Changes in steroid hormone profiles and ovarian histology during salmon pituitary‐induced vitellogenesis and ovulation in female New Zealand longfinned eels, Anguilla dieffenbachii gray

Abstract

To assess whether induced vitellogenesis in longfinned eels mimics that in naturally maturing conspecifics, female eels were artificially matured and steroid hormone status and oocyte cytology during oogenesis were evaluated. Successful induction of vitellogenesis was evident from the presence of yolk granules in the ooplasm of salmon pituitary homogenate (SPH)-injected, but not saline-, 17-hydroxyprogesterone-, and/or gonadotropin-releasing hormone-treated fish. In SPH-treated females, the migratory nucleus stage was reached after 33-53 days, followed by ovulation around 30 hours after induction of final maturation and ovulation. Only a portion of the germ cells matured, although resumption of vitellogenesis was seen in the majority of oocytes. In contrast, in ovaries of saline-injected controls, the most advanced oocytes were early vitellogenic. Atretic follicles were observed in ovaries of all eels, but abundance was greater in controls than in SPH-treated fish. SPH injections elevated plasma levels of estradiol-17beta and androgens, but not pregnenes, from within three days of treatment. Our results indicate that sex steroid levels in midvitellogenic hormone-treated females are similar to those in wild midvitellogenic females. In contrast, differences in yolk morphology of midvitellogenic follicles were seen between SPH-treated and wild females, especially in the second crop of midvitellogenic-sized oocytes measuring 300-400 microm in diameter. We discuss whether the observed differences affect egg quality, and perhaps explain the short life span of captive-bred eel larvae. J. Exp. Zool. 289:119-129, 2001.

Water temperature manipulation can induce oocyte maturation and ovulation in the common Japanese conger, Conger myriaster

“…Although the spawning type of this species is unknown, female common Japanese conger may spawn multiple times in a spawning season and/or during their lives under captive conditions. The variations in plasma steroid levels observed during ovarian development in the present study were different from those in other anguilliform fish, such as anguillid eels, in which maturation was induced by exogenous hormone treatment (Chiba et al, 1994;Ijiri et al, 1995;Lokman et al, 2001;Matsubara et al, 2005;Sato et al, 2000). Plasma E2 levels increased rapidly at the end of vitellogenesis in these anguillid eels and were maintained at a high level during oocyte maturation.…”

“…In anguilliform fish, artificial maturation techniques have been improving markedly, although these methods depend on exogenous hormone treatments Boëtius, 1967, 1980;Horie et al, 2001Horie et al, , 2003Horie et al, , 2008Lokman et al, 2001;Ohta et al, 1996;Yamamoto et al, 1974). However, little is known regarding the maturation process containing endocrine conditions without exogenous hormone treatments because the majority of oocyte development occurs during the spawning migration, which has yet to be described in anguilliform fishes.…”

Effects of reproductive stage and 11-ketotestosterone on LPL mRNA levels in the ovary of the shortfinned eel

“…This was further reinforced by the great increase in stored lipid by two orders of magnitude, an increase that was refl ected by the presence of large numbers of lipid droplets in the cytoplasm of EV oocytes. Hormonal treatment with SPH successfully advanced gonadal development ( 36,37 ) and led to dramatic increases in stored lipid in both the MV and P-OV stages. Fig.…”

The gonad growth of Anguilla bicolor bicolor induced by hormone combination of HCG, MT, E2, and antidopamine

“…Berdasarkan pada tingkat pertumbuhan gonad yang digunakan oleh Lokman et al (2001), Le Menn et al (2007, dan Tomkiewicz et al (2007), perkembangan oosit pada minggu kedua dan keempat telah mencapai fase IIIa dan IIIb yaitu fase pre-vitelogenesis yang ditandai dengan mulai terbentuknya butir kuning telur. Fase IIIa merupakan tahap perkembangan perinukleolus seperti terlihat pada Gambar 4B, yang ditandai dengan terbentuknya nukleolus di sekitar selubung inti.…”