伊乐藻抗椭圆萝卜螺牧食损害能力研究

Ability of Elodea nuttallii to Resist Grazing by Radix swinhoei

观测椭圆萝卜螺（Radix swinhoei）对伊乐藻（Elodea nuttallii）植株造成的牧食损害程度,研究伊乐藻的抗牧食损害能力以及受损后的生长特性,进一步了解伊乐藻生态适应性以及入侵能力,为合理利用和控制伊乐藻提供依据。选取15~20 cm的伊乐藻嫩枝,除去附生生物,用蒸馏水冲洗干净,快速称量鲜重2 g。螺的类型据重量分为大螺（0.17±0.02）g、中螺（0.1±0.01）g和小螺（0.03±0.01）g。玻璃缸水平置于室内靠窗户的位置,加入2 L稀释10倍的Hoaglands培养液。试验组分3组,每组放1种大小的螺4只,螺在培养液中饥饿48 h后用于试验;对照组不放螺。每种处理3个重复,试验期15 d。螺主要取食伊乐藻茎干和顶芽,取食优先顺序为茎干、顶芽、叶。中螺危害最甚,该组中伊乐藻的生物量增量约为对照组的40%;大螺危害次之,小螺危害最小,2组中伊乐藻生物量增量分别占对照组的92%和96%。受牧食损害后的伊乐藻仍有较高的成活率,形成的断枝也有较高的萌发率,大螺、中螺、小螺组伊乐藻断枝上腋芽萌发的数量占原枝条数的比例分别为41.7%、22.6%和10%。椭圆萝卜螺可对伊乐藻造成明显的牧食损害,但伊乐藻抗牧食损害能力较强。

Elodea nuttallii,an annual submerged plant,was introduced to China in the 1980’s from North America and is widely used in water body restoration and aquaculture because of fast growth and high yield,with adequate nutrition and good palatability for fish. Research has confirmed that E. nuttallii growth is limited by environmental factors including illumination,p H and nutrients. However,we know little about E. nuttallii response to grazing by aquatic animals. In order to understand the resistance of this non-native species to grazing by herbivorous Radix swinhoei,we cultured E. nuttallii with R. swinhoei to study the effects of R. swinhoei grazing on E. nuttallii. Shoots of E. nuttallii（ 15- 20 cm） were rinsed with distilled water and co-cultured with R. swinhoei in Hoagland solution.Three treatments of R. swinhoei of differing size were prepared,（ 0. 17 ± 0. 02） g,（ 0. 1 ± 0. 01） g,（ 0. 03 ±0. 01） g,along with a control group,and the experiment was run in triplicate. Each treatment received four R.swinhoei and the cultures were observed for 15 days. During the experiment,the number and position of lesions caused by grazing were recorded. After 15 days,the biomass of E. nuttallii and R. swinhoei were measured and the germination of E. nuttallii buds was noted. Results show that stems and terminal buds were most damaged and the feeding priorities of R. swinhoei were stems,terminal buds and leaves. R. swinhoei in all cultures grazed on E. nuttallii,but those of medium size（ 0. 1 ± 0. 01） g had the most negative impact on the biomass gain of E. nuttallii,with a 40% biomass gain compared to that of the control group. The large size R. swinhoei（ 0. 17 ± 0. 02） g were next（ 92%） and the small size（ 0. 03 ± 0. 01） g had the least impact（ 96%）. Damaged E. nuttallii had high survival rates and the buds had high germination rates. Axillary buds germinated at the lesions,most frequently in cultures containing large individuals,where 41. 7% of the original branches developed axillary buds. The number of the axillary buds in the medium size group was 22. 6% and 10% in the small size group. R. swinhoei caused distinct damage to E. nuttallii,but it has strong resistance to grazing by R. swinhoei.