Department of Entomology, University of Kentucky, S-225 Agriculture Science Center North, Lexington, KY 40546-0091, USA.
Oecologia. 2010 Jun;163(2):313-22. doi: 10.1007/s00442-009-1551-2. Epub 2010 Jan 5.
Egg predation and cannibalism are common phenomena in predatory ladybirds despite the presence of defensive alkaloids. Consumption of heterospecific eggs negatively affects survivorship and development; however, intraspecific variation in quantities of alkaloids and post-ingestion responses to con- and hetero-specific alkaloids, are not well understood. We examined variation in the quantity of alkaloids in eggs of Harmonia axyridis (Pallas), Coccinella septempunctata L., and Hippodamia convergens (Guérin) using gas chromatography-mass spectrometry, and show a link between heterospecific alkaloids and their toxicity and/or costs by feeding high and low alkaloid eggs to first instar H. axyridis and C. septempunctata. The repeatability of alkaloid measurements in eggs in an egg cluster was high; however, the amount of alkaloids varied significantly between egg clutches within and among females. This variation affected egg consumption by C. septempunctata when fed H. axyridis eggs. Harmonia axyridis accumulated their own alkaloid by cannibalism and synthesized it de novo, but C. septempunctata lost some portion of the consumed conspecific alkaloids. Both species lost most of the consumed heterospecific alkaloids, but C. septempunctata died within 3 days. Most H. axyridis survived to the second instar, but C. septempunctata alkaloids led to a significant reduction in weight gain compared to an aphid control. In addition, ingestion of high alkaloid C. septempunctata extended development of H. axyridis compared to the aphid control or conspecific eggs. Harmonia axyridis had greater abilities to process ingested con- and hetero-specific alkaloids compared with C. septempunctata, which may, in part, explain their interspecific interactions in nature.
尽管捕食性瓢虫体内存在防御性生物碱，但卵捕食和同类相食仍是常见现象。摄食异种卵会对存活率和发育产生负面影响；然而，同种内生物碱含量的变化以及对同种和异种生物碱的摄入后反应尚不清楚。我们使用气相色谱-质谱法检测了异色瓢虫（Pallas）、七星瓢虫（L.）和茄二十八星瓢虫（Guérin）卵中的生物碱含量，并通过向异色瓢虫和七星瓢虫的一龄幼虫投喂高、低生物碱卵，显示了异种生物碱与其毒性和/或成本之间的联系。在卵簇中，卵内生物碱测量的可重复性很高；然而，卵内生物碱的含量在同一雌虫的不同卵簇和不同雌虫之间存在显著差异。这种变异影响了七星瓢虫对异色瓢虫卵的摄食。异色瓢虫通过同类相食积累自身生物碱并从头合成，但七星瓢虫会失去部分消耗的同种生物碱。两种物种都会失去大部分消耗的异种生物碱，但七星瓢虫在 3 天内死亡。大多数异色瓢虫存活到二龄，但七星瓢虫的生物碱导致体重增加明显减少，与蚜虫对照相比。此外，与蚜虫对照或同种卵相比，摄食高生物碱七星瓢虫延长了异色瓢虫的发育。与七星瓢虫相比，异色瓢虫具有更强的处理摄入的同种和异种生物碱的能力，这在一定程度上可以解释它们在自然界中的种间相互作用。
