|Freeman, Thomas - NORTH DAKOTA STATE UNIV|
Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 18, 1999
Publication Date: February 1, 2000
Citation: Nelson, D.R., Freeman, T.P., Buckner, J.S. 2000. Waxes and lipids associated with the external waxy structures of nymphs and pupae of the giant whitefly, Aleurodicus dugesii. Comparative Biochemistry and Physiology B. 125(2):265-278. Interpretive Summary: The giant whitefly, Aleurodicus dugesii, has been a pest of hibiscus in southern California and more recently it has become a concern on avocado, where heavy infestations prevent fruit formation. They have been found on bananas, citrus and bird of paradise plants, etc. As with other whitefly adults, the adults produce copious amounts of waxy particles with which they cover themselves and also shed particles over their surroundings, including their eggs and immature stages. However, this species differs from other whiteflies in that the nymphs also produce copious amounts of several types of waxy materials. Filaments which hang down from the leaf surface like hair with a length of 5 to 8 cm and appear to form a barrier which would be difficult for parasites and predators to penetrate to attack either immature stages or adults. Copious amounts of two types of waxy particles which cause both the upper and lower leaf surfaces to appear a light gray color, completely camouflage the nymphs, and may interfere with plant photosynthesis and respiration. The external lipids of whiteflies form the interface between the predator and its prey and thus, may play a role in the parasitization or predation of the insect. In another whitefly, Aleyrodes singularis, it has been shown that the waxy particles of the whitefly interfered with the host seeking and parasitization by the parasitoids Encarsia spp., a genus of parasitoids being widely studied as biological control agents. In this report, we describe the external lipids of the immature stages of A. dugesii.
Technical Abstract: The nymphs and pupae of the giant whitefly, Aleurodicus dugesii, produce large quantities of external lipids, both as waxy particles and as waxy filaments. The nymphs and pupae extrude filaments from two dorsal rows of 5 pores each. Filaments can attain lengths of 5 to 8 cm. The external lipids of nymphs and pupae consist largely of long-chain aldehydes, alcohols, acetate esters and wax esters. Hydrocarbons are minor components. Soon after hatching, the nymph produced an unidentified waxy fringe extruded laterally from its margin. After molting to the second instar, long, hollow, waxy filaments were produced by the immature stages. The major lipid class associated with the filaments was saturated wax esters (89%); mainly C44, C46 and C60. Associated with formation of the filaments were waxy particles in the shape of curls, which peeled off of the extruding filaments. Similar but more tubular-shaped curls were also produced by numerous lateral pores so that eventually the curls completely camouflaged the nymph. The major lipid class of the curls was wax esters (50%), mainly C44 and C46. The cuticular surface lipids of the nymphs were mainly long-chain aldehydes (43%) and wax esters (27%). Unsaturated fatty acid moieties constituted 2% and 19% of the wax esters of curls and nymph cuticular surface lipids, respectively. The major lipid classes of pupae and of their palisade were long-chain aldehydes and alcohols. No unsaturated wax esters were detected in the filaments, but 30% of pupal and 21% of palisade surface wax esters were unsaturated in their fatty acid moieties, 16:1, 18:1 and 20:1.