Gonadotropin-releasing hormone analogue (GnRH-A) induces multiple ovulations of high-quality eggs in a cold-water, batch-spawning teleost, the yellowtail flounder (Pleuronectes ferrugineus)

TitleGonadotropin-releasing hormone analogue (GnRH-A) induces multiple ovulations of high-quality eggs in a cold-water, batch-spawning teleost, the yellowtail flounder (Pleuronectes ferrugineus)
Publication TypeJournal Article
Year of Publication1997
AuthorsLarsson, DGJ, Mylonas CC, Zohar Y, Crim LW
JournalCanadian Journal of Fisheries and Aquatic Sciences
Volume54
Issue9
Pages1957 - 1964
Abstract

Sustained delivery systems for a gonadotropin-releasing hormone analogue (GnRH-A) were used for the first time in a cold-ocean teleost for inducing multiple ovulations. Intramuscular implants of 75-224 μg/kg GnRH-A ((D-Ala6,Pro9-NHEt)LHRH) were administered to female yellowtail flounder (Pleuronectes ferrugineus) either as a cholesterol pellet or as biodegradable microspheres. Females implanted with GnRH-A ovulated 3-4 weeks earlier than controls, producing multiple batches of high-quality eggs (average rates of fertilization 66-68% and hatching 55-60%); control fish eggs had significantly lower fertilization (39%) and hatching rates (25%). GnRH-A treatment doubled the egg production, synchronized the females, and shortened the interovulatory periods. The proportion of round, clear, and floating eggs lacking a perivitelline space before fertilization was an indicator of the fertilization (r2= 0.60) and hatching (r2 = 0.56) success. Moreover, egg collections of less than 10 mL varied greatly in quality, whereas larger batches, generally promoted by GnRH-A, consisted of relatively high-quality eggs. GnRH-A treated fish had increased plasma levels of estradiol- 17β 4 days after implantation. A model for prediction of the time between hormone treatment and first spawning (T; days) was developed using the initial follicle diameter (D; μm) as the only predictor (T = 365(D - 380)-082; r2 = 0.91).

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