The regulation of branchial blood flow in the blacktip reef shark, Carcharhinus melanopterus (Carcharhinidae: Elasmobranchii)

The innervation of the branchial vasculature of the blacktip reef shark, Carcharhinus melanopterus, appears similar to that described for other elasmobranchs. Isolated perfused gill arch preparations were used in a study of vascular responses to branchial nerve stimulation. The pre-addition of 10-5 M concentrations of pancuronium to the perfusate prevented skeletal muscle contractions and significantly reduced (P -5 M. The use of antagonists demonstrated the presence of both α-, and β-adrenoceptors in the branchial vasculature. Anatomical studies failed to show adrenergic nerves in the gills, suggesting a lack of a spinal autonomic ('sympathetic') innervation. Adrenergic regulation of gill blood flow may involve the release of catecholamines into the blood stream from chromaffin tissue stores.