| 11. |
- Bailly, X, et al.
(författare)
-
The chimerical and multifaceted marine acoel Symsagittifera roscoffensis: from photosymbiosis to brain regeneration
- 2014
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- A remarkable example of biological engineering is the capability of some marine animals to take advantage of photosynthesis by hosting symbiotic algae. This capacity, referred to as photosymbiosis, is based on structural and functional complexes that involve two distantly unrelated organisms. These stable photosymbiotic associations between metazoans and photosynthetic protists play fundamental roles in marine ecology as exemplified by reef communities and their vulnerability to global changes threats. Here we introduce a photosymbiotic tidal acoel flatworm, Symsagittifera roscoffensis, and its obligatory green algal photosymbiont, Tetraselmis convolutae (Lack of the algal partner invariably results in acoel lethality emphasizing the mandatory nature of the photosymbiotic algae for the animal's survival). Together they form a composite photosymbiotic unit, which can be reared in controlled conditions that provide easy access to key life-cycle events ranging from early embryogenesis through the induction of photosymbiosis in aposymbiotic juveniles to the emergence of a functional “solar-powered” mature stage. Since it is possible to grow both algae and host under precisely controlled culture conditions, it is now possible to design a range of new experimental protocols that address the mechanisms and evolution of photosymbiosis. S. roscoffensis thus represents an emerging model system with experimental advantages that complement those of other photosymbiotic species, in particular corals. The basal taxonomic position of S. roscoffensis (and acoels in general) also makes it a relevant model for evolutionary studies of development, stem cell biology and regeneration. Finally, it's autotrophic lifestyle and lack of calcification make S. roscoffensis a favorable system to study the role of symbiosis in the response of marine organisms to climate change (e.g., ocean warming and acidification). In this article we summarize the state of knowledge of the biology of S. roscoffensis and its algal partner from studies dating back over a century, and provide an overview of ongoing research efforts that take advantage of this unique system.
|
|
| 12. |
- Basse, W. C., et al.
(författare)
-
A sea urchin Na+K+2Cl- cotransporter is involved in the maintenance of calcification-relevant cytoplasmic cords in Strongylocentrotus droebachiensis larvae
- 2015
-
Ingår i: Comparative Biochemistry and Physiology A. - : Elsevier BV. - 1095-6433. ; 187, s. 184-192
-
Tidskriftsartikel (refereegranskat)abstract
- The cellular mechanisms of calcification in sea urchin larvae are still not well understood. Primary mesenchyme cells within the larval body cavity form a syncytium to secrete CaCO3 spicules from intracellular amorphous CaCO3 (ACC) stores. We studied the role of Na+K+2Cl- cotransporter (NKCC) in intracellular ACC accumulation and larval spicule formation of Strongylocentrotus droebachiensis. First, we incubated growing larvae with three different loop diuretics (azosemide, bumetanide, and furosemide) and established concentration-response curves. All loop diuretics were able to inhibit calcification already at concentrations that specifically inhibit NKCC. Calcification was most effectively inhibited by azosemide (IC50=6.5μM), while larval mortality and swimming ability were not negatively impacted by the treatment. The inhibition by bumetanide (IC50=26.4μM) and furosemide (IC50=315.4μM) resembled the pharmacological fingerprint of the mammalian NKCC1 isoform. We further examined the effect of azosemide on the maintenance of cytoplasmic cords and on the occurrence of calcification vesicles using fluorescent dyes (calcein, FM1-43). Fifty micromolars of azosemide inhibited the maintenance of cytoplasmic cords and resulted in increased calcein fluorescence within calcification vesicles. The expression of NKCC in S. droebachiensis was verified by PCR and Western blot with a specific NKCC antibody. In summary, the pharmacological profile of loop diuretics and their specific effects on calcification in sea urchin larvae suggest that they act by inhibition of NKCC via repression of cytoplasmic cord formation and maintenance.
|
|
| 13. |
- Bednarsek, Nina, et al.
(författare)
-
Polar Ocean Acidification : LOSS OF RESOURCES FROM THE “OTHER” CO2 PROBLEM
- 2015
-
Ingår i: Thresholds and Closing December. RISKS OF IRREVERSIBLE CRYOSPHERE CLIMATE CHANGE. The International Cryosphere Climate Initiative. ; , s. 19-22
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Although technically not “cryosphere” (which is frozen water), the Arctic Ocean, and Southern Ocean around Antarctica make up some of the world’s richest fisheries, with diverse marine ecosystems. These cold waters are however highly vulnerable to ocean acidification from increased carbon dioxide (CO2) in the atmosphere. We already are crossing important ocean acidification thresholds in these regions, with early impacts possibly observed on some polar ocean species. There is substantial risk that ocean acidification will damage ecosystems and weaken the food chain in these important resource waters, even should countries meet the stated 2 degree goal, which entails atmospheric CO2 levels peaking at 450ppm. However, CO2 concentrations associated with current INDCs in the 2.7–3.5 degree range are far higher still, anticipated to peak potentially above 600ppm. At such high levels, and because of the very long time scales required for acidity to decrease, there is high risk for irreversible impacts on biodiversity in the Arctic and Southern oceans, with consequences for polar and near-polar fisheries and human activities.
|
|
| 14. |
- Bednarsek, N., et al.
(författare)
-
Synthesis of Thresholds of Ocean Acidification Impacts on Echinoderms
- 2021
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Assessing the vulnerability of marine invertebrates to ocean acidification (OA) requires an understanding of critical thresholds at which developmental, physiological, and behavioral traits are affected. To identify relevant thresholds for echinoderms, we undertook a three-step data synthesis, focused on California Current Ecosystem (CCE) species. First, literature characterizing echinoderm responses to OA was compiled, creating a dataset comprised of >12,000 datapoints from 41 studies. Analysis of this data set demonstrated responses related to physiology, behavior, growth and development, and increased mortality in the larval and adult stages to low pH exposure. Second, statistical analyses were conducted on selected pathways to identify OA thresholds specific to duration, taxa, and depth-related life stage. Exposure to reduced pH led to impaired responses across a range of physiology, behavior, growth and development, and mortality endpoints for both larval and adult stages. Third, through discussions and synthesis, the expert panel identified a set of eight duration-dependent, life stage, and habitat-dependent pH thresholds and assigned each a confidence score based on quantity and agreement of evidence. The thresholds for these effects ranged within pH from 7.20 to 7.74 and duration from 7 to 30 days, all of which were characterized with either medium or low confidence. These thresholds yielded a risk range from early warning to lethal impacts, providing the foundation for consistent interpretation of OA monitoring data or numerical ocean model simulations to support climate change marine vulnerability assessments and evaluation of ocean management strategies. As a demonstration, two echinoderm thresholds were applied to simulations of a CCE numerical model to visualize the effects of current state of pH conditions on potential habitat.
|
|
| 15. |
- Behbehani, M., et al.
(författare)
-
Ocean Acidification-Mediated Food Chain Transfer of Polonium between Primary Producers and Consumers
- 2023
-
Ingår i: Toxics. - : MDPI AG. - 2305-6304. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify Po-210 by 3-4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F-20,F- 215 = 176.84, p < 0.001; time: F-3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F-2 = 169.15, p < 0.0001; algae species: F-2 = 10.21, p < 0.0001; pH: F-1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F-2 = 19.48, p < 0.0001; copepod x pH: F-2 = 10.54, p < 0.0001; algae x pH: F-2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification.
|
|
| 16. |
- Behbehani, M., et al.
(författare)
-
Response of corals Acropora pharaonis and Porites lutea to changes in pH and temperature in the Gulf
- 2019
-
Ingår i: Sustainability (Switzerland). - : MDPI AG. - 2071-1050. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- Coral reefs are harboring a large part of the marine biodiversity and are important ecosystems for the equilibrium of the oceans. As a consequence of anthropogenic CO2 emission, a drop in pH and an increase in seawater temperature is observed in the Gulf coastal waters that potentially threaten coral assemblages. An experimental study was conducted on two species of corals to assess the effect of ocean warming and ocean acidification on the net calcification rate. Two pH conditions 8.2 and 7.5 and three temperatures, 22.5, 27.5 and 32.5 °C, were considered. Net calcification rates were measured using 45Ca radiotracer. Both temperature and pH had a significant effect on net calcification rates following a similar pattern for both species. The highest calcification rate was observed at low temperature and high pH. Increased temperature and decreased pH led to a decrease in net calcification rates. An interactive effect was observed as the effect of pH decreased with increasing temperature. However, the two species of coral were able to calcify in all the tested combination of temperature and pH suggesting that they are adapted to short term changes in temperature and pH. Ability to calcify even at a high temperature of 32.5 °C that is identical to the summertime Gulf seawater temperature under both the ambient and low pH condition with no mortalities, raises a question: are these corals adapted to high seawater temperatures and low pH? More in-depth assessments will be required to confirm if this is an adaptation to higher temperatures in Persian Gulf corals. © 2019 by the authors.
|
|
| 17. |
- Belivermis, M., et al.
(författare)
-
Physiological and gene expression responses of the mussel Mytilus galloprovincialis to low pH and low dissolved oxygen
- 2023
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- The prevalence and frequency of hypoxia events have increased worldwide over the past decade as a conse-quence of global climate change and coastal biological oxygen depletions. On the other hand, anthropogenic emissions of CO2 and consequent accumulation in the sea surface result in a perturbation of the seawater car-bonate system, including a decrease in pH, known as ocean acidification. While the effect of decreases in pH and dissolved oxygen (DO) concentration is better understood, their combined effects are still poorly resolved. Here, we exposed adult mussels (Mytilus galloprovincialis) to two pHs (8.27 and 7.63) and DO concentrations (7.65 and 2.75 mg L- 1) over 17 days in a full-factorial design. These levels correspond to extremes of the present natural variability and are relevant in the context of ocean acidification and hypoxia. No mortality was observed during the experiment. However, sublethal effects were observed for clearance and oxygen consumption rates, as well as total haemocytes count and haemocytes viability and gene expression in mussels exposed to the combination of low pH and low DO. Respiration and excretion rates were not significantly impacted by low pH and DO, alone or in combination. Overall, low pH alone led to a decrease in all tested physiological parameters while low DO alone led to a decline in clearance rate, haemocyte parameters and an increase in carbohydrate content. Both pa-rameters led to up-or down-regulation of most of the selected genes. Not surprisingly, the combined effect of low pH and low DO could not be predicted by a simple arithmetic additive response at the effect level, highlighting more complex and non-linear effects.
|
|
| 18. |
- Biressi, A., et al.
(författare)
-
Wound healing and arm regeneration in Ophioderma longicaudum and Amphiura filiformis (Ophiuroidea, Echinodermata): comparative morphogenesis and histogenesis
- 2010
-
Ingår i: Zoomorphology. - : Springer Science and Business Media LLC. - 0720-213X .- 1432-234X. ; 129:1, s. 1-19
-
Tidskriftsartikel (refereegranskat)abstract
- All species of the Ophiuroidea have exceptional regenerative capabilities; in particular, they can replace arms lost following traumatic or self-induced amputation. In order to reconstruct this complex phenomenon, we studied arm regeneration in two different ophiuroids, Ophioderma longicaudum (Retzius, 1805) and Amphiura filiformis O. F. Muller, 1776, which are quite distantly related. These species present contrasting regeneration and differentiation rates and differ in several ecological traits. The aim of this paper is to interpret the primary sequence of morphogenetic and histogenetic events leading to the complete reconstruction of a new arm, comparing the arm regenerative processes of these two ophiuroid species with those described in crinoids. Arm regeneration in ophiuroids is considered an epimorphic process in which new structures develop from a typical blastema formed from an accumulation of presumptive undifferentiated cells. Our results showed that although very different in some respects such as, for instance, the regeneration rate (0.17 mm/week for O. longicaudum and 0.99 mm/week for A. filiformis), morphogenetic and histogenetic aspects are surprisingly similar in both species. The regenerative process presents similar characteristics and follows a developmental scheme which can be subdivided into four phases: a repair phase, an early regenerative phase, an intermediate regenerative phase and an advanced regenerative phase. In terms of histogenesis, the regenerative events involve the development of new structures from migratory pluripotent cells, which proliferate actively, in addition in both cases there is a significant contribution from dedifferentiated cells, in particular dedifferentiating myocytes, although to varying extents. This evidence confirms the plasticity of the regenerative phenomenon in echinoderms, which can apparently follow different pathways in terms of growth and morphogenesis, but nevertheless involve both epimorphic and morphallactic contributions at the cellular level.
|
|
| 19. |
|
|
| 20. |
- Bouquet, J. M., et al.
(författare)
-
Increased fitness of a key appendicularian zooplankton species under warmer, acidified seawater conditions
- 2018
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Ocean warming and acidification (OA) may alter the fitness of species in marine pelagic ecosystems through community effects or direct physiological impacts. We used the zooplanktonic appendicularian, Oikopleura dioica, to assess temperature and pH effects at mesocosm and microcosm scales. In mesocosms, both OA and warming positively impacted O. dioica abundance over successive generations. In microcosms, the positive impact of OA, was observed to result from increased fecundity. In contrast, increased pH, observed for example during phytoplankton blooms, reduced fecundity. Oocyte fertility and juvenile development were equivalent under all pH conditions, indicating that the positive effect of lower pH on O. dioica abundance was principally due to increased egg number. This effect was influenced by food quantity and quality, supporting possible improved digestion and assimilation at lowered pH. Higher temperature resulted in more rapid growth, faster maturation and earlier reproduction. Thus, increased temperature and reduced pH had significant positive impacts on O. dioica fitness through increased fecundity and shortened generation time, suggesting that predicted future ocean conditions may favour this zooplankton species. © 2018 Bouquet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
|
|
