Tunicate Eggs Utilize Ammonium Ions for Flotation

Science  07 Apr 1978:
Vol. 200, Issue 4337, pp. 64-65
DOI: 10.1126/science.200.4337.64


Unlike most solitary ascidians, Corella willmeriana retains its eggs and embryos well past hatching. The early stages float to the top of the enlarged atrium from which they cannot escape. Ammonium ions replace other more dense substances in the cell sap of the float cells surrounding the embryo. Energy derived from glycolysis but not mitochondrial processes supports this process.