Development of the follicle complex and oocyte staging in red drum, sciaenops ocellatus linnaeus, 1776 (perciformes, sciaenidae)

Abstract

Pelagic egg development in red drum, Sciaenops ocellatus, is described using tiered staging. Based on mitosis and meiosis, there are five periods: Mitosis of Oogonia, Active Meiosis I, Arrested Meiosis I, Active Meiosis II, and Arrested Meiosis II. The Periods are divided into six stages: Mitotic Division of Oogonia, Chromatin Nucleolus, Primary Growth, Secondary Growth, Oocyte Maturation and Ovulation. The Chromatin Nucleolus Stage is divided into four steps: Leptotene, Zygotene, Pachytene, and Early Diplotene. Oocytes in the last step possess one nucleolus, dispersed chromatin with forming lampbrush chromosomes and lack basophilic ooplasm. The Primary Growth Stage, characterized by basophilic ooplasm and absence of yolk in oocytes, is divided into five steps: One-Nucleolus, Multiple Nucleoli, Perinucleolar, Oil Droplets, and Cortical Alveolar. During primary growth, the Balbiani body develops from nuage, enlarges and disperses throughout the ooplasm as both endoplasmic reticulum and Golgi develop within it. Secondary growth or vitellogenesis has three steps: Early Secondary Growth, Late Secondary Growth and Full-Grown. The Oocyte Maturation Stage, including ooplasmic and germinal vesicle maturation, has four steps: Eccentric Germinal Vesicle, Germinal Vesicle Migration, Germinal Vesicle Breakdown and Resumption of Meiosis when complete yolk hydration occurs. The period is Arrested Meiosis II. When folliculogenesis is completed, the ovarian follicle, an oocyte and encompassing follicle cells, is surrounded by a basement membrane and developing theca, all forming a follicle complex. After ovulation, a newly defined postovulatory follicle complex remains attached to the germinal epithelium. It is composed of a basement membrane that separates the postovulatory follicle from the postovulatory theca. Arrested Meiosis I encompasses primary and secondary growth (vitellogenesis) and includes most of oocyte maturation until the resumption of meiosis (Active Meiosis II). The last stage, Ovulation, is the emergence of the oocyte from the follicle when it becomes an egg or ovum.

Ovarian nests in cultured Russian sturgeon Acipenser gueldenstaedtii and North American paddlefish Polyodon spathula comprised of previtellogenic oocytes

“…In anurans, cystoblasts were located within germ cell nests and in germ patches on the surface of the ovaries (Kloc et al , ; Ogielska & Kotusz, ). Investigations of sexually mature teleosts have shown that within their ovaries germline stem cells, cystoblasts and cysts composed of cystocytes were located peripherally in germ cell nests, also termed oogonia nests (Grier et al , ; Quagio‐Grassiotto et al , ; Grier, ; Wildner et al , ). In the ovary of the spotted pimelodus Pimelodus maculatus Lacépède 1803, undifferentiated cells (germline stem cells) and differentiated cells (cystoblasts) were distinguished.…”

Sexual development and maturity scale for the angel shark Squatina squatina (Elasmobranchii: Squatinidae), with comments on the adequacy of general maturity scales

“…This need for further analysis is particularly the case for the extra-testicular ducts and OE to distinguish the regenerating and regression phases as described by Brown-Peterson et al (2011), if these phases are present in this species. On the other hand, the proposal of Brown-Peterson et al (2011) is not adaptable to all teleosts because interspecific variations in fish oocyte development do not lend themselves to a standard terminology across all fishes (Grier 2012). Specific for elasmobranchs, the proposal of ICES (2013) includes a unique scale for viviparous species, despite the large number of reproductive strategies available within this group, until scientific evidence suggests otherwise (ICES 2013).…”

“…Yet, specific characteristics from gonad development do not correlate directly with the reproductive cycles or modes (Koob & Callard 1999), and consequently general scales based on appearances of the reproductive tract will likely benefit from considering the gonad development type apart from the reproductive mode. Notwithstanding, staging schemes need to be adaptable to species' variations that can account for the extreme reproductive diversity of fishes (Grier 2012), which indicates the need for the development of adaptable staging techniques. Additionally, Poulakis (2013) pointed out the importance of considering the methods used to as sign maturity and the consistency of these across studies.…”

“…Therefore, this study sought to enhance the recent standardisation efforts by using a flexible classification system which is based on an ontogenic approach, providing a comprehensive description of the maturity phases of an under-studied species and genus, by complementing unambiguous descriptions and criteria and by highlighting the relevant difficulties in maintaining uniformity with the most recent proposals. Grier (2012) pointed out the need for species-specific macroscopic and microscopic techniques with adaptable staging systems given the reproductive diversity and variability of fishes, which do not allow a standard terminology across all species with different life history strategies. …”

“…Additionally, interspecific variations in fish oocyte development do not lend themselves to a standard terminology across all fishes. Therefore, a staging schema for oocyte development needs to be adaptable to species' variations (Grier 2012). The most recent proposals of general maturity scales for elasmobranchs, viz.…”