Energy is conserved in all physical systems. In animals, this means that the amount of mechanical energy (i.e. work) available for movement is limited by that released by musculoskeletal systems from chemical stores (such as ATP). If the amount of energy available from a given mass of muscle is relatively constant, than the energy available to power a behavior ought to be limited by the mass of muscle devoted to that by behavior. To capture elusive or evasive prey by high performance suction feeding, a fish must rapidly expand its mouth inducing a flow of water sufficient to entrain the prey animal, drawing it into the mouth before it can escape. Such rapid movement in water incurs high-magnitude hydrodynamic pressures. The product of these pressures and the total volume drawn by the predator is equal to the work expended during the behavior and, divided by time, is equal to the power expended. According to conservation of energy, these values, and thus, suction feeding performance, ought to be limited by available muscle mass. We tested this relationship in three species of suction-feeding fish by estimating muscle mass capable of expanding the mouth and comparing it to measured work and power during high-performance suction feeding on evasive prey. We found a strong relationship between muscle mass and energetic variables among individuals, and that investment in muscle mass is an important morphological requirement for high performance suction feeding. As a corollary to this relationship, a strong trade-off between volumetric expansion and mean hydrodynamic pressure was found when muscle mass was taken into account. Suggesting that a fish with a given muscle mass devoted to suction feeding can invest the work available from that muscle mass into volumetric expansion (allowing larger, more energetic prey to be taken) or into hydrodynamic pressure (allowing greater suction feeding force.) Thus, two straightforward morphological measures muscle mass and mouth volume, appear to be useful and general predictors of suction feeding performance in fish.
Carroll, A. M. & P. C. Wainwright. 2009. Energetic limitations on suction feeding performance in Centrarchidae. Journal of Experimental Biology. 212: 3241-3251. download pdf.
posted October 25, 2009
Energetic constraints drive the major trade-off in design of suction feeding fishes