Feeding Biology of the Silverleaf Whitefly (Homoptera: Aleyrodidae)

銀葉粉蝨（同翅目：粉蝨科）的取食生物學

Allen Carson Cohen ； 朱昌祺(Chang-chi Chu) ； Thomas J. Henneberry ； Thomas Freeman ； Dennis Nelson ； James Buckner ； Dennis Margosan ； Patrick Vail ； Louis H. Aung

《中華昆蟲》 18卷2期 (1998/06) Pp. i+65-82

https://doi.org/10.6660/TESFE.1998007

摘要

Whitefly feeding biology is complex and includes the location of appropriate sites to probe leaves so that minor veins can be located. Since survival of the nymphal stage of the silverleaf whitefly Bemisia argentifolii Bellowa and Perring (Homoptera: Aleyrodidae) requires stylet penetration of the smallest veins in host plant leaves, an elaborate series of behavioral acts must be performed for the insect to reach its target. Our studies, using light and electron microscopy as well as confocal imaging, reveal that successful feeding always involves probing of minor veins that contain no more than three xylem elements. There are distinct surface structures such as lamina trichomes and elongated epidermal cells that serve as guides for a first instar nymph (crawler) to begin its probing at appropriate places. The nymphs use a specialized saliva to produce a sleeve-like structure called a salivary sheath that guides the stylets (hollowed, elongated and interlocking maxillae and mandibles) to the minor veins. The sheaths are often sinuous and branched. Branching takes place both in the mesophyll and at veins. Most of the sheath material inside the leaf is extra-cellular and is built in the extensive air space between spongy parenchyma cells. Only a small portion of the sheath is found inside cells, that portion being in epidermal cells. We found almost no evidence of stylet or sheath penetration into parenchyma or palisade cells. When a sectioning technique was used, it appeared that some feeding sheaths led from the plant surface to sites other than vascular tissue. However, when non-sectioned leaves were stained and cleared so that entire sheaths could be viewed intact, it became apparent that nymphs that succeeded in developing beyond the first instar always made contact, via salivary sheaths, with veins. Sheaths were up to 140μm long and about 2μm in diameter at their widest dimension. Sheaths had the appearance of fused beads. The sheaths were occasionally glued to cell walls and made contiguous contact between the plant leaf surface where penetration originated, proceeding all the way to the veins. Some sheaths terminated blindly without reaching a vascular bundle, and these sheaths were invariably sealed at the end. It appeared from our studies that successful feeding always involved intact sheaths. The relative success of silverleaf whitefly on different species of host plants is, in part, attributable to the geometry of the feeding arrangement in relationship to the availability of minor veins in the host plants. This accounts for the high success of this species on cantaloupe and other cucurbit hosts and the low success on lettuce, the former having more than twice the amount of vascular bundle tissue than the latter.

關鍵字

Bemisia argentifolii ； Aleyrodidae ； Homoptera ； salivary sheaths ； feeding biology ； cotton ； stylets ； vascular bundles

並列摘要

銀葉粉蝨(Bemisia argentifolii Bellows & Perring)具有刺吸式口器，其取食習性複雜。粉蝨必需在寄主植物葉片背面尋找適宜部位，使其口針容易穿刺到葉片內的細小葉脈以便取食。因為銀葉粉蝨若蟲的生存需要把口針穿刺到最細小的葉脈，它們必定採用一系列的靈巧動作才能達到目的。我們用光學顯微鏡、電子顯微鏡和影像顯微鏡觀測發現，粉蝨取食都是穿刺到木質部不超過三根導管的小葉脈。第一齡爬行若蟲總是以差別明顯的表皮結構(如葉片絨毛和細長形的上表皮細胞)為線索，在葉片上尋找適宜場所開始進行穿刺。這些若蟲用其特殊的唾液形成一袖狀結構，稱為唾液鞘(asalivary sheath)，用來引導口針找到小葉脈。唾液鞘常彎曲分枝，而分枝的部位發生在葉肉和維管束內。唾液鞘在葉片內位於細胞外面，海綿狀薄壁細胞之間空間，只有很小部分的唾液鞘位於外表皮細胞內。我們還沒有發現口針或唾液鞘深入到薄壁細胞或柵欄細胞中。應用切片技術，我們在維管束外的組織中發現過一些從植物面到取食點的取食痕跡。然而，當我們用整葉染色透明技術使唾液鞘清晰可辨時發現，凡是發育超過第一齡的若蟲，其口針都是通過唾液鞘與維管束相連。唾液鞘可長達140μm，最寬處的直徑約2μm，看起來像一連串合併的空泡，有的黏附在細胞壁上，經過鄰近的細胞表面，一直延伸到維管束。沒有達到維管束的唾液鞘，其未端總是封閉的。我們的研究證明，形成完整的唾液鞘是取食成功的關鍵。銀葉粉蝨對不同寄主植物種類的喜好，往往取決於維管束的數量。銀葉粉蝨喜好甜瓜和其它葫蘆科寄主而不喜好萵苣就是一個證明。

並列關鍵字

銀葉粉蝨 ； 維管束 ； 取食行為 ； 唾液鞘