1,720,991 research outputs found
EGG CHORION ARCHITECTURE IN STICK INSECTS (PHASMATODEA)
No full textComparative analysis of egg chorion architecture by scanning and transmission electron microscopy is reported in about 50 species of stick insects (Phasmatodea). Particular attention has been paid to: (1) synthesis and structure of egg shell layers; (2) egg shape; (3) morphology of the external chorionic surface; (4) position and structure of the micropylar plate and its cup; (5) morphology and details of the operculum, including capitulum or pseudocapitulum; and (6) posterior pole differentiation (the so-called polar mound). The taxonomic value of the various characters is discussed: some are clearly species-specific, while others (such as general egg shape and micropylar plate) appear to reflect phylogenetic relationships of higher rank. Intraspecific features, such as the fine chorionic and opercular patterns of Bacillus and Clonopsis, have been recognized. In natural hybrids, egg chorion architectures were related to that of the parent species, resembling one of the parents in some cases and being intermediate between the 2. The study of the Phasmatodea egg can provide much taxonomic information that is useful in the definition of natural groups
An ultrastructural investigation on vitellophage invasion of the yolk mass during and after germ band formation in the stick insect Carausius morosus
No full textIl disco terminale delle larve di Pachyteles (Coleoptera: Carabidae: Paussinae): morfologia e ultrastruttura
No full textFURTHER OBSERVATIONS ON THE ULTRASTRUCTURE OF MATURE SPERM OF SCUTIGERA-COLEOPTRATA (L) (CHILOPODA, SCUTIGEROMORPHA)
No full textMature sperm of Scutigera coleoptrata, taken from the spermatheca, were investigated by scanning (SEM) and transmission (TEM) electron microscopy. The only sperm type observed was of enormous length, the head measured about 500-mu-m and the tail up to 3.5 mm. The acrosome, the smallest found in Chilopoda sperm (0.25-mu-m), showed a bilayered arrangement, described here for the first time. The tail exhibited the typical 9 + 2 microtubular pattern surrounded by a striated cylinder and four mitochondrial derivatives. These were anchored to the striated cylinder by peculiar mitochondrial bridges. The end-piece, never previously described in Scutigeromorpha, showed a small 'plume' under TEM
Spermatophore development and sperm ultrastructure in Craterostigmus tasmanianus (Chilopoda, Craterostigmomorpha)
No full textSpermatophore development and ultrastructure of the mature sperm of Craterostigmus tasmanianus were studied using light and electron microscopy. In C. tasmanianus, as in the Scolopendromorpha, the spermatophore develops within the vas deferens. The latter consists of three parts, each with a different morphology. The first may be involved in guiding the sperm to roll up into typical ring-like structures, while the other two, which show an evident secretory activity, secrete the acellular wall of the spermatophores. The ultrastructure of mature spermatozoa showed that a very close similarity exists between Craterostigmorpha and Lithobiomorpha, especially regarding the organization of the connecting piece. Based on this similarity, we consider the Craterostigmomorpha together with the Scolopendromorpha, Geophilomorpha and Lithobiomorpha (=Pleurostigmophora) to be the sister group of the Scutigeromorpha
AN ULTRASTRUCTURAL INVESTIGATION ON VITELLOPHAGE INVASION OF THE YOLK MASS DURING AND AFTER GERM BAND FORMATION IN EMBRYOS OF THE STICK INSECT CARAUSIUS-MOROSUS BR
No full textDeveloping embryos of the stick insect Carausius morosus were examined ultrastructurally with a view to studying vitellophage invasion of the yolk mass during and after germ band formation. Newly laid eggs in C.morosus have a unique yolk fluid compartment surrounded by a narrow fringe of cytoplasm comprising several small yolk granules. Vitellophages originate mainly from a thin layer of stem cells, the so-called yolk cell membrane, interposed between the germ band and the yolk mass. Throughout development, a thin basal lamina separates the yolk cell membrane from the overlying embryo. Vitellophages extend from the yolk cell membrane with long cytoplasmic processes or filopodia to invade the central yolk mass. Along their route of entrance, filopodia engulf portions of the yolk mass and sequester it into membrane-bounded granules. As this process continues, the yolk mass is gradually partitioned into a number of yolk granules inside the vitellophages. Later in development, the yolk cell membrane is gradually replaced by the endodermal cells that emerge from the anterior and posterior embryonic rudiments. From this stage of development onwards, vitellophages lophages remain attached to the basal lamina through long filopodia extending between the endodermal cells. Yolk confined in different vitellophagic cells appears heterogeneous both in density and texture, suggesting that yolk degradation may be spatially differentiated
Biology and functional morphology of Pachyteles larvae (Coleoptera: Carabidae: Paussinae)
No full textConfocal scanning laser microscopy of the follicular epithelium in stick insect ovarioles
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The terminal disk of Pachyteles larvae (Coleoptera: Carabidae: Paussinae): morphology and ultrastructure
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