References of "Mélard, Charles"
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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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See detailEffects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions
Mandiki, S. N. M.; Blanchard, G.; Mélard, Charles ULg et al

in Aquaculture (2004), 229(1-4), 117-128

Survival, growth, and food intake of Eurasian perch (Perca fluviatilis) juveniles from different stocks originating from various geographic regions of Europe were compared under the same conditions of ... [more ▼]

Survival, growth, and food intake of Eurasian perch (Perca fluviatilis) juveniles from different stocks originating from various geographic regions of Europe were compared under the same conditions of laboratory-scale intensive culture. In Experiment 1, four stocks originating from Italy (1), southwest (SF) and northwest (NF) France, and Belgium (B) were examined at larval and early juvenile (initial body weight, IBW = 0.53 g) stages. In Experiment 2, B stock was compared to a Finnish (F) one in two trials, including small (IBW = 1.26 g) and large (IBW = 32 g) juveniles. In Experiment 3, small (IBW = 1.29 g) and large (IBW = 7.33 g) juveniles from Polish (P), F, and B stocks were examined. In Experiment 1, body weight means at hatching and survival at the end of the larval stage were significantly lower in the I and SF stocks than in the B and NF stocks. In the early juvenile stage, survival and growth rates were significantly lower in the I and SF stocks than in the B and NF ones. In Experiment 2, {early juvenile stage} survival in the F stock was significantly lower than in the B stock, partly due to a higher incidence of cannibalism. During this stage, growth rates and food intake or feed efficiency in the F and B stocks were comparable, but at the end of the juvenile stage, the F stock outperformed the B one. In Experiment 3, survival in all the three stocks was comparable both in small and large juveniles. In contrast to the higher performance of F juveniles in Experiment 2, growth rates were comparable between the B and F stocks, and fish from the P stock had the highest growth rates. The results indicate a high level of variation within and between hatchery stocks in survival rates, growth rates, and food intake. These variations depended on the geographic origin of the fish, with the lowest survival and growth potentials being in the stocks originating from the southern regions. These findings highlight the interest in evaluating growth and food consumption of different Eurasian perch stocks. Such evaluation is a necessary tool for genetic selection in improving performance in perch aquaculture. (C) 2004 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailSize heterogeneity, cannibalism and competition in cultured predatory fish larvae: biotic and abiotic influences
Kestemont, P.; Jourdan, S.; Houbart, M. et al

in Aquaculture (2003), 227(1-4), 333-356

Growth heterogeneity is a central problem in larviculture and especially in predatory species. It can be influenced by a wide range of intrinsic and environmental factors, of which the respective ... [more ▼]

Growth heterogeneity is a central problem in larviculture and especially in predatory species. It can be influenced by a wide range of intrinsic and environmental factors, of which the respective influences are largely unknown. The role of non-interactive (temperature, day length, light intensity, food availability and composition) and interactive factors (stocking density, initial size heterogeneity, hatching time) on growth, survival and size heterogeneity was measured in larvae and post-larvae of the European seabass Dicentrarchus labrax and Eurasian perch Perca fluviatilis. Embryos hatching later than others were found less competitive than those hatching earlier in both species, but to a greater extent in perch. By contrast, the final size heterogeneity in both species was independent from the initial size heterogeneity or recurrent size sorting. High stocking density had a positive effect on perch larvae, no effect on seabass larvae and a negative impact on the post-larvae of both species, owing principally to density-dependent access to food. Day length and light intensity produced contrasting results in larvae and post-larvae. Larvae of both species performed better under bright light and continuous day length. Post-larvae of seabass performed equally well at different light levels but did better under short day lengths, whereas post-larvae of perch were unaffected by day length but performed better under reduced light levels. Increasing food availability resulted in increasing performance of perch larvae, although cannibalism was higher for submaximal than for maintenance rations. The similarity between the two species at the larval stage, and differences at the post-larval stage can be accounted for by the increasing specialisation towards specific environments and niches. Regarding the impact of rearing factors on growth, survival and size heterogeneity, interactive variables impacted essentially on growth and survival, whereas size heterogeneity was chiefly influenced by non-interactive variables, either directly or indirectly via interactive mechanisms such as cannibalism and size-dependent mortality. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailEffect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions
Baras, E.; Kestemont, P.; Mélard, Charles ULg

in Aquaculture (2003), 219(1-4), 241-255

The effect of stocking density (10, 31.6 and 100 larvae 1(-1); three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared ... [more ▼]

The effect of stocking density (10, 31.6 and 100 larvae 1(-1); three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared from eyed-egg stage in 100-1 cages (16L:8D, 20.0 +/- 0.5 degreesC, O-2 greater than or equal to 6.0 mg 1(-1); feeding in excess with live Artemia nauplii during the photophase) during the first 3 weeks of exogenous feeding. Larvae unable to achieve the transition to exogenous feeding died in between 7 and I I days post-hatch. Later, mortality from causes other than cannibalism never exceeded 1% day(-1). Cannibalism did not start before days 10 - 11 and first consisted in the incomplete ingestion of prey attacked tail first, exclusively. This type of cannibalism never caused losses higher than 2.0% of the initial stock, and ceased after days 16-18. From days 12-14 onwards, differential growth was apparent, and cannibals turned to complete cannibalism of small prey ingested head first, which caused greater losses (28-53% of the stock). Increasing the stocking density did not compromise growth and decreased the overall impact of cannibalism through several complementary mechanisms: (i) a postponed emergence of cannibalism, (ii) a lower proportion of cannibals in the population, and (iii) probably a lower rate of cannibalism per capita as predation was complicated and less directed at high stocking density. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailInheritance of sex in two ZZ pseudofemale lines of tilapia Oreochromis aureus
Desprez, D.; Mélard, Charles ULg; Hoareau, M. C. et al

in Aquaculture (2003), 218(1-4), 131-140

This paper reports a study on the sex determination system of the blue tilapia, Oreochromis aureus. Investigations were carried out using a pseudofemale line in two populations of O. aureus, known as ... [more ▼]

This paper reports a study on the sex determination system of the blue tilapia, Oreochromis aureus. Investigations were carried out using a pseudofemale line in two populations of O. aureus, known as Egyptian Population (EP) and Israel Population (IP). In O. aureus, males are the homogametic sex (ZZ/ZW), and sex reversal of fry with estradiol results in the production of some functional sex-reversed fish with a female phenotype and ZZ male genotype, known as pseudofemales or A-females. Crosses between ZZ pseudofemales and ZZ males theoretically should provide monosex ZZ male progeny only. We have studied the sex ratios of progeny from 43 IP (F-2 to F-3 generations) and 51 EP (F-1 to F-5 generations), pair-matings between normal males and pseudofemales. In IP, the male percentage in progenies ranged between 83% to 100% in F-2 and 66% to 100% in F-3. In EP, male percentage was more constant, varying from 88% to 100% in F-1, from 96% to 100% in F-3 and from 97% to 100% in F-5. In EP, F-2 and F-4 pseudofemales produced only monosex male progeny. This apparent difference in sex ratio frequency distributions between the two O. aureus pseudofemale lines could be due to the selection of males. EP pseudofemales were mated with their siblings for F-2 and F-3 pseudofemales or with closely related males for F-4 and F-5 pseudofemales. Conversely, IP pseudofemales were crossed with nonrelated males originating from research center broodstock, resulting in a higher proportion of females in sex ratio of progenies from successive generations of pseudofemales. The role of inbreeding is discussed in the context of predominantly monofactorial sex chromosome determination system operating in this species, influenced by other factors (genetic and environmental). The present study also shows that it is possible to fix the male sex determining factors (Z sex chromosome and genetic factors) in a line of pseudofemales, producing a high percentage of male progeny in five successive generations. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailProduction of a high percentage of male offspring with a natural androgen, 11 beta-hydroxyandrostenedione (11 beta OHA4), in Florida red tilapia
Desprez, D.; Geraz, E.; Hoarea, M. C. et al

in Aquaculture (2003), 216(1-4), 55-65

This paper reports the effects of a natural androgen, 11beta-hydroxyandrostenedione (11betaOHA4), on sex-reversed fry of the Florida red tilapia. In a first approach, the optimal dosage and duration were ... [more ▼]

This paper reports the effects of a natural androgen, 11beta-hydroxyandrostenedione (11betaOHA4), on sex-reversed fry of the Florida red tilapia. In a first approach, the optimal dosage and duration were determined in the laboratory. The sex-reversal treatment was applied on post-yolksac stage fry (10 days after fertilisation at 27degreesC. Dosages of 20, 30, 40 and 50 mg of 11betaOHA4 kg(-1) of food were used during periods ranging from 10 to 35 days. Dosages of 40 or 50 mg of 11betaOHA4 kg(-1) of food during 21-35 days significantly increased the male percentage in sex-reversed groups in comparison to control groups. A lower but still significant deviation of the male percentage was observed when a dosage of 40 mg kg-1 was given during at least 28 days. Lower dosages did not significantly affect the sex ratio of treated groups. Based on the results of these observations, a follow-up study was conducted to evaluate the efficiency of this natural androgen for an intensive production of sex-reversed fry. Optimal dosage (50 mg kg-1) and treatment duration (28 days) were applied to increasing stocking density of fry (8000-11,000 fish m(-2)), producing a mean male percentage of 99.1% on the 510,000 treated fry. This study demonstrates the masculinizing efficiency of 11betaOHA4 in Florida red tilapia. Interest of a natural androgen, used in sex-reversal treatment, is discussed, particularly for the Florida red tilapia strain. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailInduce triploidy by heat shock in Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Minet, Laurent; Prignon, Christian ULg et al

in Aquatic Living Resources (2003), 16(2, MAR-APR), 90-94

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce ... [more ▼]

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce sterility, triploidy induction was attempted by subjecting fertilised eggs to heat shocks. Different combinations of temperature (28, 30, 34, 35 and 36 degreesC), duration (2, 5, 10 and 25 min) and time of shock initiation (TI = 3, 5 and 7 min post-fertilisation) were tested. Flow cytometry analysis was used to assess ploidy level of control and heat-shocked larvae. Low intensity (28-30 degreesC) and long duration (10 and 25 min) shocks lead to significantly higher survival (44 +/- 26%) and triploidisation (71 +/- 26%) rates than high intensity (34-36 degreesC) and short duration (2 and 5 min) shocks (17 +/- 19% and 21 +/- 26%, respectively). The most effective conditions for efficient triploidy induction were low intensity shock of 30 degreesC, applied 5 min post-fertilisation for 25 min. This treatment led to the production of all-triploid populations (100%) with up to 43% survival rate. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/IRD/Inra/Cemagref. All rights reserved. [less ▲]

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