Characterization and functions of the whitefly egg pedicel.

For the silverleaf whitefly, Bemisia argentifolii (Bellows and Perring) (Homoptera: Aleyrodidae), scanning and transmission electron microscopic techniques were used to observe the characteristics of egg oviposition into both plant cells/tissues and artificial membranes, and to document the morphology of mature egg pedicles removed from the ovaries of females. The exterior of the distal portion of the pedicel consisted of a tangled array of fibrous structures (0.2-0.3 microm in diameter) that constituted about 20-25% of the outer diameter of the pedicel. The attachments of the fibers to the core of the pedicle suggested that the pedicel functions as the collector and conduit for water (vapor), and perhaps solute movement into the egg. Silverleaf whitefly eggs on membranes were incubated at various levels of relative humidity and the eggs were scored for egg hatch. At 98-100% rh, the percentage egg hatch was 86-98%. At lower humidity ranges of 0-20, 55-65, and 75-85% rh, none of the eggs hatched. Media (solute) uptake by silverleaf whitefly egg pedicels was determined by exposing the pedicel side of eggs oviposited on membranes to media solutions containing the high molecular weight polysaccharide, [(14)C]-inulin. Solute uptake by the pedicel and movement into developing silverleaf whitefly eggs were demonstrated using [2-(14)C]-acetate, and assaying for radioactivity in hatched nymphs. These studies, using exposure of pedicels to relative humidity and radiolabeled materials, demonstrate that whitefly egg hatch is dependent upon water uptake by the pedicel, and that the pedicel has the ability to transport solutes into the developing egg.