Cellular activity helps chicks survive fasting in the cold

King penguin chick at
Possession Island, Crozet Archipelago
Credit: Pierre-Axel Monternier

SUBANTARCTIC – A new study shows that king penguin chicks survive harsh winters with almost no food by minimising the cost of energy production.

The study, presented at the Society for Experimental Biology meeting in Valencia on the 3 July, shows that mitochondria – the powerhouses of the cell – are more efficient in fasted king penguin chicks.

King penguin chicks are socially and structurally well adapted to harsh environmental conditions, but they experience a severe energy challenge during the cold sub-Antarctic winter, when food is not readily available.

Research led by Pierre-Axel Monternier and Prof Damien Roussel at the Ecology of Natural and Man-Impacted Hydrosystems Laboratory in France looked, for the first time, at how the mitochondria in king penguin chicks' skeletal muscle (the main heat-producing tissue in birds) work while the birds are fasting in the winter.       

Pierre-Axel Monternier said they found that mitochondrial functioning was more efficient in fasted winter-acclimatised king penguin chicks. He said this indicates that less substrate/oxygen was used to produce the same amount of energy in the form of ATP (adenosine triphosphate), showing that mitochondria from fasted chicks adjust their functioning to minimise the cost of energy production.

The study shows how king penguins are able to produce heat to survive in low temperatures without using up their energy stores, an essential way to survive the cold when food is scarce. The chicks' biological adjustments increase their chances of survival – they have a fasting endurance of up to five months, which is unrivalled among birds.

Fasting in the cold represents a energy transformation trade-off between sparing energy for body maintenance and dissipating energy for heat production and body temperature maintenance. In this challenging context, chicks develop a range of ways to spare energy (social huddling behaviour, reduction in muscle activity and basal metabolic rate, short periods of hypothermia and high thermal insulation) that lead to reducing the energy allocated to heat production and growth.

Source
Surviving fasting in the cold [press release], 2 July 2013, Society for Experimental Biology