Ultrastructure and cytochemistry of the pearl gland in Piper regnellii (Piperaceae)

Pearl glands are scattered throughout the lamina of developing leaves and rarely found on adult leaves of Piper regnellii (Piperaceae). The pearl gland is a bicellular secretory trichome composed of a short broad basal cell and a spatula-like, semiglobular apical cell. Four different stages of the pearl grand were determined during its ontogenesis: origin, pre-secretory, secretory and post-secretory. During the pre-secretory stage, mitochondria, ribosomes, dictyosomes, rough endoplasmic reticulum, and plastids with electron dense inclusions were present in the cytoplasm of the apical cell. During the secretory stage, the most remarkable characteristics of the apical cell are the proliferation of dictyosomes and their vesicles, rough endoplasmic reticulum, and modified plastids. At this stage, electron-dense oil drops occur in the plastids as well as scattered within the cytoplasm, proteins and polysaccharides are seen in the plastids, vesicles, and vacuoles. Only polysaccharides are present in the periplasmic space, wall cavities, and on the surface of the apical cell. The polysaccharides are one of the main components of the mucilagenous exudate that covers the developing leaf structures. The apical cell of the senescing trichomes undergoes a progressive degeneration of its cellular components, the plastids being the first organelles to undergo lysis.

Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): Developmental ultrastructure and secretion in relation to function

center dot Background and Aims Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc.center dot Methods Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber.center dot Key Results Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative.center dot Conclusions the continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality.

Ontogenesis, structure and ultrastructure of Hymenaea stigonocarpa (Fabaceae : Caesalpinioideae) colleters

The genus Hymenaea is characterized by a great diversity of secretory structures, but there are no reports of colleters yet. The objectives of this study are to report the occurrence and describe the origin and structure of colleters in Hymenaea stigonocarpa Mart. ex Hayne. Shoot apex samples were collected, fixed, and processed for light microscopy, scanning electron microscopy, and transmission electron microscopy as per usual methods. Colleters occur predominantly on the stipule's adaxial side. These structures are found at the base on a narrow strip, corresponding to the median vein up to half the length of the stipule. When present on the abaxial side, they are concentrated at the base and restricted to the margins. Colleters develop from the protoderm; they are elongate and club-shaped. Their body has no stratification; their surface cells differ from the inner cells only in position and presence of cuticle. Colleter cells have thin walls, dense cytoplasm, large nuclei, many mitochondria, rough endoplasmic reticulum, and abundant dictyosomes. Histochemical tests with Ruthenium red showed pectic compounds in the cytosol. In H. stigonocarpa, colleter arrangement is compatible with the hypothesis that they protect shoot apex. In this species, protection is reinforced by the sheath formed by the stipule pairs.

Ultrastructure of the intercellular protuberances in leaves of Paepalanthus superbus Ruhl. (Eriocaulaceae)

Folhas adultas de Paepalanthus superbus mostram protuberâncias intercelulares, entre a parede periclinal interna das células epidérmicas e superfície de células parenquimáticas; depósitos semelhantes ocorrem na superfície das células parenquimáticas do mesofilo. Estas protuberâncias são mais proeminentes ao redor de células parenquimáticas, formando uma estrutura que lembra uma cápsula gelatinosa. Testes histoquímicos com vermelho de rutênio evidenciam sua natureza péctica, com inclusões lipídicas dispersas, detectadas por sudan IV e sudan black B. Ultra-estruturalmente as protuberâncias mostram matriz fibrilar permeada por estruturas fimbriadas e tubulares, com margem distinta formada por estrutura membranosa. Nossos resultados sugerem que estas protuberâncias são derivadas de atividade secretora, sendo formadas após o desenvolvimento dos espaços intercelulares. em P. superbus esta estrutura pode representar uma especialização da parede celular, relacionada com adesão e mecanismos de transporte entre células.

Dendroid colleters on vegetative and reproductive apices in Alibertia sessilis (Rubiaceae) differ in ultrastructure and secretion

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ultrastructure of spermiogenesis and spermatozoa of Gymnotus cf. anguillaris and Brachyhypopomus cf. pinnicaudatus (Teleostei : Gymnotiformes)

The ultrastructure of spermiogenic stages and spermatozoa of representatives of two gymnotiform families, Gymnotus cf. anguillaris (Gymnotidae) and Brachyhypopomus cf. pinnicaudatus (Hypopomidae) were studied. Spermiogenesis of both species is characterized by lateral development of the flagellum and formation of a nuclear fossa. Some differences were found between these species, such as whether (B. cf. pinnicaudatus) or not (G. cf. anguillaris) nuclear rotation occurs, permanence of the cytoplasmic channel, and type and localization of the nuclear fossa. In the G. cf anguillaris spermatozoon the nucleus is spherical with highly condensed chromatin. The nuclear fossa is shallow and lateral and is associated with the centriolar complex through stabilizing fibrils. The midpiece is short, with many vesicles, a cytoplasmic channel, and elongate mitochondria. In the B. cf. pinnicaudatus spermatozoon the ovoid nucleus is elongated lateral and posterior to the centriolar complex, and has highly condensed chromatin. The eccentric nuclear fossa is of the moderate type, and contains the entire centriolar complex. The midpiece is long, with numerous vesicles, elongate mitochondria, and no cytoplasmic channel. In both species the flagella are laterally disposed in relation to the nucleus and comprise of the classical 9 + 2 axoneme. Most of the characteristics found in the spermatozoa of these two species of Gymnotiformes are shared with species of Characiformes, whereas only a few are also found in Siluriformes. This suggests that Gymnotiformes and Characiformes may be more closely related than previously proposed. (C) 2007 Elsevier Ltd. All rights reserved.

Spermiogenesis and introsperm ultrastructure of Scoloplax distolothrix (Ostariophysi : Siluriformes : Scoloplacidae)

Spermiogenesis in scoloplacids is characterized by initial lateral development of the flagellum, nuclear rotation, medial nuclear fossa formation, complex centriolar migration, and cytoplasmic channel formation. The scoloplacid spermiogenesis is similar to those found in Diplomystidae, the most primitive siluriform family. The scoloplacid spermatozoa have all the main characteristics of introsperm. They exhibit a conic head, a symmetric midpiece, a medial flagellum, and no acrosome. The conic forward-elongated nuclei contain homogeneous chromatin. The thin extremity of the nuclei is strongly curved and along its internal face there is a well-developed membranous compartment. The centrioles are completely inside the medial nuclear fossa, perpendicular to each other and with an electron-dense material between them. In a cross view of the midpiece, the mitochondria form a ring surrounding internally the cytoplasmic channel, and in a longitudinal view they are organized in a row along it. Several elongated vesicles are distributed peripherally, mainly concentrated in the mid-piece basal region. The flagellum contains the classical axoneme (9 + 2) and has two lateral projections or fins. The spermatozoa of scoloplacids share several characteristics with those of Auchenipteridae. Since these two families are not phylogenetically related this similarity seems to be due to convergence once both families are, until now, the only known siluriform families with introsperm.

Ultrastructure of spermiogenesis in Plagioscion squamosissimus (Teleostei, Perciformes, Sciaenidae)

Spermiogenesis in Plagioscion squamosissimus occurs in cysts. It involves a gradual differentiation process of spermatids that is characterized mainly by chromatin compaction in the nucleus and formation of the flagellum, resulting in the spermatozoa, the smallest germ cells. At the end of spermiogenesis, the cysts open and release the newly formed spermatozoa into the lumen of the seminiferous tubules, the spermatozoa do not have an acrosome and are divided into head, midpiece, and tail or flagellum, the spermatozoa of P. squamosissimus are of perciform type with the flagellum parallel to the nucleus and the centrioles located outside the nuclear notch. (C) 1999 Harcourt Publishers Ltd.

Ultrastructure of spermatogenic cells and spermatozoa in Hoplias malabaricus (teleostei, characiformes, erythrinidae)

The differentiation of spermatids in Hoplias malabaricus is characterized by chromatin compaction, flagellum development, nuclear rotation, nuclear fossa formation, and excess cytoplasm elimination. In the resulting spermatozoon, the head is round and the nucleus contains chromatin compacted in thick filaments, peripherically arranged, to a central electron-lucent area. The acrosome is absent. The nuclear fossa is eccentric but not pronounced. The proximal centriole penetrates it and is oblique to the flagellum. The long midpiece has several converging elongate vesicles, forming membranous hoops in the initial segment of the flagellum, but has no cytoplasmic channel. The mitochondria are elongate and branched or C-shaped and located around the initial segment of the axoneme. The lateral flagellum does not show lateral projections. The ultrastructural characteristics of H. malabaricus spermatozoa are similar to the Cypriniformes. (C) 2001 the Fisheries Society of the British Isles.

Spermatogonia and spermatocyte ultrastructure in Hoplias malabaricus (Teleostei, Characiformes : Erythrinidae)

The Hoplias malabaricus primary spermatogonium shows a large nucleus, central nucleolus, and low electron-dense cytoplasm containing nuages. In cysts, they undergo several mitotic divisions with incomplete cytokinesis, giving rise to secondary spermatogonia. These are smaller than the primary spermatogonia and their nuclei have one or two eccentric nucleoli. Spermatocytes I can be identified by the presence of synaptonemal complexes. Spermatocytes II are smaller than spermatocytes 1, displaying roughly compacted chromatin. All these cell types remain interconnected by thick-walled intercellular bridges, which have membranous reinforcements during mitosis and meiosis. These cell types show a well-developed endomembranous system, one of the centrioles anchored to the plasma membrane and small nuages. Their mitochondria are large and circular, with few cristae. In the last generations of spermatogonia, the mitochondria are smaller, elongate and have more cristae. In the spermatocytes, the mitochondria are small and round. Similarities found in relation to germ cells of other teleosts are discussed.

Spermiogenesis and spermatozoa ultrastructure in Salminus and Brycon, two primitive genera in Characidae (Teleostei : Ostariophysi : Characiformes)

In Salminus, spermiogenesis is cystic and gives origin to a type I aquasperm. Spermatid differentiation is characterized by chromatin condensed into thick fibres, nuclear rotation, nuclear fossa formation, cytoplasmic channel formation, mitochondrial fusion producing long and ramified mitochondria, and the presence of several membranous concentric rings around the plasma membrane that encircles the cytoplasmic channel. In Salminus and Brycon, spermatozoa are very similar. They exhibit a spherical nucleus and chromatin condensed into fibre clusters, and a deep nuclear fossa. They show a long midpiece with few elongate mitochondria at the initial region and a cytoplasmic channel completely encircled by one or two membranous concentric rings. The flagellar axis is perpendicular to the nucleus and exhibits the classic axoneme (9 + 2). The very strong similarity observed between Salminus and Brycon spermatozoa supports the hypothesis that these subfamilies are likely to have a monophyletic origin.

Spermatozoa ultrastructure in Sciaenidae and Polynemidae (Teleostei : Perciformes) with some consideration on Percoidei spermatozoa ultrastructure

Spermatozoa ultrastructure was studied in five marines (Paralonchurus brasiliensis, Larimus breviceps, Cynoscion striatus, Micropogonias furnieri, Menticirrhus americanus, Umbrina coroides, Stellifer rastrifer), and one freshwater (Plagioscion squamosissimus) species of Sciaenidae and one species of Polynemidae (Polydactylus virginicus). The investigation revealed that, in all species, spermatozoa display a round head, a nucleus containing highly condensed, filamentous chromatin clusters, no acrosome, a short midpiece with a short cytoplasmic channel, and a flagellum showing the classic axoneme structure (9 + 2) and short irregular lateral fins. In Sciaenidae, the spermatozoa are type II, the flagellar axis is parallel to the nucleus, the lateral nuclear fossa is double arched, the centriolar complex is outside the nuclear fossa, the proximal centriole is anterior and perpendicular to the distal centriole, and no more than ten spherical (marine species) or elongate (freshwater species) mitochondria are observed. Polynemidae spermatozoa are of the intermediate type with the flagellar axis eccentric to the hemi-arc-shaped nucleus, and exhibit no nuclear fossa, the centriolar complex close to the upper nuclear end, the proximal centriole lateral and oblique to the distal centriole, and one large ring-shaped mitocondrion. The data available show that no characteristic is exclusively found in the spermatozoa of members of the Sciaenidae family when compared to other Percoidei with type II spermatozoa. However, three characteristics were exclusively found in Polynemidae: (1) the hemi-arched nucleus; the positioning of the centrioles; and (2) the ring-shaped mitocondrion. The interrelationships between Sciaenidae and Polynemidae as well as between these two families and other Percoidei are herein discussed. (c) 2005 Elsevier Ltd. All rights reserved.

The ultrastructure of Sorubim lima (Teleostei, Siluriformes, Pimelodidae) spermatogenesis: premeiotic and meiotic periods

The ultrastructure of Sorubim lima spermatogenesis during the premeiotic and meiotic periods was studied. Our observations showed that the germ cells in the cysts are connected by cytoplasmic bridges and the mitotic and meiotic divisions are slightly asynchronous, the first and the last spermatogonial generations differ in the cellular and nuclear volume, nucleolus, chromatin condensation, distribution, size, density, and shape of the mitochondria, presence of 'lamellae anulata', amount and dimension of the 'nuages', and movement of the centrioles. In addition to the nuclear prophase structures, the spermatocyte I shows changes in all other cellular organelles and elongated vesicles appear in the cytoplasm. The accentuated cytoplasmic density and thickened walled vesicles are morphological characteristics that differentiate spermatocytes II from the other germ cells in the cysts of Sorubim lima testis. (C) 1999 Harcourt Publishers Ltd.

Spermiogenesis and sperm ultrastructure in Cichla intermedia with some considerations about Labroidei spermatozoa (Teleostei, Perciformes, Cichlidae)

Spermiogenesis and spermatozoal structure were studied in Cichla intermedia, a primitive species of Neotropical cichlids. The analysis shows that spermiogenesis is characterized by chromatin compaction, flagellum development, nuclear rotation, nuclear fossa formation and residual cytoplasm elimination. In the spermatozoa, the head is round, the nucleus contains highly condensed filamentous clusters of chromatin and an acrosome is absent. The nuclear fossa is slightly eccentric and shows a projection that penetrates into the nuclear outline. The proximal centriole is located in the initial segment of the nuclear fossa. The midpiece and the cytoplasmic channel are long. The mitochondria, about 10 in number, are round or slightly elongated, disposed in two layers around the initial segment of the flagellum. The flagellum has a classical 9 + 2 axoneme and two lateral fins. The data available show that no characteristics of spermiogenesis or spermatozoa are exclusively found in members of the suborder Labroidei. However, three characteristics seem to be exclusively observed in Cichlidae: (1) compact filamentous clusters of chromatin; (2) slightly eccentric nuclear fossa; and, (3) number of mitochondria. (C) 2003 Elsevier Ltd. All rights reserved.

Morphometry of the midgut epithelium of Diatraea saccharalis Fabricius, 1794 (Lepidoptera) parasitized by Cotesia flavipes Cameron, 1891 (Hymenoptera)

The morphometric study of the midgut in Diatraea saccharalis (Lepidoptera) larvae parasitized by the Cotesia flavipes (Hymenoptera) showed that there was significant increase in the columnar, goblet and regenerative cells and their nuclei; the midgut lumen diameter and the epithelial height were also increased in the parasitized larvae. The multivariate analysis showed that parasitism affected the columnar cell only in the posterior region, and the goblet cells along the midgut length (anterior and posterior regions). (c) 2006 Elsevier B.V. All rights reserved.