Thyroxine-Accelerated Larval Development in the Crown-of-Thorns Starfish, Acanthaster planci.

Dramatic population increases (outbreaks) of the coraleating crown-of-thorns starfish, Acanthaster planci, have resulted in damage to many Indo-Pacific coral reefs, especially on Australia's Great Barrier Reef. Research on factors that could affect Acanthaster distribution and abundance has included investigation of larval development, dispersal, settlement, and metamorphosis. For example, various substrates, particularly crustose coralline algae with bacterial surface films, induce Acanthaster's planktonic larvae to settle and metamorphose (1, 2). but little investigation has thus far been devoted to specific chemical substances that affect various phases of Acanthaster development. We report here that thyroxine, which accelerates development in three sea urchin species (3), also accelerates Acanthaster's developmental progress through larval stages and that this acceleration is concentration dependent. Our results suggest the need for research on possible roles of iodinated organic molecules in Acanthaster development in situ, and on the effects of additional substances known to accelerate the development of other echinoderm larvae.