EMBRYOLOGICAL DEVELOPMENT OF Tetranychus cinnabarinus (Boisduval) (ACARI: TETRANYCHIDAE), PEST OF CARNATION (Dianthus caryophyllus L.)

Abstract

The pursuit of several stages in the embryo­logy of carmine spider mite Tetrany­chus cinnabarinus (Boisduval) (Acari: Tetranychidae) was realized on sec­tionated eggs by optic and electronic microscopy. The egg of this species is the centro­lecithal type, spheric in form, its sur­face is soft and its consistency smooth and flexible. lt's envelope results of three layers or strata ultrastructurally well-differentiated each one. The egg­diameter varíes from 125 to 150 The initial development stage is the combination cleavage, at last of which, it is formed, the blastoderm, a single layer of cells covering completely the yolk, is formed. The development process continues then in the 24-34 hours egg with the germ band forma­tion by cell proliferation of blastod­derm. The segmentation (metameriza­tion) to germ band begins at 36 hours and results in the formation of six prosomatic segments at 60 hours. These prosomatic segments give origin to the definitive larval appendages, at 96 hours. The central nervous system is totally formed about 72 hours mean­while the germ band retirement. In the 96 hours developing egg, it is possible to observe the embryonic respiratory system through the egg envelope. The digestive and excretory system forma­tion is shared by endodermic cells of the posterior proliferation and vitel­lophags cells. In the mouthparts, for­mation intervenes the two former appendages pairs. The musculature is completely formed in the 144 hours egg, with main muscle groups well differentiate. The structures as ocular spots and tegument, of endodermic origin, were only observed to 144 hours. The total egg stadium takes 168 hours to be completed.