Experimental and field studies on foraging behavior and activity rhythm of hard-spined sea urchin Anthocidaris crassispina

摘要

Foraging behavior and activity rhythms of hard-spined sea urchin Anthocidaris crassispina were analyzed in experimental and wild conditions. The behavior in captivity could be categorized into ‘biting’, ‘migration’ and ‘resting’. Biting was very slow (35.8±3.8 s/bite) and never observed during migration. Biting and short migrations within 5 min were significantly more frequent in the starved group than in the well-fed group, although the total migration was not significantly different between the groups. Analysis of the behavior sequence suggested that foraging behavior consisted of a series of short migrations and bitings. Biting increased in the dark while resting showed the inverse tendency, suggesting a nocturnal activity rhythm. The tube feet at the body side were of medium length, while they were long during migration, and short during resting. During biting, some spines were observed moving, while all spines stuck out radially during both migration and resting. Diel change in behavior of the wild sea urchins estimated from the length of tube feet and movement of spines also suggested a nocturnal activity rhythm.