Morphological and quantitative evaluation of the ovarian recrudescence in Nile tilapia (Oreochromis niloticus) after spawning in captivity

Abstract

The Nile tilapia is one of the most important fish species for aquaculture worldwide. Understanding their reproductive biology is essential for improving their aquaculture methods. The morphological and quantitative dynamics of ovarian recrudescence of Oreochromis niloticus was studied for 21 days postspawning. To accomplish this, breeding females were kept in controlled conditions and ovarian samples were collected weekly for histological, ultrastructural and morphometric analyses. Ovarian follicle morphology revealed an intense synthesis activity of the follicular cells, which actively contributed to formation of the zona radiata and oocyte development following spawning. Recently spawned ovaries contained follicles at all developmental stages, but they were predominantly early primary growth (∼ 42%) and full-grown follicles (∼ 20%). Remnants of spawning, postovulatory follicle complexes represented approximately 5% of the former ovarian follicles immediately after spawning, and less than 1% after 7 days. Atretic follicles accounted for approximately 2% of the follicles studied during the period. The stock of primary growth follicles was stable during ovarian recrudescence, indicating their availability for continuous recruitment. Only the frequency of full-grown follicles significantly increased in the ovaries during recrudescence, representing approximately 35% of the follicles 21 days postspawning. The diameters of all follicles were significantly different between the periods analyzed. The ovaries' morphological characteristics, the maintenance of young follicles stocks and the gradual and significant increase in the proportion and diameter of full-grown follicles showed a rapid ovarian recovery and follicular growth of O. niloticus, in 21 days at 29.5°C, necessary for the next spawning.

Dynamics of ovarian maturation throughout the reproductive cycle of the Neotropical cichlid fishCichlasomadimerus(Teleostei, Cichliformes)

“…niloticus (Rocha and Reis-Henriques 1996;Costa Melo et al 2014), the spotted metynnis, Metynnis maculatus (Kner, 1858) (Pereira et al 2013) and the zebrafish, Danio rerio (Hamilton, 1822) (Connolly et al 2014). However, unlike them, late vitellogenic oocytes were not observed in the ovary of C. dimerus during the first days following spawning.…”

Autophagy and Cathepsin D mediated apoptosis contributing to ovarian follicular atresia in the Nile tilapia

“…As well as in other teleost species, follicular atresia in Nile tilapia occurs during follicular growth but is more frequent in vitellogenic follicles that were not spawned in the reproductive season (Miranda, Bazzoli, Rizzo, & Sato, ; Santos et al, ). In this species, the follicular atresia is a good model to study the cell death pathways since females breed every three to 4 weeks under optimum cultivation conditions, and atretic follicles (AF) are present throughout the reproductive cycle (Melo, Martins, Luz, Rizzo, & Bazzoli, ; Melo et al, ). To improve the knowledge of cell death mechanisms regulating follicular atresia, we investigated the expression, interaction, and dynamics existing between key proteins of autophagy and apoptosis pathways and the crosstalk with lysosomal proteins in different phases of follicular atresia in Nile tilapia.…”

Effects of biofloc technology on reproduction and ovarian recrudescence in Nile tilapia

“…To evaluate the system effects, we needed to compare animals in the same stage of reproductive cycle. However, the Nile tilapia has an asynchronous gonad development (Melo et al., ). In a tank, for example, there are fish in different gonad development stages.…”