Periods of cardiovascular susceptibility to hypoxia in embryonic american alligators (Alligator mississippiensis).
During embryonic development, environmental perturbations can affect organisms' developing phenotype, a process known as developmental plasticity. Resulting phenotypic changes can occur during discrete, critical windows of development. Critical windows are periods when developing embryos are most susceptible to these perturbations. We have previously documented that hypoxia reduces embryo size and increases relative heart mass in American alligator, and this study identified critical windows when hypoxia altered morphological, cardiovascular function and cardiac gene expression of alligator embryos. We hypothesized that incubation in hypoxia (10% O2) would increase relative cardiac size due to cardiac enlargement rather than suppression of somatic growth. We exposed alligator embryos to hypoxia during discrete incubation periods to target windows where the embryonic phenotype is altered. Hypoxia affected heart growth between 20 and 40% of embryonic incubation, whereas somatic growth was affected between 70 and 90% of incubation. Arterial pressure was depressed by hypoxic exposure during 50-70% of incubation, whereas heart rate was depressed in embryos exposed to hypoxia during a period spanning 70-90% of incubation. Expression of Vegf and PdgfB was increased in certain hypoxia-exposed embryo treatment groups, and hypoxia toward the end of incubation altered β-adrenergic tone for arterial pressure and heart rate. It is well known that hypoxia exposure can alter embryonic development, and in the present study, we have identified brief, discrete windows that alter the morphology, cardiovascular physiology, and gene expression in embryonic American alligator.
Department of Biology, McMaster University, Hamilton, Ontario, Canada;
Kevin B
KB
Tate
Department of Biology, University of North Dakota, Grand Forks, North Dakota;
Turk
T
Rhen
Department of Biological Sciences, California State University San Marcos, San Marcos, California;
John
J
Eme
Department of Biological Sciences, University of North Texas, Denton, Texas; and.
Zachary F
ZF
Kohl
Department of Biological Sciences, University of North Texas, Denton, Texas; and.
Janna
J
Crossley
Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, Louisiana.
Ruth M
RM
Elsey
Department of Biological Sciences, University of North Texas, Denton, Texas; and dane.crossley@unt.edu.
Dane A
DA
Crossley
D000489:Alligators and Crocodiles / Q000196:embryology*; D000818:Animals; D001794:Blood Pressure; D006332:Cardiomegaly / Q000196:embryology* / Q000503:physiopathology*; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000503:physiopathology*; D006339:Heart Rate; D000860:Hypoxia / Q000196:embryology* / Q000503:physiopathology*
critical windows; embryo; gene expression; hypoxia; reptile