CHEMICAL DEFENCE AND ECOLOGY OF THE TROPICAL SEA STAR ICONASTER LONGIMANUS (MOBIUS) : (ASTROIDEA : ECHINODERMATA)

Abstract

The potential use of defensive chemicals in the Indo-Pacific goniasterid sea star, Iconaster longimanus (Mobius) was demonstrated in this thesis. Methanol extracts of the body wall of Iconaster adults were found to be toxic at high concentrations to the larvae of a local colonial ascidian, Polyclinum nudum Kott, while possessing antisettling properties at low concentrations. The eggs of this sea star were shown to possess antipredatory and antimicrobial activities. Chemical defence in the eggs of these Icon Stars is of interest as the eggs are large (ca 1mm) and undergo pelagic lecithotrophy, hence they are at risk of predation losses while in the plankton. Pre-adult development in Iconaster was also documented using light and scanning electron microscopy. The larvae go through a simplified pear shaped, non-feeding brachiolarian stage which is common in asteroids with planktonic lecithotrophy but which is little known for taxa at low latitudes.