Influence of photosynthetic bacteria on breeding of Holothuria scabra larvae

Taking Holothuria scabra auricularia larvae hatched after 24 h fertilization as objects, we studied the influence of photosynthetic bacteria on their growth, survival and digestive enzymatic activities as well as on water quality. The experiments lasted 41 d and four groups were set up, each with three replicates. Photosynthetic bacteria（11011cfumL-1）of 0 mL (Group 1,control), 50 mL(Group 2), 100 mL(Group 3) and 150 mL (Group 4) were added respectively into tanks (5 m3 m1.5 m) once every 5 d. Each tank was added with 4104 larvae. The results show that the body weight and survival rate in thetreatment groups(Group 2,Group 3 and Group 4) were significantly higher than those in the control group (P0.05), while the body weight and survival rate in Group 3 and Group 4 were significantly higher than those in Group 2 (P0.05), but there was no significant difference between Group 3 and Group 4 (P0.05). Photosynthetic bacteria also affected the activities of protease, amylase and cellulose in intestines of larvae which in the treatment groups were significantly higher thanthose in the control group (P0.05). The enzyme activities of protease and cellulose in Group 3 and Group 4 were significantly higher than those in Group 2 (P0.05), but there was no significant difference in the enzyme activity of amylase among treatment groups (P0.05). The ammonia nitrogen and nitrite contents in treatment groups were significantly lower than those in the control group (P0.05) after 10 d; the chemical oxygen demand (COD) in treatment groups was significantly lower than that in control group (P0.05) after 20 d but no significant difference in total phosphorus (TP). The results indicate that photosynthetic bacteria canaccelerate the growth, increasethe survival rate and digestive enzymes activities of H.scabra larvae, and improve aquaculture water quality.