Light and electron microscope structural study of the zona radiata in the oocyte of zebrafish (Danio rerio)

Abstract

Teleosts account for more than half of the vertebrate species. A key feature of the evolutionary success of teleosts is their reproductive systems, which are efficient and functional under all aquatic environmental conditions. The zona radiata (ZR) is a non- cellular envelope over oolemma of teleost fish oocytes. The morphology of the ZR varies in different ovarian developmental stages and also among various fish species, which reflects adaptation to ecological conditions. In this research the structure of the ZR in the oocytes of zebrafish in different stages of ovarian development and oocyte growth were studied. The fish ovary was fixed in Bouin's solution. Histological sections were studied by light and scanning electron microscope after subjecting them to tissue preparation stages. In immature and primary growth stages (I and II), the ZR was not observed. In stage III, the ZR was observed as a thin layer around the oocyte. It increased in thickness at stage IV (vitellogenesis) but reduced in stage V (maturation). In early stage III, the ZR striations started to appear and in stage IV (vitellogenesis) fence-like striations were completely formed. SEM micrographs showed stria to be deep with crenelated margin. In late stage IV fence-like striations disappeared gradually and in matured egg (V) the stria turned into pit-like remnants. In zebrafish no adhesive filaments were observed and the ZR surface was smooth.

Single-Cell Atlas of the Chinese Tongue Sole (Cynoglossus semilaevis) Ovary Reveals Transcriptional Programs of Oogenesis in Fish

“…Studies on fish reproduction assist the conservation of germplasm resources and the investigation of animal reproductive regulation mechanism in fish model. Most studies on fish oogenesis focus on the structural changes during oocyte maturation observed by light and electron micrograph sections and the regulation of endocrine factors ( Selman et al, 1993 ; Tyler and Sumpter, 1996 ; Patiño et al, 2005 ; Kaviani et al, 2013 ). Conventional genome analysis approaches have been used to capture global gene expression patterns and chromatin conformation of fish ovaries or oocytes ( Shao et al, 2014 ; Can et al, 2020 ; Dong et al, 2021 ).…”

Morphological description of gametes in cave and surface populations of Astyanax mexicanus (De Filippi, 1853)

“…Therefore, the oocytes collected from our Astyanax mexicanus populations were between the vitellogenesis and maturation phase (555.9-822.4 μm). Kaviani et al (2013) described a similar classification for oocyte maturation stages in zebrafish (Danio rerio), so when comparing those with our Astyanax mexicanus, our oocytes were at the maturation stage. In zebrafish the diameter of the oocytes in this phase was 412.75 μm and the thickness of the chorion was 1.6 μm, very similar to values observed for our Astyanax mexicanus oocytes (555.9-822.4 μm, 1.1-1.5 μm respectively).…”

Long-Term Exposure of Lead Acetate on Rabbit Renal Tissue

“…The kidneys were taken after dissection and fixed in formaldehyde 10%, dehydrated by alcohol, impregnated, paraffin embedded, and 3 µm sections were prepared. The haematoxylin and eosin H & E and periodic acid-schiff (PAS) staining were performed for light microscopy ( 14 ). For electron microscopy, after fixation in glutaraldehyde 2.5% and dehydration in acetone, the samples were embedded in araldite resin medium (Proscitech, Australia) and 50 nm sections were prepared and stained with uranyl acetate and lead nitrate ( 15 ).…”