[Suffocation point and diurnal metabolism pattern of Hemifusus tuba (Gmelin)]

The individuals of Hemifusus tuba (Gmelin) were divided into 3 groups, i. e., small [S, (6.48 +/- 0.46) cm], medium[ M, (7.59 +/- 0.41) cm], and large [L, (9.08 +/- 0.37) cm], according to their shell height, and their suffocation points and diurnal metabolism patterns were investigated at water temperature (22 +/- 0.5) degrees C. The results indicated that the oxygen consumption rate of H. tuba was relatively stable and maintained at 1.81 mg x g(-1) x h(-1) when dissolved oxygen (DO) content was higher than 4.37 mg x L(-1), but decreased with decreasing DO when DO content was lower than 4.37 mg L(-1) x 0.43 mg L(-1) of DO was the suffocation point of H. tuba, with the oxygen consumption rate being 0. The standard metabolism (SM) and routine metabolism (RM) of H. tuba decreased significantly with increasing body mass, and changed with the same pattern in the 3 groups, i. e., being higher at night than in daytime. There was a significant difference in the SM (F = 36.263, P < 0.01) and RM (F = 6.788, P < 0.01) among the 3 groups. The peak values of the specific dynamic metabolism of groups S, M, and L were 2.11, 1.62, and 1.42 mg x g(-1) h(-1), being 1.09, 0.75, and 0.71 times higher than their SM, respectively, and maintained about 15 h. The ammonia excretion rates of groups S, M, and L reached the peak after 24, 24, and 27 hours of feeding, with the peak values being 3.94, 2.64, and 1.71 micromol x g(-1) x h(-1), and 0.87, 0.73 and 0.31 times higher than those in starvation state, respectively,.