The Israeli Journal of Aquaculture – Bamidgeh 61(1), 2009, 5-26.
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Spawning Induction in the Carp: Past Experience and Future Prospects - A Review Z. Yaron1*, A. Bogomolnaya1, S. Drori1, I. Biton2, J. Aizen3, Z. Kulikovsky2 and B. Levavi-Sivan3 1 Department of Zoology, Tel Aviv University, Tel Aviv 69978, Israel2 Gan Shmuel Fish Breeding Center, D.N. Hefer 38810, Israel3 Department of Animal Sciences, Faculty of Agriculture, Food and Nutrition, The HebrewUniversity of Jerusalem, Rehovot 76100, Israel
Key words: Cyprinus carpio, spawning induction, oocyte maturation, GnRH, pituitary,
17β-estradiol, 17α 20β-dihydroxy-4-pregnen-3-one, hypothalamus, extract, germinal vesicle,
gonadotropin, cGtH, cLH, Dagin, GnRHa, metoclopramide, hCG, hypothalamus, dopamine,
vitellogenesis, maturation-promoting factor, cyclin B, cdc2 kinase, Pichia pastoris, Abstract
Most fish in aquaculture either fail to breed in captivity or their spawningoccurs sporadically and late in the season. This is mainly due to the lack ofnatural cues in captivity, which leads to dysfunction of the endocrine axisregulating oocyte maturation and ovulation. Hypophysation as a remedy forthis situation in fish has been employed in aquaculture since the 1930s andis still widely practiced. However, using crude pituitary homogenates in localhatcheries has frequently ended in failures that were attributed to the incon-sistent potency of the injected material and the unknown ovarian stage ofthe recipient fish. Since the mid 1980s, hypophysation has improvedthrough the introduction of a standardized dry carp pituitary extract in which
* Corresponding author. Fax: +972-3-6409403, e-mail: [email protected]. Parts of thismanuscript have been published earlier (Yaron et al., 1984, 2002a,b)
the luteinizing hormone (LH) content and activity have been calibrated (cal-ibrated carp pituitary extract = CCPE). Induction of spawning, however, issuccessful mainly in female cohorts in which 65% or more of the oocytes inan ovarian biopsy have migrating germinal vesicles. Further, due todecreasing quantities of industry-processed common carp and the expan-sion of ornamental carp production (koi and goldfish), the growing demandfor CCPE could not be met, and an alternative had to be found. A hypo-thalamic approach, introduced into Israeli aquaculture in 1993 (calledDagin), combines a superactive analog of sGnRH (10 µg/kg), with thewater-soluble dopamine (D2) receptor antagonist, metoclopramide (20mg/kg). The progress of oocyte maturation in ovarian biopsies has beenstudied in parallel with changes in levels of LH, estradiol, and the matura-tion-inducing steroid (MIS; 17α, 20β, dihydroxy-4-pregnene-3-one). Thehormone profile indicated that the gradual increases in LH and MIS follow-ing a single administration of Dagin were similar to those in fish treated withpriming and resolving doses of CCPE. This would explain why Dagin iseffective even when only a single injection is given, saving labor and reduc-ing handling stress. CCPE and Dagin were tested in parallel on commoncarp in a commercial hatchery. The spawning ratio and embryo viabilitywere similar, although the latency between injection and ovulation was con-siderably longer and more variable in Dagin-treated than in CCPE-treatedcarp. It is recommended to use CCPE at the beginning and end of thespawning season when the LH content in the pituitary is low, and Dagin inmid-season and in field spawning. Future prospects raise the possibility thatby employing molecular tools, a recombinant carp LH will be produced thatwill have the regular and expected potency of the hypophyseal approachwithout the risk of spreading pathogens from donor fish to broodstock. Workalong this line is currently in progress.
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