A biflagellate spermatozoon in the African bonytongue Heterotis niloticus (Teleostei, Osteoglossidae).

In this transmission electron microscopy study, we describe the ultrastructure of the spermatozoon of Heterotis niloticus (Osteoglossiformes), which is distinguished by having two flagella. Our investigation also highlights the great diversity of sperm cell structures observed across osteoglossiform families, such as aflagellate (Gymnarchidae, Mormyridae), monoflagellate (Notopteridae, Pantodontidae) and biflagellate spermatozoa. As biflagellate spermatozoa are rare in vertebrates, we also summarize the orders and families known to possess this ultrastructural character, most of which are fishes.

Maturation of mosquito spermatozoa during their transit throughout the male and female reproductive systems.

The testes, seminal vesicles and spermathecae of 22 species of mosquitoes belonging to the genera Aedes, Anopheles, Culex, Mansonia and Toxorhynchites are investigated under the electron microscope. Modifications of the acrosome and sperm wall occur during the transit of the spermatozoon from the lower region of the testes to the spermathecae throughout the seminal vesicles. The origin and fate of the cell coat and the possible roles of somatic cell layers both in the testes and the seminal vesicles are discussed.

Quantification of macrophage aggregates in the liver of Mugil cephalus.

Macrophages are involved in the recycling, storage and detoxification of cellular debris/waste products and exogenous substances their presence is quite normal. An accumulation of these cells, however, can be the sign of an alteration. A quantification of the surface area occupied by macrophage aggregates (1.

Spermatogenesis in mosquitoes (Diptera: Culicidae).

An ultrastructural study of spermatogenesis has been carried out on 18 species of mosquitoes of the Anophelinae, Culicinae and Toxorhynchitinae sub-families. In this spermatogenesis, which follows a classical way, primordial cells, primary and secondary spermatogonia, as well as primary and secondary spermatocysts are considered. We have identified 9 stages of development all along the spermiogenesis.

Extracellular and intracellular rickettsia-like microorganisms in gonads of mosquitoes.

The mosquitoes Culex tigripes, C. decens and C. quinquefasciatus have been investigated by electron microscopy.

Podophyllotoxin-induced modifications of the nuclear envelope.

In spermatids of Culex tigripes (Culicidae) the manchette is composed of numerous expansion-bearing microtubules which surround the nucleus. Under the action of podophyllotoxin, in zones where manchette microtubules are absent, the nuclear envelope bulges and forms abnormal extranuclear vesicles. We hypothesize that this newly recognized capacity of podophyllotoxin is due to its action on microtubule-membrane relationships.

Process of nuclear envelope reduction in spermiogenesis of a mosquito, Culex tigripes.

When the Culex tigripes spermatid begins to elongate, the nucleus exhibits on its surface invaginations of the nuclear envelope. These invaginations have a uniform diameter of 0.3 microns.

Endosymbiotic relationship between a rickettsia-like microorganism and the male germ-cells of Culex tigripes.

The male mosquitoes of the species Culex tigripes possess endosymbionts localized in the cytoplasm of the germ-cells. The somatic cells of the testis do not exhibit this particularity. The spermatogonia, spermatocytes and spermatids all possess a few symbionts.

Polarity of microtubular structures in manchette-like formations: possible role of the "11th filament".

Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures.

Natural degenerating mitochondria in ovarian follicles of a cyprinodontidae fish, Epiplatys spilargyreus (teleost).

This study examines the evolution of mitochondria in the follicular cells during the development of the ovarian follicle in the teleostean fish Epiplatys spilargyreus. The mitochondria are few in number until the end of previtellogenesis; their matrix is dense, and their cristae are well developed. They proliferate during vitellogenesis and then are modified by deterioration of their matrix.

Demonstration of the orientation of the Cestodes spermatozoon illustrated by the ultrastructural study of spermiogenesis and the spermatozoon of a Cyclophyllidea: Thysaniezia ovilla, Rivolta, 1874.

Spermiogenesis in Thysaniezia ovilla begins with the appearance of a differentiation zone equipped with peripheral microtubules, surrounded by arched membranes and containing two parallel centrioles surrounded by electron dense granular material. One of the centrioles aborts, the other gives rise to a flagellum which quickly grows in the cytoplasmic extension in which the nucleus migrates and protein granules form. During the nuclear migration crested-like bodies appear among the peripheral microtubules in the differentiation zone.

Morphogenesis of the secondary envelope of the oocyte in a teleostean fish of the family Cyprinodontidae: Aphyosemion splendopleure.

The follicular epithelium of the oocyte in Aphyosemion splendopleure is made up of prismatic cells in which the density of the cytoplasm is variable. At the end of vitellogenesis the follicular cells show polarity. The rough endoplasmic reticulum is localized in the cytoplasm situated between the nucleus and the basal lamina.

Evidence for nucleating microtubules in microtubular associations and for an opening polarity under colchicine action.

Bundles of microtubular structures appear in the cytoplasm of germinal cells of the African frog Dicroglossus occipitalis. They are made of several associated microtubules. Every bundle contains one normal singlet and numerous arch-shaped microtubular structures growing in all directions from the singlet wall.

The flagellar apparatus of spermatozoa in fish. Ultrastructure and evolution.

Chondrichthyes possess an evolved type of spermatozoa. Their flagellar apparatus is characterized by the presence of flagellar roots which form the axis of the midpiece, and the existence of one or two lateral elements associated with the axoneme. Osteichthyes, mainly teleosteans, show a great diversity of spermatic forms.

Reinvestigation of spermatic flagella structure: the teleostean Cyprinodontidae.

The study of 7 genera and 15 species of teleostean fishes belonging to the family Cyprinodontidae shows a similar morphology of mobile spermatozoa and a wide diversity of structure of the spermatic flagellum. The flagellar membrane has one, two, or three lateral expansions depending on the species. Peripheral doublets of axonema show only the external arm, except for two species that completely lack them.

[Giant mitochondria in the A cells of the pancreas of a lizard: Varanus niloticus].

Pancreatic A cells of the lizard Varanus niloticus are characterized by the presence of two types of mitochondria: (a) normal, small mitochondria (about 0.4 X 1 micron), and (b) giant mitochondria, measuring up to 9 micron in length and 1 micron in diameter. Giant mitochondria show various shapes.

[Crystallization of reptile hemoglobin during its digestion in a pentastomide].

The hemoglobin of the lizard Tarentola annularis has been studied within erythrocytes being digested in the gut of a parasitic pentastomide, Raillietiella sp. The hemoglobin is crystallized in the form of bundles comprised of numerous tubules (up to 2000). These tubules are simple or complex.

The aflagellate spermatozoon of Diplozoon (Platyhelminthes: Monogenea: Polyopisthocotylea): a demonstrative case of relationship between sperm ultrastructure and biology of reproduction.

Diplozoon is known to display an exceptional biology of reproduction: the hermaphroditic adults are permanently fused together and their genital ducts communicate. In contrast to all other polyopisthocotylean monogeneans in which the spermatozoa show an homogeneous biflagellate structure, the spermatozoon of Diplozoon is aflagellate. It is filiform, and composed of a cytoplasmic region and a nuclear region.

Microtubules and macrotubules in fish meiosis.

During meiosis in the male of a cyprinodontid fish, Aphyosemion splendopleure, and during the organization of the spindle of division, the spindle is made of two types of tubules: microtubules (20-25 nm) and macrotubules (30-50 nm). The macrotubules are associated only with the polar region of the meiotic apparatus and are located outside the spindle of microtubules. At the end of meiosis, the spindle microtubules depolymerize whereas the macrotubules remain.

Alterations of endocrine pancreas B cells in a sahelian reptile (Varanus exanthematicus) during starvation.

During the long starvation period (November to June) of the lizard (Varanus exanthematicus), pancreatic B cells undergo profound modification. The degeneration of beta granules observed in electron microscopy appears correlated with the diminution of the immunoreactive insulin-like content of the pancreas. The analogy between the phenomena observed here and those reported in animals treated with alloxan is discussed.

[Ultrastructure of the spermatozoon of the monogenean Hexostoma (Polyopisthocotylea, Hexostomatidae)].

The middle region of the spermatozoon of Hexostoma exhibits two 9 + "1" axonemes, the nucleus, the mitochondrion, and cortical longitudinal microtubules. The ultrastructure is similar to that of other Polyopisthocotylean monogeneans and this confirms the position of the family Hexostomatidae within Polyopisthocotyleans.

Ultrastructure of the exocrine pancreas in a sahelian reptile (Varanus exanthematicus) during starvation.

During the sahelian dry season (November to June) the lizard Varanus exanthematicus fasts, and during these 8 months its pancreatic acinar cells lack zymogen granules and show an inactive Golgi body and damaged mitochondria. The main peculiarity can be observed in the granular endoplasmic reticulum (GER): Each acinar cell posesses a great number of GER vesicles (mean diameter 0.15 μm) and a large spheroid GER resulting from either the nesting of some cisternae or the rolling up of a single cisternae on itself.

[Comparative ultrastructural study of spermiogenesis in Monogenea. 1. Megalocotyle (Monopisthocotylea Capsalidae)].

In Megalocotyle the zones of differentiation (ZD) are short and incomplete; there is no median cytoplasmic process or free flagella. Some peripheral microtubules are present in early ZD, but they disappear. Each nucleus of the common cytoplasmic mass inserts one extremity into a ZD.