Effect of Temperature on Filtration,Oxygen Consumption and Ammonia Excretion Rates of Sea Squirt Halocynthia roretzi
One-,two-and three-year-old sea squirt(Halocynthia roretzi)with body weight of(23.95±9.83)g,(68.95±23.84)g and(117.99±38.42)g were domesticated to 16 ℃,20 ℃,24 ℃ and 28 ℃ at temperature rising rate of 1 ℃·h-1,and the water filtration rate,oxygen consumption rate and ammonia excretion rate were determined 2 days later,and the survival rate was calculated.The 12℃ group was used as control group.Six sea squirt were randomly taken from each group and transferred into a beaker containing 1 L of seawater,fed microalga with a final concentration of 104 cells·mL-1 with aeration,and water filtration,oxygen consumption rate,ammonia excretion rate and oxygen consumption rate/ammonia excretion ratio(O/N)were determined every 30-60 min to evaluate effect of temperature on filtration,oxygen consumption and ammonia excretion rates of the sea squirt.The results showed that the water filtration rate,oxygen consumption rate,ammonia excretion rate and O/N value were ranged from 1.33 mL·g 1·h-1 to 5.51 mL·g1·h-1,5.32 μg g-1·h-1 to 29.24 μg·g-1·h-1,0.04 μg·g1·h-1 to 0.41 μg g1·h-1 and 62.50 to 122.93,respectively.With the temperature increasing from 12 ℃ to 24 ℃,the water filtration rate of the sea squirt was changed into inverted bell shape,with the maximum value at 25.64 ℃.Oxygen consumption and ammonia excretion rate were both shown to be increased with rising temperature within 12 ℃ to 28 ℃.O/N values decreased significantly with the temperature raising,but fluctuated slightly after 20 ℃,indicating that the turn point for metabolic process was around 20 ℃ to 24 ℃.The relationship between temperature(t)and feeding rates(FR),oxygen consumption rates(RO),ammonia excretion rates(RN),O/N values(RO/N)was described as FR=-0.013 9t2+0.712 8t2-4.772 8(r2=0.540 1),RO=1.049 2t-6.242 3(r2=0.826 8),RN=0.0 16 9t-0.170 3(r2=0.857 4)and RO/N=-69.294 0 ln(t)+292.967 5(r2=0.890 0),respectively.In summary,the upper temperature limit of reasonable cultivation of the sea squirt should be about 24 ℃.
Halocynthia roretzitemperaturefeeding rateoxygen consumption rateammonia excretion rateO/N value
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