Jehan-Hervé LIGNOT
Informations
EMAIL : jehan-herve.lignot umontpellier.fr
Institut : /BOUCLE_groupemots>
UM
LIEU GEOGRAPHIQUE : /BOUCLE_groupemots>
MONTPELLIER
GRADE : /BOUCLE_groupemots>
PU2
Gouvernance : /BOUCLE_groupemots>
CDE-Suppléant(e) Représentant(e) de thème
Thèmes de recherche : /BOUCLE_groupemots>
Écologie évolutive et adaptation
//B_mots>
Publications
2020 |
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Alix, M., et al. "Description of the unusual digestive tract of Platax orbicularis and the potential impact of Tenacibaculum maritimum infection." PeerJ. 8 (2020): e9966.
Résumé: Background Ephippidae fish are characterized by a discoid shape with a very small visceral cavity. Among them Platax orbicularis has a high economic potential due to its flesh quality and flesh to carcass ratio. Nonetheless, the development of its aquaculture is limited by high mortality rates, especially due to Tenacibaculum maritimum infection, occurring one to three weeks after the transfer of fishes from bio-secure land-based aquaculture system to the lagoon cages for growth. Among the lines of defense against this microbial infection, the gastrointestinal tract (GIT) is less studied. The knowledge about the morphofunctional anatomy of this organ in P. orbicularis is still scarce. Therefore, the aims of this study are to characterize the GIT in non-infected P. orbicularis juveniles to then investigate the impact of T. maritimum on this multifunctional organ. Methods In the first place, the morpho-anatomy of the GIT in non-infected individuals was characterized using various histological techniques. Then, infected individuals, experimentally challenged by T. maritimum were analysed and compared to the previously established GIT reference. Results The overlapped shape of the GIT of P. orbicularis is probably due to its constrained compaction in a narrow visceral cavity. Firstly, the GIT was divided into 10 sections, from the esophagus to the rectum. For each section, the structure of the walls was characterized, with a focus on mucus secretions and the presence of the Na+/K+ ATPase pump. An identification key allowing the characterization of the GIT sections using in toto histology is given. Secondly, individuals challenged with T. maritimum exhibited differences in mucus type and proportion and, modifications in the mucosal and muscle layers. These changes could induce an imbalance in the trade-off between the GIT functions which may be in favour of protection and immunity to the disadvantage of nutrition capacities.
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Rind, K., et al. "Morphological and physiological traits of Mediterranean sticklebacks living in the Camargue wetland (Rhone river delta)." J. Fish Biol. (2020).
Résumé: Three-spined sticklebacks (Gasterosteus aculeatus L.) living at the southern limit of the species distribution range could possess specific morphological and physiological traits that enable these fish to live at the threshold of their physiological capacities. Morphological analysis was carried out on samples of sticklebacks living in different saline habitats of the Camargue area (Rhone delta, northern Mediterranean coast) obtained from 1993 to 2017. Salinity acclimation capacities were also investigated using individuals from freshwater-low salinity drainage canals and from mesohaline-euryhaline lagoons. Fish were maintained in laboratory conditions at salinity values close to those of their respective habitats: low salinity (LS, 5 parts per thousand) or seawater (SW, 30 parts per thousand). Fish obtained from a mesohaline brackish water lagoon (BW, 15 parts per thousand) were acclimated to SW or LS. Oxygen consumption rates and branchial Na+/K+-ATPase (NKA) activity (indicator of fish osmoregulatory capacity) were measured in these LS or SW control fish and in individuals subjected to abrupt SW or LS transfers. At all the studied locations, only the low-plated “leiurus” morphotype showed no spatial or temporal variations in their body morphology. Gill rakers were only longer and denser in fish sampled from the LS-freshwater (FW) drainage canals. All fish presented similar physiological capacities. Oxygen consumption rates were not influenced by salinity challenge except in SW fish transferred to LS immediately and 1 h after transfer. However, and as expected, gill NKA activity was salinity dependent. Sticklebacks of the Camargue area sampled from habitats with contrasted saline conditions are homogenously euryhaline, have low oxygen consumption rates and do not appear to experience significantly greater metabolic costs when challenged with salinity. However, an observed difference in gill raker length and density is most probably related to the nutritional condition of their habitat, indicating that individuals can rapidly acclimatize to different diets.
Mots-Clés: 3-spined stickleback; ecological causes; Gasterosteus aculeatus; gasterosteus-aculeatus l; gill rakers; ion regulation; k+-atpase activity; morphometry; na+/k+-atpase; NKA activity; osmoregulation; oxygen consumption; oxygen-consumption; pelvic reduction; plate morph evolution; salinity; stickleback; threespine stickleback
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Slama, T., et al. "The gametogenic cycle of the non-native false limpet Siphonaria pectinata (Linnaeus, 1758) in the easternmost limit of its distribution range: implications for its future in the Eastern Mediterranean Basin." Mediterr. Mar. Sci.. 21.3 (2020): 599–607.
Résumé: The gametogenic cycle of the false-limpet Siphonaria pectinata from the Bizerte channel (Northern Tunisia) was studied through histological characterization of the hermaphroditic gonad during a 1-year study period (May 2015 – May 2016). Spawning intensity in the field as well as the gonadic index were calculated monthly. Both female and male gametes Were observed simultaneously within acini of adult individuals and continuously throughout the year. Oogenesis started in the mid-autumn (October), with gonads characterized mainly by proliferation of female cells. After that, oocytes progressively increased in number and volume until summer, when the evacuation stage frequency was the highest. From summer to autumn, some acini were empty from their oocyctes while some others had already begun the proliferation stage, suggesting the lack of a resting phase. Spermatogenesis was also a continuous process throughout the year, with spermatozoa being mainly observed in late spring (March). These findings suggested that environmental conditions are suitable for the establishment of S. pectinata, first mentioned in 1998 on the Tunisian coast and even suggest that it could continue spreading eastward in the Mediterranean Basin.
Mots-Clés: alien species; gastropoda; invasion success; pulmonate limpet; reproduction; Siphonariid; temperature; Tunisia
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Theuerkauff, D., et al. "Wastewater bioremediation by mangrove ecosystems impacts crab ecophysiology: In-situ caging experiment." Aquat. Toxicol.. 218 (2020): 105358.
Résumé: Mangroves are tidal wetlands that are often under strong anthropogenic pressures, despite the numerous ecosystem services they provide. Pollution from urban runoffs is one such threats, yet some mangroves are used as a bioremediation tool for wastewater (WW) treatment. This practice can impact mangrove crabs, which are key engineer species of the ecosystem. Using an experimental area with controlled WW releases, this study aimed to determine from an ecological and ecotoxicological perspective, the effects of WW on the red mangrove crab Neosarmatium africanum. Burrow density and salinity levels (used as a proxy of WW dispersion) were recorded, and a 3-week caging experiment was performed. Hemolymph osmolality, gill Na+/K+-ATPase (NKA) activity and gill redox balance were assessed in anterior and posterior gills of N. africanum. Burrow density decreased according to salinity decreases around the discharged area. Crabs from the impacted area had a lower osmoregulatory capacity despite gill NKA activity remaining undisturbed. The decrease of the superoxide dismutase activity indicates changes in redox metabolism. However, both catalase activity and oxidative damage remained unchanged in both areas but were higher in posterior gills. These results indicate that WW release may induce osmoregulatory and redox imbalances, potentially explaining the decrease in crab density. Based on these results we conclude that WW release should be carefully monitored as crabs are key players involved in the bioremediation process.
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2018 |
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Maugars, G., et al. "The effects of acute transfer to freshwater on ion transporters of the pharyngeal cavity in European seabass (Dicentrarchus labrax)." Fish Physiol. Biochem.. 44.5 (2018): 1393–1408.
Résumé: Gene expression of key ion transporters (the Na+/K+-ATPase NKA, the Na+, K+-2Cl(-) cotransporter NKCC1, and CFTR) in the gills, opercular inner epithelium, and pseudobranch of European seabass juveniles (Dicentrarchus labrax) were studied after acute transfer up to 4days from seawater (SW) to freshwater (FW). The functional remodeling of these organs was also studied. Handling stress (SW to SW transfer) rapidly induced a transcript level decrease for the three ion transporters in the gills and operculum. NKA and CFTR relative expression level were stable, but in the pseudobranch, NKCC1 transcript levels increased (up to 2.4-fold). Transfer to FW induced even more organ-specific responses. In the gills, a 1.8-fold increase for NKA transcript levels occurs within 4days post transfer with also a general decrease for CFTR and NKCC1. In the operculum, transcript levels are only slightly modified. In the pseudobranch, there is a transient NKCC1 increase followed by 0.6-fold decrease and 0.8-fold CFTR decrease. FW transfer also induced a density decrease for the opercular ionocytes and goblet cells. Therefore, gills and operculum display similar trends in SW-fish but have different responses in FW-transferred fish. Also, the pseudobranch presents contrasting response both in SW and in FW, most probably due to the high density of a cell type that is morphologically and functionally different compared to the typical gill-type ionocyte. This pseudobranch-type ionocyte could be involved in blood acid-base regulation masking a minor osmotic regulatory capacity of this organ compared to the gills.
Mots-Clés: atlantic salmon; atpase alpha-1 isoforms; branchial chloride cells; carbonic-anhydrase; Dicentrarchus labrax; gill na+/k+-atpase; Gills and extrabranchial organs; Ion transporters; k+-atpase; mitochondrion-rich cells; Osmoregulation; salinity transfer; salmon salmo-salar; seawater acclimation; Seawater to freshwater transfer; Teleost fish
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Paital, B., et al. "Increasing frequency of large-scale die-off events in the Bay of Bengal: reasoning, perspectives and future approaches." Indian J. Geo-Mar. Sci.. 47.11 (2018): 2135–2146.
Résumé: The Bay of Bengal has been suffering from increasing frequency of large-scale die-off events for the past decades. Most frequently, these events are attributed to high-speed human development and its harmful effects on environment, which is nevertheless, the biggest challenges currently faced by the world. Increasing urbanization, environmental pollution and climate change are leading to unsustainable ecosystem exploitation and raising health and disease management challenges. Considerable modulations in major ecosystems and major disturbances in the global food chain are some of the most significant consequences of this uncontrolled urbanization. Global warming and El Nino events are few particular phenomena that drive mass deterioration of terrestrial foliages and fauna as well as aquatic organisms, respectively. We here review and discuss the die-off events occurring in the Bay of Bengal for the last decades as well as all the data obtained from the analyses of such events to provide a future perspective on potential management and monitoring strategies directed towards the protection of the flora and fauna of several major ecosystems from such die-off events.
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Theuerkauff, D., et al. "Effects of domestic effluent discharges on mangrove crab physiology: Integrated energetic, osmoregulatory and redox balances of a key engineer species." Aquatic toxicology (Amsterdam, Netherlands). 196 (2018): 90–103.
Résumé: Mangroves are increasingly used as biofiltering systems of (pre-treated) domestic effluents. However, these wastewater discharges may affect local macrofauna. This laboratory study investigates the effects of wastewater exposure on the mangrove spider crab Neosarmatium meinerti, a key engineering species which is known to be affected by waste waters in effluent-impacted areas. These effects were quantified by monitoring biological markers of physiological state, namely oxygen consumption, the branchial cavity ventilation rate, gill physiology and morphology, and osmoregulatory and redox balance. Adults acclimated to clean seawater (SW, 32 ppt) and freshwater (FW, 0 ppt) were compared to crabs exposed to wastewater for 5 h (WW, 0 ppt). Spider crabs exposed to WW increased their ventilation and whole-animal respiration rates by 2- and 3-fold respectively, while isolated gill respiration increased in the animals exposed to FW (from 0.5 to 2.3 and 1.1 nmol O2 min-1 mg DW-1 for anterior and posterior gills, respectively) but was not modified in WW-exposed individuals. WW exposure also impaired crab osmoregulatory capacity; an 80 mOsm kg-1 decrease was observed compared to FW, likely due to decreased branchial NKA activity. ROS production (DCF fluorescence in hemolymph), antioxidant defenses (superoxide dismutase and catalase activities) and oxidative damage (malondialdehyde concentration) responses varied according to animal gender. Overall, this study demonstrates that specific physiological parameters must be considered when focusing on crabs with bimodal breathing capacities. We conclude that spider crabs exposed to WW face osmoregulatory imbalances due to functional and morphological gill remodeling, which must rapidly exhaust energy reserves. These physiological disruptions could explain the ecological changes observed in the field.
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Theuerkauff, D., et al. "Salinity Variation in a Mangrove Ecosystem: A Physiological Investigation to Assess Potential Consequences of Salinity Disturbances on Mangrove Crabs." Zool. Stud.. 57 (2018): 36.
Résumé: Dimitri Theuerkauff, Georgina A. Rivera-Ingraham, Jonathan A.C. Roques, Laurence Azzopardi, Marine Bertini, Mathilde Lejeune, Emilie Farcy, Jehan-Herve Lignot, and Elliott Sucre (2018) Salinity is one of the main environmental factors determining coastal species distribution. However, in the specific case of mangrove crabs, salinity selection cannot be understood through ecological approaches alone. Yet understanding this issue is crucial in the context of mangrove conservation, since this ecosystem is often used as biofilter of (low-salinity) wastewater. Crabs are keystone species in this mangrove ecosystem and are differentially affected by salinity. We hypothesize that crab salinity selection may be partly explained by specific salinity-induced physiological constraints associated with osmoregulation, energy and redox homeostasis. To test this, the response to salinity variation was analysed in two landward mangrove crabs: the fiddler crab Tubuca urvillei, which inhabits low-salinity areas of the mangrove, and the red mangrove crab Neosarmatium meinerti, which lives in areas with higher salinity. Results confirm that both species are strong hypo-/hyper-osmoregulators that deal easily with large salinity variations. Such shifts in salinity do not induce changes in energy expenditure (measured as oxygen consumption) or in the production of reactive oxygen species. However, T. urvillei is physiologically suited to habitats with brackish water, since it presents i) high hemolymph osmolalities over a wider range of salinities and lower osmoregulatory capacity in seawater, ii) high Na+/K+-ATPase (NKA) activity in the posterior osmoregulatory gills and iii) a thicker osmoregulatory epithelium along the posterior gill lamellae. Therefore, while environmental salinity alone cannot directly explain fiddler and red mangrove crab distributions, our data suggest that salinity selection is indeed influenced by specific physiological adjustments.
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2017 |
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Alix, M., et al. "Effects of fasting and re-alimentation on gill and intestinal morphology and indicators of osmoregulatory capacity in genetically selected sea bass (Dicentrarchus labrax) populations with contrasting tolerance to fasting." Aquaculture. 468 (2017): 314–325.
Résumé: Fasting and refeeding occur naturally in predators but this is largely ignored when dealing with farmed fish. Therefore,the effects of 3-week fasting and re-alimentation (2.5% of the individual body mass) were investigated using two genetically selected populations (F2 generation) of 250 g juvenile sea bass (Dicentrarchus labrax L.). Blood osmolarity, gill and intestinal morphology and expression of the sodium pump (Na+, K+-ATPase, NKA) were studied on two phenotypes showing different degrees of body mass loss during food deprivation: one group losing body mass rapidly during fasting (F+) and the other one limiting body mass loss during the same period (F-). Blood osmotic pressure significantly decreases due to re-alimentation in both groups, but this is compensated in the F+ group. In this group, gill ionocytes are smaller and less numerous, but a significantly higher NKA gene expression is noted in the gills in comparison to the F- individuals 48 and 72 h after re-alimentation, and also in the posterior intestine 72 h after re-alimentation. This most probably occurs to compensate for a higher salt intake during nutrient absorption in comparison to the F- group. Furthermore, refed F- fish absorb more lipids along the proximal anterior intestine, and take longer to digest than the F+ group, and show enterocyte vacuolization in the posterior intestine. Therefore, the two selected populations have different postprandial digestive strategies: the F- fish optimize feed efficiency first at the cost of optimal hydromineral adjustment, while the F+ group invests in osmoregulatory performance at the expense of digestive physiology. Statement of relevance: Our paper is highly relevant to the general field of commercial aquaculture. There is an increasing number of research articles dealing with fasting and refeeding in commercial fish and how to improve fish nutrition based oh these physiological data and genetic selection. (C) 2016 Elsevier B.V. All rights reserved.
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Dayras, P., et al. "Osmoregulatory responses to cadmium in reference and historically metal contaminated Gammarus fossarum (Crustacea, Amphipoda) populations." Chemosphere. 180 (2017): 412–422.
Résumé: In order to better understand the variable sensitivities of crustaceans to metals, we investigated the impact of cadmium exposure in 3 populations of Gammarus fossarum from different rivers of France. The first population lives in a Cd-contaminated river from a geochemical background, while the others inhabit Cd-free sites. Osmoregulation, a relevant biomarker to evaluate crustacean health following metal contamination, was used as a proxy to evaluate the intra- and inter-populationnal sensitivities to Cd. Specimens from each population were experimentally exposed to 9 μg Cd2+/L Cd for 7 days and hemolymph osmolality (HO) was then individually measured. In exposed populations, high inter-individual variations in HO values were noted, resulting in their separation into non-impacted and slightly or highly Cd-impacted (with lower HO) animals. In gills of impacted organisms, deep histopathological alterations and protein overexpression of Na+/K+-ATPase and V-H+-ATPase were observed through histology and immunolocalization, while non-impacted animals showed profiles comparable to controls. Moreover, the osmoregulatory processes in the population living in the Cd-contaminated site were impacted by acute Cd exposure in the laboratory as much as for one of the two populations originating from Cd-free sites. The observed changes did not reveal any obvious adaptive osmoregulatory phenomena at the population scale, but they may be due to differences in fitness between individuals and between populations in relation to the features of their respective environments, unrelated with the presence of the metal.
Mots-Clés: Cadmium; Crustacean; Histology; immunolocalization; Na+/K+-ATPase; V-H+-ATPase
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Rind, K., et al. "Effects of different salinities on the osmoregulatory capacity of Mediterranean sticklebacks living in freshwater." Journal of Zoology. 303.4 (2017): 270–280. |
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Rivera-Ingraham, G. A., and J. - H. Lignot. "Osmoregulation, bioenergetics and oxidative stress in coastal marine invertebrates: raising the questions for future research." J. Exp. Biol.. 220.10 (2017): 1749–1760.
Résumé: Osmoregulation is by no means an energetically cheap process, and its costs have been extensively quantified in terms of respiration and aerobic metabolism. Common products of mitochondrial activity are reactive oxygen and nitrogen species, which may cause oxidative stress by degrading key cell components, while playing essential roles in cell homeostasis. Given the delicate equilibrium between pro- and antioxidants in fueling acclimation responses, the need for a thorough understanding of the relationship between salinity-induced oxidative stress and osmoregulation arises as an important issue, especially in the context of global changes and anthropogenic impacts on coastal habitats. This is especially urgent for intertidal/estuarine organisms, which may be subject to drastic salinity and habitat changes, leading to redox imbalance. How do osmoregulation strategies determine energy expenditure, and how do these processes affect organisms in terms of oxidative stress? What mechanisms are used to cope with salinity-induced oxidative stress? This Commentary aims to highlight the main gaps in our knowledge, covering all levels of organization. From an energy-redox perspective, we discuss the link between environmental salinity changes and physiological responses at different levels of biological organization. Future studies should seek to provide a detailed understanding of the relationship between osmoregulatory strategies and redox metabolism, thereby informing conservation physiologists and allowing them to tackle the new challenges imposed by global climate change.
Mots-Clés: Antioxidants; callinectes-sapidus; cell-volume regulation; clibanarius-vittatus bosc; copepod tigriopus-brevicornis; crab chasmagnathus-granulata; different salinity levels; free amino-acids; Free radicals; Hyper-/hypo-osmoregulator; Hyper-/iso-osmoregulators; Hypometabolism; metabolic depression; Mitochondria; Osmoconformers; oxygen species production; reactive oxygen
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Shirangi, S. A., et al. "Immunolocalization of Na+/K+-ATPase, Na+/K+/2Cl- co-transporter (NKCC) and mRNA expression of Na+/K+-ATPase +α-subunit during short-term salinity transfer in the gills of Persian sturgeon (Acipenser persicus, Borodin, 1897) juveniles." J. Appl. Ichthyol.. 33.3 (2017): 347–353.
Résumé: The study tests the physiological responses of Persian sturgeon, Acipenser persicus, during the abrupt release of juveniles from freshwater (FW) into brackish waters (BW=11 parts per thousand) of the Caspian Sea. Fish weight at release was 2-3g (2.55 +/- 0.41g; 8.8 +/- 0.58cm TL). Totals of 160 individuals were randomly distributed into four fiber-glass aerated tanks (volume 60-L). Two tanks served as controls (FW groups), and two as exposure tanks for BW (Caspian Sea water=CSW). Fish were sampled at 0, 3, 6, 12, 24, 48 and 96hr after abrupt transfer to CSW. Plasma osmolality, immunolocalization of Na+, K+ -ATPase (NKA) and Na+/K+/2Cl(-) (NKCC) Co-transporter, NKA activity and the NKA -subunit mRNA expression were analyzed. Blood osmolality of fish transferred from FW to CSW increased significantly within hours post-transfer (p<.05) and remained at a high level for up to 96hr. Immunolocalization of NKCC indicated co-localization with NKA in the chloride cells in the gill epithelium. A partial sequence of the NKA -subunit (632bp) is described. Its expression levels were up-regulated at 12 and 48hr following salinity transfer (p<.05). However, NKA activity sharply increased in CSW specimens by almost 2.8-fold (p<.05) between 48 and 96hr after transfer. Gill NKCC co-transporter abundance increased, coinciding with increased gill NKA activity. The increased activity of NKCC during salt excretion in CSW may lead to an influx of Na+ into the chloride cells. Consequently, NKA activity increases to maintain intracellular Na+ homeostasis.
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2016 |
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Blondeau-Bidet, E., et al. "Molecular characterization and expression of Na+/K+-ATPase α1 isoforms in the European sea bass Dicentrarchus labrax osmoregulatory tissues following salinity transfer." Fish Physiology and Biochemistry. 42.6 (2016): 1647–1664. |
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Ituarte, R. B., et al. "Immunolocalization and expression of Na+/K+ -ATPase in embryos, early larval stages and adults of the freshwater shrimp Palaemonetes argentinus (Decapoda, Caridea, Palaemonidae)." Cell Tissue Res.. 364.3 (2016): 527–541.
Résumé: The euryhaline shrimp Palaemonetes argentinus exemplifies an evolutionary transition from brackish to freshwater habitats that requires adequate osmoregulatory capacities. Hyperosmoregulation is functional at hatching and it likely begins during the embryonic phase allowing this species to develop entirely in fresh water. Here, we investigated the Na+/K+-ATPase alpha-subunit gene (nka-alpha) expression using quantitative real-time PCR and localized Na+/K+-ATPase (NKA) in ion-transporting epithelia through immunofluorescence microscopy. We reared shrimps from spawning to juvenile stages at two salinities (1, 15 aEuro degrees) and maintained adults for 3 weeks at three salinity treatments (1, 15, 25 aEuro degrees). nka-alpha gene expression was measured in: (1) embryos at an early (SI), intermediate (SII) and late (SIII) stage of embryonic development; (2) newly hatched larvae (Zoea I, ZI); and (3) isolated gill tissue of adults. The nka-alpha expression was low in SI and SII embryos and reached maximum levels prior to hatching (SIII), which were similar to expression levels detected in the ZI. The nka-alpha expression in SIII and ZI was highest at 15 aEuro degrees, whereas salinity did not affect expression in earlier embryos. In SIII, in ZI and in a later zoeal stage ZIV, NKA was localized in epithelial cells of pleurae, in the inner-side epithelium of branchiostegite and in the antennal glands. Gills appeared in the ZIV but NKA immunolabeling of the cells of the gill shaft occurred in a subsequent developmental larval stage, the decapodid. Extrabranchial organs constitute the main site of osmoregulation in early ontogenetic stages of this freshwater shrimp.
Mots-Clés: Antennal gland; antennal glands; branchial chamber; crayfish astacus-leptodactylus; dorsal organ; Extrabranchial organs; Gill; h+-atpase; hemigrapsus-crenulatus; kinetic characterization; lobster homarus-gammarus; Ontogeny; Osmoregulation; osmoregulatory organs; prawn macrobrachium-rosenbergii
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Rivera-Ingraham, G. A., et al. "Osmoregulation and salinity-induced oxidative stress: is oxidative adaptation determined by gill function?" J. Exp. Biol.. 219.1 (2016): 80–89.
Résumé: Osmoregulating decapods such as the Mediterranean green crab Carcinus aestuarii possess two groups of spatially segregated gills: anterior gills serve mainly respiratory purposes, while posterior gills contain osmoregulatory structures. The co-existence of similar tissues serving different functions allows the study of differential adaptation, in terms of free radical metabolism, upon salinity change. Crabs were immersed for 2 weeks in seawater (SW, 37 ppt), diluted SW (dSW, 10 ppt) and concentrated SW (cSW, 45 ppt). Exposure to dSW was the most challenging condition, elevating respiration rates of whole animals and free radical formation in hemolymph (assessed fluorometrically using C-H(2)DFFDA). Further analyses considered anterior and posterior gills separately, and the results showed that posterior gills are the main tissues fueling osmoregulatory-related processes because their respiration rates in dSW were 3.2-fold higher than those of anterior gills, and this was accompanied by an increase in mitochondrial density (citrate synthase activity) and increased levels of reactive oxygen species (ROS) formation (1.4-fold greater, measured through electron paramagnetic resonance). Paradoxically, these posterior gills showed undisturbed caspase 3/7 activity, used here as a marker for apoptosis. This may only be due to the high antioxidant protection that posterior gills benefit from [superoxide dismutase (SOD) in posterior gills was over 6 times higher than in anterior gills]. In conclusion, osmoregulating posterior gills are better adapted to dSW exposure than respiratory anterior gills because they are capable of controlling the deleterious effects of the ROS production resulting from this salinity-induced stress.
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Rivera-Ingraham, G. A., et al. "Salinity stress from the perspective of the energy-redox axis: Lessons from a marine intertidal flatworm." Redox Biology. 10 (2016): 53–64.
Résumé: In the context of global change, there is an urgent need for researchers in conservation physiology to understand the physiological mechanisms leading to the acquisition of stress acclimation phenotypes. Intertidal organisms continuously cope with drastic changes in their environmental conditions, making them outstanding models for the study of physiological acclimation. As the implementation of such processes usually comes at a high bioenergetic cost, a mitochondrial/oxidative stress approach emerges as the most relevant approach when seeking to analyze whole-animal responses. Here we use the intertidal flatworm Macrostomum lignano to analyze the bioenergetics of salinity acclimation and its consequences in terms of reactive oxygen/nitrogen species formation and physiological response to counteract redox imbalance. Measures of water fluxes and body volume suggest that M. lignano is a hyper-/iso-regulator. Higher salinities were revealed to be the most energetically expensive conditions, with an increase in mitochondrial density accompanied by increased respiration rates. Such modifications came at the price of enhanced superoxide anion production, likely associated with a high caspase 3 upregulation. These animals nevertheless managed to live at high levels of environmental salinity through the upregulation of several mitochondrial antioxidant enzymes such as superoxide dismutase. Contrarily, animals at low salinities decreased their respiration rates, reduced their activity and increased nitric oxide formation, suggesting a certain degree of metabolic arrest. A contradictory increase in dichlorofluorescein fluorescence and an upregulation of gluthathione-S-transferase pi 1 (GSTP1) expression were observed in these individuals. If animals at low salinity are indeed facing metabolic depression, the return to seawater may result in an oxidative burst. We hypothesize that this increase in GSTP1 could be a “preparation for oxidative stress”, i.e. a mechanism to counteract the production of free radicals upon returning to seawater. The results of the present study shed new light on how tolerant organisms carry out subcellular adaptations to withstand environmental change.
Mots-Clés: Energetic balance; Flatworms; Live-imaging; Mitochondrial membrane potential; Osmoregulation; Rns; Ros
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Shirangi, S. A., et al. "Salinity effects on osmoregulation and gill morphology in juvenile Persian sturgeon (Acipenser persicus)." Fish Physiol Biochem. 42.6 (2016): 1741–1754.
Résumé: The effect of abrupt and 5-day gradual salinity transfers from freshwater (FW) to 11 ‰ Caspian Sea brackish water (BW) was investigated in juvenile Persian sturgeon Acipenser persicus with three different weight groups: 1–2 g (1.62 ± 0.27 g), 2–3 g (2.55 ± 0.41 g) and 3–5 g (4.28 ± 0.76 g). Mortality rates, blood osmotic pressure, gill morphology and branchial Na+, K+-ATPase (NKA) activity were measured 4 and 10 days after abrupt transfer and 9 and 15 days after the initial gradual transfer (i.e. 4 and 10 days after reaching Caspian Sea salinity). Fish under 3 g could not survive increased salinity, and the blood osmotic pressure of the remaining surviving fish increased and remained elevated. However, heavier fish were able to survive and successfully acclimate, even to rapid salinity change with osmotic pressure reduced to Caspian Sea osmolality levels. At the gill level, the developmental increase in chloride cell volume and a higher NKA content most probably allow juveniles weighing more than 2 g to sharply increase NKA activity if the fish are transferred to BW. The rapid chloride cell proliferation occurring with increased salinity should strengthen this acclimation response. Therefore, a drastic physiological change occurs when fish weigh more than 2 g that allows migration to higher salinities. The triggering signal on chloride cells must be further investigated in order to optimize this functional step.
Mots-Clés: Chloride cell; Juvenile; K+-ATPase activity; Na+; Osmoregulation; Persian sturgeon; Salinity acclimation
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2014 |
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Taghizadeh Rahmat Abadi, Z., et al. "Ontogeny and osmoregulatory function of the urinary system in the Persian sturgeon, Acipenser persicus (Borodin, 1897)." Tissue and Cell. 46.5 (2014): 287–298.
Mots-Clés: Ionocytes; K+-ATPase; Larval immunocytochemistry; Mesonephros; Na+; Pronephros; ontogeny
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2012 |
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Reichardt, F., et al. "Kaolinite ingestion facilitates restoration of body energy reserves during refeeding after prolonged fasting." Fundam. Clin. Pharmacol.. 26.5 (2012): 577–588.
Résumé: Clay consumption is a spontaneous behavior currently observed in animals and humans, particularly during undernutrition. Often regarded as intestinal care products, ingested clays also enhance food efficiency, notably by increasing intestinal lipid uptake. Clay complementation could then optimize the reconstitution of energy reserves in animals with low lipid stocks consecutive to intensive fasting. The aim of this study was therefore to observe the effects of voluntarily kaolinite complementation during the refeeding of fasted rats to determine whether body mass, food uptake, lipid and mineral contents as intestinal morphology and protein profile were modified. This study examined two types of refeeding experiments after prolonged fasting. Firstly, rats with ad libitum access to food were compared to rats with ad libitum access to food and kaolinite pellets. Animals were randomly put into the different groups when the third phase of fasting (phase III) reached by each individual was detected. In a second set of experiments, rats starting phase III were refed with free access to food and kaolinite pellets. When animals had regained their body mass prior to fasting, they were euthanized for chemical, morphological, and proteomic analyses. Although kaolinite ingestion did not change the time needed for regaining prefasting body mass, daily food ingestion was seen to decrease by 6.8% compared with normally refed rats, without affecting lipid composition. Along the intestinal lining, enterocytes of complemented animals contained abundant lipid droplets and a structural modification of the brushborder was observed. Moreover, the expression of two apolipoproteins involved in lipid transport and satiety (ApoA-I and ApoA-IV) increased in complemented rats. These results suggest that kaolinite complementation favors intestinal nutrient absorption during refeeding despite reduced food uptake. Within the intestinal lumen, clay particles could increase the passive absorption capacity and/or nutrient availability that induce mucosal morphological changes. Therefore, clay ingestion appears to be beneficial for individuals undergoing extreme nutritional conditions such as refeeding and limited food supplies.
Mots-Clés: adaptation; apolipoprotein A-IV; clay; enterocytes; fat; geophagy; intestinal mucosa; kaolinite; lipids; mucosa; protein; rat; refeeding; small-intestine; starvation
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Voinot, F., et al. "Effects of controlled ingestion of kaolinite (5%) on food intake, gut morphology and in vitro motility in rats." Fundamental & Clinical Pharmacology. 26.5 (2012): 565–576.
Résumé: Geophagia is found in various animal species and in humans. We have previously shown that spontaneously ingested kaolinite interacts with the intestinal mucosa modifies nutrient absorption and slows down gastric emptying and intestinal transit in rats in vivo. However, the precise mechanisms involved are not elucidated. The aim of this work was to investigate the effects of controlled kaolinite ingestion on food intake, gut morphology and in vitro motility in rats. Male Wistar rats were fed with 5% kaolinite in standard food pellets during 7, 14 and 28 days. Body mass and food consumption were measured daily. Intestinal morphological and proteomic analyses were conducted. The length of mucosal lacteals was evaluated. Plasmatic levels of leptin and adiponectin were determined. Finally, organ bath studies were conducted to evaluate smooth muscle contractility. Food consumption was significantly increased during the first two weeks of kaolinite ingestion without any mass gain compared to controls. Kaolinite induced weak variations in proteins that are involved in various biological processes. Compared to control animals, the length of intestinal lacteals was significantly reduced in kaolinite group whatever the duration of the experiment. Leptin and adiponectin plasmatic levels were significantly increased after 14 days of kaolinite consumption. Changes in spontaneous motility and responses to electrical nerve stimulation of the jejunum and proximal colon were observed at day 14. Altogether, the present data give evidence for a modulation by kaolinite-controlled ingestion on satiety and anorexigenic signals as well as on intestinal and colonic motility.
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Barboza, P. S., et al. "Digestive Challenges for Vertebrate Animals: Microbial Diversity, Cardiorespiratory Coupling, and Dietary Specialization." Physiol. Biochem. Zool.. 83.5 (2010): 764–774.
Résumé: The digestive system is the interface between the supply of food for an animal and the demand for energy and nutrients to maintain the body, to grow, and to reproduce. Digestive systems are not morphologically static but rather dynamically respond to changes in the physical and chemical characteristics of the diet and the level of food intake. In this article, we discuss three themes that affect the ability of an animal to alter digestive function in relation to novel substrates and changing food supply: (1) the fermentative digestion in herbivores, (2) the integration of cardiopulmonary and digestive functions, and (3) the evolution of dietary specialization. Herbivores consume, digest, and detoxify complex diets by using a wide variety of enzymes expressed by bacteria, predominantly in the phyla Firmicutes and Bacteroidetes. Carnivores, such as snakes that feed intermittently, sometimes process very large meals that require compensatory adjustments in blood flow, acid secretion, and regulation of acid-base homeostasis. Snakes and birds that specialize in simple diets of prey or nectar retain their ability to digest a wider selection of prey. The digestive system continues to be of interest to comparative physiologists because of its plasticity, both phenotypic and evolutionary, and because of its widespread integration with other physiological systems, including thermoregulation, circulation, ventilation, homeostasis, immunity, and reproduction.
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Secor, S. M., and J. - H. Lignot. "Morphological plasticity of vertebrate aestivation." Progress in molecular and subcellular biology. 49 (2010): 183–208.
Résumé: Aestivation or daily torpor is an adaptive tactic to survive hot and dry periods of low food availability, and has been documented for species of lungfishes, teleost fishes, amphibians, reptiles, birds, and mammals. Among these species, aestivation is characterized by inactivity and fasting, and for lungfishes and amphibians the formation of a cocoon around the body to retard water loss. While metabolic and physiological changes to aestivation have been well examined, few studies have explored the morphological responses of organs and tissues to aestivation. Predictably, inactive tissues such as skeletal muscles and those of the gastrointestinal tract would regress during aestivation, and thus aid in the reduction of metabolic rate. African lungfishes experience changes in the structure of their skin, gills, lungs, and heart during aestivation. For anurans, the group most thoroughly examined for morphological responses, aestivation generates significant decreases in gut mass and modification of the intestinal epithelium. Intestinal mucosal thickness, enterocyte size, and microvillus length of anurans are characteristically reduced during aestivation. We can surmise from laboratory studies on fasting reptiles, birds, and mammals that they likewise experience atrophy of their digestive tissues during torpor or aestivation. Aestivation-induced loss of tissue structure may be matched with a loss of cellular function generating an integrative decrease in tissue performance and metabolism. Ample opportunity exists to remedy the paucity of studies on the morphological plasticity of organs and tissues to aestivation and examine how such responses dictate tissue function during and immediately following aestivation.
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