Feeding preferences of red swamp crayfish (Procambarus clarkii) grazing on six living and decaying submerged macrophyte species

原产美国南部和墨西哥东北部的克氏原螯虾是目前全球入侵最广的小龙虾,也是对淡水生态系统最具破坏性的物种之一,其对栖息地沉水植物的现存量构成严重威胁,然而目前对克氏原螯虾摄食沉水植物的机制还知之甚少.本文选择6种沉水植物,研究克氏原螯虾对浅水湖泊常见的沉水植物穗花狐尾藻(Myriophyllum spicatum)、密刺苦草(Vallisneria denseserrulata)、轮叶黑藻(Hydrilla verticillata)、菹草(Potamogeton crispus L.)、马来眼子菜(Potamogeton malaianus)和金鱼藻(Ceratophyllum demersum)的新鲜植株和分解腐烂后的植株的摄食偏好及原因,结果表明克氏原螯虾对沉水植物新鲜植株选择逗留偏好为:最偏爱逗留在轮叶黑藻区,在穗花狐尾藻、密刺苦草和马来眼子菜3种植株区逗留频次无区别,而在金鱼藻区逗留频次显著最低,6种植物湿重减少量与逗留偏好趋势相似;相对各新鲜植株,克氏原螯虾均更喜欢逗留在分解腐烂8 d或12 d后的植物碎屑区域,相应分解腐烂8 d或12 d植物湿重降低量也显著更高.6种植物新鲜植株总酚类含量均显著高于分解腐烂后的植株,其中穗花狐尾藻新鲜和分解腐烂后的植株的总酚类含量始终显著高于其他5种植物.结合植物总酚类指标和摄食偏好结果,表明克氏原螯虾对沉水植物的摄食具有选择性,相对新鲜植物更喜摄食腐烂后的碎屑,总酚类不是影响其选择的关键因子.;The Procambarus clarkii, native to the southern United States and north-eastern Mexico, is currently the most widely distributed craysh and one of the invasive species with the most devastating impacts on freshwater ecosystems. It poses a serious threat to the standing stocks of native submerged macrophyte, yet little is known about the feeding mechanisms of this introduced crayfish on submerged macrophytes. In this study, we assessed the preference of P. clarkii forsix living and decaying submerged macrophytes, namelyMyriophyllum spicatum,Vallisneria denseserrulata,Hydrilla verticillata, Potamogeton crispus L., Potamogeton malaianus,andCeratophyllum demersum. These macrophyte species are widely distributed in Chinese shallow lakes. The habitat preferences of P. clarkii for living submerged macrophytes was in the following order:H. verticillata > M. spicatum=V. denseserrulata=P. malaianus >P. crispus L. >C. demersum, and losses in macrophyte weight were consistent with staying preferences. Compared with living submerged macrophyte treatments, P. clarkii preferred to stay in macrophyte areas decaying for 8 or 12 days. The wet weight of decaying macrophytes also decreased more rapidly than that of living macrophytes. The contents of total phenols (TPh) of each living macrophyte were significantly higher than the decaying macrophyte. Contents of TPh of living and decaying M. spicatum were significantly higher than those of other macrophytes. In summary, our results suggested thatP. clarkii preferred decaying to living macrophytes. The contents of TPh of submerged macrophytes were not critical in P. clarkii's feeding selection.