Effects of Ca 2+ and catecholamines on swimming cilia of the trochophore larva of the polychaete Spirobranchus giganteus (Pallas)

Abstract

Trochophore larvae of the tropical serpulid Spirobranchus giganteus (Pallas) swim by means of prototrochal and metatrochal rings of cilia. A system of developing neuntes carrying vesicles of several kinds is located on the inner surfaces of both prototrochal and metatrochal cells. The swimming cilia arrest on exposure to EDTA, Ba(OH) 2, lanthanum chloride, trifluoperazine and Ca 2+ -free sea water, i.e. under conditions that interfere with the supply of external Ca 2+. Swimming cilia are also arrested by the β-blocker alprenolol, an effect ameliorated by the α 1 agonist phenylephrine or the β agonist isoproterenol. We conclude that there is a Ca 2+ -dependent, catecholaminergic excitation of the swimming cilia of the S. giganteus trochophore larva, involving β receptors and probably neurally mediated. Other cilia on the larval body are insensitive to the agents affecting the activity of swimming cilia.