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Effect of Ocean Acidification on Deep Sea Spotted Ratfish Hydrolagus Colliei

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Effect of Ocean Acidification on Deep Sea Spotted Ratfish Hydrolagus Colliei Effect of ocean acidification on deep sea spotted ratfish Hydrolagus colliei: physiological consequences on acid-base balance, ion-regulation and nitrogenous waste dynamics Jyotsna Shrivastava (Jo) University of Antwerp Belgium, Europe Overview Introduction Methodology Results Discussion Conclusion The decrease in the pH of earth’s oceans caused by the uptake of CO2 from atmosphere. The pH Scale pH scale is logarithmic meaning a difference of one pH unit is equal to a ten-fold change in acidity. A small change in pH is equal to a LARGE change in acidity. Experimental fish species Taxonomical classification Chondrichthyes (cartilaginous fish) Elasmobranchii Holocephali (primitive fish) Sharks, rays and skates Chimeras Ratfish, Rabbitfish and elephant fish Ratfish are non-elasmobranchs cartilaginous fish Introduction Morphological Characteristic of Ratfish • It is a chimaera found in the north-eastern Pacific Ocean. • It is most common between 200 and 400 m below sea level. • This cartilaginous fish gets its characteristic name from a pointed rat- like tail. • They have a venomous spine located at their dorsal fin which is used in defense. Introduction… Ocean acidification / Hypercapnia (increase in CO2 level) -ambient CO2 levels induce a respiratory acidosis in a number of fish species- Blood pH is compensated by Background • Among Cartilaginous fish, the most extensive studies on acid-base regulation during ocean acidification (hypercapnia) are done in elasmobranch -typically the spotted dogfish (Randall et al., 1976; Heisler et al. 1976). • Dogfish are able to compensate ocean acidification induced acidosis very quickly by - – by extracting HCO3 from the surrounding water – Increasing the rate of H+ excretion and/or + – elevating NH4 excretion Overall, suggesting dogfish and also teleosts are efficiently regulator of acid/base balance during hypercapnic events. Till date, no study has been done in non-elasmobranch cartilaginous fish (e.g. ratfish) Objectives Extracellular Excretion Intracellular Ion- pH rate regulation pH Blood pH H+ RBC Na+ Plasma TCO2 Ammonia - Hepatic cells Cl Osmolality Experimental Site: Bamfield Marine Science Research Centre, Canada Experimental design • Test species: Ratfish • Exposure to 1.5% PCO2 (15,000 ppm) • Exposure period: Pre-exposure (0 h), 4 h, 12h, 24 h and 48 h • At the end of each exposure period fish (n= 6) were sacrificed. • Water samples were taken at each time point (and some intermediate points) at an interval of 4 hrs. -Cannulation!!!!!! the arterial/venous tension is too low Experimental set up Flux box of 20 L (flux vol. 16L) Fish were acclimated overnight in the box. CO2 level was controlled by an automated Loligo CO2 system via CapCTRL software. Results Blood pH 7.6 Hypercapnia 7.5 7.4 7.3 * 7.2 ** ** 7.1 7 6.9 Blood pH 6.8 6.7 6.6 Control 4 h 12 h 24 h 48 h Results Plasma TCO2 11 * 10 ** mmo/L 2 9 ** ** 8 7 Plasma TCO Plasma 6 5 Control 4 h 12 h 24 h 48 h Results Blood pH and Plasma TCO2 7.6 10.5 * 10 7.5 ** 9.5 7.4 ** 9 7.3 8.5 8 /L) 7.2 ** * 7.5 7.1 pH 7 mmol ( 7 ** 6.5 2 6.9 ** 6 5.5 TCO 6.8 pH 5 6.7 TCO2 4.5 6.6 4 Control 4 h 12 h 24 h 48 h Extracellular pH was not restored to control level Results Intracellular pH: RBC 7.20 7.10 7.00 6.90 6.80 6.70 * 6.60 6.50 6.40 pH level pH in RBC 6.30 6.20 6.10 6.00 Control 4 h 12 h 24 h 48 h pH level in RBC was strictly maintained with in control level Results Intracellular pH: Hepatic tissue 7.1 6.9 6.7 6.5 6.3 6.1 5.9 pH level pH in Liver 5.7 5.5 Control 4 h 12 h 24 h 48 h Similar to RBC, pH in liver cells were strictly maintained with in control level Suggesting that intracellular pH was maintained quite well (contrast to extracellular pH) Results Ammonia excretion rate -4 -0 h 0 -4 h 4-8 h 8-12 h 20-24 h 32-36 h 44- 48 h 0 -25 -50 -75 -100 (µmol/kg/hr) -125 amm -150 J -175 Control -200 HC -225 Ammonia excretion rate did not contribute to reduce extracellular acidosis Results + H excretion rate 400 Control 200 HC 0 -200 -400 ** * -600 Flux Rate µmol/Kg/Hr -800 + * H -1000 -1200 -4 -0 h 0 -4 h 4-8 h 8-12 h 20-24 h 32-36 h 44- 48 h A slight (and temporary) increment was revealed Results Na+ level 480 460 440 420 400 380 content (mM) 360 + Na 340 320 300 Control 4 h 12 h 24 h 48 h Results Osmolality 1100 1050 1000 950 900 850 Osmolality Osmolality (mOsm/kg) 800 750 Control 4 h 12 h 24 h 48 h Similar to Na+ concentration, osmolality remained unchanged Discussion Extracellular pH (blood pH) was not compensated -Level remained below control level - Fish seems to suffer acidosis in extracellular fluid. Intracellular pH (RBC and liver cell) was regulated efficiently -suggesting that ratfish prioritize intracellular pH over extracellular pH Ratfish does not seem to utilize ammonia excretion pathway to cope with acidosis. Plasma sodium concentration (and H+ excretion) remains constant throughout the experiment -does not favor the Na+/H+ exchange as the operative mechanism in ratfish Conclusion Ratfish seems to be a poor acid-base regulator during ocean acidification (hypercapnia). • Net bicarbonate uptake from the environment might be the compensation of the intracellular acidosis. - - • Additional bicarbonate is gained by active HCO3 /C1 ion exchange. Thanks to Prof. Gudrun De Boeck, Prof. Ronny Blust and others……… Prof. G. Goss Alex Amit Alyssa .
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