盐度骤降对幼仿刺参生长、免疫指标及呼吸树组织结构的影响

Effects of abrupt decline in salinity on growth,immunity and histological structure of respiratory trees in juvenile sea cucumber Apostichopus japonicus

在水温为10.0-13.0℃下,将暂养在盐度为33水中的仿刺参Apostichopus japonicus幼参（2.42 g和3.5 g）直接放入盐度为33、30、26、22的塑料水槽（50 cm×40 cm×30 cm）中,过量投喂,正常饲养,研究了盐度骤降对幼参存活、生长、某些免疫指标及呼吸树组织学的影响。结果表明：在60 d饲养过程中,各组幼参的排脏率为2.23%-11.11%,盐度为33时,幼参的排脏率显著低于盐度为30时（P〈0.05）,而与盐度为26和22时差异均不显著（P〉0.05）;但生长却随着盐度的降低而降低,盐度为30和26时,幼参的生长速度分别比盐度为33时减少了5.0%和62.5%,表明盐度为26时是明显抑制幼参生长的拐点;随着盐度的降低,各试验组幼参体腔液上清液中溶菌酶活力升高,超氧化物歧化酶活力降低,但均未检测出酸性磷酸酶的活性。盐度为29时,幼参体腔上皮细胞逐渐消失,内皮层中出现大量空泡,血腔不明显,中央腔变小;盐度为24、18时,幼参体腔上皮细胞增多,血腔增厚,内皮层细胞向中央腔延伸。

The juvenile sea cucumber Apostichopus japonicus with body weight of 2.42 g and 3.5 g held in sea water with a salinity of 33 was directly stocked into tanks of each 50 cm × 40 cm× 30 cm with a salinity of 33,30,26 and 22 ,ad libitum fed and reared routinely at water temperature of 10.0 - 13.0 ℃ for 60 days to elucidate the effects of abrupt decline in salinity on growth, survival, immunity and histological structure of respiratory trees in the sea cucumber juveniles. It was found that 2.23% - 11.11% of the juveniles exposed to abrupt decline in salinities showed evisceration in the experimental groups, significantly higher in the group with a salinity of 30 ppt than in the group with a salinity of 33 （ P 〈 0.05 ）. However, the juveniles had decrease in weight gain by 5.0% and 62.5 % under a salinity of 30 and 26,indicating that the lower limit of salinity is 26 for the growth in the sea cucumber juveniles. The activity of serum lysozyme increased with increase in salinity while the serum superoxide distmutase （SOD） activity decreased with increase in salinity. No acid phosphatase （ACP） activity was determined in the juveniles exposed to abrupt decline in salinity. The respiratory tree consists of coelothelial cells layer, muscular coat layer,and endothelial cell layer, indistinct haemocoel and wide center antrum. At a salinity of 29, there were no coelothelial cells, many vesicles in the endothelial cells, and narrow center antrum. At a salinity of 24, and 18, coelothelial cells were found to increase, haemocoel to thicken and endothelial cells to extend into the center antra.