颗石藻Pleurochrysis carterae不同细胞状态对卤虫的致死效应研究

颗石藻Pleurochrysis carterae对卤虫具有显著的致死效应,但其机理尚未明确.P.carterae的细胞生活史中会出现钙化细胞、非钙化细胞以及分枝丝状体的细胞状态.为了探明该种颗石藻对卤虫的致死原因,通过人为干预,分别获取了几种状态的细胞或相关组分,包括:钙化细胞(指钙化单细胞C-cell)、从非钙化单细胞N-cell动态释放的钙化细胞(N-C-cell)、非钙化单细胞(N-cell)、非钙化分枝丝状体(F)、带有机质基板的颗石粒外壳(L)、钙化细胞的冻干藻粉(Ly).以喂养组和饥饿组为对照,比较研究了P.carterae不同细胞状态或组分在作用密度和作用时间上对卤虫(Artemia salina nauplii)无节幼虫的致死效应差异.结果显示:钙化细胞和非钙化单细胞可以对卤虫幼虫产生显著的致死效应,这种致死效应显著差异于饥饿致死效应(p<0.05).致死效应与作用时间及藻密度显著相关,钙化细胞对卤虫的半致死密度为72hLD50=6.16×103cells·mL-1,96hLD50=2.19×103cells·mL-1,高密度时(105、106cells·mL-1)的卤虫半致死时间分别为68.4h和53.3h.非钙化丝状体、颗石粒和冻干藻粉对卤虫的致死效应与饥饿致死效应一致.非钙化丝状体、颗石粒、冻干藻粉以及裸露细胞重新钙化过程均不向水中释放有害物质.颗石藻P.carterae对卤虫的致死效应与卤虫对生活颗石藻单细胞的摄食过程有关.

Lethal Effects of Different Pleurochrysis carterae Cells on Brine Shrimp

Pleurochrysis carterae has significant lethal effect on Artemia salina nauplii. However, the mechanism of the effects is poorly understood. Cell morphology changed in the life cycle of P. carterae, from unicellular cells that are coccolith -bearing or not, to non -calcified filamentous colonies. In order to make clear of the lethal mechanism, we detected the mortalities of A. salina nauplii caused by different P. carterae cells that were got from different cultures or from special treatments. The different P. carterae cells used in the experiments included: unicellular coccolith -bearing cells (C-cell), coccolith-bearing cells germinating from non-calcified unicellular cells (N-C-cell), non-calcified unicellular cells (N-cell), non-calcified filamentous colonies(F), coccoliths(L), and lyophilized calcified cells(Ly). Compared with the feeding control and starving control, the lethal effects of different P. carterae cells were studied in the function of density and time. The results showed that: calcified cells and non -calcified unicellular cells exhibited obvious lethal effects on A. salina nauplii. The mortalities had significant differences compared with the starving controls (p <0.05). The mortalities caused by calcified cells were density and time related: LD50 in 72h and 96h were 6.16×103cells·mL-1 and 2.19×103cells· mL -1, respectively. LT50 of the cell density of 105 and 106cells·mL -1 were 68.4h and 53.3h, respectively. Non -calcified filamentous colonies, pure coccoliths and lyophilized calcified cells showed no difference to starving control. It is obviously that no harmful substances to A. salina nauplii were released to water by non -calcified filamentous colonies, coccoliths, lyophilized calcified cells, or during re -calcification process. The significant lethal effects of P. carterae on A. salina nauplii showed relationship with the predation activities of A. salina nauplii. Lethal effects began when A. salina nauplii predation activities began.