A possible pathway of chitin synthesis as revealed by electron microscopy in Tetranychus urticae (Acari, Tetranychidae)

Enhanced acaricidal activity of ricinine achieved by the construction of nano-formulation using amphiphilic block copolymer

Amphiphilic block copolymer PEO–PCL improves the encapsulation of ricinine and enhances the acaricidal efficiency of the pesticide on V. unguiculata (L.) when compared to the formulations made by surfactants.

The fine structure of secretion in Hyalophysa chattoni: formation of the attachment peduncle and the chitinous phoretic cyst wall

The settling tomite stage of the apostome Hyalophysa chattoni secretes a phoretic cyst wall composed of chitin, mucopolysaccharides, and protein. Within 1 1/2 h after settling, an electron-dense proteinaceous cyst layer (the outer layer) is formed from secretions originating at the base of the kineties and from the thick pellicular layer between the kineties. The inner cyst layer, composed primarily of chitin (acidic and neutral polysaccharides are also present), is secreted across the entire cell surface. Cyst wall formation is completed within 6 h. The fine structure of endocyst secretion resembles stages in the secretion of chitin by fungi, yeasts, and arthropods. A proteinaceous attachment peduncle is secreted to anchor the cell to a shrimp host and is formed by the release of electrondense dense secretory bodies from the cell's ventral surface.

Ultrahistology of oogenesis and vitellogenesis in the spider mite Tetranychus urticae

Histology of the ovary of the spider mite Tetranychus urticae is described light and electron microscopically with special reference to oogenesis and vitellogenesis of this mite. Morphology of the ovary is comparable to the typical sac-like chelicerate ovary with oocytes protruding from the ovarian surface, thus resulting in a grape-like appearance. According to different oogenetic stages, a germ, pre-vitellogenic and vitellogenic region can be observed. Oogonia and primary oocytes characterized by extranuclear material or 'yolk nuclei' are situated in the germ region. Primary oocytes develop into three-nucleated nurse cells situated in the periphery of the pre-vitellogenic region, and into pre-vitellogenic oocytes protruding from the ovarian surface. Growth of oocytes is performed while they are in ovarian pouches by uptake of nurse cell cytoplasm and following extraovarian yolk precursors. Intraoocyte yolk synthesis interpreted from altered cytoplasmic organelles also occurs. Processes taking place during oogenesis and vitellogenesis in T. urticae are compared to published information on yolk synthesis of other animal species.