[Effects of temperature and salinity on oxygen consumption rate and asphyxiation point of Sagitta crassa].

A laboratory test was conducted to study the effects of different temperature and salinity on the oxygen consumption rate and asphyxiation point of chaetognath Sagitta crassa. Both temperature and salinity had significant effects on the oxygen consumption rate (IO) and specific oxygen consumption rate (SO) of S. crassa. When the temperature raised from 5 degrees C to 25 degrees C, the IO and SO of S. crassa increased first, and then presented an obvious decreasing trend, with the regression function being y = 0.0058x3-0.2956x2 +4.415x-8.7816 (R2 = 0.99, P < 0.05) for IO and y = 0.0011x3-0.0546x2+0.8161x-1.6232 (R2 = 0.99, P < 0.05) for SO. The IO and SO at different temperature were in the ranges of 6.30-11.71 microg x ind(-1) x h(-1) and 1.22-2.16 microg x mg(-1) x h(-1), respectively, and the asphyxiation point was 4.18-6.87 mg x L(-1). When the salinity increased from 10 to 40, the IO and SO of S. crassa decreased gradually, with the regression function being y = -0.0068x2-0.1412x+21.702 (R2 = 0.89, P < 0.05) for IO and y = -0.0013x2 -0.0261x+ 4.0114 (R2 = 0.89, P < 0.05) for SO. The IO and SO at different salinity were in the ranges of 4.98-17.73 microg x ind(-1) x h(-1) and 0.92-3.56 microg x mg(-1) x h(-1), respectively, and the asphyxiation point was 4.02-6.24 mg x L(-1). Based on the differences in the oxygen consumption rate and asphyxiation point between S. crassa and other aquatic animals, it was concluded that S. crassa was a stenooxybiotic zooplankton species.