赤潮异弯藻(Heterosigma akashiwo)对蒙古裸腹溞(Moina mongolica)和日本新糠虾(Neomysis japonica)的毒性影响

采用生物急性和慢性毒性实验的方法,研究了赤潮异弯藻对蒙古裸腹溞和日本新糠虾的毒性影响,并初步探讨了赤潮异弯藻导致二者较快死亡的机制。结果发现,赤潮异弯藻不仅对蒙古裸腹溞和日本新糠虾的存活有显著影响,而且使其个体变小、产幼前发育时间延长、总生殖量降低、平均存活时间缩短,种群数量增长受抑制。显微观察发现,蒙古裸腹溞能摄食赤潮异弯藻,但摄食后,其粪便紧紧地粘在蒙古裸腹溞的肠道末端;日本新糠虾不摄食赤潮异弯藻,但该藻粘附在其触须、附肢以及腹部、尾部的刚毛上,以及作为食物的卤虫幼体也被大量粘附在一起,聚集成团,或通过赤潮异弯藻粘附在日本新糠虾的附肢上。因此赤潮异弯藻很可能通过干扰蒙古裸腹溞和日本新糠虾正常的生理活动,而导致其快速死亡。

THE TOXIC EFFECT OF HETEROSIGMA AKASHIWO ON MOINA MONGOLICA AND NEOMYSIS JAPONICA

Zooplankton is an important link between phytoplankton and higher consumers in the marine food chain. Experiments were designed to investigate the harmful effects of Heterosigma akashiwo on Moina mongolica and Neomysis japonica under laboratory conditions. The results show that, after 96h, the survival rate of M. mongolica exposed to 1×10⁴, 5×10⁴, 10×10⁴, and 20×10⁴cells/ml of H. akashiwo is 10%, 23.3%, 21.67% and 0%, respectively, significantly lower than that of the control (98.4%); while the survival rates of N. japonica exposed to 1×10⁴, 5×10⁴, and 10×10⁴cells/ml of H. akashiwo are 33.3%, 27.8%, and 33.7%, respectively, obviously lower than that of the control at 66.7%. The harmful effect of 2×10⁴, 4×10⁴ cells/ml of H. akashiwo on M. mongolica is as follows, (1) the body length of M. mongolica was reduced slightly to 1.44mm and 1.37mm after 13 days, respectively, while that of the control was 1.46mm; (2) the development was delayed, as the time for the first brood of M. mongolica was 4.0 and 4.1d, while that in of control was 3.7d; (3) the gross fecundity was decreased to 30.2, and 26.7, respectively, and that in control was 35.5; (4) the average life-time was shortened to 11.4 and 12.5d, respectively, and that of control was 14.5d. Moreover, H. akashiwo inhibited obviously the population dynamics of M. mongolia, as the population number of M. mongolia exposed to 2×10⁴cells/ml and 5×10⁴cells/ml of H. akashiwo was 36.5% and 0% of the control after 17 days, respectively. Microscope observation shows, M. mongolica could feed on H. akashiwo filled with in intestinal tract; however, it seemed that M. mongolica could not digest very well, and H. akashiwo could excrete some materials to stick on the intestinal tract end of M. mongolica; moreover, H. akashiwo also stuck to the setae of N. japonica. Thus, H. akashiwo can disturb normal activities of the zooplankton, and cause them death rapidly.