Meeting Abstract

P1.101  Thursday, Jan. 3  Hydrodynamics of gill ventilation in a bony fish STROTHER, J.A.; Univ. of California, Irvine strother@uci.edu

The gills of teleost fishes have been described as a model counter-current exchanger. The coordinated movements of the buccal cavity and the opercula drive water through the gills in a direction opposite to that of the perfusing blood flow. While counter-current exchange has the potential for very efficient transport, these exchange rates may be compromised by streams of water that pass around the gills (non-respiratory shunting) or by variation in the flow of water through different parts of the gills. To examine how morphology affects the performance of the gills as a counter-current exchanger, a physical model of the respiratory tract was constructed and the flow around excised gills was measured. The model was constructed from morphological measurements of Tilapia (Oreochromis mossambicus) and the gills were excised from individuals of the same species. Particle tracking velocimetry (PTV) was used to measure the velocity of water along the efferent edge of the primary lamellae, from which several measures of respiratory efficiency were calculated. The net flow rate and the distance between the gill arches was varied, and the effect on flow through the gills was quantified. We found that, with the measured morphology, non-respiratory shunting and flow heterogeneity remained low. However, as the flow rates or spacing between the gills arches was increased these effects began to compromise respiratory performance. It is possible that such effects impose functional constraints on the rate of ventilation and the morphology of the gills in teleost fishes.