References of "Mélard, Charles"
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See detailOvarian steroidogenesis inhibition by constant photothermal conditions is caused by a lack of gonadotropin stimulation in Eurasian perch
Milla, S.; Mandiki, S. N. M.; Hubermont, P. et al

in General and Comparative Endocrinology (2009), 163(3), 242-250

In fish, the reasons for the inhibition of reproduction by constant photothermal conditions of rearing are far from clear. In an in vivo experiment, two groups of females reared under natural (4-28 ... [more ▼]

In fish, the reasons for the inhibition of reproduction by constant photothermal conditions of rearing are far from clear. In an in vivo experiment, two groups of females reared under natural (4-28 degrees C) or constant photothermal conditions (20-22 degrees C, photoperiod 12/12) were investigated for gonad development, sex-steroids (testosterone-T, 17-beta-estradiol-E2 and 11 Keto-Testosterone-11KT) dynamics and brain aromatase activity in January, February and March. Two days before each sampling date, a group of females reared under constant conditions was injected with HCG (Human Chorionic Gonadotropin: 100 Ul/kg) and evaluated for the same parameters. In addition, in vitro ovarian steroidogenesis capacity for each female was determined with or without stimulation by HCG and/or IGF-1 (insulin-like Growth Factor-1). The results indicate that vitellogenesis stage is the limit ovarian stage never reached in females submitted to constant photothermal conditions. This was associated with gonadogenesis delay and low levels of circulating sex-steroids (T, E2 and 11KT). Nevertheless, HCG injections partly counteracted the plasma steroid deprivation, indicating that ovaries from fish reared under constant photothermal conditions suffer from a lack of gonadotropin stimulation, maybe caused by plasma LH suppression. Such finding was confirmed by the in vitro ovary incubation test. HCG and IGF-1 treatments induced broad testosterone and 17-beta-estradiol elevations and the exposure to constant photothermal conditions, in some cases, decreased that response to HCG. In conclusion, we show that the inhibition of reproductive cycle in Eurasian perch females by constant photothermal conditions of rearing may be related to lower sex-steroid levels and to an inhibition of ovarian regulation by gonadotropins (at least LH), probably stopping gonadogenesis before vitellogenesis stage. (C) 2009 Elsevier Inc. All rights reserved. [less ▲]

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See detailSexual dimorphism in two pure cichlid species, Oreochromis niloticus and Sarotherodon melanotheron, and their intergeneric hybrids
Toguyeni, A.; Fauconneau, B.; Mélard, Charles ULg et al

in African Journal of Aquatic Science (2009), 34

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See detailGenetic Improvement of Growth in perch production: domestication, sex control, hybridization and strain selection.
Rougeot, Carole ULg; Mélard, Charles ULg

in Proceedings of the internationl workshop on Percid Fsih Culture (2008)

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See detailChapter6 : Genetic Improvement of Growth
Rougeot, Carole ULg; Mélard, Charles ULg

in Farming Of Eurasian perch. Volume 1: Juvenile production. (2008)

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See detailEffect of high temperature during embryogenesis on the sex differentiation process in the Nile tilapia, Oreochromis niloticus.
Rougeot, Carole ULg; Prignon, Christian ULg; Ngouana Kengne, Cyrille Valence et al

in Aquaculture (2008), 276

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See detailEarly sex reversal during the embryonic development in the Nile tilapia
Rougeot, Carole ULg; Kanfitine, Samane, Yadja; Prignon, Christian ULg et al

in Cybium (2008), 32(2), 104-105

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See detailEffect of sexual genotype on the reproductive biology of the Nile tilapia, O.niloticus.
Rougeot, Carole ULg; Badiane, A. A.; Prignon, Christian ULg et al

Poster (2007, June)

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See detailSex steroid dynamics during embryogenesis and sexual differentiation in Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Krim, A.; Mandiki, S. N. et al

in Theriogenology (2007), 67(5), 1046-1052

It is widely accepted that sex steroid hormones play an important and a specific role during the process of sex differentiation in fish. In order to describe the role of the three main sex steroid ... [more ▼]

It is widely accepted that sex steroid hormones play an important and a specific role during the process of sex differentiation in fish. In order to describe the role of the three main sex steroid hormones (testosterone--T, 17beta-estradiol--E2 and 11keto-testosterone--11KT) during embryogenesis and sex differentiation in Eurasian perch, Perca fluviatilis, eggs, larvae and juveniles originating from two mixed-sex and two all-female progenies were regularly sampled from fertilization to hatching (D0) and from hatching to day 70 post-hatching (D70). Just after spawning, a significant amount of sex steroids [T (1634.2pgg(-1)), E2 (554.4pgg(-1)) and 11KT (1513.2pgg(-1))] was measured in non-fertilised eggs suggesting a maternal transmission of these steroids. From D2 to D70 post-hatching, E2 levels were significantly higher in mixed-sex progenies (median: 725.7pgg(-1)) than in all-female progenies (156.2pgg(-1)) and significantly increased after the onset of the histological differentiation of the gonad in both progenies (D35). Levels of 11KT were significantly higher in mixed-sex (median: 431.5pgg(-1)) than in all-female progenies (below the limit of assay detection) and significantly increased at D35 in all-female progenies (median value: 343.2pgg(-1)). Mean 11KT to E2 ratio was six-fold higher in mixed-sex progenies (1.35) than in all-female progenies (0.24). The data suggest that the 11-oxygenated androgen (11KT) plays a major role in the male differentiation process, and that sex differentiation in Eurasian perch is probably determined by the 11KT to E2 ratio. [less ▲]

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See detailStudy of sex ratio in progeny of a complex Oreochromis hybrid, the Florida red tilapia
Desprez, D.; Briand, C.; Hoareau, M. C. et al

in Aquaculture (2006), 251(2-4), 231-237

This paper reports a study on the progeny sex-ratio distribution in the Florida red tilapia. This hybrid originated as a cross between O. mossambicus male and O. urolepis hornorum female, which was then ... [more ▼]

This paper reports a study on the progeny sex-ratio distribution in the Florida red tilapia. This hybrid originated as a cross between O. mossambicus male and O. urolepis hornorum female, which was then crossed with 0. niloticus and 0. aureus in order to improve its growth rate and its resistance to low temperature. We have studied the sex-ratio of I I I progenies from 46 females and 12 males, where the male percentage varied between 5% to 89%. The analysis of distribution showed three groups characterised by a mean male percentage of 26.7 +/- 9.81; 50.0 +/- 8.9 and 70.3 +/- 5.5%. The stability of sex ratios in repeated single pair matings and the parental influence on progeny sex ratios obtained are in agreement with a polygenic basis of sex determination in this complex hybrid. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailGynogenesis induction and sex determination in the Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Ngingo, J. V.; Gillet, Laurent ULg et al

in Aquaculture (2005), 243(1-4), 411-415

In the present study, we used meiotic gynogenesis, widely used in studies on sex determination, to confirm female homogamety in Eurasian perch, Perca fluviatilis. Sperm irradiated with UV for 400 s was ... [more ▼]

In the present study, we used meiotic gynogenesis, widely used in studies on sex determination, to confirm female homogamety in Eurasian perch, Perca fluviatilis. Sperm irradiated with UV for 400 s was used to artificially fertilized eggs. The diploid of the resulting embryos was restored by a heat shock (30 degreesC) applied to the eggs 5 min postfertilization, for 25 min. Fertilization (ranging between 45% and 75%) and survival rates at hatching (ranging between 3.4% and 46.6%) were not significantly different (P>0.05) between the diploid control and gynogenetics. The diploid controls and two batches of gynogenetics contained 100% diploid larvae, whereas two other batches of gynogenetics contained 6.7% and 10.0% triploid larvae. The sex ratios of the diploid controls were not significantly different from 1:1, whereas all gynogenetic families were 100% female. These results confirm female homogamety in Eurasian perch, demonstrated by the use of hormonally mascilinized breeders in a previous study. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailComparative study of the reproductive characteristics of XY male and hormonally sex-reversed XX male Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Nicayenzi, F.; Mandiki, S. N. et al

in theriogenology (2004), 62(5), 790-800

In order to compare the reproductive capacity of XY male versus XX male (neomales) Eurasian perch (Perca fluviatilis), we determined the sperm quality (sperm concentration and motility) and reproductive ... [more ▼]

In order to compare the reproductive capacity of XY male versus XX male (neomales) Eurasian perch (Perca fluviatilis), we determined the sperm quality (sperm concentration and motility) and reproductive characteristics such as gonadosomatic index (GSI), fertilization rate and sex steroid levels (testosterone, T; 17 beta-estradiol, E2 and 11-ketotestosterone, 11KT) during the reproductive season. Median GSI was not significantly different between XY males (7.9%) and XX males (7.5%). Fertilization rates ranged between 30.0 and 98.0%. Sperm concentration ranged between 27.9 x 10(9) and 42.0 x 10(9) spermatozoa ml(-1). Median level of T, 11KT and E2 levels increased in the middle of the reproductive season (2136.0, 2409.0 and 3252.0 pg ml(-1), respectively) and decreased at the end (1657.0, 2006.6 and 431.0 pg ml(-1) respectively). Sperm motility was assessed by CASA and expressed by the curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), linearity (LIN), percentage of motile sperm (% MOT) and motile concentration (MOC). Overall, there were not any significant differences between XY and XX males. In conclusion, no differences of reproductive capacities were observed between XY males and XX males suggesting that the last can be crossed with females to improve the productivity of Eurasian perch by producing all-female stock. (c) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailDynamics of total body fatty acids during early ontogeny of pikeperch (Sander lucioperca) larvae
Abi-Ayad, SMEA; Boutiba, Z.; Mélard, Charles ULg et al

in Fish Physiology and Biochemistry (2004), 30(2), 129-136

The fatty acid composition of pikeperch (Sander lucioperca) was determined according to their physiological status, during starvation (10 days) and feeding (28 days). In starved larvae, polyunsaturated ... [more ▼]

The fatty acid composition of pikeperch (Sander lucioperca) was determined according to their physiological status, during starvation (10 days) and feeding (28 days). In starved larvae, polyunsaturated, monounsaturated and saturated fatty acids were utilized as metabolic substrates until day 9. At day 10, all fatty acid levels remained stable or, at least, increased in larval body. Among fatty acids, docosahexaenoic acid 22:6 n-3 was used preferentially (20.3% from total fatty acids utilized) followed by palmitoleic acid 16:1 n-7 (13.9%) and then by oleic 18:1 n-9 (12.3%), linoleic 18:2 n-6 (10.1%), linolenic 18:3 n-3 (9.7%) and eicosapentaenoic 20:5 n-3 (9.1%) acids. On the other hand, arachidonic acid 20:4 n-6 was utilized very lowly (0.3%). In fed larvae, no utilization of body fatty acids was observed during the experiment. It seems that energy requirements (and others) of fed larvae were satisfied by feed. [less ▲]

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