Reproductive phase and seawater temperature modulate locomotion and chemosensory-guided orientation in crown-of-thorns starfish.

Population outbreaks of crown-of-thorns starfish (COTS) are a major issue in the management of coral ecosystems. Elucidating foraging behavioral patterns in COTS caused by chemoreception is important understand because chemoreception is the principal sensory modality for prey detection in Asteroidea. Using Y-maze behavioral assays, we quantified how reproductive phase (pre- vs. post-spawning) and seawater temperature modulate (i) locomotor activity and (ii) odor-guided orientation toward live-coral cues in adult COTS. Elevated seawater temperature was associated with increased locomotion in COTS, likely caused by temperature-driven increases in metabolic rate. Y-maze experiments further indicated that COTS orientation toward prey chemical cues was greater during the pre-spawning period than during the post-spawning period. In line with heightened pre-reproductive nutritional demand, COTS were significantly more attracted to coral-derived chemical cues before spawning than afterward. These findings provide the first quantitative evidence that chemosensory-driven foraging in COTS is modulated by reproductive phase and seawater temperature.