Morphological changes in branchial mitochondria-rich cells of the teleost Paralichthys olivaceus as a potential indicator of CO2 impacts

Abstract

We studied the morphological and biochemical changes of mitochondria-rich cells (MRCs) of a demersal teleost, Paralichthys olivaceus, during exposure to 0.98, 2.97 and 4.95kPa pCO2. The apical opening area of MRCs increased 2.2 and 4.1 times by 24h exposure to 2.97 and 4.95kPa pCO2, respectively, while the cross-sectional area or density of MRCs did not change. Gill Na(+)/K(+)-ATPase activity more than doubled at 72h and then returned to the pre-exposure level at 168h in 0.98kPa pCO2, while it increased 1.7 times at 24h at 4.95kPa. These results indicate that the apical opening area of MRCs and the gill Na(+)/K(+)-ATPase activity may be used as an indicator of acute (up to 72h), but not chronic, impacts of high (>1kPa) seawater CO2 conditions in P. olivacues. Limitations of those parameters as indices of CO2 impacts are discussed.

Keywords: CO(2) leakage; Carbon dioxide; Environmental hypercapnia; Mitochondria-rich cell; Na(+)/K(+)-ATPase activity; Paralichthys olivaceus.