02483nas a2200181   4500008004100000020001400041245012900055210006900184260000800253300001200261490000700273520190200280100001902182700001602201700001702217700002102234856004602255       2002                        eng d  a0168-817000aUltrastructural study of cuticle formation during embryogenesis of the free-living marine nematode Enoplus demani (Enoplida)0 aUltrastructural study of cuticle formation during embryogenesis   cDec  a189-2030 v423 aCuticle formation during embryogenesis in the free-living marine nematode Enoplus demani (Enoplida) was studied electron microscopically. Cuticle formation begins in the three-fold loop embryo where epidermal microvilli with rounded tips are associated with the filamentous primordial cuticle. This coincides with proliferation of the cisternae of RER, Golgi bodies, multivesicular bodies and numerous transparent vesicles in the epidermal cells. In the four-fold loop embryo the epidermal microvilli are associated with the primordial cuticle, which is represented by a dense filamentous layer of uniform thickness. These microvilli are arranged into regular rows; their apical tips are flattened and filled with dense material. At pretzel I stage the space between epidermal microvilli becomes transparent and the first stratification occurs in the primordial cuticle. At pretzel 2 stage the cuticle is clearly stratified. The transparent space with longitudinally orientated fibres separates the filamentous basal layer from the dense striated cortex. A thin osmiophilic layer (epicuticle) covering the cortex appears. The number of Golgi bodies, cisternae of RER and multivesicular bodies in the epidermal cells peaks at pretzel 3 stage, the cuticle becomes much thicker and its filamentous basal layer is now distinctly stratified. The epidermal microvilli are slightly shorter than at previous stages. At pretzel 4 stage (1-2 days before hatching), the epidermal microvilli disappear at the interchordal regions. The cuticle of newly hatched first stage juveniles includes an external amorphous layer, an osmiophilic epicuticle, a striated cortex, a layer of thick longitudinal fibres and a basal layer consisting from several sublayers of different structure. Cuticle formation in nematodes is discussed in the light of the hypothesis of monophyly of the moulting invertebrates (Ecdysozoa).1 aYushin, V., V.1 aCoomans, A.1 aBorgonie, G.1 aMalakhov, V., V.  uhttps://nematodes.myspecies.info/node/192