Remodelling during the development of nematocysts in a siphonophore

Abstract

Remodelling of a smoothly tapering internal tubule to form the enlarged shaft of microbasic mastigophores of the siphonophore Rosacea takes place very late in development. It occurs after deployment of the nematocyst in its final position, and after the pleats of the internal tubule have been completely obliterated in the shaft region by the growth of spine material. The optical and mechanical properties of the internal tubule at the earlier (bedspring) stage give no hint that a shaft will develop. The possible ways in which remodelling might occur inside the capsule and remote from the cytoplasm are discussed.