Estudos ultraestruturais da glândula de Mehlis de Metamicrocotyla macracantha (Monogenea, Microcotylidae) parasito de Mugil liza (Teleostei)

A ultraestrutura da glândula de Mehlis de Metamicrocotyla macracantha, parasita de brânquia coletado de Mugil liza do Rio de Janeiro, Brasil, foi estudado através da microscopia eletrônica de transmissão. A glândula de Mehlis consiste de dois tipos de células secretoras, S1 e S2, cada uma produzindo um corpo secretor diferente. Os corpos S1 são esféricos, em forma de lamelas e observados em diferentes estágios de desenvolvimentos no citoplasma dessas células. Os corpos S2 são esféricos a ovais com conteúdos densos, apresentando uma estrutura cristalina. O citoplasma das células da glândula de Mehlis apresenta também ribossmas livres, retículo endoplasmático granular e complexo de Golgi, organelas características de células secretoras.The ultrastructure of Mehlis' gland of Metamicrocotyla macracantha, a gill parasite collected from Mugil liza from Rio de Janeiro, Brazil, was studied by transmission electron microscopy. The Mehlis' gland consists of two types of secretory cells, S1 and S2, each producing a different secretory body. The S1 bodies are spherical, lamellae-like and were observed in different stages of development in the cytoplasm of these cells. The S2 bodies are spherical to ovoid with dense content, showing a crystalline structure. The cytoplasm of Mehlis' gland cells contains also free ribosomes, granular endoplasmatic reticulum and Golgi complex, characteristic organelles of secretory 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

Ultrastructural aspects of spermatogenesis in Metamicrocotyla macracantha (Alexander,1954) Koratha,1955 (Monogenea; Microcotylidae)

Ultrastructural aspects of spermatogenesis, spermiogenesis and of the mature spermatozoon of a microcotylid monogenean Metamicrocotyla macracantha parasite from Mugil liza, are described. The irregularly-shaped spermatogonia divides by successive mitoses, forming the primary spermatocytes, identified by the presence of synaptonemal complexes in their nuclei. The spermatids formed by meiotic cell divisions of the secondary spermatocytes, differentiate into a mature spermatozoon. Cross sections of the head and the middle region of mature spermatozoa show the nucleus with strong condensed chromatin, the mitochondria with short cristae, peripheral microtubules and two axonemes with a 9+1 pattern, confirming the characteristics of this genus