American alligator (Alligator mississippiensis) embryos tightly regulate intracellular pH during a severe acidosis

Crocodilian nests naturally experience high CO2 (hypercarbia), which leads to increased blood PCO2 and reduced blood pH (pHe) in embryos; their response to acid-base challenges is not known. During acute hypercarbia, snapping turtle embryos preferentially regulate tissue pH (pHi) against pHe reductions. This is proposed to be associated with CO2 tolerance in reptilian embryos and is not found in adults. In the present study, we investigated pH regulation in American alligator Alligator mississippiensis (Daudin, 1802) embryos exposed to 1 h hypercarbia hypoxia (13 kPa PCO2, 9 kPa PO2). Hypercarbia hypoxia reduced pHe by 0.42 pH units while heart and brain pHi increased, with no change in pHi of other tissues. The results indicate American alligator embryos preferentially regulate pHi, similar to snapping turtle embryos, which represents a markedly different strategy of acid-base regulation than what is observed in adult reptiles. These findings suggest that preferential pHi regulation may be a strategy of acid-base regulation used by embryonic reptiles.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author