Karameta, E., V. Litsi Mizan, K. Sagonas, S. Sfenthourakis, E. D. Valakos & P. Pafilis

Ontogenetic shifts in the digestive efficiency of an insectivorous lizard (Squamata: Agamidae). pp. 321-326.

Abstract. Most animals undergo an impressive sequence of shifts during ontogeny. Their overall biology changes to support the requirements of adult life. Digestion represents no exception and, in order to ensure a constant energy flow, the digestive system adapts accordingly. In this study we assessed the impact of age on the digestive performance of an insectivorous lizard (Stellagama stellio), focusing on gut passage time (GPT) and apparent digestive efficiencies (ADE) for the major nutrients (lipids, sugars and proteins). Age affected digestive efficiency even though not in a cohesive way: ADE for lipids and sugars were higher in adults whereas juveniles absorbed proteins at higher levels. While absolute GPT did not differ between the two age groups, food lingered longer in the gut of juveniles. We believe that the observed differences should be attributed to the idiosyncratic demands of each age group. Mature individuals have to support energy-consuming processes such as reproduction, whereas juveniles need to fuel rapid somatic growth with building blocks such as amino acids.
Key words. Ontogeny, digestion, energy flow, Agamidae, Reptilia, Greece.