Blood flow distribution in embryonic common snapping turtles Chelydra serpentina (Reptilia; Chelonia) during acute hypoxia and α-adrenergic regulation.

Embryonic turtles have four distinct vascular beds that separately perfuse the developing embryo's body and the extra-embryonic yolk sac, amnion and chorioallantoic membrane (CAM). The mechanisms enabling differential regulation of blood flow through these separate beds, in order to meet the varying demands of the embryo during development, is of current interest. The present investigation followed the changes in blood flow distribution during an acute exposure to hypoxia and after α-adrenergic blockade.

Convective oxygen transport during development in embryos of the snapping turtle .

This study investigated the maturation of convective oxygen transport in embryos of the snapping turtle (). Measurements included: mass, oxygen consumption ( ), heart rate, blood oxygen content and affinity and blood flow distribution at 50%, 70% and 90% of the incubation period. Body mass increased exponentially, paralleled by increased cardiac mass and metabolic rate.

Commentary on: "Vascular distensibilities have minor effects on intracardiac shunt patterns in reptiles" by Filogonio et al. (2017).

The recent study by Filogonio et al. (2017) suggested that net cardiac shunt patterns in two species of reptiles (Trachemys scripta and Crotalus durissus) were not significantly influenced by the vascular distensibilities of the systemic and pulmonary vasculatures. This is in contrast to a previously published study (Hillman et al.

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.

Embryonic common snapping turtles (Chelydra serpentina) preferentially regulate intracellular tissue pH during acid-base challenges.

The nests of embryonic turtles naturally experience elevated CO2 (hypercarbia), which leads to increased blood PCO2  and a respiratory acidosis, resulting in reduced blood pH [extracellular pH (pHe)]. Some fishes preferentially regulate tissue pH [intracellular pH (pHi)] against changes in pHe; this has been proposed to be associated with exceptional CO2 tolerance and has never been identified in amniotes. As embryonic turtles may be CO2 tolerant based on nesting strategy, we hypothesized that they preferentially regulate pHi, conferring tolerance to severe acute acid-base challenges.

Dynamics of blood viscosity regulation during hypoxic challenges in the chicken embryo (Gallus gallus domesticus).

Hypoxia in chicken embryos increases hematocrit (Hct), blood O2 content, and blood viscosity. The latter may limit O2 transport capacity (OTC) via increased peripheral resistance. Hct increase may result from increased nucleated red blood cell concentration ([RBC]) and mean corpuscular volume (MCV) or reduced plasma volume.

Critical Windows of Cardiovascular Susceptibility to Developmental Hypoxia in Common Snapping Turtle (Chelydra serpentina) Embryos.

Environmental conditions fluctuate dramatically in some reptilian nests. However, critical windows of environmental sensitivity for cardiovascular development have not been identified. Continuous developmental hypoxia has been shown to alter cardiovascular form and function in embryonic snapping turtles (Chelydra serpentina), and we used this species to identify critical periods during which hypoxia modifies the cardiovascular phenotype.

Net cardiac shunts in anuran amphibians: physiology or physics?

Amphibians have a single ventricle and common conus arteriosus that produces an equal pressure to the parallel pulmocutaneous and systemic vascular circuits. The distribution of blood flows between the pulmocutaneous (Qpul) and systemic (Qsys) circuits (net cardiac shunt) varies with a number of environmental conditions and behaviours; although autonomic regulation of pulmonary vascular resistance conductance has been emphasized, little attention has been paid to the possible contribution of the passive physical characteristics of the two circuits to pressure changes associated with variation in cardiac output. In this study, we re-analysed three recent studies that recorded net cardiac shunts in the cane toad (Rhinella marina) under a variety of conditions and treatments.

Separating the contributions of vascular anatomy and blood viscosity to peripheral resistance and the physiological implications of interspecific resistance variation in amphibians.

Amphibian pulmonary and systemic vascular circuits are arranged in parallel, with potentially important consequences for resistance (R) to blood flow. The contribution of the parallel anatomic arrangement to total vascular R (R T), independent of blood viscosity, is unknown. We measured pulmonary (R P) and systemic (R S) vascular R with an in situ Ringer's solution perfusion technique using anesthetized anuran and urodele species to determine: (1) relative contributions of vascular anatomy and blood viscosity to R T; (2) distensibility index (%Δ flow kPa(-1)) of the pulmonary and systemic vascular circuits; and (3) interspecific correlates of variation in these parameters with red blood cell size, cardiac power output, and aerobic capacities.

Plasticity of cardiovascular function in snapping turtle embryos (Chelydra serpentina): chronic hypoxia alters autonomic regulation and gene expression.

Reptile embryos tolerate large decreases in the concentration of ambient oxygen. However, we do not fully understand the mechanisms that underlie embryonic cardiovascular short- or long-term responses to hypoxia in most species. We therefore measured cardiac growth and function in snapping turtle embryos incubated under normoxic (N21; 21% O₂) or chronic hypoxic conditions (H10; 10% O₂).

Alternative developmental pathways associated with diapause regulated by temperature and maternal influences in embryos of the annual killifish Austrofundulus limnaeus.

Embryos of the annual killifish Austrofundulus limnaeus enter a state of developmental arrest termed diapause as part of their normal developmental program. Diapause can occur at two distinct developmental stages in this species, termed diapause II and III. When incubated at 25°C, most embryos enter diapause II, whereas a small percentage of 'escape' embryos develop continuously past diapause II and enter diapause III.