Spermatogenesis and spermiogenesis in Microcotyle sp. (Microcotylidae, Monogenea).

Ultrastructural observations of spermatogenesis and spermiogenesis in Microcotyle sp. a microcotylid monogenean parasite from the gills of Hypostomus sp., are described. The spermatogonia were irregularly shaped, forming a peripheral layer of cells; spermatocytes were larger than spermatogonia and a nuclear synaptonemal complex was observed; young spermatids were joined by a central cytophore forming rosettes. Spermiogenesis was characterized by the outgrowth of a cytoplasmic protuberance, the zone of differentiation, containing the basal bodies, separated by an intercentriolar body, from which flagella grow out and fuse posteriorly with the median process. Cross sections of the anterior and the middle regions of spermatozoa revealed nuclei, mitochondria, peripheral microtubules, and paired axonemes each with a 9+1 pattern.

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae).

The ultrastructure of the body tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasite of Mugil liza from Brazil, was studied by transmission electron microscopy. The body tegument is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium consists of a matrix containing three types of body inclusions and mitochondria. The musculature is constituted of several layers of longitudinal and circular muscle fibers. The tegumental cells present a well-developed nucleus, cytoplasm filled with ribosomes, rough endoplasmatic reticulum and mitochondria, and characteristic organelles of tegumental cells.

Report of Didymocystis wedli Ariola, 1902 (Digenea; Didymozoidae) from Thunnus albacares in Brazil.

Didymocystis wedli a parasite from the gills of Thunnus albacares from the coast of the State of Rio de Janeiro, is described by use of light and scanning electron microscopy. This is the first report of this species in Brazil and South America. New data are presented on the surface topography as demonstrated by scanning electron microscopy.

Ultrastructure of spermatogenesis and sperm development in Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea, Haploporidae).

Ultrastructural observations of spermatogenesis and sperm development of Saccocoelioides godoyi, an intestinal parasite of Leporinus friderici (Bloch, 1794) are described. The irregular-shaped spermatogonia form a peripheral layer, and show a prominent nucleus. Spermatocytes are larger than spermatogonia, and in the early stage present synaptonemal complex. Spermatids show nuclei smaller than the spermatocytes. Spermiogenesis is characterized by outgrowth of the zone of differentiation, presenting basal bodies, separated by an intercentriolar body. At the end of this process, the spermatozoa are released into the residual cytoplasmic mass. The spermatozoa of S. godoyi are elongate, similar to the pattern described for other Digenea, showing nuclei, mitochondria and two axonemes with the 9+1 configuration. The peripheral cortical microtubules on the dorsal and ventral faces are laterally interrupted.

Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani.

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes.

A new species of Nasicola Yamaguti, 1968 (Monogenea: Capsalidae) from the nasal cavities of Thunnnus obesus and a redescription of N. klawei (Stunkard, 1962) from T. albacares off Brazil.

Two species of Nasicola Yamaguti, 1968 are described from the nasal cavities of tunas ( Thunnus spp.) from off the coast of Brazil: N. brasiliensis n. sp. from T. obesus (Lowe) and the type-species, N. klawei (Stunkard, 1962), from T. albacares (Bonn.). The new species is differentiated from N. klawei on the basis of the large number of testes and from N. hogansi Wheeler & Beverley-Burton, 1986 by its greater body-size, proportionately smaller haptor and smaller number of marginal spines. The host-specificity of Nasicola spp. is commented upon.

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae)

Foi realizado o estudo do tegumento do corpo de Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasito de Mugil liza (tainha) do Canal de Marapendi, Rio de Janeiro, Brasil, pela microscopia eletrônica de transmissão. O tegumento é formado por uma camada externa sincicial, uma camada muscular e uma camada interna contendo células tegumentares. O sincício consiste em matriz com três tipos de corpos de inclusão e mitocôndrias. A musculatura é formada por diversas camadas de fibras musculares longitudinais e circulares. As células tegumentares apresentam núcleo bem desenvolvido, citoplasma preenchido por ribossomas, retículo endoplasmático rugoso e mitocôndrias, organelas características das células tegumentares.

Ultrastructure of spermatogenesis and sperm development in Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea, Haploporidae)

Ultrastructural observations of spermatogenesis and sperm development of Saccocoelioides godoyi, an intestinal parasite of Leporinus friderici (Bloch, 1794) are described. The irregular-shaped spermatogonia form a peripheral layer, and show a prominent nucleus. Spermatocytes are larger than spermatogonia, and in the early stage present synaptonemal complex. Spermatids show nuclei smaller than the spermatocytes. Spermiogenesis is characterized by outgrowth of the zone of differentiation, presenting basal bodies, separated by an intercentriolar body. At the end of this process, the spermatozoa are released into the residual cytoplasmic mass. The spermatozoa of S. godoyi are elongate, similar to the pattern described for other Digenea, showing nuclei, mitochondria and two axonemes with the 9+1 configuration. The peripheral cortical microtubules on the dorsal and ventral faces are laterally interrupted

Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes