Diurnal rhythm of serum steroid hormone levels in the Japanese whiting, Sillago japonica, a daily-spawning teleost

Abstract

Ovarian developmental stages and serum steroid hormone levels were examined at six different times of day (0100, 0600, 1000, 1300, 1600, 2000 h) in a marine teleost, the Japanese whiting Sillago japonica, which has an asynchronous-type ovary containing oocytes at various stages of development and spawns every day during a period ranging up to three months. The largest oocytes in the ovaries at the active vitellogenic or post-vitellogenic stages were found between 0100 and 1300 h. Oocyte maturation indicated by germinal vesicle breakdown (GVBD) occurred at 1600 h, and ovulated oocytes were observed in the ovaries collected at 2000 h. These processes were accompanied by a significant daily change in serum steroid hormone levels. The serum level of estradiol-17β showed a peak in fish with mature oocytes sampled at 1600 h. In these fish, the second-largest oocytes in the ovaries were at the initial stage of vigorous vitellogenesis, the secondary yolk stage. Therefore the highest level of serum estradiol-17β was considered to be due to the second-largest oocytes. Testosterone levels remained low and constant throughout the experimental period. The serum levels of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-diOHprog) peaked at 1600 h at which time all fish had mature oocytes. These results indicate that the Japanese whiting possesses a diurnal rhythm of oocyte development including vitellogenesis, oocyte maturation and ovulation, and further suggest that daily cycles in oocyte growth and maturation which simultaneously take place in an ovary are regulated by diurnal secretions of estradiol-17β and the maturation-inducing steroid, 17α,20β-diOHprog.

Sex ratio, reproduction, and growth of the gilthead sea bream, Sparus aurata (Pisces: Sparidae), in the Gulf of Gabes, Tunisia

“…Subsamples of gonadal tissues were fixed in Bouin's solution for two to three days and then dehydrated before being embedded in paraffin wax; after cutting, transverse sections of 5 m width were stained with hematoxylin and eosin. Reproductive phases and gamete stages were determined following Matsuyama et al (1990) and Brown-Peterson et al (2011).…”

“…Se cortaron secciones transversales de 5 m de grosor y se tiñieron con hematoxilina y eosina. Las fases reproductivas y de desarrollo de los gametos se determinaron según Matsuyama et al (1990) y Brown-Peterson et al (2011.…”

Serum 17,20β-dihydroxy-4-pregnen-3-one Levels in Pregnant and Non-pregnant Female Rockfish, Sebastes schlegeli, Viviparous Teleost, and its Production by Post-ovulatory Follicles

“…The post-ovulatory follicles of the medaka, Oryzias latipes, the Japanese whiting, Sillago japonica, and the sea bream, Pagrus major, which are all daily spawners, degenerate within one day after ovulation (Kagawa and Takano, 1979;Matsuyama et al, 1988Matsuyama et al, , 1990. On the other hand, the post-ovulatory follicles of the black rockfish in our study remained at the dorsal ovarian hilus throughout the gestation period, and degenerated soon after parturition.…”

Spawning Aggregation of Beardfish, Polymixia lowei, in a Deep-water Sinkhole off the Florida Keys

“…Terminology associated with various types of viviparity follows that of Wourms (1981). Terminology for oocyte stages, including atresia, follows that suggested by Lowerre- Barbieri et al (2011a) and is based on a compilation of terminologies presented by Wallace and Selman (1981), Macewicz (1985a, 1985b), Matsuyama et al (1990), Jalabert (2005, and . All vitellogenic oocytes are secondary growth oocytes.…”

“…For this reason, vitellogenesis is normally subdivided into various stages, although these divisions are often based on rather arbitrary features. In this study, vitellogenic oocytes are separated into three stages (primary [Vtg1], secondary [Vtg2], and tertiary [Vtg3] vitellogenesis) based on the diameter of the oocyte, the amount of cytoplasm filled with yolk, and the presence and appearance of oil droplets (in species that have oil droplets) following the work of Matsuyama et al (1990) and Murua et al (1998). However, since vitellogenic oocyte growth represents a continuum from Vtg1 to Vtg3, the exact appearance and description of these stages are species specific.…”