EXCYSTATION OF THE APOSTOMATOUS CILIATE, HYALOPHYSA CHATTONI, WITHOUT METAMORPHOSIS

¹ North Carolina State University at Raleigh, Raleigh, North Carolina 27607

Pieces of exoskeleton bearing Hyalophysa phoronts from the bases of the eye-stalks of intermolt and premolt Palacmonetes were placed in antibiotic brackish-water solution containing 0.05 M Tris-HCl buffer at pH 9.0, 0.5% glycogen, 0.5% -D glucose, 0.5% N-acetylglucosamine, and 10^-7 M ecdysterone. Controls were placed in antibiotic brackish water alone. In all experiments, the phoronts showed the same rates of excystation in control and experimental solutions. The phoronts excysted as tomites from intermolt shrimps, while both trophonts and tomites excysted from premolt shrimps. Experiments using body fluids from the host shrimp have indicated that the substance causing this unexpected excystation of tomites is in the body fluids of the host.

The resulting excystation of tomites from the phoretic cysts of Hyalophysa establishes the separation of metamorphosis and excystation in apostome ciliates.