ABSTRACT

A population of wild carp in the Donau River basin possibly gave rise to the form used in aquaculture. Carp ventilates the gills in a periodic manner, when in normoxic conditions. Normoxic carp ventilates the gills in an intermittent manner, which is synchronized with increased cardiac frequency during ventilation. The modulations of ventilatory and cardiovascular responses confirm the carp is a very efficient oxyregulator, when confronted with moderate or severe hypoxia. The dourado, Salminus maxillosus, is a fast swimming species of lotic waters of Southern Brazil. The ventricular muscle of teleosts, including the carp, consists of an inner spongy layer and an outer compact layer. In carp, gill ventilation increased by 58% as soon as the external O2 receptors were exposed to light hypoxia. In this situation, there was no significant change in PaO2 and acid-base status.