ORCID Profile
0000-0001-9183-2731
Current Organisation
University of California Davis
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Publisher: The Company of Biologists
Date: 2018
DOI: 10.1242/JEB.172551
Abstract: Vertebrates reduce arterial blood pH (pHa) when body temperature increases. In water-breathers this response occurs primarily by reducing plasma HCO3− levels with small changes in the partial pressure of CO2 (PCO2). In contrast, air-breathers mediate the decrease in pHa by increasing arterial PCO2 (PaCO2) at constant plasma HCO3− by reducing lung ventilation relative to metabolic CO2 production. Much less is known in bimodal breathers that utilize both water and air. Here, we characterize the influence of temperature on arterial acid-base balance and intracellular pH (pHi) in the bimodal breathing sw eel, Monopterus albus. This teleost uses the buccopharyngeal cavity for gas exchange and has very reduced gills. When exposed to ecologically relevant temperatures (20, 25, 30 and 35°C) for 24 and 48h, pHa decreased by -0.025 pH units/°C (U/°C) in association with an increased PaCO2, but without changes in plasma [HCO3−]. Intracellular pH (pHi) was also reduced with increased temperature. The slope of pHi of liver and muscle was -0.014 and -0.019 U/°C, while the heart muscle showed a smaller reduction (-0.008U/°C). When exposed to hypercapnia (7 or 14 mmHg) at either 25 or 35°C, Monopterus albus elevated plasma [HCO3−] and therefore seemed to defend the new pHa set-point, demonstrating an adjusted control of acid-base balance with temperature. Overall, the effects of temperature on acid-base balance in Monopterus albus resemble air-breathing amniotes, and we discuss the possibility that this pattern of acid-base balance results from a progressive transition in CO2 excretion from water to air as temperature rises.
Publisher: Wiley
Date: 25-10-2020
Publisher: eLife Sciences Publications, Ltd
Date: 28-07-2020
Publisher: Elsevier BV
Date: 06-2023
Publisher: The Royal Society
Date: 02-2022
Abstract: Puffer and porcupine fishes (families Diodontidae and Tetraodontidae, order Tetradontiformes) are known for their extraordinary ability to triple their body size by swallowing and retaining large amounts of seawater in their accommodating stomachs. This inflation mechanism provides a defence to predation however, it is associated with the secondary loss of the stomach's digestive function. Ingestion of alkaline seawater during inflation would make acidification inefficient (a potential driver for the loss of gastric digestion), paralleled by the loss of acid–peptic genes. We tested the hypothesis of stomach inflation as a driver for the convergent evolution of stomach loss by investigating the gastric phenotype and genotype of four distantly related stomach inflating gnathostomes: sargassum fish, swellshark, bearded goby and the pygmy leatherjacket. Strikingly, unlike in the puffer orcupine fishes, we found no evidence for the loss of stomach function in sargassum fish, swellshark and bearded goby. Only the pygmy leatherjacket (Monochanthidae, Tetraodontiformes) lacked the gastric phenotype and genotype. In conclusion, ingestion of seawater for inflation, associated with loss of gastric acid secretion, is restricted to the Tetraodontiformes and is not a selective pressure for gastric loss in other reported gastric inflating fishes.
Publisher: eLife Sciences Publications, Ltd
Date: 25-08-2020
DOI: 10.7554/ELIFE.58995
Abstract: Previously, we showed that the evolution of high acuity vision in fishes was directly associated with their unique pH-sensitive hemoglobins that allow O 2 to be delivered to the retina at PO 2 s more than ten-fold that of arterial blood (Damsgaard et al., 2019). Here, we show strong evidence that vacuolar-type H + -ATPase and plasma-accessible carbonic anhydrase in the vascular structure supplying the retina act together to acidify the red blood cell leading to O 2 secretion. In vivo data indicate that this pathway primarily affects the oxygenation of the inner retina involved in signal processing and transduction, and that the evolution of this pathway was tightly associated with the morphological expansion of the inner retina. We conclude that this mechanism for retinal oxygenation played a vital role in the adaptive evolution of vision in teleost fishes.
Publisher: Wiley
Date: 05-04-2021
DOI: 10.1002/JEZ.2456
Abstract: The obligate air‐breathing Amazonian fish, Arapaima gigas , hatch as water‐breathing larvae but with development, they modify their swim bladder to an air‐breathing organ (ABO) while reducing their gill filaments to avoid oxygen loss. Here, we show that significant changes already take place between 4 weeks (1.6 g) and 11 weeks (5 g) post hatch, with a reduction in gill lamellar surface area, increase in gill diffusion distance, and proliferation of the parenchyma in the ABO. By using a variety of methods, we quantified the surface area and diffusion distances of the gills and skin, and the swim bladder volume and anatomical complexity from hatch to 11‐week‐old juveniles. In addition, we identified the presence of two ionocyte types in the gills and show how these change with development. Until 1.6 g, A. gigas possess only the H + ‐excreting/Na + ‐absorbing type, while 5‐g fish and adults have an additional ionocyte which likely absorbs H + and Cl − and excretes HCO 3 − . The ionocyte density on the gill filaments increased with age and is likely a compensatory mechanism for maintaining ion transport while reducing gill surface area. In the transition from water‐ to air‐breathing, A. gigas likely employs a trimodal respiration utilizing gills, skin, and ABO and thus avoid a respiratory–ion regulatory compromise at the gills.
Location: United States of America
Location: United States of America
Location: United States of America
Location: United States of America
No related grants have been discovered for Garfield Kwan.