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International audience; We previously reported the isolation of a partial cDNA clone encoding the rainbow trout estrogen receptor (rtER). A 0.4 kb 5'-end insert of this cDNA was used to screen the trout liver lambda gt10 cDNA library, and a full-length cDNA was isolated and sequenced. The principal structural characteristics of the complete coding sequence of the rtER are: first a remarkable homology of the DNA binding (C) and hormone binding (E) domains with those of other species, and second the lack of an A region, the function of which is not yet known but which is well conserved in other species. In vitro expression of the full-length rtER cDNA was carried out after transcription by T7 RNA polymerase and translation in rabbit reticulocyte lysate. Translation product analysis shows three major proteins, the largest one of which probably corresponds to the translation of the complete open reading frame of mRNA. The rtER in vitro translation products specifically bind estrogens (estradiol and diethylstilbestrol), without competition from testosterone or cortisol. The equilibrium dissociation constant (Kd), deduced from the Scatchard plot, is in the same order of magnitude as those determined heretofore in salmon livers during classical experiments. The tissue distribution of rtER mRNA shows that the same mRNA size (3.5 kb) is also present in the pituitary and hypothalamus. However, in the pituitary, a smaller sized mRNA (1.4 kb) is also detected.

International audience; lusters, from spermatogenic and mature trout testes, according to Loir (MB), and cultured for 10-14 days. Sertoli cells are 3p-HSD negative when prepared from testes resuming spermatogenesis and from mature testes, but they are 3βHSD positive in spennatogenic testes. Progesterone, 17α-hydroxyprogesterone (17α-OH-P), and free androgens are secreted by interstitial cells, 11-ketotestosterone (11KT) being the predominating steroid produced immediately after seeding. These cells also produce high levels of glucuronated androgens. At least in mature spermiating testes they do not secrete estradiol. After isolation, interstitial cells would lose most of their ability to secrete 17α-hydroxy,20β-dihydroprogesterone (17α20β-OH-P) but they would recover it later. Testicular spermatozoa, which convert 17α-OH-P independently of s-GtH, constitute a second source of this progestagen. In addition, our results suggest that Sertoli cells could be able to secrete 17α-OH-P and also progesterone. A possible participation of the intlalobular production of the former progestagen to the local regulation of germ cell maturation is evoked.

A rapid and sensitive heterologous enzyme-linked immunosorbent assay (ELISA) was developed to measure rainbow trout maturational gonadotropin. Purified salmon maturational gonadotropin (sGtH II) was used as reference hormone. Optimization of the procedure was performed by using an anti-beta sGtH serum. Two procedures were developed: an equilibrium assay (which did not involve a preincubation step) which lasted for 8 hr and a nonequilibrium assay (which involved a preincubation step) which lasted for 26 hr. The nonequilibrium assay gave the best sensitivity (70 pg/ml sample). GtH II measurements on in vivo and in vitro samples from GnRH analogs or sGnRH experiments showed that the ELISA procedure could be used over a wide range of concentrations. The method was validated by comparing GtH II concentrations measured by both RIA and ELISA.

International audience; The protein composition of seminal fluid, blood serum, sperm plasma membrane and flagellum of rainbow trout were analysed by SDS-polyacrylamide gel electrophoresis. Immunological identity between proteins of the 2 fluids and sperm components was studied using crossed immunoelectrophoresis, rocket immunoelectrophoresis and immunoblotting. Results indicate that many seminal proteins are antigenically-related to serum proteins, proteins of sperm origin are present in seminal fluid in varying amounts, depending on the animals and sampling time, and several serum-like seminal proteins are bound to spermatozoa. Lipoproteins were isolated from seminal fluid (mean level: 33 C/g/ml) and characterized. They were identified as being HDL-like lipoproteins. A possible physiological role is proposed for these seminal lipoproteins.

International audience; In rainbow trout, a variable in vivo pituitary sensitivity to GnRH has been previously observed, depending on the stage of oogenesis. The purpose of the present work was to study, in vitro, the role of oestradiol (E2) and 17α-hydroxy,20β-dihydroprogesterone (17α20βP), respectively, involved in vitellogenesis and in oocyte maturation, upon this variability. The study was performed using primary cultures of whole pituitary cells from animals at different stages of oogenesis and subjected to increasing doses of salmon GnRH (sGnRH) after a 3-day pretreatment with control medium or medium supplemented with the steroid at levels corresponding to those circulating at the time of particular events of the sexual cycle (maturation and vitellogenesis). In control cultures, pituitary GtH responsiveness to sGnRH was maximal at ovulation, since at this time the gonadotrophs were able to respond to 10−9 M sGnRH, whereas during vitellogenesis and preovulatory stages, the minimal effective dose of sGnRH ranged between 10−6 and −8 M. We have demonstrated that 17α20βP has a positive or negative effect by acting directly on pituitary cell responsiveness to sGnRH, depending on the stages at which it is applied; its effect is positive during early vitellogenic and preovulatory stages whereas it is negative at the time of ovulation. E2 also increased pituitary responsiveness to sGnRH when applied during early vitellogenesis at low doses, corresponding to circulating levels at the time of ovulation; higher levels of E2, corresponding to circulating levels found during the last stages of vitellogenesis, did not modify pituitary responsiveness but increased cell GtH content. Results obtained are discussed in relation to hormonal changes (gonadotropin and steroid hormones) observed by different authors during the sexual cycle.

International audience; 1. The composition and protein synthesis rates of the liver, digestive tract, muscle, skin and remains were analysed in mature diploid (2.1 kg) and triploid (1.8 kg), 3 year-old rainbow trout reared at 8-degrees-C. 2. The lipid and DNA concentration of the digestive tract were respectively 16-17% and 30% higher in the triploids than in the diploids. 3. The DNA and RNA concentration in the other tissues were relatively similar between the diploids and triploids, except in the male gonad. 4. In vivo protein synthesis rates were measured using a single high dose injection of L-[U-C-14]-arginine (0.55 mmol/kg). 5. A small amount of radioactivity was found in the lipid of the whole trout (2-3% of the injected dose). 6. According to their mean Fractional Protein Synthesis Rates (FSR) of protein, tissues were ranked as follows: liver (1.6-44%.d-1), male gonads (12-30%.d-1), digestive tract (7-9%.d-1), skin (5%/d), carcass (0.4-0.6%.d-1) and muscle 0.2-0.6%/d). 7. The FSR in the liver of female diploid was almost 2 times higher than in that of the sterile triploids. 8. The FSR in the muscle, carcass and male gonad were lower in the triploids than in the diploids. 9. Mean whole body protein synthesis (WBPS) in the female and male diploids and in the sterile and male triploids was respectively 4.8, 3.1, 2.0 and 2.3 g/kg.d. 10. The contribution of the muscle to WBPS was greatly lower than that of the liver, the gonad and digestive tract in all the fish studied.

International audience; Manipulation of the opportunity to spawn was used to investigate the relationship between endocrine events, egg viability and spawning behaviour in female rainbow trout. Females were prevented from spawning by isolating them from males and gravel for up to 21 days after ovula- tion. Blood samples were taken before pairing with a male, at the onset of nesting activity, and at the completion of spawning. Plasma hormone levels of gonadotropin (GtH) and 17α,20β-dihydroxy-4-pregnen-3-one (17,20P) were measured by specific radioimmunoassays. There were no qualitative or quantitative differences in the spawning behaviour of females paired on the day of ovulation or 7. 14, or 21 days after ovulation. There was a general decrease in the viability of eggs with increasing retention times. In females paired on the day of ovulation, or after 7 or 14 days, GtH levels increased with the onset of nesting behaviour and declined as fish reached the post-spawning condition. By day 21, GtH levels before pairing were significantly higher than prepairing levels in the other three treatment groups, and did not increase at the onset of nesting, or decrease in post-spawning fish. Plasma 17,20P remained high in prepairing and nesting samples of all four groups and declined to low levels in fish in post-spawning condition. In females paired on the day of ovulation there was a significant increase in 17,20P from the prepairing to the nesting stage. These results suggest that 1,20P plays a key role in the synchronization of behavioural and maturational events at the time of spawning.

International audience; Isolated trout steroidogenic testicular cells were cultured for 10-15 days, either mixed with other round cells or after enrichment in interstitial cells. Free and conjugated progestagen and androgen secretions were assayed using specific radioimmunoassays (RIA). Free progesterone, 17 alpha-hydroxyprogesterone (17 alpha-OH-P), 17 alpha-hydroxy,20 beta-dihydroprogesterone (17 alpha,20 beta-OH-P), androstenedione, testosterone (T), and 11-ketotestosterone (11KT) were produced by testicular cells prepared from testes in spermatogenesis and mature testes. Discrete amounts of dehydroepiandrosterone (DHA) and of estradiol were secreted by mixed testicular cells prepared from mature testes, but no estradiol was detected in interstitial cell media. Conjugated androgens were produced by interstitial cells. While the production of progestagens by cells from spermatogenetic and mature testes either remained constant or increased throughout culture duration, those of free and conjugated androgens progressively decreased to low values whatever the components added to the medium. When salmon gonadotropin (s-GtH) was present permanently, androgen (free and conjugated) and progestagen secretions were stimulated for 3 to 4 days. When GtH was present discontinuously (1 day in every 3 days), the sensitivity of the cells was maintained for at least 7 days. While the GtH-stimulated/basal ratio was high for androgens, it was rather low for 17 alpha 20 beta-OH-P as compared to the values obtained with testis fragments. Trout serum (5%) stimulated the secretion of free and conjugated T and 11KT when testes were mature, but not when they were in spermatogenesis, while it stimulated 17 alpha 20 beta-OH-P secretion at the two stages. Total trout lipoproteins (125-500 micrograms/ml) stimulated 17 alpha 20 beta-OH-P secretion by cells from spermatogenetic testes, but not 11KT secretion.

International audience; The action of neuropeptide Y (NPY) and gonadotropin releasing hormone (s-GnRH) have been compared on the release of gonadotropin (GtH) by perifused rainbow trout pituitary glands sampled from freshly ovulated female rainbow trout. We have already demonstrated that NPY stimulated the secretion of GtH in vitro. The pituitary responses to s-GnRH and NPY were similar either after repeated 10 min infusions or a one hour prolonged application. In both cases, after the first application, the pituitary did not responded to subsequent secretagogues stimulations, and appeared to be desensitized. The stimulatory action of s-GnRH was partly inhibited (60%) by LH-RH antagonist (DpGlu1, DPhe2, DTrp3-6) LH-RH, which completely inhibited the response to NPY in perifused pituitary glands sampled from freshly ovulated females, but did not modify the response of pituitaries taken from vitellogenic animals in which NPY induced a transient inhibition of the GtH secretion. These results may indicate that the mode of action of NPY would differ between vitellogenic and matured animals. NPY also stimulated the GtH secretion from perifused pituitary dispersed cells prepared from pituitaries taken from freshly ovulated rainbow trout, indicating that NPY may act directly on the pituitary gonadotropic cells to stimulate GtH secretion.

International audience; This work investigated the action of neuropeptide Y (NPY) on thein vitro pituitary release of the maturing gonadotropic hormone (GtH) of the rainbow trout using a perifusion system employing trout balanced salt solution (pH 7.5) at 15°C and a 12.5 ml/h flow rate. In vitellogenic females a 20 minutes NPY application (10−7 M) induced a 20–30% decrease in GtH secretion. Removal of NPY was followed by a rebound in GTH secretion. On the contrary, in ovulated females, NPY (15 minutes, 10−7 M) directly stimulated GTH secretion. The greatest stimulation was obtained the day of ovulation where the stimulatory effect of NPY was similar to those induced by s.GnRH in the same conditions, reaching 400% of the basal GTH level. In vitellogenic females treated with 1-4-6 androstadien 3–7 dione, an inhibitor of aromatase activity, the pituitary response to NPY was similar to that obtained in ovulated females. Thus thein vitro action of NPY might depend on thein vivo steroidogenic environment.

L'évolution de la fécondabilïté des ovules de Truite arc-en-ciel laissés dans la cavité abdominale au cours de la période post-ovulatoire a été étudiée, sur trois populations différentes (P, G et K), en relation avec quelques caractéristiques relevées sur les femelles : date de ponte, âge, poids du corps, variation du poids individuel des ovules au cours de la période de rétention. La survie des ovules laissés dans la cavité générale après ovulation dépend des populations étudiées ; la fécondabilité se maintient au-dessus de 90 % pendant 8 jours dans la population K et 15 jours dans les populations P et G, et elle est indépendante du poids du corps des femelles et du poids moyen des ovules. Par contre, la diminution de l'aptitude à la fécondation des ovules peut être mise en relation avec leur variation de poids et leurs modifications morphologiques au cours de leur séjour intra-abdominal., The change in fertilizability of rainbow trout eggs, left in the abdominal cavity during the post-ovulatory period, was studied in three different populations (P, G and K) in relation to laying, age, body weight and variation of the individual weight of the eggs during their sojourn in the abdomen. The survival of eggs left in the abdominal cavity after ovulation depended on the population studied. Fertilizability remained higher than 90 p. 100 for 8 days in population K and for 15 days in populations P and G ; it was independent of female body weight and of mean egg weight. On the other hand, the decrease in egg fertilizability might be correlated with variability in the weight of the eggs and with their morphological changes during their sojourn in the abdomen.

La supplementation en carotenoides de synthese, repliques exactes de ceux existant dans la nature, des aliments de pisciculture a pour but immediat de rehausser la pigmentation de la robe et de la chair des poissons. Apres presentation des proprietes physico-chimiques de la canthaxanthine, les effets de ce pigment sont etudies sur la couleur, la fixation et la retention musculaire chez la truite arc-en-ciel.

La croissance d'alevins de truite arc-en-ciel est étudiée pendant les 58 jours qui suivent l'éclosion. Les alevins comparés sont des animaux plein-frères, élevés à une temperature moyenne de 10,30 °C. Ils sont issus de lots d'œufs de tailles différentes séparés par un tri mécanique au stade œillé et sont nourris soit dès l'ouverture de l'œsophage, soit 9,14 et 22 jours plus tard selon les lots. Les alevins atteignent un poids final d'autant plus grand qu'ils proviennent d'œufs plus gros et qu'ils sont nourris plus tôt. Le poids des alevins à 58 jours apparaît lié au poids initial (au moment du premier repas) et au nombre de jours d'alimentation. Le taux de croissance spécifique des différents lots nourris ne paraît influencé ni par la taille de l'œuf ni par le retard d'alimentation. Pendant la période étudiée les gros alevins gardent leur avantage initial sur les petits et les alevins nourris plus tôt conservent leur avance sur ceux qui sont nourris plus tard.

International audience; The number of germ cells in fry gonads was determined from histological sections sampled periodically over a 10-week post-hatching period. Several successive types of germ cells were identified: primordial germ cells (PGC), two kinds of gonocytes (G1 and G2) and all the stages of female meiotic prophase. The mean diameters are shown in table 1. The number of germ cells increased regularly from 47 +/- 35 (SD) after hatching (PGC) to 166 +/- 25 at 2 post-hatching weeks (G1). At 5 post-hatching weeks, two groups of fish could be distinguished by the number of their germ cells (G2) - one group had less than 926 cells and the other more than 1 577 - and by their gonadal morphology (Filiform or with an enlarged anterior part due to germ cell concentration). At 6 post-hatching weeks, the ovary differentiated with organization of the ovarian lamellae and the appearance of oocytes in meiotic prophase (4 out of 10 trout). The gonads of the other fish stayed at the indifferent stage. The number of germ cells was significantly higher in female-type gonads (6 335 +/- 3 558) than in indifferent gonads (1 696 +/- 467). The situation was the same at 8 to 10 weeks.

International audience; Two-year old male rainbow trout, Salmo gairdnerii, were exposed to the following photoperiods at 80 or 16 °C from February 24 to June 19 : constant short photoperiod (8 L +16 D), constant long photoperiod (16 L + 8 D), and gradually decreasing photoperiod (from 16 L to 8 L). Control fish were exposed to natural photoperiod and temperature. Plasma and pituitary gonadotropin levels were determined by radioimmunoassay and correlated with spermatogenic response in testes. Control fish did not show advancement of spermatogenesis, whereas those exposed to decreasing photoperiod at 80 or 16 °C showed complete induction of spermatogenesis. While cooler temperature favoured production of spermatogonia and spermatocytes, the warmer temperature stimulated formation of spermatids and spermatozoa. On the other hand, in trout exposed to constant short or constant long photoperiod, spermatogenic response was weak at both temperatures. Plasma GtH levels increased in groups kept under decreasing photoperiod at both 8 °C as well as 16 °C ; the magnitude of rise of GtH was greater at 16 °C than at 8 °C. GtH levels were significantly higher in trout exposed to gradually decreasing photoperiod than in animals kept under constant short or constant long photoperiod at 80 or 16 °C. The data suggest that the optimum photothermal combination for GtH release and induction of spermatogenesis in the rainbow trout is a gradually decreasing photoperiod (from 16 L to 8 L) at 16 °C.; Les effets de la température et de la photopériode sur le cycle reproducteurde la truite Arc-en-ciel mâle sont appréciés par l’analyse quantitative de la spermatogenèse et la dynamique de sécrétion d’hormone gonadotrope (GtH) mesurée par radioimmunologie. Seule une photopériode décroissante de 16 à 8 h de lumière par jour, appliquée dès le mois de février en fin de période de spermiation naturelle est susceptible d’induire un nouveau cycle spermatogénétique dans les 4 mois qui suivent. Dans ces conditions, une élévation de la température stimule la spermatogenèse qui est complète (formation de spermatozoïdes) à 16 °C. Sous photopériode constante longue ou courte, l’activité spermatogénétique est faible, une légère stimulation des divisions spermatogoniales et une augmentation du nombre de spermatocytes sont enregistrées sous photopériode constante 16 L - 8 N, spécialement à 8°C. Quel que soit le rythme photopériodique, le taux d’hormone gonadotrope circulante est plus élevé à 16

Ovarian early postovulatory development and oestrogen production were studied in rainbow trout from a spring-spawning strain, 5 to 50 days postovulation (PO). Early postovulatory development was assessed by the ovarian development index, corresponding to the relative volume occupied in the ovary by oocytes in an advanced stage of differentiation (containing cortical alveoli). This index was shown to be related to the maximal oocyte diameter and to the time since ovulation, as well as to metabolic criteria. In contrast, gonadosomatic index was not correlated with any of these, confirming its unreliability for assessing the gonadal development, at least at this stage. Size of follicles and presence of vitellus (lipoprotein) in the oocytes of several animals indicate that ovarian development was more advanced in our females than in other studies. It is suggested that young follicles start developing before ovulation of the preceding batch of oocytes. Oestradiol (E2) plasma levels were low but detectable, and showed, in some females, peak values (max 5.5 ng/ml) within the first month PO. Besides, in vitro metabolism was studied using two isotopes of androstenedione as precursors. No sharp discrepancies were observed between the two types of incubation. Conjugation of the precursor or its metabolites was high but decreased with time postovulation. This suggests that it proceeds from postovulatory follicles. E2 production potential was demonstrated from the shortest time postovulation. Moreover, it increased with ovarian development, suggesting that E2 is synthesized in developing follicles.

Les populations d'alevins de truite commune (Salmo trutta L.) ont ete etudiees de 1967 a 1969 dans le ruisseau Lissuraga, affluent de la Nivelle. Un piege visite chaque jour a montre qu'une partie des alevins du ruisseau (environ 1 % a 20 %, selon les annees) emigrait vers l'aval, en mars, avril ou mai ; la plupart mesurent alors entre 2 et 3,5 cm ; ce deplacement se situe essentiellement dans la premiere moitie de la nuit. Aucune influence des temperatures ni des debits n'est decelable. En 1969, des alevins captures dans ce piege, et dits « nomades » (N), sont places en observation dans une section de rigole experimentale. Dans deux autres sections sont introduits, a la meme date, des alevins captures a l'electricite dans le Lissuraga, dits « residents » (R). Les densites initiales sont de 3 alevins/mJ dans les 3 sections. Dans les 10 j suivant ce transfert, 28 % des N emigrent vers l'aval, contre 6 % des R, ce qui tend a montrer que la tendance a la devalaison est un caractere « interne » chez une partie des tres jeunes alevins de truites du Lissuraga. Les differences de comportement s'estompent ensuite. En fin d'experience (140 j apres transfert), les « taux d'emigration » (nombre d'alevins sortis de leur section, vers l'amont ou vers l'aval, rapporte au nombre introduit) sont de 58 % chez N et de 41 % chez R. Les densites d'alevins restes dans leurs sections respectives sont alors nettement plus faibles chez N (0,8/m2 ) que chez R (1,35/m2 ). Les taux de mortalite naturelle (nombre d'alevins disparus, rapporte au nombre introduit) sont nettement plus faibles que les taux d'emigration : 17 % chez N et 8 % chez R. Ces observations tendent a montrer l'importance des deplacements (notamment de devalaison) d'alevins tres jeunes dans la dynamique d'une population de truites. Elles sont discutees et comparees avec celles d'autres auteurs.

A new branch of agro-business, fresh water and marine aquaculture starts a world wide expansion from years sixties. Specific technologies are integrated with different socio-economic systems. Now, in a growing process, aquaculture is building up new sea-shore landscape and open the gate for an inland water more valuable use. From catching spores, spats, baby shrimps and fry in their natural environment water farming need first a safe supply of hatchery and nursery man made seeds. Water organism specific biology must be take in account not only for reproduction but also for nutrition and pathology. High technologies and water environment control need heavy public investment and plenty of private funding. Average capital for starting a penaeid shrimp, catfish or salmon farm is on between one and two million $. When market and space are open aquaculture production promote an exponential curb until reaching economic or spatial saturation. Many cases with different strategies occured not only in Japon (laver and sea mustard seaweed, yellowtail and sea bream, eel) in Europ (rainbow trout in France, atlantic salmon in Norway and Scotland) or in USA (catfish) but also in developping countries (penaeid shrimp in Taiwan, Thailand and Ecuador). Socio economic and spatial systems express a specific organisation : chinese carp farming integrated inside an intensive labour agriculture, East European and Russian carp farming using the lower food productive chain, West European rainbow trout farming giving a high quality standard food converting hight protein fish meal, Scandinavian atlantic salmon farming giving a new chance to remote island and fjordland, intensive aquaculture (bait fish, rainbow trout, catfish) developping a new sectorial activity in USA, etc. Taiwan and East Asian countries are pushing high standard intensive farming for fishes and crustaceans. In Japon aquaculture take in account a very strong market and a long history of integrated coastal life throught the « kumiai » system. Present production is a very hight standard but for the future « marinovation » looks to use marine farming as a support for a multipurpose socio economic progressive organisation. Looking now to the status and trends of aquaculture the present « blue revolution » is stronger and deeper than the former agriculture « green revolution »., L'aquaculture d'eau douce et d'eau de mer, dont le développement a démarré vers 1960, occupe une place originale dans l'économie agroalimentaire. De nouveaux paysages soulignent ces formes d'organisation technique et socio-économique. La domestication de la flore et de la faune aquatique a ouvert la voie aux techniques de cultures et d'élevages aussi bien pour les algues que pour les poissons, les crustacés et les mollusques dont la production atteint désormais un volume significatif. Les techniques aquacoles ont dû s'adapter aux caractères biologiques des espèces et aux conditions spécifiques des milieux aquatiques. L'aquaculture, exigeante en investissements publics et en capitaux privés, réclame aussi un niveau technologique élevé. Les stratégies d'occupation de l'espace et d'insertion dans les marchés produisent des croissances exponentielles qui se sont manifestées entre 1965 et 1985 pour de nombreux secteurs aussi bien au Japon (algues nori et wakamé, sériole et daurade, anguille) qu'en Europe (truite en France, saumon en Norvège et Ecosse) qu'aux USA (poisson-chat), etc. L'insertion socio-économique et l'occupation de l'espace permettent de distinguer différents types de systèmes : la carpiculture chinoise, indienne et russo-danubienne, la valliculture adriatique, l'ostréiculture française, la truiticulture et la salmoniculture de l'Europe occidentale, l'aquaculture de loisir et agro-alimentaire aux USA, la forte croissance du Sud-Est asiatique. Le Japon pratique une politique de développement intégré qui lui est propre. Les fronts pionniers en Amérique du Sud et Extrême-Orient ne sont pas encore stabilisés. Par son ampleur et les répercussions de ses multiples effets, la « révolution aquacole » est déjà un phénomène plus marquant que la « révolution verte »., Doumenge François. La révolution aquacole, II . In: Annales de Géographie, t. 95, n°531, 1986. pp. 529-586.

Genetic experiments were conducted using either random independent full-sib families (9 and 11 respectively) or sire-half-sib families (18) of rainbow trout who were fed an experimental diet supplemented with canthaxanthin. The resulting orange-red colour of the flesh from each fish was analyzed through spectrophotometry and expressed in standard terms of luminosity (Y), dominant wavelength (λd) and excitation purity (Pe). The following results were obtained : - There is a substantial genetic variability among families in each colorimetric parameter. Estimated values of heritability from full-sib and from half-sib families do not differ significantly. - Positive correlation between λd . and Pe, and negative correlations between Y and λd and between Y and Pe, are consistent with the pattern of canthaxanthin deposition in the flesh. Genetic correlations do not differ significantly from phenotypic ones. - Pigmentation intensity is correlated to fish weight. This relationship, however, accounts for but a minor part of colour variation among market-size fishes., Des expériences génétiques ont été réalisées chez la Truite arc-en-ciel sur des familles aléatoires et indépendantes de pleins-frères (au nombre de 9 et 11) ou demi-frères de pères (18), alimentées par un régime expérimental supplémenté en canthaxanthine. La couleur de chair orange-rouge obtenue chez chaque poisson a été analysée par spectrophotométrie et exprimée en termes standards de luminosité (Y), longueur d’onde dominante (λd) et pureté d’excitation (Pe). Les résultats obtenus sont les suivants : - Il y a une variabilité génétique notable entre familles pour chaque paramètre colorimétrique. Les valeurs d’héritabilité estimées à partir des familles de plein-frères et de demi-frères ne diffèrent pas significativement. - Les corrélations, positives entre λd et Pe et négatives entre Y et λd et entre Y et Pe, sont conformes au mode d’action de la canthaxanthine se déposant dans la chair. Les corrélations génétiques ne diffèrent pas significativement de leurs homologues phénotypiques. - L’intensité de la pigmentation est corrélée avec le poids des poissons. Cette relation toutefois n’explique qu’une part minime de la variation de couleur chez des animaux de taille marchande.

Population dynamics of brown trout (Salmo trutta) in a breton stream (France) : The non-migrant spawners. The biological factors of the population dynamic of brown trout in a tributary of the Scorff river, have been studied during 4 years . The characteristics of the spawners, present in the stream before the spawning migration from the main river, are described . These spawners were born in the stream and stayed there during their entire life-span . Among mature fish the sex ratio was always in favour of males . During the third and the fourth years of life, annual mortality rate was 70% for males and 50% for females . 1+ spawners were these which had the best 0+ growth rate. A majority of males first matured at 1 + years of age . On an average, 1 + females were responsible for 25 016 of the total reproductive potential . The number of 3 + and 4+ females seemed to depend on the fishing effort ., Population dynamics of brown trout (Salmo trutta) in a breton stream (France): The non-migrant spawners. The biological factors of the population dynamic of brown trout in a tributary of the Scorff river, have been studied during 4 years. The characteristics of the spawners, present in the stream before the spawning migration from the main river, are described. These spawners were born in the stream and stayed there during their entire life-span. Among mature fish the sex ratio was always in favour of males. During the third and the fourth years of life, annual mortality rate was 70% for males and 50% for females. 1+ spawners were these which had the best 0+ growth rate. A majority of males first matured at 1+ years of age. On an average, 1+ females were responsible for 25% of the total reproductive potential. The number of 3+ and 4+ females seemed to depend on the fishing effort.

Une maladie de la truite arc-en-ciel, connue sur le continent nord-americain et en Australie sous le nom de "Enteric red mouth disease" (ERM disease), a ete mise en evidence pour la premiere fois en France. Il s'agit d'une enterosepticemie hemorragique; l'agent pathogene est Yersinia ruckeri.

L'efficacité de la 17 alpha-hydroxy-20 beta-dihydroprogestérone (17 alpha-20 beta Pg) ou d'un extrait gonadotrope hypophysaire de Truite sur la maturation intrafolliculaire in vitro des ovocytes de Truite peut être modulée par des stéroïdes qui ne présentent pas d'action maturante directe: l'efficacité de l'extrait gonadotrope est abaissée par l'oestradiol et l'oestrone et augmentée par la testostérone. Comme ces mêmes stéroïdes n'ont aucun effet significatif sur la maturation induite par la 17 alpha-20 beta Pg, leur site d'action se situe probablement au niveau des enveloppes folliculaires. Les corticostéroïdes et en particulier le cortisol et la cortisone augmentent l'efficacité de l'extrait gonadotrope, mais stimulent encore plus fortement l'efficacité de la 17 alpha-20 beta Pg, suggérant un effet direct sur la sensibilité ovocytaire à ce «progestagène»., The efficiency of 17 alpha-hydroxy-20 beta-dihydroprogesterone (17 alpha-20 beta Pg) or of a Trout pituitary gonadotropic extract to induce intrafollicular maturation of trout oocytes can be modulated by some steroids which do not present any direct maturing action: gonadotropic extract efficiency is lowered by estradiol and estrone, and enhanced by testosteron. As these steroids do not present a significant effect on 17 alpha-20 beta Pg induced maturation, their site of action may be located in the follicular tissues. The corticosteroids, particularly cortisol and cortisone enhance the maturing efficiency of gonadotropin and stimulate much more strongly the efficiency of 17 alpha-20 beta Pg. This suggests a direct effect on oocyte sensitivity to 17 alpha-20 beta Pg.

La production de truites stériles par voie génétique

International audience

Trout testes at various stages of maturation were dissociated by perfusion at 12 degrees C with collagenase plus pronase and then with collagenase alone, followed by slight shaking overnight in 1% bovine albumin. This step provided a suspension of isolated somatic and germ cells, clusters of interstitial cells, and either intact spermatogenetic cysts (meiotic testes) or clusters of Sertoli cells (other testes). Most of the spermatozoa were removed from the testis cell suspension by centrifugation in Percoll (density 1.065 g/ml). Sertoli and Leydig cells were prepared by a two-step separation method: 1) the testis cell suspension was separated by sedimentation at unit gravity into "isolated cell" and "cell cluster" populations; 2) these populations were fractionated by isopyknic centrifugation in Percoll gradients. In terms of somatic cell composition, a nearly pure Sertoli cell (clusters) population was obtained between 1.017 and 1.033 g/ml and a Leydig cell (clusters) enriched population of between 1.033 and 1.048 g/ml (testes resuming spermatogenesis) or 1.048 and 1.062 g/ml (other testes). These various cell populations were cultured in modified Leibovitz L15 medium for 10-15 days. When seeded, the Sertoli cells had a normal ultrastructure that remained unchanged for at least 10 days, and the steroidogenic activity of Leydig cells could be stimulated by salmon gonadotropin. Leydig cells remained 3 beta-HSD positive and produced progesterone and 17 alpha, 20 beta-OH progesterone for at least 11 days. This study points out that viable and differentiated trout somatic testicular cells can be prepared and cultured for several days.

For freshwater fish the motile period of sperm is extremely brief, even after a dilution in isotonic media. This result is in contrast to most other animals (ranging from invertebrates to mammals), in which sperm are generally motile for at least several hours. We have analyzed the reasons for the brevity of this movement by studying the relationships between the metabolism of trout sperm and the activation of their motility upon dilution. Sperm motility was not initiated when the dilution medium contained an elevated concentration of potassium (20–40 mM), but dilution in an isotonic solution of sodium chloride triggered an immediate activation of motility, and sperm swam vigorously. Motility of sperm decreased rapidly and 15 s after dilution sperm were moving slowly in small circles. Sperm became abruptly immotile at 20–30 s and flagella straightened. When millimolar concentrations of Ca2+ were also present in the dilution medium, movement did not not stop abruptly, flagella kept beating and stopped only after 1–2 min. When sperm remained immotile they retained a high concentration of ATP. The activation of motility induced a rapid decrease of ATP. In the absence of calcium, and after the cessation of motility, ATP increased slowly back to its original concentration. In the presence of millimolar concentrations of calcium the concentration of ATP decreased to a very low level and remained low thereafter. The progressive decrease of the flagellar beat frequency, that had been observed during the period of trout sperm movement, might be related to the rapid exhaustion of intraflagellar ATP. Motility could be reinduced in sperm that had recovered high concentrations of ATP, demonstrating the functional integrity of the motile apparatus even after flagellar arrest. In conclusion we suggest that the maximum duration of trout sperm motility, at most 2 min (as a consequence of a depletion of ATP during the movement), is due to a low mitochondrial oxidative phosphorylation capacity.

To determine the effect of gonadal feedback on plasma GTH level, female rainbow trout were ovariectomized at three stages at the end of the reproductive cycle: at the end of vitellogenesis, during germinal vesicle migration and during the post-ovulatory period. A group of controls and one of castrates in each experiment were given an injection of physiological salt solution, and a third group of castrates was supplemented with estradiol-17 beta (E2) twice a week (200 micrograms/kg) from the day of surgery. The blood was sampled twice a week, and the GTH measured by RIA. At the end of vitellogenesis, castration induced a significant rise in the gonadotropic hormone level (P less than 0.001 from post-surgical day 5), and that response, unimpeded by E2, was homogeneous in all the fish. During germinal vesicle migration, the response to castration and to supplementary E2 varied with the individual. Ovariectomy induced a significant increase in GTH (P less than 0.005 from day 3), but that increase was immediate in 5 females and delayed in the other 4; E2 prevented GTH rise in only 6 females. At the post-ovulatory period we found no significant difference between the control fish and the castrates and E2, at least temporarily, prevented the post-ovulatory rise in GTH which is usually found in trout.

Quatre facteurs pouvant rendre compte de la variabilité intra et inter-populations du nombre de caeca pyloriques de la Truite arc-en-ciel ont été examinés. - Aucune variation liée à l’âge n’est décelable après 6 mois, même lorsque les individus sont soumis à un changement des conditions de milieu. - L’élevage des individus depuis le stade ceillé dans deux piscicultures ayant des moyennes thermiques très différentes (8 °C et 16 °C) conduit à une différence importante entre les moyennes du nombre de caeca (5,55 à 8 °C, 51,0 à 16 °C). - L’utilisation d’un aliment à forte teneur en polyholosides augmente le nombre de caeca (+ 2,7 p. 100 en moyenne) par rapport à un aliment riche en protéines dans la pisciculture à 8 °C, mais n’a pas d’effet dans l’autre pisciculture. - La réalisation de croisements entre parents ayant un nombre connu de caeca pyloriques permet de mettre en évidence une forte corrélation (γ = 0,92) entre le parent moyen et la moyenne des descendants. Une estimation assez élevée ( h2 = 0,53 ± 0,07) est obtenue pour l’héritabilité (part de la variance génétique additive dans la variance phénotypique totale). Par contre les effets génétiques non additifs semblent de faible importance. Le mode d’action conjoint de ces différents facteurs de variation a été examiné et obéit essentiellement à un modèle de type additif. Il apparaît donc possible d’obtenir rapidement par sélection divergente des lots ayant des nombres moyens de caeca différents et de préciser ainsi la liaison de ce paramètre avec d’autres caractères quantitatifs comme la croissance ou les performances nutritionnelles., Four factors liable to affect the within and between-population variability of the number of pyloric caeca in Rainbow Trout were studied. After six months, no variation due to age was observed even after transferring the fishes from one fish farm to another. Rearing of fishes from the eyed-stage in two fish farms with very different mean temperatures (8 °C and 16 °C) induced a large difference between the mean number of pyloric caeca (5,55 at 8 °C; 51,0 à 16 °C). At 8 °C, a diet with a hight level of polyholosids slightly increased the number of caeca (+ 2,7 p. 100 in average) as compared to one with a high level of proteins. No effect was detected at 16 °C. Study of the progenies of crosses between parents having a known number of caeca showed a high correlation (γ = 0,92) between the mean parent and the mean of progenies. A quite high estimate was obtained for heritability ( h2 = 0,53 ± 0,07), the non-additive genetic variance being quite low. The conjoined effect of those different factors was analysed and described by alinear additive model. Therefore, it seems to be possible to obtain, by a two way selection, strains with different numbers of caeca and to analyse the effect of this trait on other quantitative ones like growth rate or nutritional parameters.

International audience; We describe the isolation and characterization of a cDNA for trout (Salmo gairdneri ) prolactin (tPrl). An extensive analysis of tPrl recombinant clones by restriction analysis and sequencing revealed the presence of only one form of tPrl mRNA. The deduced protein sequence consists of 210 amino acids, including a signal peptide of 23 amino acids. The amino acid sequence of the mature protein is compared among teleosts and mammals, showing two domains of strong similarity that may be involved in biological activity.

International audience; [début du texte] Des travaux antérieurs ont permis de suggérer que la truite pourrait posséder un cofacteur de la lipase jouant un rôle analogue à celui que joue la colipase chez les mammifères étudiés jusqu'à ce jour.

International audience; In order to characterize trout Sertoli cells and germ cells obtained after testis dissociation and cell separation, we have studied their morphology, ultrastructure, survival, and ability to express differentiated activities in primary cultures. After dissociation, the fine structure of Sertoli cells does not differ from that observed in situ and only minor changes are shown for at least 13 days. Until they are flattened in a monolayer, they keep the ability to retain germ cells on their surface. When flattened, some of them are able to divide. At the opposite of meiotic germ cells, spermatogonia can develop independently of Sertoli cells. They are able to proliferate during at least 10 days. Spermatocytes and spermatids are obtained as single cells and multinucleated giant cells (symplasts). In the absence of somatic cells, their maximal viability is approximately 5 days, whereas spermatocytes adhering to Sertoli cells can survive at least 10-12 days, provided trout lipoproteins are present. Spermatocytes are able to differentiate to spermatids, although this process is impaired for some cells. The adhesion of spermatogonia and spermatocytes to Sertoli cells is specific, mediated by desmosome-like junctions and favored by lipoproteins. These data are compared to what is known in mammals and in amphibians.

Maturational glycoproteique gonadotropin and estradiol-17β during the reproductive cycle of the female brown trout (Salmo trutta). Female brown trout were sacrificed every month or twice a month during the reproductive season. Plasma gonadotropin (GtH) and estradiol-17β (E2-17β) were measured using radioimmunological techniques, in relation with the state of gametogenesis. From ovulation to July egg's diameters remained less than 1 mm, and ovogenesis was characterized from the histological appearance of three types of vitellus: glycoproteique (type I), lipidique (type II), lipidoproteique (type III), and the immunological plasma detection of the vitellogenin. During this period GtH levels remained lower than 1 ng/ml except in March, when they increased around 5 ng/ml, both with pituitary GtH and plasma E2 17β. This rise occurred just before the appearance of the type III vitellus within the oocyte, and might correspond to a critical phase of the reproductive cycle during which vitellogenin could not be detected in 70% of the animals. During rapid growth of the oocyte from 1 to 5 mm, mean GtH levels increased from 0.75 to 2.5 ng/ml when those of the E2-17β increased more rapidly but began to drop before the end of vitellogenesis. Maturation and ovulation were accompanied by a rise of the GtH level, in correlation with the lower levels of E2-17β measured during the cycle, GtH remained high even after ovulation, and more in fish which had kept their eggs within the body cavity. Correlation among GtH, E2-17β, and the diameters of eggs had been calculated. There was a positive correlation among GtH, E2-17β levels, and the diameters of eggs during exogenous vitellogenesis, and a negative between GtH and E2-17β at the end of the reproductive cycle. These results were discussed, in relation to the existence of a pulsatile mode of GtH secretion.

Des hybridations artificielles représentant 17 combinaisons ont été, réalisées à, partir de 6 espèces de Salmonidés, à, savoir les saumons chinook et coho, la truite arc-en-ciel, la truite brune, le saumon Atlantique et l'omble de fontaine. La réussite au stade oeillé, les taux de survie jusqu'au 15e jour après l'éclosion, la durée d'incubation et la dispersion des éclosions ont été, examinés par référence aux lots témoins monospécifiques. Les taux de réussite et de survie des hybrides se sont révélés inférieurs ou au mieux semblables à, ceux des espèces parentales. Des effets maternels significatifs ont été, observés dans la plupart des types de croisements. Des facteurs d'interaction très variables se sont avérés agir sur la durée d'incubation des hybrides, qui pouvait dépasser celles des espèces parentales. La dispersion des éclosions était plus importante chez les hybrides que dans les espèces pures et tendait à, être négativement corrélée à, la survie. Quelques types d'hybrides ont donné, des résultats prometteurs au terme de cette expérience. Leur intérêt potentiel pour l'aquaculture est considéré, dans la discussion., Artificial hybridizations were carried out with 17 combinations using six species of Salmonidae, namely chinook and coho salmon, rainbow and brown trout, Atlantic salmon and brook trout. Success at the eyed stage, survival rates up to the 15th day after hatching, length of the incubation period and dispersion of hatching times were examined with reference to monospecific control lots. Success and survival rates of hybrids were found to be inferior or at the best similar to those of parental species. Significant maternal effects were observed within most types of crosses. Highly variable interaction factors were found to influence length of incubation of hybrids, which could exceed that of either parental species. The dispersion of hatching times was greater in hybrids than in pure species and tended to be negatively correlated to survival. A few types of hybrids showed promising results at the end of the experiment and their potential interest for aquaculture is discussed.

International audience; In fish there are few data on the gonadotropin-releasing hormone (Gn-RH) neurosecretory activity, which could explain long- and short-term variations of the gonadotropin secretion. There is no biological species specificity between mammal and fish Gn-RH; although there is a structural difference, they are, on the contrary, characterized by a high immunological specificity which does not allow measurement of fish Gn-RH using radioimmunoassay for LH-RH. We have synthesized salmon Gn-RH according to the formula recently proposed by Sherwood (N. Sherwood, L. Eiden, M. Brownstein, J. Spies, J. Rivier, and W. Vale, 1983. Proc. Natl. Acad. Sci. USA 80, 2794-2798). Its activity has been tested by its ability to stimulate the gonadotropin hormone (GtH) secretion in vivo in testosterone-implanted juvenile rainbow trout, and for the recognition of synthesized Gn-RH (s-Gn-RH) perykaria by a specific antibody raised against the s-Gn-RH in regions of the brain described as containing LH-RH immunoreactive-like material. A radioimmunoassay has been developed for the salmon Gn-RH, and its specificity to measure trout Gn-RH has been tested. Using this assay, the brain and pituitary Gn-RH contents have been measured throughout the final phases of maturation and ovulation. Brain Gn-RH increases from the end of vitellogenesis (8.9 +/- 0.76 ng/brain) to ovulation (more than 15 ng/brain). Pituitary Gn-RH is lower (1.58 +/- 0.69 ng/pituitary) at the end of vitellogenesis and follows a similar profile as in the brain, except for a significant decrease just prior the beginning of oocyte maturation. The correlations between Gn-RH levels and GtH pituitary and plasma levels show that total brain Gn-RH is never correlated to the GtH, suggesting that the increase in the brain Gn-RH content is related to a Gn-RH system closely related to maturation and ovulation, which remains to be investigated. On the contrary, pituitary Gn-RH levels are well correlated with pituitary and plasma GtH levels, indicating that pituitary Gn-RH levels might represent a good index of the Gn-RH neurosecretory activity in the fish hypothalamohypophysial complex, given the absence of a portal system in teleost.

This report presents a critical review of interspecific hybridization in salmonids and discusses the potentiality of hybrids for water management and fish farming.

International audience; Gonadal development and gametogenesis have been studied in the brown trout ( Salmo trutta) beginning at the establishment of the first reproductive cycle. Monthly samples were taken from 14-month old fishes beginning in July and extending over a 20-month period. Complete gametogenesis was observed in males from the first year of sampling and from the following year in females. Spermatogenesis was analysed over the first two cycles and a quantitative study showed that the volume of spermatozoa produced in relation to body weight was slightly higher at the end of the second cycle. At the end of the second reproductive cycle, the process of spermiation ceased while there were still spermatozoa in the testes, although most of them had been evacuated at the end of the first cycle. Spermatogenesis seemed to be more efficient during the second cycle but spermiation yield was higher during the first cycle. Oogonia were always present in the female ovaries and there was mitotic activity in July of the second year of life and in October-November of the third year. Previtellogenetic stages (accumulation of RNA and lipid) were already present at 14 months of age when sampling started. During the second year of life there was limited accumulation of yolk in the oocytes but it did not modify total ovary weight. In this population, vitellogenesis was complete and most of the females began to ovulate only in the third year. Before the end of the cycle in October-November, the number of previtellogenetic oocytes (stages 1, 2 and 3) increased markedly. This was followed in December by an increase in the number of oocytes containing yolk bodies, representing no doubt the class of oocytes undertaking vitellogenesis in the next cycle. the patterns of initiation of the first and second cycles thus appeared to be very different.

International audience; Juvenile rainbow trout (weighing 10 or 20 g) were treated thrice weekly for 10 weeks with salmon-gonadotropin (S-GTH), salmon pituitary extract (S-PE), S-GTH plus estradiol-17β, and estradiol-17β alone. The effects of these treatments on the oocytes were studied at ultrastructural level. Saline-injected control fish contained oocytes at previtellogenic stage of development. S-GTH (0.1 or 0.5 µg/g) induced a synthesis of endogenous yolk in the oocyte cytoplasm but failed to initiate incorporation of exogenous yolk or vitellogenin into the oocytes. S-GTH (0.1 µg/g) in combination with estradiol-17β (1 µg)g) produced similar results to those with S-GTH alone. Estradiol-17β alone failed to induce vitellogenesis. In contrast, S-PE (10 µkg/g) induced the incorporation of exogenous yolk into the oocyte indicated by an extensive pinocytotic activity at the oocyte membrane. It is suggested that gonadotropin is necessary for the induction of endogenous yolk synthesis and that some other pituitary hormone(s) is involved in the process of incorporation of exogenous yolk or vitellogenin into the oocyte.

International audience; Le phénomène de maturation in vitro des ovocytes de Truite a été utilisé pour mettre au point une méthode de dosage biologique de l’hormone gonadotrope hypophysaire. Chaque extrait à doser a subi une série de dilutions dont l’effet a été testé sur des lots de 25 ovocytes au stadede la vésicule germinale périphérique incubés 4 jours à 10 C°. La dose théorique provoquant 50 p.1 00 de maturation (DE50) a été déterminée avec précision pour chaque extrait. Les DE50 relatives à différents extraits ou hormones ont pu être comparées directement ; ainsi c-GtH(hormone gonadotrope de Carpe) et SG-G100 (extrait gonadotrope de Saumon) se sont révélés environ 1000 fois plus efficaces que o-LH.Malgré la variabilité de sensibilité observée pour un même extrait entre les ovocytes de femelles différentes, la conservation des rapports d’efficacité entre couples d’extraits identiques permet de comparer toutes les séries de dosages, par référence à l’efficacité d’une préparationgonadotrope standard testée sur les ovocytes de chaque femelle. La sensibilité du dosage est suffisante pour déterminer l’activité gonadotrope de l’hypophyse d’une truitelle immature. Elle peut être doublée par l’adjonction d’hydrocortisone (0,5 µg/ml) au milieu d’incubation. Dans l’ensemble la méthode de dosage biologique proposée apparaît sensible et précise, spécifique et représentative de l’activité gonadotrope des Salmonidés, applicable aussi au dosage de l’hormone gonadotrope de Carpe et éventuellement d’autres poissons. Elle ne peut cependant être employée directement pour le dosage plasmatique et son utilisation paraît devoir être limitée au dosage d’extraits hypophysaires. spécifique et représentative de l’activité gonadotrope des Salmonidés, applicable aussi au dosage de l’hormone gonadotrope de Carpe et éventuellement d’autres poissons. Elle ne peut cependant être employée directement pour le dosage plasmatique et son utilisation paraît devoir être limitée au dosage d’extraits hypophysaires.

L'utilisation de la méthode Auxotab a permis la mise en évidence semi-quantitative de 16 enzymes dans les spermes de la Carpe et de la Truite, ainsi que dans le liquide cœlomique de la Truite. Il existe des différences d'équipement enzymatique sensibles entre le sperme total, le liquide séminal et les spermatozoïdes isolés ; elles portent essentiellement sur les phosphatases. Deux liquides cœlomiques dont l'activité biologique sur l'ovulation in vitro était connue, ont pu être différenciés par l'apparition d'une activité trypsique.