Influences of food particle size and dietary energy content on patterns of gastric evacuation in fish: test of a physiological model of gastric emptying

Abstract

The evacuation of food from the stomach is probably not a continuous smooth process but may occur in a pulse-like (step-wise) fashion. It is hypothesised that the pattern of emptying is influenced by feedback signals from receptors located in the upper intestinal tract and by factors affecting the rate of physical/chemical breakdown of the food particles. Mathematical functions used for describing evacuation patterns imply that emptying is continuous and they are, therefore, at best, only approximations. It was predicted that different mathematical expressions would give best fit to empirical data from gastric evacuation studies dependent upon the experimental conditions employed. An analysis of published data supported the predictions and revealed that an exponential function best described the evacuation of small, easily digested prey items, but a linear expression gave the best fit to data of the emptying of large food items. It is suggested that differences in surface-to-volume ratios between large and small food particles and the friabilities of different food types are important in determining the pattern of emptying. Whilst dietary energy content also appears to be an important factor in the governing of gastric evacuation, it appears that emptying pattern in fish species is rather less sensitive to changes in dietary composition than is gastric emptying in mammals.

Influência do tipo de alimento e da temperatura na evacuação gástrica da piranha caju (Pygocentrus nattereri) em condições experimentais

“…A privação de alimento, ingestão de re¬ feições subseqüentes, combinação da compo¬ sição do alimento, temperatura da água e a fisiologia do predador, também influenciam no tempo de evacuação gástrica (Jobling, 1987;Salvanes et al, 1995).…”

Do cannibalistic fish forage optimally? An experimental study of prey size preference, bioenergetics of cannibalism and their ontogenetic variations in the African catfishHeterobranchus longifilis

“…A similar interest has been raised in aquacultural studies aiming to understand the relative benefits of using a small or large food particle size (for fishes: Wankowski and Thorpe 1979;Goldan et al 1997;Hasan and Macintosh 2008;Azaza et al 2010). Small prey are more difficult to detect at long distance (Folkvord 1997), but easier to capture and handle (Knights 1983;Mittelbach and Persson 1998), and unless their gut residence time is excessively brief (Hossain et al 2000) they can be digested more completely (Persson 1986;Jobling 1987). On the other hand, their absolute energy content is low, so the net energy gain per unit of time can be less than for big a Corresponding author: etienne.baras@ird.fr prey, depending on food search time and energy invested into foraging (e.g., Jobling and Wandsvik 1983;Dos Santos et al 1993).…”

A dieta e o consumo diário de alimento de Cichla monoculus na Amazônia Central

“…A combinação da composição, forma e tamanho da presa, com a fisiologia do predador e a temperatura, pode influenciar a taxa de evacuação gástrica (Persson, 1979;Jobling, 1987;Salvanes et al, 1995). A temperatura é o principal fator abiótico que age sobre a taxa de metabolismo dos peixes, e consequentemente no consumo de alimento e no processo digestivo (Smith, 1989).…”