EFFECTS OF SALINITY AND TEMPERATURE ON THE OXYGEN CONSUMPTION, AMMONIA EXCRETION RATES AND SUFFOCATION THRESHOLD OF DIFFERENT SIZES OF JUVENILE SEPIA PHARAONIS

This research was conducted to explore the effects of body weight, salinity and temperature on oxygen consumption rates (OR), ammonia excretion rates (NR) and the suffocation threshold of juvenile Sepia pharaonis. The relationship between OR and NR of juvenile S. pharaonis and body weights (0.212, 0.385, 0.476, 0.597, 0.754, 0.946 g), suffocation threshold and body weights (0.476, 0.673, 1.341, 3.873, 4.205 g) were studied. Meanwhile, the effects of various salinities (19, 22, 25, 28, 31), and temperature (18, 21, 24, 27, 30℃) for three sizes of cuttlefish (A: body weight 0.366±0.042 g, B: body weight 0.556±0.038 g, C: body weight 0.844±0.051 g) were revealed by using single-factor design and sealed hydrostatic method. The results were as follows: 1) body weights of juvenile S. pharaonis showed a significant effect on OR and NR (P<0.05), which decreased significantly with the increase of body weights. 2) Salinity had significant effects on the OR and NR (P<0.05), all of which were reduced with the increase of salinity, and then rose. For sizes A and B, the OR and NR of juvenile S. pharanis at salinity 25 were significantly lower than that at salinity 19, 22 and 31 (P<0.05), with the exception of salinity 28 (P>0.05). For size C, the OR of juvenile S. pharanis was significantly lower at salinity 28 than that at salinity 19 (P<0.05). Meanwhile, the NR was significantly lower at salinity 25 than at salinity 19 and 31 (P<0.05). The salinity had significant effects on O/N of juvenile S. pharaonis for size A (P<0.05), but not for sizes B and C (P>0.05). 3) The temperature had significant effects on the OR and NR (P<0.05), both of which were elevated with the increase of temperature, and then decreased. For sizes A and C, the OR of juvenile S. pharanis were significantly higher at 27℃ than at 18℃ and 30℃ (P<0.05). For size B, the OR of juvenile S. pharanis were significantly higher at 24℃ than at 18℃ and 30℃ (P<0.05). For sizes A and B, the of juvenile S. pharanis were significantly higher at 24℃ and 27℃ than at other temperatures (P<0.05). For size C, the NR of juvenile S. pharanis were significantly higher at 27℃ than at 18℃ and 30℃ (P<0.05). The temperature had significant effects on O/N of juvenile S. pharaonis of size A (P<0.05), but not of sizes B and C (P>0.05). 4) The suffocation threshold of juvenile S. pharaonis was 0.84—1.62 mg/L, which decreased with increasing body weights.