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

Supplementary Material for: Sex-Biased Expression of Sex-Differentiating Genes <b><i>FOXL2</i></b> and <b><i>FGF9</i></b> in American Alligators, <b><i>Alligator mississippiensis</i></b>

Across amniotes, sex-determining mechanisms exhibit great variation, yet the genes that govern sexual differentiation are largely conserved. Studies of evolution of sex-determining and sex-differentiating genes require an exhaustive characterization of functions of those genes such as <i>FOXL2</i> and <i>FGF9</i>. <i>FOXL2</i> is associated with ovarian development, and<i> FGF9</i> is known to play a role in testicular organogenesis in mammals and other amniotes. As a step toward characterization of the evolutionary history of sexual development, we measured expression of <i>FOXL2</i> and <i>FGF9</i> across 3 developmental stages and 8 juvenile tissue types in male and female American alligators, <i>Alligator mississippiensis. </i>We report surprisingly high expression of <i>FOXL2</i> before the stage of embryonic development when sex is determined in response to temperature, and sustained and variable expression of <i>FGF9</i> in juvenile male, but not female tissue types. Novel characterization of gene expression in reptiles with temperature-dependent sex determination such as American alligators may inform the evolution of sex-determining and sex-differentiating gene networks, as they suggest alternative functions from which the genes may have been exapted. Future functional profiling of sex-differentiating genes should similarly follow other genes and other species to enable a broad comparison across sex-determining mechanisms