Oroboros trace flie.DLD

Aim: It is well-established that adult
vertebrates acclimatising to hypoxic environments undergo mitochondrial
remodelling to enhance oxygen delivery, maintain ATP balance, and limit
oxidative stress. However, many vertebrates also encounter oxygen deprivation during
embryonic development. The effects of hypoxia on mitochondrial function are
likely to be more profound during embryonic development because environmental
stress during early life can lead to permanent physiological and morphological changes
that can sometimes be inherited by subsequent generations. To this end, we
investigated the long-term effects of developmental hypoxia on mitochondrial
function in a species that regularly encounters oxygen deprivation during
development; the common snapping turtle (Chelydra serpentina).

Methods: Common snapping turtle eggs were
incubated in 21% or 10% oxygen from 20% of embryonic development until hatching.
Once hatched, turtles were reared in 21%
oxygen for up to one year, and ventricular mitochondria were isolated by
differential centrifugation. Mitochondrial respiration and reactive oxygen
species (ROS) production were measured with an Oroboros microrespirometer.

Results: Compared to their normoxic counterparts,
juvenile turtles from hypoxic incubations had lower levels of Leak respiration,
higher P:O ratios, improved oxygen affinity, and reduced rates of ROS
production. Interestingly, these same attributes occur in adult vertebrates
that acclimatise to high-altitude hypoxia.

Conclusions: Developmental hypoxia remodelled
turtle mitochondria, leading to improvements in mitochondrial efficiceny, oxygen
delivery, and ROS management. We speculate that these adjustments permanently
improve snapping turtle mitochondrial hypoxia tolernace, which would be
beneficial for this species during breath-hold diving and overwintering in
anoxic environments.