Induction to final maturation and ovulation of lambari (Astyanax altiparanae) with gonadotropin-releasing hormone (GnRH) analogs

Author(s)

Mariana Roza de Abreu

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2020-09-14.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2020-08-05
• Advisor: Sergio Ricardo Batlouni

Abstract

The present thesis was divided into three chapters, in the first one a review of the themes related to the thesis is presented, the other two chapters are manuscripts prepared from the experiments carried out during the doctorate. In the manuscript I (chapter II) we evaluated lambari (Astyanax altiparanae) reproductive performance using different protocols of reproduction in captivity, such as the administration of analogue of salmon gonadotropin-releasing hormone (sGnRHa) and carp pituitary extract (CPE) as well as without the use of hormonal therapy. We performed two consecutive experiments with mature lambari males and females (six months old) using single (Exp. 1) or fractioned doses (10% + 90% - 12h interval) (Exp. 2). In Exp. 1, six sGnRHa doses (ranging from 1 to 160 µg kg-1) were applied in three replicates (five females and 10 males each); in Exp. 2, three sGnRHa doses (10, 100 and 1000 µg kg-1) were applied in four replicates (five females and 10 males each). In both experiments 6 mg of CPE kg-1 and saline solution were used as positive and negative controls, respectively. Quantification of 17α-20β-dihydroxy-4-pregnen-3-one (17,20β-P) and prostaglandin F2α plasma levels and ovarian histological evaluations were introduced in Exp. 2 via the separation of spawned and unspawned females. Using a single dose, the spawning rate was low and similar between all groups (from 0 to 20%). Using fractioned doses, the spawning rate of CPE (60%) was higher than all other groups (from 10 to 25%), with the exception of the highest sGnRHa dose (40%). Spawning and elevation of 17,20β-P levels occurred in some females of the negative control (Exp. 2). Therefore, only CPE fractioned doses therapy improved lambari ovulation but were not conditional for obtaining ovulation. Only unspawned females treated with fractioned CPE doses, but neither sGnRHa nor negative control, attained final oocyte maturation.In addition, spawning in sGnRHa groups occurred in a similar extent as in negative control and sGnRHa-treated groups did not show any dose dependent response considering all variables measured. Therefore, it was possible that spawning in sGnRHa groups were just due to grouping of fish, similar to negative control. In conclusion, the fractioned dose of CPE was the only treatment that provoked final oocyte maturation in all treated females and a significant enhance in reproductive performance comparing to all other treatments. In the manuscript II (chapter III) we evaluated the effect of luteinizing hormone-releasing hormone ethylamide analogue (LHRHa) with and without domperidone on reproductive performance of lambari and the quantification of plasma levels of 17,20β-P and PGF2α, as well as histological evaluation of ovarian structures in two independent and consecutive experiments. In the first, five doses of LHRHa (20, 60, 180, 540 and 1620 μg kg-1) were tested with three replicates each, while in the second the dose of 180 μg kg-1 was tested in combination with 20 mg kg-1 domperidone (D) with four replicates. In both experiments, we used 0.9% saline as a negative control and 6 mg CPE kg-1 as a positive control and the females of all groups received two injections (10%; and 90% after 12 h). The doses we tested of LHRHa did not show results superior to those of the negative control. When associating LHRHa with D, we did not obtain results superior to LHRHa without association, suggesting that dopamine does not seem to play a role in the neuroendocrine control of the reproduction of this species or that this antidopaminergic is not the most suitable for lambari. The group treated with CPE was the only one with better performance than the negative control, indicating that CPE was the best hormonal therapy to induce spawning in lambari (among those tested by us). There was a decrease in fertilization and hatching rates that coincided with the two highest doses of LHRH (540 and 1620 μg kg-1), suggesting that these doses may have caused an overstimulation of the pituitary in the production of LH, which may have affected egg quality. (AU)

• FAPESP's process: 16/25988-7 - Induction to final maturation and ovulation of lambari (Astyanax altiparanae) with salmon GnRH analogue
• Grantee: Mariana Roza de Abreu
• Support Opportunities: Scholarships in Brazil - Doctorate