MYCETOCYTE INCLUSION IN THE OOCYTES OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE)

This study investigates the process of transfer of endosymbiotic organ isms from adult silverleaf whitefly, Bemisia argentifolii Bellows & Pe rring (Bellows et al. 1994) (also known as Bemisia tabaci B biotype), into the developing ova. In dissected females, individual mycetocyte c ells containing microorganisms were scattered singly among developing oocytes. Oocytes with mycetocytes included were first observed in fema les 16 h after emergence. The mean number of oocytes >0.1 mm in length per female increased through the 4th d after adult eclosion then leve led off. The number of oocytes containing mycetocytes followed a simil ar pattern. Stages of mycetocyte inclusion followed a pattern based on the size of the oocyte. Oocytes became associated with a single mycet ocyte cell when they were a mean of length of 0.135 +/- 0.003 mm (mini mum of 0.11 mm). All mature oocytes examined contained a mycetocyte. M ycetocytes were observed inside a common membrane with oocytes, at wha t becomes the pedicel end of the ova, when oocytes were an average of 0.147 +/- 0.004 mm long. In the final stages of ovum development, the plasma of the oocyte completely surrounded the mycetocyte and the chor ion was thickened. Mycetocytes included in oocytes had a mean length o f 33 +/- 0.4 mu m and width of 27 +/- 0.5 mu m. Although the females t hat were dissected had the opportunity to oviposit, some retained seve ral fully developed ova. Because inclusion of mycetocytes into oocytes is a continuous process, manipulations of endosymbionts before inclus ion into the oocytes should be possible at any time during adult life; however, earlier treatment of an individual would probably affect a g reater proportion of their offspring.