GILL BLOOD-FLOW CONTROL

The arrangement of the fish gill vasculature is quite complex, and var ies between the different fish groups. The use of vascular casting tec hniques has greatly enhanced our knowledge of the anatomy of the branc hial microcirculation, not least through the contributions of Pierre L aurent and co-workers at Strasbourg. At different physiological situat ions, the contact surface between water and blood (functional surface area) varies to balance oxygen uptake against osmotic water flow (''re spiratory-osmoregulatory compromise''). This is controlled by nerves a nd by blood borne or locally released substances that affect blood flo w patterns in the gill. Histochemical techniques have been used to dem onstrate neurotransmitter substances in the branchial innervation. In combination with physiological experiments on isolated tissues, perfus ed gill preparations and whole animals it has become possible to produ ce models for the vascular control in fish gills and the role of this control in optimising the ''respiratory-osmoregulatory compromise'' at different physiological situations. COMP BIOCHEM PHYSIOL 119A;1:137-1 47, 1998 (C) 1998 Elsevier Science Inc.