The Ecology of the Tropical Compound Ascidian Trididemnum solidum. I. Reproductive Strategy and Larval Behaviour

Abstract

Colonies in populations of Trididemnum solidum (Van Name) on the reefs of Curacao release larvae throughout the year. The number of tadpoles released daily between 10.15 and 14.00 h runged to over 200 larvae colony super(-1) and appears to be influenced by temperature and quantity of sunlight. The free-swimming period of the larvae is short, the moajority settling within 15 min. Settlement was stimulated in the presence of attached larvae. Upon release, the larvae display positive phototaxis and a weaker negative geotaxis. At a later stage this is replaced by negative phototaxis. When offered a range of light intensities (1250-1.3 mu Em super(-2)s super(-1)) most larvae preferred to settle at an intermediate but low radiation level.