Long-term fasting and re-feeding in penguins

Area of Science:

• Animal Physiology
• Behavioral Ecology
• Endocrinology

Background:

• Penguins undergo annual cycles characterized by spontaneous fasting during reproduction and molting.
• Long-term fasting, particularly in emperor penguins, necessitates significant fat and protein accumulation prior to these periods.
• Lipids are the primary energy source during incubation fasts, with protein sparing mechanisms in place.

Purpose of the Study:

• To investigate the physiological and behavioral adaptations of penguins during prolonged fasting periods.
• To identify the endogenous re-feeding signal that prevents lethal energy depletion.
• To understand the metabolic and hormonal changes associated with the transition from fasting to re-feeding.

Main Methods:

• Observational studies on penguin fasting behavior and physiology.
• Analysis of body composition changes (fat and protein stores).
• Hormonal assays (corticosterone, prolactin) and metabolic profiling during fasting stages.

Main Results:

• Below critical fat store depletion, penguins exhibit increased locomotor activity and egg abandonment.
• An endogenous re-feeding signal is activated before complete energy depletion.
• This signal involves increased protein catabolism, reduced lipid utilization, elevated corticosterone, and decreased prolactin.

Conclusions:

• The re-feeding signal is effective, enabling penguins to survive near-total lipid depletion and rapidly restore energy stores.
• Penguins serve as valuable models for studying the interplay of energy reserves, fasting, breeding, and feeding physiology.
• Understanding these mechanisms can provide insights into long-term energy balance and survival strategies in animals.