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ARTICLE

Oogenesis in the swamp eel Synbranchus marmoratus (Bloch, 1795) (Teleostei; synbranchidae). Ovarian anatomy, stages of oocyte development and micropyle structure

by MARIO ALDO RAVAGLIA , MARÍA CRISTINA MAGGESE

Laboratorio de Embriología Animal. Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires – ARGENTINA.

Corresponding Author: Mario Aldo Ravaglia, Fax: (+54- 11) 4576 3384. E-mail:

BIOCELL 2002, 26(3), 325-337. https://doi.org/10.32604/biocell.2002.26.325

Abstract

Synbranchus marmoratus (Synbranchidae), commonly known as the swamp eel, is a protogynous diandric teleost fish widely distributed throughout South America. The purpose of this work was to study the ovarian anatomy and to describe oocyte developmental stages in the swamp eel, Synbranchus marmoratus.
S. marmoratus has a unique sacular ovary. It is covered by a conspicuous muscular wall, probably involved in an egg-releasing system acting as a peristaltic-like mechanism. The internal ovarian anatomy shows a Ushaped ovarian lamella delimiting a dorsal ovarian lumen. The microscopic study shows evidence of the existence of a germinal epithelium in the inner surface of the lamella, which contains germinal cells, prefollicular cells and epithelial cells. The complete oogenesis process is divided into four stages: oogonia, primary growth, cortical alveoli and vitellogenesis. Besides, the ovulated oocytes, and atretic structures were described. The structure of the micropyle was studied by scanning electron microscopy (MEB). Near the animal pole the vitelline envelope forms crests that fuse together becoming furrow-like structures with a slightly spiraled direction that converge into the micropyle pit where is located the micropylar canal. Although the sex reversal process of Synbranchids has been subject of many studies, this is the first complete description of the ovarian anatomy and oogenesis.

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