Marcella Carcupino

Uterine morphology during the annual cycle in Chalcides ocellatus tiligugu (Gmelin) (Squamata: Scincidae)

ABSTRACT

Morphological organization of the male brood pouch epithelium of Syngnathus abaster Risso (Teleostea, Syngnathidae) before, during, and after egg incubation.

The morphological organization of the male brood pouch epithelium of Syngnathus abaster, before, during, and after the breeding period, was observed by light and electron microscopy. Before gestation, the epithelium of the pouch wall was compact and consisted of three kinds of cells: typical epithelial cells (pavement cells), mitochondria-rich cells (MR cells), and, presumably, differentiating MR cells. In this stage, very few capillaries were observed beneath the epithelium. During egg incubation, the capillaries increased in number and size, large intercellular spaces formed among epithelial cells at their basal sides, MR cells were abundant, and differentiating MR cells were only occasionally observed. After incubation, MR cells degenerated by necrosis and apoptosis. The intercellular spaces between the epithelial cells disappeared and the number and size of the capillaries beneath the epithelium decreased. The presence of MR cells during gestation and their degeneration after incubation suggest that these cells play a pivotal role in the physiological functions of the brood pouch. The similar cytological characteristics of syngnathid pouch MR cells and chloride cells of the teleostean gills suggests that the Syngnathidae brood pouch is involved in osmoregulation of the fluid surrounding the developing embryos.

Egg chorion architecture in stick insects (Phasmatodea)

Abstract Comparative 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.

Spermiogenesis in Chalcides ocellatus tiligugu (Gmelin) (Squamata, Scincidae): An electron microscope study

Abstract At the end of spermiogenesis in Chalcides ocellatus tiligugu the acrosomal complex is constituted by a homogeneous anterior cap derived from the acrosomal vesicle and by a paracrystalline posterior cap that arises from nuclear membrane proliferation. During the spermiogenetic process, the spherical nucleus becomes elongated and cylindrical in shape, and assumes a homogeneous appearance because its chromatine condenses. At the onset of spermatid elongation, a set of microtubules appears as a helix surrounding the nucleus. At the end of elongation, the microtubules become parallel to the main axis of the nucleus. From the early stage of spermiogenesis, the two centrioles (proximal and distal) and the flagellum are situated at the posterior pole of the nucleus. The two centrioles are encircled by the dense connecting piece, which is continuous with the nine accessory fibers surrounding the flagellum. At a later stage, the mitochondria form the mitochondrial sheath and four rings of electron‐dense ma...

The diverticulated crop of adult Phormia regina.

The crop of adult Phormia regina consists of a duct that diverges from the esophagus, just in front of the cardia, and extends ventrally and posteriorly into the thorax and abdomen where it forms a bilobed sac. Flattened epithelial cells produce the cuticular lining of the crop. When empty, or partially full, the epithelial cells and cuticular lining form folds extending into the lumen, thus providing for expansion as the crop sac fills. Covering the sac on the hemolymph side is a layer of anastomosed, intrinsic muscles connected to one another by intercellular cytoplasmic bridges. Mitochondria are located at the periphery of the sarcomere. Also inside the sarcomere are glycogen, sarcoplasmic reticula, and transverse tubular systems (T-system). I, A, and Z-bands are present and the Z-bands are not in register making the muscle-type supercontractile. Important structures, not previously researched and associated with the crop muscles, are the crop nerves. Coming off the corpora cardiaca, and running down each side of the crop duct, is a pair of nerves, each housing several axons. These nerves extend to and branch over the crop sac. Here they penetrate the muscle mass and form neuromuscular junctions where electron-dense droplets of neurosecretion are released. Based on the literature, and research in our laboratory, it has now been shown that these nerves carry adipokinetic hormone, Drosophila insulin-like peptide, and a dromyosuppressin-like neuropeptide.

Fine structure of the chorion and micropyle of the sea bass egg Dicentrarchus labrax (Teleostea, Percichthydae)

Abstract The fine structure of the chorion and micropyle of mature unfertilized eggs of the sea bass Dicentrarchus labrax was examined by scanning and transmission electron microscopy. The chorion consists of three layers: a thin electrondense outer layer, a paracrystalline middle layer and a thick inner layer consisting of 12 electrondense filamentous lamellae alternating with interlamellar material of lower electrondensity. The two more external layers are crossed by pore canals opening on the egg surface. The funnel‐type micropyle is located at the animal pole of the egg. The walls of the micropylar canal have circular, rib‐like thickenings reflecting the stratified inner layer of the chorion. The results are discussed and compared with those in other Teleostea.

Fine structure of the spermatozoon of the strepsipteran Xenos moutoni.

Spermatozoa of Xenos moutoni De Buysson belonging to the order Strepsiptera (Insecta) were examined by electron microscopy. The spermatozoon was seen to have an elongated head and a tail containing a 9+9+2 axoneme and two mitochondrial derivatives of equal size. The pear-shaped acrosome is characterised by a mono-layered structure and terminates anteriorly forming two pyramidal evaginations. The nucleus exhibits an external portion of dense chromatin and an internal one of uncondensed material. The latter occupies a central position at the base and becomes progressively peripheral at the apex. The tail is long and in its final portion the axoneme loses its elements progressively. These results have been compared with the ultrastructure of the spermatozoa of Coleoptera which have been considered as a sister group of Strepsiptera.

Ultrastructure of the spermatozoon ofElenchus japonicus and its bearing on the phylogeny of strepsiptera

The fine structure of the mature spermatozoon of the strepsipteranElenchus japonicus Esaki and Hashimoto (Elenchidae) is described using transmission electron microscopy. The spermatozoon was seen to have an elongated head, a tail containing a 9 + 9 + 2 axoneme, two mitochondrial derivatives and two accessory sheaths. The monolayered acrosome is conical in shape while the nucleus exhibits an internal channel of uncondensed chromatin. The tail is long, and in its final portion, the axoneme, loses its elements progressively. These results are compared with the sperm ultrastructure ofXenos moutoni De Buysson (Stylopidae) and with those of other insect orders, particularly the Coleoptera.

Morphology and ultrastructure of the cephalic vesicles in two species of the Gonatopus genus: Gonatopus camelinus Kieffer and Gonatopus clavipes (Thunberg) (Hymenoptera, Dryinidae, Gonatopodinae)

Summary The cephalic vesicles of the immature endo-ectoparasitic larvae of Gonatopus camelinus Kieffer and Gonatopus clavipes (Thumberg) were studied using light and electron microscopy. The vesicles appear as hollow evaginations of the cephalic body wall and their tegument consists of a monolayered epithelium externally surrounded by a permeable cuticle. In the first larval instars, the epithelial cells are pyramid-shaped and separated by large intercellular spaces. In the last larval instars they are polyhedral and the intercellular spaces are no longer evident. The vesicles have no connection with the gut of either the host or the larva. These data suggest that nutrients are absorbed by the dryinid larva from the haemolymph of the host through the permeable surface of the cephalic vesicles, where they are stored in the lumen and enter the larval haemolymph without passing through the gut. In all immature larval instars the mouth is closed.

Testis morphology and spermatogenesis in two species of Elenchus (Strepsiptera : Elenchidae)

Testes ultrastructure and spermatogenesis were studied in two species of Strepsiptera (Insecta), namely, Elenchus tenuicornis and E. japonicus, using light and electron microscopy. In both species, the testis is paired and consists of several large irregularly shaped follicles. Each follicle consists of a single clone of germ cells surrounded by a thin epithelium. During the larval and pupal stages, all the germ cells of each testis develop synchronously, and at eclosion, the gonads contain solely mature sperm. One of the most interesting findings is the morphogenesis of a large nuclear vesicle bounded by the fenestrate part of the nuclear envelope. This vesicle contains an electron-dense spherical structure, the chromatoid body. At the end of spermiogenesis, both the nuclear vesicle and its chromatoid body are eliminated with the excess cytoplasm. Large drops of residual cytoplasm containing several nuclear vesicles are present in the lumen of the testis and inside the cytoplasm of phagocytic cells. 0 1998