饥饿时间对大型溞摄食行为的影响

Effects of fasting time on food selectivity of water fleas Daphnia magna

研究了不同饥饿时间下大型溞Daphnia magna(体长约3 mm)对沙角衣藻Chlamydomonas sajao和蛋白核小球藻Chlorella pyrenoidos的摄食选择性。沙角衣藻与蛋白核小球藻相比,具有较高的适口性,但营养价值相对较低。按照沙角衣藻和蛋白核小球藻的比例分别为5×104∶35×104、20×104∶20×104、35×104∶5×104cells/m L混合投喂饥饿0、0.25、1、4、8 d的大型溞,3 h后测定大型溞的摄食率、滤水率和食物选择系数。结果表明:与饱食组和短时间饥饿(0.25、1 d)组相比,长时间饥饿(4、8 d)导致大型溞对蛋白核小球藻的摄食率和滤水率显著增加(P<0.05),而对沙角衣藻的摄食率和滤水率显著降低(P<0.05);饱食和短时间饥饿状态下大型溞优先摄食沙角衣藻,而在长时间饥饿状态下大型溞优先摄食蛋白核小球藻;大型溞在长时间饥饿和短时间饥饿状态(含饱食)下的最优觅食行为不受食物中沙角衣藻与蛋白核小球藻相对密度的影响。研究表明,大型溞的饥饿状态可以影响其对藻类食物的选择性。

In the present work we evaluated the influence of fasting time on foraging behavior of water fleas Daphnia magna. The water fleas were fasted for 0,0. 25,1,4,or 8 d,and then were allowed to graze on a mixture of algae Chlamydomonas sajao（ Cs） and Chlorella pyrenoidosa（ Cp） with a proportion of 5 ×10^4 cells / mL（ Cs）∶ 35 ×10^4 cells / mL（ Cp）,20 ×10^4 cells / mL（ Cs）∶ 20 ×10^4 cells / mL（ Cp） and 35 ×10^4 cells / mL（ Cs）∶ 5 ×10^4 cells / mL（ Cp） for three hours. Then the ingestion rate,filtration rate and food selectivity coefficient of water fleas on the two algae were analyzed and evaluated. The results showed that significantly high ingestion rate and filtration rate on Chlorella pyrenoidosa and significantly low ingestion rate and filtration rate on Chlamydomonas sajao were found in the water fleas fasted for long period（ 4,and 8 d）. In satiation or short fasting period（ 0. 25,and 1 d）（ P〈0. 05）,however,the water fleas was found to prefer to Cs,and prefer Cp in long fasting period（ 4,and 8 d）（ P〈0. 05）. Moreover,the foraging behaviors were not influenced by the relative food abundance of each green alga and the mechanisms of feeding selectivity were discussed based on the optimal foraging theory. The findings indicate that starvation affects the selectivity of wate fleas for algal food.