Effect of diets on the feeding behavior and physiological properties of suspension-feeding sea cucumber Cucumaria frondosa

The suspension-feeding sea cucumber Cucumaria frondosa has become commercially important in recent years. Finding proper diets is the first important step for intensive aquaculture of this sea cucumber. In this study, adult C frondosa were exposed to one of the following diet treatments: control (no diet provided), two powdered seaweeds (Ascophyllum nodosum and Saccharina latissima), a commercially available microalgal diet (shellfish diet) and natural seston. The effects of diets on the feeding behavior and physiological properties of sea cucumbers were investigated after a 5-week rearing period. Results show that sea cucumbers fed with shellfish diet exhibited a significantly higher tentacle insertion rate (1.80 +/- 0.20 insertion/min) than these fed with seaweed powders, and there was no significant different between the two groups fed by seaweed powders. No significant difference was found on the fecal production rate among the feeding groups. The minimum oxygen consumption rate was observed in the control group (5.76 +/- 0.99 mu g O (2) /(g center dot h)), which is significantly lower than individuals fed with A nodosum, shellfish diet, and natural seston; however, no significant difference was shown between those of control and S latissimi groups. The maximum ammonium excretion rate was found in the A nodosum group (0.03 +/- 0.01 mu mol/ (g center dot h)), which is significantly higher than other groups. The minimum O/N ratio was observed in the A nodosum group (14.57 +/- 1.04), which is significantly lower than the S latissima, shellfish diet, and natural seston groups. Individuals fed with seaweed powders had similar physiological properties with these fed with microalgae diet and natural seston, indicating that A nodosum and S latissima can be explored as promising diets for intensive aquaculture of C. frondosa.