Selective Feeding on Five Species of Bivalves and Feeding Rhythm of Asterias amurensis

Abstract:

Asterias amurensis is one of the primary predators of bivalves that often cause massive death of cultured bivalves. Better understanding of the feeding ecophysiology of A. amurensis is the key for developing effective control strategies. In this study, we recorded the selective feeding and feeding rhythm of A. amurensis on five species of bivalves including Patinopecten yessoensis, Chlamys farreri, Ostrea plicatula, Mytilus galloprovincialis and Ruditapes philippinarum, and thus identified the characteristics of feeding of A. amurensis. The experimental animals were collected from the sea area of Zhangzi Island and then transported to our seaside laboratory at low temperature. The A. amurensis was acclimated to laboratory conditions for 10 d before the experiment. The experiment was conducted between October 22 and November 12, 2013, at the water temperature of 13−15℃, and at the salinity of 30−31, and at the dissolved oxygen level of 7.8−9.7 mg/L in a concrete tank (L×W×H=5.5 m×2.5 m×1.5m). The results showed that A. amurensis had the highest feeding rate (P<0.05) on R. philippinarum, no matter whether interfering baits, such as Charybdis japonica and Apostichopus japonicus Selenka, were present. The values were 5.7 ind/d, 5.0 ind/d, 5.7 ind/d, 5.3 ind/d and 6.0 ind/d respectively. There was no significant difference in the feeding rate when A. amurensi was fed with different interfering baits. We also observed an active feeding rhythm of A. amurensi in a diurnal cycle by feeding them with C. farreri every four hours. The percentage of food intake between 18:00 and 06:00 was apparently higher than that between 06:00 and 18:00 (60% vs 40%, P<0.05). Furthermore, we found that the feeding frequency of A. amurensis peaked between 18:00 and 22:00 (58%, P<0.05).