Gross Elisabeth M, Brune Andreas, Walenciak Oliver
Limnological Institute, Biology Department, University of Konstanz, Konstanz, Germany.
J Insect Physiol. 2008 Feb;54(2):462-71. doi: 10.1016/j.jinsphys.2007.11.005. Epub 2007 Nov 24.
Larvae of the freshwater moth Acentria ephemerella (Pyralidae, Lepidoptera) can fully develop on Myriophyllum spicatum, a submerged macrophyte containing 7-10% of its dry mass as tannins. We investigated the physicochemical gut parameters of larvae fed with M. spicatum or Potamogeton perfoliatus, a food plant lacking tannins, and the chemical fate of ingested polyphenols. Microelectrode studies revealed that larval midguts were slightly alkaline (pH 8) and had a positive redox potential. Whole guts were oxygen sinks owing to the oxygen demand of the gut contents. Oxygen penetrated the midgut up to 100 microm, but the centres of the foregut and midgut were always anoxic. The physicochemical parameters of the guts did not change with the food plant. The major tannin from M. spicatum, tellimagrandin II, was significantly depleted in the midgut and was not detected in faeces. In vitro studies indicated that tellimagrandin II is rapidly depleted mainly through oxidation, and hydrolysis might also occur. Our findings for A. ephemerella are compared with those for terrestrial Lepidoptera, and possible mechanisms for adaptations to tannin-rich food plants are discussed.
淡水蛾Acentria ephemerella（螟蛾科，鳞翅目）的幼虫能够在狐尾藻上完全发育，狐尾藻是一种沉水大型植物，其干物质中含有7%-10%的单宁。我们研究了以狐尾藻或穿叶眼子菜（一种不含单宁的食物植物）为食的幼虫的肠道理化参数，以及摄入的多酚类物质的化学命运。微电极研究表明，幼虫中肠呈弱碱性（pH 8），具有正的氧化还原电位。由于肠道内容物的需氧需求，整个肠道是氧气汇。氧气可穿透中肠达100微米，但前肠和中肠的中心始终缺氧。肠道的理化参数不会因食物植物而改变。狐尾藻中的主要单宁tellimagrandin II在中肠中显著减少，在粪便中未检测到。体外研究表明，tellimagrandin II主要通过氧化迅速减少，也可能发生水解。我们将A. ephemerella的研究结果与陆生鳞翅目的研究结果进行了比较，并讨论了适应富含单宁食物植物的可能机制。
