Meeting Abstract

24.4  Monday, Jan. 5  The hydrodynamics of gill ventilation in teleost fishes 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 (flow heterogeneity). To determine how such issues might affect gas exchange, the flow around the gills of a bony fish was measured using particle image velocimetry (PIV). The freshly-excised gill arches of a tilapia (Oreochromis mossambicus) were placed in a closely fitting flow-through chamber, and the flow rate and distance between the arches was varied. PIV was used to measure the velocity of water along the trailing edge of the primary lamellae, from which several measures of respiratory efficiency were calculated. We found that, with the observed 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.