Sustained hormone release. III. Use of gonadotropin releasing hormone analogues to induce multiple spawnings in sea bass, Lates calcarifer
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Two gonadotropin releasing hormone analogues (GnRHa), [D-Ala6, Pro9-ethylamide] mammalian GnRH and [D-Arg6, Pro9-ethylamide] salmon GnRH, were shown to induce spawning in see bass. A single injection of GnRHa induced one spawning, but multiple (two to four) injections spaced 24 h apart produced one to four spawnings in individual females. More striking were the sea bass that spawned up to five times after an osmotic pump, which releases GnRHa for 14 days, was implanted. A less expensive, but equally effective method was implantation of GnRHa in pellets with a cholesterol-cellulose matrix. Multiple spawnings in a single female were produced by only two pellets implanted at one time; individual fish released up to 7 million eggs with good fertility and hatching rates. Individual sea bass were shown to remature in the same season and produce multiple spawnings in both June and September if stimulated with GnRHa in pellets. Stimulation of multiple spawnings was not clearly different if the mammalian or salmon GnRH analogues were used or if the stimulation occurred at the new or first quarter moon. Finally, an individual male was shown to be capable of fertilizing the eggs of one female for at least four sequential spawnings, although the fertility and hatching rates were higher if two males were placed with a female. In conclusion, pellets, pumps and repeated injections produced multiple spawnings in sea bass, but the pellets were more reliable, cheaper, and less stressful to the fish.
CitationAlmendras, J. M., Duenas, C., Nacario, J., Sherwood, N. M., & Crim, L. W. (1988). Sustained hormone release. III. Use of gonadotropin releasing hormone analogues to induce multiple spawnings in sea bass, Lates calcarifer.
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Milt production of sea bass Lates calcarifer Bloch administered an analogue of luteinizing hormone-releasing hormone and 17α-methyltestosterone GV Hilomen-Garcia, RB Baldevarona & F Lacanilao -
The Israeli Journal of Aquaculture-Bamidgeh, 2002 - Society of Israeli Aquaculture and Marine BiotechnologyThe milt production responses of sexually mature sea bass Lates calcarifer to (D-Ala6, Pro9-N- ethylamide) luteinizing hormone-releasing hormone (LHRHa) and 17α-methyltestosterone injections were examined. At 24 h after injection of a low dose of LHRHa (20 μg/kg BW), the sperm count decreased significantly compared to saline-treated fish, but it returned to pre-treatment levels 48 h after injection, suggesting a possible hydration of the milt. Other milt parameters (milt volume, spermatocrit, sperm production) in LHRHa-treated fish did not vary from their controls at 24 or 48 h after injection but the overall pattern suggested a reduction in milt viscosity. Total expressible milt and spermatozoa collected over the 48-h experiment was approximately three-fold higher in LHRHa-injected fish than in saline-injected fish, indicating a stimulation of spermatozoa production, not merely milt dilution due to hydration. In a second experiment, sperm count and spermatocrit were significantly lower than those of saline-injected fish at 17 and 48 h after a single injection of a high dose of LHRHa (80 μg/kg BW). A methyltestosterone injection combined with the LHRHa injection also resulted in a significantly lower sperm count, but the spermatocrit remained comparable to the control group, suggesting a suppression of the LHRHa-induced milt hydration response. Results demonstrate that LHRHa stimulates milt hydration and spermatozoa production in milting sea bass and that a simultaneous methyltestosterone injection partially suppresses this response.
Spermiation response of mature rabbitfish, Siganus guttatus Bloch, to luteinizing hormone-releasing hormone analogue (LHRHa) injection LMB Garcia -
Aquaculture, 1991 - ElsevierA method to quantify the spermiation response of mature rabbitfish to hormonal therapy is described. Spermatocrit or packed sperm volume was measured after milt loaded in non-heparinized microhematocrit capillary tubes was centrifuged for 45 min at 15 000 × g. Sperm density was estimated by a standard hemacytometer method. However, sperm density can be predicted from spermatocrit since their relationship is highly and positively correlated (Y = 29.5 + 2.95 Xr = 0.83; P < 0.01). Milt production by mature rabbitfish was highest (4.9 ml per kg body weight) at 24 h after injection of 20 μg of luteinizing hormone-releasing hormone analogue (D-Ala6, Pro9-LHRH-ethylamide) per kg body weight and coincided with low spermatocrit (68%) and sperm density (14.1 × 106 spermatozoa per μl milt) levels. These results demonstrate that spermiation in mature rabbitfish can be reliably assessed by a spermatocrit method and that LHRHa can effectively stimulate spermiation in this species.
Milt-egg ratio in artificial fertilization of the Asian freshwater catfish, Clarias macrocephalus, injected salmon gonadotropin-releasing hormone analogue and domperidone MVP Tambasen-Cheong, JD Tan-Fermin, LMB Garcia & RB Baldevarona -
Aquatic Living Resources, 1995 - Cambridge University PressThe author deals with the catfish Clarias macrocephalus which are artificially fertilized by inducing females to spawn using various hormones. This paper investigates the effect of Ovaprim on milt production and fertilizing ability of Clarias macrocephalus and determines the optimal milt-egg ratio required for artificial fertilization. Materials and methods used are: fish collection and handling, hormone administration, preparation of testicular homogenate, measurement of sperm density, dry fertilization, statistical analysis.