Dynamics and cytochemistry of oogenesis in Astyanax fasciatus (Cuvier) (Teleostei, Characiformes, Characidae) from Rio Sapucaí, Minas Gerais State, Brazil

Abstract

ABSTRACT. Oogenes is involves a set of transformations which are undergone by female germ cell s These cells change into oogonias and then into mature oocytes. Sex uall y mature female fi sh were co llected monthly, during one year, from the Sapucaf Ri ver, a tributary of the Rio Grande, which is part of the Furnas Reservoir in the state of Minas Gerais. During the several stages of maturation, we observed small round oogonias with a large nucleus, a single nucleolus, and weakly stai ned cytoplas m wi th eos inophilic granules. The primary oocytes showed a large basophilic nucle us, with a developed peripheral nucleol us and a reduced cytoplas m. The previtell ogenic oocytes presented voluminous cytoplasm and nucleus with several small peripheral nucleoli. The oocytes underwent vitellogenesis with the development of the zona radiata and the fo lli cle cells. Their cytochemical reactions indi cated that the two layers of the zona radiata of A.fasciatlls contained proteins and polysaccharides. The initially squamous fo llicle cell s, became cuboidal. In mature oocytes , the nucleus moved toward the periphery, next to the micropyle, and the yolk granules formed by proteins, fulfilled the cytoplas m. The clear unstained vesicles are likely to be the cortical alveoli in the perivitelline region . KEY WORDS . Teleostei, Characidae, Astyanax!asciatus, oogenesis, cytochemicalThe Cha rac idae family, with about 400 species, comprises the maj o rity of fres hw a te r fishes in South America. Most of the Brazilian scaled fishes (l a mba ri s, p iracanjubas, piranhas , d o urad os, etc.), which are very a pprecia ted in game fishing (BRISTSK I 1972), are found in thi s famil y.AstyanaxJasciatus (Cuvier, 1819), co mm o n ly kn o wn "as red -tail-lambari ", is the m os t geog ra phica ll y spread lambari s pec ies in th e neo tro pica l regio n . Its caudal a nd d o rsal fin s are red , a nd its ventral a nd p ec to ral fins a re hy a line, with go lden reflexes. It is a small sized fish that feed s on algae, vegetation, larvae and adult insects (NOM URA 1984).

Oogenesis: From Oogonia to Ovulation in the Flagfish, Jordanella floridae Goode and Bean, 1879 (Teleostei: Cyprinodontidae)

“…The lamellae are lined by the germinal epithelium composed of scattered oogonia and the somatic epithelial cells, which are derived from coelomic epithelial cells. The consistent form and function of the germinal epithelium has been described in several teleosts (Grier, ; Dias Garcia et al, ; Parenti and Grier, ; Grier et al, ; Quagio‐Grassiotto et al, ; Uribe and Grier, ; Uribe et al, ; Meijide et al, ).…”

“…Folliculogenesis of J. floridae begins within the germinal epithelium when oogonia enter into meiosis, becoming oocytes, then, individual oocytes become encompassed by prefollicle cells. When the oogonium and prefollicle cells become fully enclosed within a basement membrane, folliculogenesis is complete and the prefollicle cells are then follicle cells, similar to those described in other teleosts (Grier, ; Dias Garcia et al, ; Grier et al, ; Quagio‐Grassiotto et al, ; Uribe et al, ; Wildner et al, ; Parenti et al, ; Meijide et al, ), and in other vertebrates species as detailed in a comprehensive review by Grier et al, ). Folliculogenesis commonly occurs in groups of somatic and germ cells that form cell nests within the germinal epithelium.…”

“…The cortical alveoli and oil droplets of J. floridae are initially developed adjacent to the germinal vesicle, during the primary growth stage, similar to what is seen in the characids Astyanax bimaculatus and A. fasciatus , in which cortical alveoli first appear in a developing oocyte at the end of the advanced perinucleolar stage, which marks the beginning of yolk formation (Anderson, ; Bazzoli and Pereira Godhino, ; Dias Garcia et al, ; Quagio‐Grassiotto et al, ).…”

“…The micropyle is the only region through which the sperm enters the oocyte during fertilization. It has been described in numerous species of teleosts, such as F. heteroclitus by Kuchnow and Scott () and Dumont and Brummett (), Oncorhynchus keta by Kobayashi and Yamamoto (), Oncorhynchus mykiss by Kagawa (), Barbus conchonius by Amanze and Iyengar (), Astyanax fasciatus by Dias Garcia et al (), F. grandis by Grier et al (), E. latos by Uribe et al (), and the hermaphrodite, C. agassizi by Parenti et al (). Morphology of the micropyle was reviewed in detail by Kunz () who described four micropyle morphotypes.…”

Environmental manipulation on Astyanax altiparanae out of season spawning

“…For each female three fields were photographed on a microscope (Nikon, Eclipse50i) with an attached camera (BEL, Stmpro-T-Led; software BEL View) under 200x magnification and analyzed using a 165-intersection grid (ImageJ 1.39p). Developmental stages of oocytes were identified based on the study of Garcia et al (2001).…”