Ovarian germinal epithelium and folliculogenesis in the common snook,Centropomus undecimalis (Teleostei: Centropomidae)

Abstract

The ovarian germinal epithelium in the common snook, Centropomus undecimalis, is described. It consists of epithelial and prefollicle cells that surround germ cells, either oogonia or oocytes, respectively. The germinal epithelium borders a body cavity, the ovarian lumen, and is supported by a basement membrane that also separates the epithelial compartment of the ovarian lamellae from the stromal compartment. During folliculogenesis, the epithelial cells, whose cytoplasmic processes encompass meiotic oocytes, transform into prefollicle cells, which become follicle cells at the completion of folliculogenesis. The follicle is a derivative of the germinal epithelium and is composed of the oocyte and surrounding follicle cells. It is separated from the encompassing theca by a basement membrane. The cells that form the theca interna are derived from prethecal cells within the extravascular space of the ovarian stroma. The theca externa differentiates from undifferentiated cells within the stromal compartment of the ovary, from within the extravascular space. The theca interna and the theca externa are not considered to be part of the follicle and are derived from a different ovarian compartment than the follicle. Meiosis commences while oocytes are still within the germinal epithelium and proceeds as far as arrested diplotene of the first meiotic prophase. The primary growth phase of oocyte development also begins while oocytes are still within the germinal epithelium or attached to it in a cell nest. The definitions used herein are consistent between sexes and with the mammalian literature. J. Morphol. 243:265–281, 2000 © 2000 Wiley‐Liss, Inc.

Reproductive apparatus and gametogenesis of Lophiosilurus alexandri Steindachner (Pisces, Teleostei, Siluriformes)

“…In L. alexandri the oogonia were the smallest of the oogenic lineage cells and displayed a morphology similar to the one found in other teleost species studied (GRIER 2000, GUIMARÃES-CRUZ et al 2005. During the primary oocyte growth in L. alexandri the formation of a yolk nucleus and a cortical alveolus was observed.…”

“…The follicular cells originate from the germ epithelium of the ovaries, when prefollicular cells emit processes that surround the oocytes during meiosis (GRIER 2000). QUAGIO-GRASSIOTTO & GUIMARÃES (2003) related that the follicular cells of the teleost Serrasalmus spilopleura Kner, 1858 are squamous during the primary growth and become cuboidal during the secondary growth phase, acquiring characteristics typical of proteins or glycoproteins producing cells.…”

“…The perinucleolar stage takes place during the primary growth while the vitellogenesis occurs during the secondary growth (PATIÑO & SULLIVAN 2002). During follicle formation morphologic changes take place in the nucleus, ooplasm, zona radiata and follicular cells (GRIER 2000). In several fish species, after the spawning and during embryonic development, specialized structures present at the oocytes surface can mediate interactions between the eggs and the different substrates where they are deposited (RIZZO et al 2002).…”

Gonadal structure and gametogenesis of Loricaria lentiginosa Isbrücker (Pisces, Teleostei, Siluriformes)

“…Oogenesis consists of the proliferation of oogonia from the germinal epithelium that covers the ovigerous lamellae (GRIER 2000), which divide by mitosis originating oocytes (SELMAN & WALLACE 1989). In the present study, early perinuclear oocytes showed a strongly basophilic cytoplasm, an important characteristic that differentiates them from oogonias, and indicates the beginning of the oogenesis (RAVAGLIA & MAGGESE 2002).…”

“…In general, most published work focuses on biometrical, morphological, physiological and/ or biochemical characters, and the distribution of the different cytoplasmic and nuclear inclusions (TYLER & SUMPTER 1996, GRIER 2000. LEGENDRE et al (1996) reports that some Siluriformes species present fringed testes while others do not.…”