Spermiogenesis and spermatozoal ultrastructure in Trichomycteridae (Teleostei: Ostariophysi: Siluriformes)

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

Spermiogenesis and sperm ultrastructure in ten species of Loricariidae (Siluriformes, Teleostei)

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

Spermatogenesis chronology in Achroia grisella Fabricius (Lepidoptera, Pyralidae) comparing eupyrene and apyrene spermiogenesis

Achroia grisella exhibit dichotomous spermatogenesis producing two types of sperm, one is eupyrene that possesses nucleus, and the other is apyrene that lacks it. Transmission electron microscopy of spermatogenesis morphology is described considering sperm type which will appear at sonic point during insect development, and differences that mark the two types of sperm formation. The differences between them are only really visible during spermiogenesis even though they were determined before meiosis. Both forms were seen in the larval stage, but there is a little difference in the time of their appearance. Eupyrene cysts were seen from the 8(th) larval stage, whereas apyrene were only found after the 10(th) stage. In early insect development stages, eupyrene cysts predominate, but as the insect ages, they are overtaken by apyrene. Although some eupyrene cysts are still present in young adult testis, the majority are apyrene. As eupyrene sperm is formed, bundles migrate to the seminal vesicle therefore in early pupae eupyrene sperm are already present there whereas apyrene cells arrive later. The exact mechanism and determining factors responsible for apyrene sperm origin are still to be clarified. The probable causes of apyrene sperm appearance are discussed as well as its role in the sperm competition.

A study of meiosis and spermiogenesis in the testicular lobes of Antiteuchus tripterus (Heteroptera : Pentatomidae)

An analysis of testicular morphology and spermatogenesis in the Heteroptera species Antileuchus tripterus (Pentatomidae) revealed that these traits differ from that recorded for other species of the same family. The testes of A. tripterus have only six lobes, while other species of the same family typically have seven lobes, including a compound lobe, i.e., a lobe containing another in its lumen. A study of meiosis and sperm structure in the different lobes of A. tripterus revealed a conventional meiosis in the lobes numbered one to three. In lobe four, however, prophase I spermatocytes exhibit the morphological characteristics of the so called diffuse stage and are larger than those in lobes 1-3 in this and the remaining phases of meiosis. Thus, the resulting spermatids are not only larger but also their head is morphologically different. Lobe 5 exhibits characteristies known from other Pentatomidae species such as an uneven distribution of chromatin to the daughter cells, which give rise to cells of different sizes. This lobe forms spermatozoa of different sizes. Lobe 6, contained within lobe 5, differs from it by having larger cells at a stage similar to the so called diffuse and spermatid tails with cross divisions, which are not found in other lobes and unreported in the literature.

Ultrastructural analysis of the nucleolar aspects at spermiogenesis in triatomines (Heteroptera, Triatominae)

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

Meiotic nucleolar cycle and chromatoid body formation during the rat (Rattus novergicus) and mouse (Mus musculus) spermiogenesis

The aims of the present study were to follow the nucleolar cycle in spermiogenesis of the laboratory rodents Rattus novergicus and Mus musculus, to verify the relationship between the nucleolar component and chromatoid body (CB) formation and to investigate the function of this cytoplasmic supramolecular structure in spermatogenic haploid cells. Histological sections of adult seminiferous tubules were analyzed cytochemically by light microscopy and ultrastructural procedures by transmission electron microscopy. The results reveal that in early spermatids, the CB was visualized in association with the Golgi cisterns indicating that this structure may participate in the acrosome formation process. In late spermatids, the CB was observed near the axonema, a fact suggesting that this structure may support the formation of the spermatozoon tail. In conclusion, our data showed that there is disintegration of spermatid nucleoli at the beginning of spermatogenesis and a fraction of this nucleolar material migrates to the cytoplasm, where a specific structure is formed, known as the "chromatoid body", which, apparently, participates in some parts of the rodent spermiogenesis process. (c) 2007 Elsevier Ltd. All rights reserved.

Morphological patterns of the heteropycnotic chromatin and nucleolar material in meiosis and spermiogenesis of some Pentatomidae (Heteroptera)

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

Comparative description and discussion of spermiogenesis and spermatozoal ultrastructure in some species of Heptapteridae and Pseudopimelodidae (Teleostei: Siluriformes)

Os dados obtidos no presente estudo sobre a ultraestrutura da espermiogênese e dos espermatozóides de Pseudopimelodidae e Heptapteridae mostram que eles compartilham algumas características, mas são bastante diferentes uns dos outros. As principais diferenças são a ocorrência de espermiogênese do tipo I em Pseudopimelodidae e do tipo III em Heptapteridae, a presença de fossa nuclear em Pseudopimelodidae e sua ausência em Heptapteridae, a presença de uma peça intermediária longa em Pseudopimelodidae e uma peça intermediária curta em Heptapteridae, a presença de um canal citoplasmático em Pseudopimelodidae e sua ausência em Heptapteridae, a presença de muitas vesículas grandes na peça intermediária de Pseudopimelodidae, e a presença de vesículas muito alongadas e dispostas em posição periférica distal em Heptapteridae e mitocôndrias distribuídas em toda a peça intermediária de Pseudopimelodidae e muito próximas ao núcleo em Heptapteridae. Heptapteridae e Pimelodidae compartilham várias características como a espermiogênese do tipo III, o mesmo padrão de condensação da cromatina e a ausência de fossa nuclear e projeções laterais ou fins. O espermatozóide de Pseudopimelodidae é mais similar aos dos Siluridae, porém a ausência de dados adicionais sobre a espermiogênese e o espermatozóide de outros siluriformes ainda limitam uma discussão mais ampla na ordem.

Comparative analysis of spermiogenesis and sperm ultrastructure in Callichthyidae (Teleostei: Ostariophysi: Siluriformes)

Em Corydoradinae, a presença de espermátides junto com espermatozóides no lúmen dos túbulos testiculares sugere uma espermatogênese do tipo semicística, enquanto que em Callichthyinae a produção do esperma ocorre inteiramente dentro dos espermatocistos no epitélio germinativo, caracterizando a espermatogênese cística. A espermiogênese em Callichthyinae é caracterizada por um desenvolvimento inicial lateral do flagelo, pela presença de rotação nuclear em diferentes graus, formação de uma fossa nuclear excêntrica ou medial, formação de um canal citoplasmático, e presença de migração centriolar, sendo mais similar à espermiogênese do tipo I. em Corydoradinae, a espermiogênese é caracterizada pelo desenvolvimento excêntrico do flagelo, ausência de rotação nuclear, fossa nuclear excêntrica, formação de um canal citoplasmático, e ausência de migração centriolar, diferindo dos tipos descritos previamente. O processo de espermatogênese e espermiogênese em Corydoradinae e Callichthyinae revelaram caracteres únicos para cada subfamília, corroborando a hipótese de que as mesmas constituem grupos monofiléticos. em relação à ultraestrutura do esperma, a análise comparativa das espécies de Callichthyidae mostra que as características gerais encontradas nos espermatozóides foram similares, reforçando a hipótese de monofilia da família.

Pattern of nucleolar activity during spermiogenesis in triatomines (Heteroptera, Reduviidae) as analysed by silver staining

Nucleoli are the sites of biosynthesis of ribosomal precursors. In this work the nucleolar activity at interphase and the meiotic cells of the testis in five species of triatomines were analysed by means of silver staining. Several nucleolar blocks in the polyploid nuclei of testicular tubules were observed, whereas only one nucleolar body could be seen in the spermatogonial nuclei of all five species. A single nucleolar body was evident in the 'confused stage' of Triatoma brasiliensis, T. delpontei, T. lecticularia and T. rubrovaria, while T. sordida presented two nucleolar dots. The existence of small, silver-stained dots in some metaphase I chromosomes of T. brasiliensis and T. sordida is reported. The number of nucleolar dots present in spermatids of each species varied within and among species. It is suggested that in addition to providing information on rRNA biosynthesis, studies of nucleolar organizing activity can also be important sources of data on differentiation patterns and species development.

Cytological steps during spermiogenesis in the house sparrow (Passes domesticus, Linnaeus)

Spermiogenesis of the domestic sparrow was investigated with the light and electron microscopes and a step by step classification is proposed. Three cell populations corresponding to early, mid and late spermatids were easily divided according to their positions in the seminiferous epithelium. In addition to this initial separation, six steps were recognized, based on nuclear morphology and the degree of chromatin condensation, in association to their acrosomal and flagellar development. Early spermiogenesis is the period previous to chromatin condensation. The first step can be recognized by the extending flagellum and the second by the pro-acrosome development in contact with the nucleus. During the third or intermediate step, chromatin condenses and the cell becomes polarized with the pro-acrosomic vesicle and the tail occupying opposite sides of the nucleus. Late spermiogenesis, including steps IV-VI, is marked by complete chromatin condensation. The final cellular modifications lead to the formation of a spiraled spermatozoon. This shape is due to the twisting of the acrosome and nucleus, as well as the helical arrangement of mitochondria around the axoneme along most of the flagellum, making an exceptionally long middle piece. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Sperm ultrastructure and a new type of spermiogenesis in two species of Pimelodidae, with a comparative review of sperm ultrastructure in Siluriformes (Teleostei : Ostariophysi)

During spermiogenesis, the spermatids of the pimelodid species Pimelodus maculatus and Pseudoplatystoma fasciatum show a central flagellum development, no rotation of the nucleus, and no nuclear fossa formation, in contrast to all previously described spermatids of Teleostei. These characteristics are interpreted as belonging to a new type of spermiogenesis, named here type III, which is peculiar to the family Pimelodidae. In P. maculatus and P. fasciatum, spermatozoa possess a spherical head and no acrosome; their nucleus contains highly condensed, homogeneous chromatin with small electron-lucent areas; and a nuclear fossa is not present. The centriolar complex lies close to the nucleus. The midpiece is small, has no true cytoplasmic channel, and contains many elongate and interconnected vesicles. Several spherical to oblong mitochondria are located around the centriolar complex. The flagellum displays the classical axoneme (9 + 2) and no lateral fins. Only minor differences were observed among the pimelodid species and genera. Otherwise, spermiogenesis and spermatozoa in the two species of Pimelodidae studied exhibit many characteristics that are not found in other siluriform families, mainly the type III spermiogenesis. (C) 2007 Elsevier GmbH. All rights reserved.

Electron microscopy study of lizard spermiogenesis in Tropidurus torquatus (Lacertilia)

In the course of an investigation on lizard spermiogenesis, the authors have observed events connected with the differentiation of the acrosome and middle-piece of the spermatozoa. Some differences from other reptilians were found as well as: the presence of a subacrosomal space, the absence of the fibrous sheath in the middle-piece, and a very short neck in the mature spermatozoa.