Strasbourg
Reproduction in king penguins and environmental constraints
Diversity of life histories is mainly explained by the concept that organisms face trade-offs. A corner-stone idea of life history theory is the ability of organisms to allocate a limited quantity of energy and resources to the main vital functions such as growth, reproduction and defence (immunity, maintenance). The balance between each of these components will ultimately define how organisms reproduce themselves and how long they will live. In addition, species adaptation ability is principally defined by how life history trade-offs will enable organisms to overcome environmental constraints.
Most of the previous studies focusing on the physiological bases of life history trade-offs considered energy differential allocation, rightly, as an important factor. However, the last decade has seen the development of non-energetic aspects of trade-offs linked to the direct negative impact of one trait on another. Still, most of the relationship between energetic and non energetic trade-offs remains mainly uncovered. Therefore, studying how this relationship evolved in a species growing and reproducing while facing a negative energy balance will bring original data and open new perspectives. Colonial birds (and among them the king penguin, Aptenodytes patagonicus) offer an exceptional opportunity to undergo this kind of research. In this project, we will explore in this species how adults and chicks cope with environmental constraints such as parasite load and food availability throughout their biological cycle according to the timing of reproduction.
As a brief outline, the king penguin chick presents one of the longer growth period among birds, with an intermediate long winter break during which feeding events are unpredictable. Therefore, both pre- and post-winter growths are determinant for chick survival and the future adult phenotype potentially because : (i) the chick has to accumulate body reserves to survive during the winter fasting, (ii) has to be in an optimal body condition throughout the growth period to reduce predation risks and (iii) small chicks at the end of the winter has to catch-up in size and reserves to fledge successfully, with the associated potential long-term fitness costs. Thus, the king penguin chick has to set-up an efficient energy balance to optimize its growth rate and one of our hypotheses is that physiological mechanisms of energy sparing are of great importance. This key idea of energy sparing stands also in the centre of other hypotheses, for example concerning the biology of reproductive adults which face a negative energy balance during incubation. In this context, the evolution of resistance to environmental stress or parasites is of great importance given the potential effect of stress on energy expenditure, body reserves mobilization and tissue development, and ultimately on reproductive success (adults) and individual survival (chicks).
In adults, the physiological responses (energy use, stress response, immune response) during the reproduction fast according to the individual quality (determined from secondary sex characteristics), the characteristics of the breeding colony and parasite load will be analysed throughout the reproductive period. In chicks the effect of the timing of reproduction and parental quality on growth trajectories and survival will be assessed.
This work will be a part of the ECONERGY project that receives the financial and logistic supports of the French Polar Institut and of the Terres Australes Françaises.
