ABSTRACT. Gametogenic and histochemical aspects of edible bivalve Iplzigellia brasiliana (Lamarck) (Bivalvia, Donacidae) from the Itaipu lagoon, Nitel'ói, Rio de Janeiro, Brazil. Gametogenic and histochemical aspects of an edible bivalve, Iphigenia brasiliana (Lamarck, 1818) from Itaipu Lagoon, Niterói, State of Rio de Janeiro, were studied. Between May 1998 and October 1999 a total of 120 c1ams were picked up . Samples of 10 animais were collected once a month. Specimens were fixed in Bouin's tixative for 4 hours or less and transferred to 10% fonnalin for 24 hours. The shell lenght has been measured with the valves lightly opened to permit the penetration of f1xative solution deeply in the tissues. Transverse seetions including digestive diverticula, mantle, gill s, gonad and foot were obtained from the total body. Aner tixative treatment, tissues see tion s were embedded in paraffin, eut routinely at 5 flm and stained with Harris's hematoxylin and eosin. Microscopic analysis was earried out at low and high dry magnifications, as well as under oi l immersion . Advaneed ova stages were measured. Speeial stai ning techniques have been app li ed as a tentative tool for searehing glyeogen, mueous eells, eollagenie and retieulin fibers, RNA and protozoan organisms. The anima is eolleeted showed variation in lenght Irom 7.20 em to 4.10 em and in height from 4.60 em to 3.10 em. The sex rati o (M:F) was 40:69. The average ova diameter of I. brasiliana was 34.70 /lm with a standard deviation of5.19 /lm. Nothing eould be observed in I. brasiliana, eoncerning to lesions and parasites at histopathologieal analysis. KEY WORDS . Gametogenic cycle, histology, special-staining methods, lphigenia brasiliana, Itaipu Lagoon, BrazilIphigenia brasiliana (Lamarck, 1818) é encontada enterrada aproximadamente a até 15 cm de profundidade, no fundo areno-argiloso ou lodoso de baías e enseadas. Seu nome vulgar é "tarioba", segundo BOFFI (1979). No Brasil, atinge os Estados do Paraná e de Santa Catarina (GOFFERJÉ 1950) e São Paulo e Rio de Janeiro (LANGE DE MORRETES 1949). Na Lagoa de Itaipu é denominada de "taioba" e é consumida não só pela população local, como também por alguns cidadãos da colônia nipônica para o preparo de sopas e outros pratos orientais. Na espécie estudada, as gônadas ocupam o espaço entre as regiões do canal alimentar na massa visceral, não se estendendo para o manto . As aberturas genitais ficam na s uperfície posterior dorsal da massa visceral, abaixo do nefrídio e abrem-se