Germline Cysts and the Formation of the Germinal Epithelium During the Female Gonadal Morphogenesis in Cyprinus carpio (Teleostei: Ostariophysi: Cypriniformes)

Abstract

The formation of both germline cysts and the germinal epithelium is described during the ovary development in Cyprinus carpio. As in the undifferentiated gonad of mammals, cords of PGCs become oogonia when they are surrounded by somatic cells. Ovarian differentiation is triggered when oogonia proliferate and enter meiosis, becoming oocytes. Proliferation of single oogonium results in clusters of interconnected oocytes, the germline cysts, that are encompassed by somatic prefollicle cells and form cell nests. Both PGCs and cell nests are delimited by a basement membrane. Ovarian follicles originate from the germline cysts, about the time of meiotic arrest, as prefollicle cells surround oocytes, individualizing them. They synthesize a basement membrane and an oocyte forms a follicle. With the formation of the stroma, unspecialized mesenchymal cells differentiate, and encompass each follicle, forming the theca. The follicle, basement membrane, and theca constitute the follicle complex. Along the ventral region of the differentiating ovary, the epithelium invaginates to form the ovigerous lamellae whose developing surface epithelium, the germinal epithelium, is composed of epithelial cells, germline cysts with oogonia, oocytes, and developing follicles. The germinal epithelium rests upon a basement membrane. The follicles complexes are connected to the germinal epithelium by a shared portion of basement membrane. In the differentiated ovary, germ cell proliferation in the epithelium forms nests in which there are the germline cysts. Germline cysts, groups of cells that form from a single founder cell and are joined by intercellular bridges, are conserved throughout the vertebrates, as is the germinal epithelium. Anat Rec, 293:1581Rec, 293: -1606

Germ Cell Migration, Proliferation and Differentiation during Gonadal Morphogenesis in All‐Female Japanese Flounder (Paralichthys Olivaceus)

“…The rapid proliferation of germ cells was earlier observed than the formation of the ovarian cavity and meiosis of germ cells in P. olivaceus . Similar results were also reported in Oryzias latipes (Kagawa, ), Cyprinus carpio (Mazzoni et al, ), and Lepomis macrochirus (Gao et al, ). As mitosis proceeded, oogonia inside the cysts formed a cluster of interconnected cells known as cell nests.…”

“…For light microscopy, the whole larvae and the gonads from juveniles and adult were dehydrated through a graded series of alcohols and embedded in paraffin wax. Serial sections (5–8 μm) were stained with haematoxylin/eosin (H&E), periodic‐acid‐Schiff (PAS)/haematoxylin/metanil yellow (Quintero hunter et al, ) and reticulin method (Mazzoni et al, ).…”

Previtellogenic oocytes of South African largemouth bass Micropterus salmoides Lacépède 1802 (Actinopterygii, Perciformes) ‐ the Balbiani body, cortical alveoli and developing eggshell

“…In many cases, the cystoblasts continue mitotic division (karyokineses), however, cytokinesis is not complete, and the female germline cysts composed of cystocytes are formed. In the ovaries of teleost fish, and also of other vertebrates and of invertebrates, some cystocytes are eliminated by cell death, the remaining begin meiosis and continue the development as the oocytes (Bilinski, Kloc, & Tworzydlo, ; Elkouby, ; Elkouby, Jamieson‐Lucy, & Mullins, ; Elkouby & Mullins, ; Ikami, Nuzhat, & Lei, ; Kloc, Bilinski, Dougherty, Brey, & Etkin, ; Lei & Spradling, ; Marlow & Mullins, ; Mazzoni, Grier, & Quagio‐Grassiotto, ; Nakamura et al, ; Żelazowska & Fopp‐Bayat, ). The karyokineses of cystoblasts that lead to the formation of cysts are sometimes stopped in the ovaries and the cystoblasts enter meiosis without producing the cysts (Grier, Porak, Carroll, & Parenti, ).…”

Testicular differentiation and development in South American catfish, surubim, Pseudoplatystoma fasciatum

“…It alters gonad morphology and affects growth rate and maturation age (Strussmann, Cota, Cota, Phonlor, Higuchi, & Takashima, 1996;Strussmann, Takashima, Takashima, & Toda, 1996); which are characteristics of commercial interest, especially in monosex farming (Marjani, Jamili, & Mostafavi, 2009). Therefore, the morphological indications of gonadal differentiation may be related to the different arrangements of somatic and germ cells during early development (Mazzoni, Grier, & Quagio-Grassiotto, 2010, 2014Valentin et al, 2016), and may precede the formation of sperm ducts in males and the start of meiosis in females (Kobayashi et al, 2011;. Early identification of the testis was possible due to the future fringes appearance of the gonad as a result of the proliferation of the stroma and also the early cellular arrangement (circular formation) of somatic cells in the distal region; which later originated the sperm ducts in P. fasciatum and which has been reported in several gonochoristic species (Kobayashi et al, 2011;Komatsu, Nakamura, & Nakamura, 2006;Meijide, Lo Nostro, & Guerrero, 2005).…”