Journalartikel

Autorenliste: RICHTER, HP

Jahr der Veröffentlichung: 1976

Seiten: 250-303

Zeitschrift: Helgoländer wissenschaftliche Meeresuntersuchungen

Bandnummer: 28

Heftnummer: 3-4

ISSN: 0017-9957

Open Access Status: Bronze

DOI Link: https://doi.org/10.1007/BF01610585

Verlag: Biologischen Anstalt Helgoland

Abstract: 
Oocyte development in L. cinereus L. was examined using EM special emphasis being given to ultrastructural changes during vitellogenesis. Oogenesis can be subdivided into 5 stages based on cytological and histochemical features. Typical oogonia is not found; only early oocytes of the meiotic prophase with an incomplete nucleolus are situated on the basallamina of the gonadal wall. The single nucleolus is formed in stage I; osmiophilic nucleolar granules pass through the nuclear envelope. Stage II-oocytes are characterized by simple Balbiani-bodies or yolk nuclei, which consist of ribosomes and a hull of mitochondria. The formerly homogenous nucleolus disintegrates into caryoplasmic vacuoles and produces paranucleoli. In the previtellogenetic stage III the yolk nuclei are reduced and large systems of endoplasmic reticula arranged concentrically or flattened and voluminous cytoplasmic vacuoles appear. Three types of vacuolar complexes can be observed: complete membrane bounded vacuoles with a filaceous content built up by Golgi dictyosomes; vacuoles with remains of membranes which seem to originate from endoplasmic cisternae; and vacuolar spaces lying free in the cytoplasm. The vacuoles contain either acid mucopolysaccharides or acid lipids. The actual vitellogenesis starts in stage IV after depression of the oocyte membrane to ooplasmic bumbs by the perioocytal follicle epithelium. Extensive piles of annulate lamellae contact the cytoplasmic vacuolar bodies. Striated long rootlets branch off microtubules at their terminal end in the direction of the oocyte membrane below the oocyte hull. Microvilli secrete mucopolysaccharides into the intercellular space between oocyte membrane and inner follicle cell membrane. The resulting 8 cup-like hull processes are composed of 3 layers. There are, probably 3 ways of forming vitelline bodies: transforming mitochondria and multivesicular bodies lead to protein yolk; mitochondria connect with cytoplasmic vacuoles and probably participate in genesis of lipid yolk; and microvesicles become protein yolk precursors. The lipoprotein yolk spheres consist of a homogenous internum and a paracrystalline structured cortex. Lipid yolk accumulates at the periphery of the cytoplasmic vacuoles, which degenerate later. The mature oocyte secretes another primary oocyte envelope, the vitelline membrane, shortly before spawning. Cortical granules appear below the oocyte membrane.

Harvard-Zitierstil: RICHTER, H. (1976) ULTRASTRUCTURAL INVESTIGATIONS OF OOGENESIS IN CHITON, LEPIDOCHITONA-CINEREUS (MOLLUSCA, POLYPLACOPHORA), Helgoländer wissenschaftliche Meeresuntersuchungen, 28(3-4), pp. 250-303. https://doi.org/10.1007/BF01610585

APA-Zitierstil: RICHTER, H. (1976). ULTRASTRUCTURAL INVESTIGATIONS OF OOGENESIS IN CHITON, LEPIDOCHITONA-CINEREUS (MOLLUSCA, POLYPLACOPHORA). Helgoländer wissenschaftliche Meeresuntersuchungen. 28(3-4), 250-303. https://doi.org/10.1007/BF01610585