Response of Acanthaster planci (Echinodermata: Asteroidea) to hypersaline solution: Its potential application to population control

Abstract

The response of Acanthaster planci or crown- of-thorns starfish (COTS) to intracoelomic injection of hypersaline solutions was investigated to establish its potential application as A. planci population control es- pecially during an outbreak. Adult A. planci when inverted had a normal righting response time (in seconds) of 163±1 (mean±SE; N=298). Injection of concentrated salt solutions led to negative effects on adult A. planci. The spines bent down, body collapsed and the starfish became comatose and died after 24-hours. The higher the salt concentration, the higher is the % comatose indivi- duals. In addition, comatose specimens failed to recover with time. Mortality was highest at the highest treatment concentration with LC90 of 285.3 and LC99 of 383.2 ppt. The effects of time, salt concentration and its interaction (salt concentration x time) were significant ( p=0.00). The ionic and osmotic disruption of the coelomic fluid can seriously affect physiological functions of the organism including neuromuscular activity. Thus, in the control of A. planci, concentrated salt solution can be used as a cheaper alternative to dry acid, acetic acid or ammonium hydroxide, all of which are expensive, may not be locally available and not environment friendly.