to develop evolutionary adaptive responses. Physiological comparisons of closely related species/populations on latitudinal gradients have proven to be very informative in determining their respective phenotypic plasticity and genetic adaptability. These macro-scale perspectives, however, overlook the role of small-scale environmental variation in the inter-individual physiological and genetic differences. In this thesis, I used the Southern Ocean protobranch bivalve Aequiyoldia cf. eightsii (Jay, 1839) from West Antarctic Peninsula (WAP) and southern South America (SSA) as a “model species” to study the genetic and phenotypic traits that support adaptation to current and future environmental change at small (i.e., local or population scale) and large -scale (i.e., continental or species scale). As recent evidence suggests the possibility of cryptic speciation between Aequiyoldia bivalves from WAP and SSA, Chapter 2 aims at analysing the genetic diversity between and within populations on both sides of the Drake Passage. In this Chapter I report several highly differentiated mitochondrial genomes (h1, h2, h3, h4) within A. cf. eightsii coexisting in Antarctic populations but also inside a subset of the individuals sampled (mitochondrial heteroplasmy). The mitochondrial differentiation pattern is mirrored in nuclear Single Nucleotide Polymorphisms (SNPs) only across the Drake Passage, whilst the equally strongly differentiated mitochondrial lineages in the Southern Ocean are part of the same distribution of SNPs. These results suggest that populations on both sides of the Drake are two reproductively isolated species, and refuted the previous suggestions of cryptic speciation in WAP A. cf. eightsii. Using SNPs from the entire nuclear and mitochondrial genomes for reference, I demonstrated that mitochondrial heteroplasmy unpredictably misleads classical molecular barcoding procedures using universal cytochrome c oxidase subunit I (COI) primers, producing wrong taxonomic inferences with high confidence. The small-scale approach (Chapter 3) involved the study of in situ gene expression patterns within an Aequiyoldia population in front of a melting glacier in the region of the WAP. This population exhibited strikingly different gene expression pattern under subtly different natural conditions. This pattern was influenced by at least three independent underlying causes: small scale habitat heterogeneity (down to a kilometre scale), and the composition of the mitochondrial and nuclear genomes. Interestingly, the expression of nuclear genes correlated strongly with the mitochondrial genotype, with the highest gene expression differences between homoplasmic and heteroplasmic organisms. This novel mechanism might serve to add another layer of flexibility to respond to the environment and turn out instrumental in the face of the ongoing rapid environmental change in Antarctic fjords. The large-scale approach (Chapter 4) involved an experimental inter-continental comparison of gene expression patterns in response to changes in thermal and oxygen regimes expected under a global warming scenario. In both populations (from WAP and SSA), the experimental temperature implied exposure scenarios simulating a crossing of the Drake Passage, and to an expected near future warming scenario at the WAP. The WAP bivalves showed a moderated physiological response to warming and a remarkable ability to cope with short-term exposure to hypoxia by switching to a metabolic rate depression strategy and activating the alternative oxidation pathway. In SSA, the high prevalence of apoptosis (cell-death)-related differentially expressed genes especially under combined higher temperatures and hypoxia indicated that the SSA Aequiyoldia are operating near their physiological limits already. While the effect of temperature per se may not represent the single most effective barrier to Antarctic colonization by South American bivalves, the current distribution patterns as well as their resilience to future conditions may be better understood by looking at the synergistic effects of temperature in conjunction with short term exposure to hypoxia. Overall, this thesis provides a molecular perspective on the adaptive capacity and cross- continental invasibility of two Aequiyoldia sibling species inhabiting WAP and SSA under a global change scenario.Dissertation424 183 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Life strategies in the long-lived bivalve Arctica islandica on a latitudinal climate gradient-Environmental constraints and evolutionary adaptations(2011-04-29); ; ; Arctica islandica reaches maximum life span potentials (MLSP) of 405 and 150 years around Iceland and Helgoland, respectively. The combined effects of a low-metabolic lifestyle, low oxidative damage, constant cellular protection and tissue maintenance, appear to slow-down the physiological aging process in A. islandica. Due to low standard metabolic rates and down-regulation of internal pO2, formation rates of reactive oxygen species (ROS) were low in the clam. Proliferation and apoptosis intensities were low, but constant over 140 years of age. Self-induced burrowing and metabolic rate depression (MRD) seem to be key energy-saving and life-prolonging parameters in A. islandica. During shell closure, mantle cavity water pO2 decreased to 0 kPa for longer than 24 h, while anaerobic metabolism was initially detected after 3.5 days of MRD. A ROS-burst was absent in isolated gills of A. islandica following hypoxia-reoxygenation, antioxidant capacities remained equally high under normoxia and MRD. Local impacts of environmental conditions on behavioral and physiological traits in the clams seem to be responsible for different population-specific MLSPs.Dissertation344 158 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Effects of UV-radiation on crustaceans from polar and temperate coastal ecosystems(2006-07-11); ; ; Solar radiation is a physical force, modulating the earth?s ecosystems. The visible range of the solar spectrum most notably comprises beneficial effects, promoting processes such as photosynthesis. The ultraviolet (UV) portion of the solar spectrum, however, induces various detrimental effects in both terrestrial and aquatic organisms on all systemic levels. I studied the effects of UV-exposure on different UV- and oxidative stress parameters and defence systems against direct and indirect UV-damage in shallow water amphipods. The UV-tolerance was compared in species from two different polar regions (Antarctic King George Island and Arctic Spitsbergen), currently undergoing different degrees of ozone depletion, in relation to a reference species from a temperate North Sea coast, which displays higher natural UV-impact, however, lower ozone depletion compared to the polar areas. I distinguished between dose- and wavelength-dependent effects and also considered the possible influence of nutrition on UV-protective capacities by comparing herbivorous and carnivorous/necrophagous amphipods.Dissertation306 182 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Extrinsic and intrinsic factors that shape the life history of the short living scallop Argopecten ventricosus(2012-02-10); ; ; The scallop Argopecten ventricosus is characterized by its high swimming activity, fast growth, high reproductive effort and the early age to get first sexual maturity. These traits may be the result of the adaptation to a specific environment that favors an active lifestyle and a short lifespan (2 years). This opens the question of how environmental factors modulate the way a short living marine ectotherm budget energy investments among life history traits and how this modulation impacts the lifespan within a cohort. Temperature and predation are two key environmental factors that affect physiological and cellular responses in marine ectotherms that have been investigated in the present study. Lifelong investments among life history traits were studied looking at trade-offs among growth, reproduction and cellular maintenance mechanisms under the different environmental conditions. The cellular maintenance mechanisms were studied in different tissues by antioxidant and damage removal capacities. In order to demonstrate the efficiency of cellular maintenance mechanisms, oxidative damage accrual of proteins and lipids and undegradable waste accumulation (lipofuscin) were assessed in parallel. The trade-offs were also investigated within a cohort raised in the field throughout the species record lifespan (2 years). The long-term elevation of temperature (5°C above the temperature measured in the field) enhanced metabolic rates, reproduction effort but also oxidative damage accrual and high mortality rates despites the conjunctly increase in antioxidant capacities. The high mortality probably exerted a strong selection of better-adapted individuals with less oxidative damage and better growth. Scallops exposed to predator pressure (the blue crab: Callinectes sapidus) developed thicker shells and bigger swimming muscles and at the meantime constrained reproduction investment as indicated by the deferment and the lower investment into gametogenesis. Lower reproductive effort was combined with lower oxidative damage accrual especially in mantle and gill tissues, and may have prevented post-spawned mortalities. When studying the trade-offs in scallops reared in the field, it appears that scallops at their first reproductive event (< 1 year of age) showed the highest levels of oxidative damage (protein carbonyls and lipid peroxidation products). While antioxidant capacities did not appear to prevent oxidative damage, young scallops seem to remove damage before the undegradable waste product lipofusin accumulates. In contrast, older individuals (>1 year of age) failed to prevent lipofuscin accumulation. For this species, the applicability of evolutionary theories of aging suggest that a rapid growth and early maturation at young age compromise later cellular maintenance. However, species may have a great variety of strategies in order to deal with the oxidative challenges throughout their lifespan, which depend strongly on the environmental conditions and state of life. The results speak for extrinsic factors (temperature and predation) to have potential roles on the lifespan in A. ventricosus scallops. This makes aging and oxidative stress mechanisms in short living bivalves an interesting but complex process influenced by a variety of interactive intrinsic and extrinsic processes that should be considered in future studiesDissertation284 99