THE BIOLOGY OF ASCIDIA NIGRA (SAVIGNY). 11. THE DEVELOPMENT AND SURVIVAL OF YOUNG ASCIDIANS

Open Access
Publisher Website
Google Scholar
Abstract
1. A time scale for the development of Ascidia nigra is given, from fertilization of the egg to the completion of black pigment formation. Embryonic and larval development are completed in less than 24 hours, and a functional ascidian is developed within 48 hours of larval settlement. Pigment first appears about the thirteenth day and the animal is completely black by the eighteenth or nineteenth day. The whole developmental process is completed about six times faster than in temperate-water ascidians at temperatures about 11° C. less. 2. The survival of populations of ascidians has been followed from settlement to the end of the sixth week of life. Most populations left only 2% to 3% survivors, but some left none and one as many as 17.5% survivors. These differences are discussed and are assumed to be due to differences in the associated biotic community arising from differences in illumination and season of growth. 3. Death is due to a number of factors, including predation by flatworms and polychaete annelids, competition for food and for space with other sessile animals or algae, and possibly in some cases protozoan infection.

This publication has 2 references indexed in Scilit: