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Localization of ionocytes in crucian carp (Carassius carassius) gills during hypoxic remodelling
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S97–S114
A5.22 Social interactions between mature and immature parr of Atlantic salmon (Salmo salar) coexisting in artificial stream tanks J. Murua (University of Exeter); R. Wilson (University of Exeter); S. Winberg (University of Uppsala); I. Mayer (University of Bergen)
In the wild and in aquaculture both mature and immature parr of Atlantic salmon coexist and compete for resources. The dynamics of the interactions between both phenotypes and how this might affect river populations and finfish production is poorly understood. Despite their exterior similarity both phenotypes have distinct physiological traits (e.g. lipid levels, reproductive hormones), but little is known about their respective behavioural traits. Considering that in young Atlantic salmon the ability to acquire lipid reserves beyond a threshold is thought to determine maturation and that food acquisition is directly related to social dominance then it can be hypothesised that the mature parr phenotype may achieve superior feeding and lipid deposition through a higher social position relative to immature parr individuals. To test this hypothesis we have video-recorded groups of 6 sizematched salmon parr (36 replicates) in stream tanks for 3 weeks. Based on antagonistic interactions and position relative to a food source within the tank each fish was assigned a social rank within its group. After the experimental period blood and brain samples were taken to obtain physiological measurements of behavioural correlates such as cortisol and brain monoamines. Other physiological indices including specific growth rate, condition factor, gonadosomatic index and hepatosomatic index were also recorded. The physiological and behavioural data was analysed to investigate if salmon of a particular phenotype show different social positions within a group and which physiological mechanisms might be involved. doi:10.1016/j.cbpa.2008.04.212
A5.23 Localization of ionocytes in crucian carp (Carassius carassius) gills during hypoxic remodelling
S103
vities of MRCs are also up-regulated with hypoxia and to quantify the effect of ILCM loss on gill water influx.
doi:10.1016/j.cbpa.2008.04.213
A5.24 Changes in gill ionocyte function and structure following transfer from fresh to hypersaline waters in the tilapia Sarotherodon melanotheron N. Ouattara (Université Montpellier 2, France; CIRAD Montpellier); C. Bodinier (Université Montpellier 2); G. Negre-Sadargues (Université Montpellier 2); S. Messad (CIRAD Montpellier); H. D'Cotta (CIRAD Montpellier); G. Charmantier (Université Montpellier 2); J. Panfili, (IRD Montpellier); J. Baroiller (CIRAD Montpellier)
The effects of salinity were investigated in the black-chinned tilapia Sarotherodon melanotheron heudelotii originating from a hypersaline estuary (Saloum, Senegal). Under controlled conditions, juvenile fish originally kept in freshwater (FW) were divided into two groups exposed to FW or directly to 35 psu seawater (SW). Part of these SW fish were then acclimatised to hypersaline waters (HW) by a step-wise increase of 7 psu/day up to 70 (HW70) and 90 (HW90). Three major ion transporters, Na+/K+-ATPase, the cotransporter Na+/ K+/2Cl− (NKCC) and the Cl− channel (CFTR) were localized by immunofluorescence in the gill ionocytes and changes regarding ionocytes localization, number and sizes were investigated. In FW, Na+/K+-ATPase immunostained ionocytes were only observed at the base of the filaments, whereas in SW and HW they were localized on both the filaments and the lamellae suggesting that lamellar ionocytes could also be functional in SW. A significant increase in ionocyte number and size (area) occurred following transfer from FW to HW. Although the cell number remained constant between HW70 and HW90, their size increased from FW to HW90, indicating that the size and shape of cells could be a sensitive indicator of osmoregulation in HW in this tilapia. In FW, NKCC staining was concentrated at the apical region and CFTR was not observed. In SW, Na+/K+-ATPase and the cotransporter NKCC were colocalized on the basolateral membrane, while CFTR was located at the apical region.
A. Dymowska, J. Stecyk, G. Nilsson (University of Oslo) In most teleosts, the ion transporting cells involved in acid-base and osmoregulation are located on gill lamellae and filaments and are in direct contact with water. In crucian carp (Carassius carassius), an intralamellar cell mass (ILCM) completely covers the gill lamellae during normoxia. In hypoxia, the ILCM recedes to increase respiratory surface area by up to 7.5-fold. However, this morphological change could lead to increased water influx and ion efflux across the gills causing osmoregulatory stress. We investigated how the presence or absence of the ILCM affected the location of gill ionocytes (i.e., the mitochondria-rich cells; MRCs), plasma ion balance and blood pH. Loss of the ILCM was induced by exposing 8 ° C-acclimated carp to hypoxia for 7 days (6–8% O2 of air saturation). MRCs were localized with immunolabeling and transmission electron microscopy. We found that MRCs were located on top of the ILCM during normoxia and hypoxia and that the abundance of MRCs increased progressively with hypoxia. Plasma concentrations of Na+, Cl−, K+ and pH were identical in normoxic and 7 d hypoxic fish. These results suggest that crucian carp may compensate against increased water and ion fluxes during hypoxia exposure by maintaining ion uptake via increased numbers of MRCs. Experiments are currently being conducted to determine if ATPase acti-
doi:10.1016/j.cbpa.2008.04.214
A5.25 Theoretical considerations underlying Na+ uptake mechanisms in freshwater fishes G. Goss, M. Tresguerres, S. Parks (University of Alberta)
Ion and acid–base regulating mechanisms have been studied at the fish gill for almost a century. Original models proposed for Na+ and Cl− uptake, and their linkage with H+ and HCO−3 secretion have changed substantially with the development of more sophisticated physiological techniques. At the freshwater fish gill, two dominant mechanisms for Na+ uptake from dilute environments have persisted in the literature. The use of an apical Na+/H+ exchanger driven by a basolateral Na+/K+-ATPase versus an apical Na+ channel electrogenically coupled to an apical H+-ATPase has been the source of debate for a number of years. Advances in molecular biology have
A5.22 Social interactions between mature and immature parr of Atlantic salmon (Salmo salar) coexisting in artificial stream tanks J. Murua (University of Exeter); R. Wilson (University of Exeter); S. Winberg (University of Uppsala); I. Mayer (University of Bergen)
In the wild and in aquaculture both mature and immature parr of Atlantic salmon coexist and compete for resources. The dynamics of the interactions between both phenotypes and how this might affect river populations and finfish production is poorly understood. Despite their exterior similarity both phenotypes have distinct physiological traits (e.g. lipid levels, reproductive hormones), but little is known about their respective behavioural traits. Considering that in young Atlantic salmon the ability to acquire lipid reserves beyond a threshold is thought to determine maturation and that food acquisition is directly related to social dominance then it can be hypothesised that the mature parr phenotype may achieve superior feeding and lipid deposition through a higher social position relative to immature parr individuals. To test this hypothesis we have video-recorded groups of 6 sizematched salmon parr (36 replicates) in stream tanks for 3 weeks. Based on antagonistic interactions and position relative to a food source within the tank each fish was assigned a social rank within its group. After the experimental period blood and brain samples were taken to obtain physiological measurements of behavioural correlates such as cortisol and brain monoamines. Other physiological indices including specific growth rate, condition factor, gonadosomatic index and hepatosomatic index were also recorded. The physiological and behavioural data was analysed to investigate if salmon of a particular phenotype show different social positions within a group and which physiological mechanisms might be involved. doi:10.1016/j.cbpa.2008.04.212
A5.23 Localization of ionocytes in crucian carp (Carassius carassius) gills during hypoxic remodelling
S103
vities of MRCs are also up-regulated with hypoxia and to quantify the effect of ILCM loss on gill water influx.
doi:10.1016/j.cbpa.2008.04.213
A5.24 Changes in gill ionocyte function and structure following transfer from fresh to hypersaline waters in the tilapia Sarotherodon melanotheron N. Ouattara (Université Montpellier 2, France; CIRAD Montpellier); C. Bodinier (Université Montpellier 2); G. Negre-Sadargues (Université Montpellier 2); S. Messad (CIRAD Montpellier); H. D'Cotta (CIRAD Montpellier); G. Charmantier (Université Montpellier 2); J. Panfili, (IRD Montpellier); J. Baroiller (CIRAD Montpellier)
The effects of salinity were investigated in the black-chinned tilapia Sarotherodon melanotheron heudelotii originating from a hypersaline estuary (Saloum, Senegal). Under controlled conditions, juvenile fish originally kept in freshwater (FW) were divided into two groups exposed to FW or directly to 35 psu seawater (SW). Part of these SW fish were then acclimatised to hypersaline waters (HW) by a step-wise increase of 7 psu/day up to 70 (HW70) and 90 (HW90). Three major ion transporters, Na+/K+-ATPase, the cotransporter Na+/ K+/2Cl− (NKCC) and the Cl− channel (CFTR) were localized by immunofluorescence in the gill ionocytes and changes regarding ionocytes localization, number and sizes were investigated. In FW, Na+/K+-ATPase immunostained ionocytes were only observed at the base of the filaments, whereas in SW and HW they were localized on both the filaments and the lamellae suggesting that lamellar ionocytes could also be functional in SW. A significant increase in ionocyte number and size (area) occurred following transfer from FW to HW. Although the cell number remained constant between HW70 and HW90, their size increased from FW to HW90, indicating that the size and shape of cells could be a sensitive indicator of osmoregulation in HW in this tilapia. In FW, NKCC staining was concentrated at the apical region and CFTR was not observed. In SW, Na+/K+-ATPase and the cotransporter NKCC were colocalized on the basolateral membrane, while CFTR was located at the apical region.
A. Dymowska, J. Stecyk, G. Nilsson (University of Oslo) In most teleosts, the ion transporting cells involved in acid-base and osmoregulation are located on gill lamellae and filaments and are in direct contact with water. In crucian carp (Carassius carassius), an intralamellar cell mass (ILCM) completely covers the gill lamellae during normoxia. In hypoxia, the ILCM recedes to increase respiratory surface area by up to 7.5-fold. However, this morphological change could lead to increased water influx and ion efflux across the gills causing osmoregulatory stress. We investigated how the presence or absence of the ILCM affected the location of gill ionocytes (i.e., the mitochondria-rich cells; MRCs), plasma ion balance and blood pH. Loss of the ILCM was induced by exposing 8 ° C-acclimated carp to hypoxia for 7 days (6–8% O2 of air saturation). MRCs were localized with immunolabeling and transmission electron microscopy. We found that MRCs were located on top of the ILCM during normoxia and hypoxia and that the abundance of MRCs increased progressively with hypoxia. Plasma concentrations of Na+, Cl−, K+ and pH were identical in normoxic and 7 d hypoxic fish. These results suggest that crucian carp may compensate against increased water and ion fluxes during hypoxia exposure by maintaining ion uptake via increased numbers of MRCs. Experiments are currently being conducted to determine if ATPase acti-
doi:10.1016/j.cbpa.2008.04.214
A5.25 Theoretical considerations underlying Na+ uptake mechanisms in freshwater fishes G. Goss, M. Tresguerres, S. Parks (University of Alberta)
Ion and acid–base regulating mechanisms have been studied at the fish gill for almost a century. Original models proposed for Na+ and Cl− uptake, and their linkage with H+ and HCO−3 secretion have changed substantially with the development of more sophisticated physiological techniques. At the freshwater fish gill, two dominant mechanisms for Na+ uptake from dilute environments have persisted in the literature. The use of an apical Na+/H+ exchanger driven by a basolateral Na+/K+-ATPase versus an apical Na+ channel electrogenically coupled to an apical H+-ATPase has been the source of debate for a number of years. Advances in molecular biology have