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1. 1. The effect of increasing amounts of dietary arginine on oxidation of other amino acids was tested. Two experiments were conducted in rainbow trout fed on diets containing grading amounts of arginine from 0.55 to 2.55%. 2. 2. The growth of fish and the efficiency of food conversion were measured and there were no significant differences between the different diets tested. 3. 3. After an oral administration of either l -[U-14C]phenylalanine or l -[U-14C]threonine, the rate of excretion of 14CO2 over a period of 3 hr and the radioactivity in the free pool and the protein pool of liver at the end of that period were measured. 4. 4. The rate of oxidation of phenylalanine and threonine was assessed using their respective specific activities in the free pool of liver. 5. 5. The rate of oxidation of phenylalanine increased from 246 ± 101 nmol/g body weight/3 hr at 0.55% dietary arginine supply to 679 + 85 nmol/g body weight/3 hr at 2.00% arginine then it decreased for higher arginine supply. 6. 6. The oxidation rate of threonine increased from 50 ± 22nmol/100g body weight/3 hr up to 774 ± 195 nmol/100 g body weight/3 hr for a dietary arginine supply of 2.45% then it decreased. 7. 7. It was concluded that oxidation of phenylalanine and threonine could not be used as an indirect indicator of arginine status.

Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries began publishing the Informationen aus der Fischereiforschung = Information on Fishery research in 2010

ÖZET Atatürk Üniversitesi Ziraat Fakültesi Su Ürünleri Bölümü'nde üretilen Gökkuşağı alabalığı yumurtalarından elde edilen yavrularla (Erzurum Ham), aynı tarihlerde Yan Tarım İl Müdürlüğü Su Ürünleri tesislerinden getirilen döllü yumurtalardan sağlanan Gökkuşağı alabalığı yavrularının (Van Hattı), çeşitli yönlerden karşılaştırılması bu araştırmanın amacım oluşturmaktadır. Araştırma iki grup ve üç tekerrürlü olarak düzenlenmiştir. Aynı gün çıkışlı yavrulardan her tekerrüre 125 adet konulmuş ve toplam 750 yavru denemeye alınmıştır. Deneme, boyutları 1.50x0.40x0.45 m olan beton yalaklarda yürütülmüştür. Araştırmada, Atatürk Üniversitesi Ziraat Fakültesi Su Ürünleri Bölümü tesislerinde bulunan arteziyen suyundan yararlanılmış ve yem olarak %43.65 proteinli, alabalık yemi kullanılmıştır. Balıklara, vücut ağırlıklarının l.ay için 967'», 2.ay için %5'i, 3.ay için %4'ü, 4.ay için 953.5'i, 5.ay için ise %3'ü kadar yem verilmiştir. Deneme 20.8.1990 tarihinde başlayıp 22.1.1991 tarihinde bitirilerek toplam 155 gün devam etmiştir. Yavrular her 30 günde bir tartılmıştır. Elde edilen genel bulgular aşağıda özetlenmiştir. 1. Deneme süresince yavrular ortalama 0.856±0.083 g'dan ortalama 16.927±0.686 g'a ulaşmıştır. Entansif Alabalık üretimi kriterlerine göre oldukça düşük olan bu ağırlık artışındaki yetersizlik, kullanılan suyun fazla soğuk olması ile açıklanmıştır. 2. Deneme süresince Erzurum Hatta, yavrular ortalama 0.915±0.032 g'dan ortalama 16.44*0.0572 g'a, Van Hattı yavrular ise ortalama 0.797±0.052 g'dan ortalama 17.41±0.663 g'a yükselmiş, ancak ağırlık artışı yönünden hatlar arasındaki farklılık istatistiki olarak önemli (p

International audience; Juvenile rainbow trout received gonadotropic hormone (GtH) treatment to investigate the response of the immature gonad and its effect on the onset of rising pituitary GtH levels, an early sign of initiation of sexual maturation in the teleost fishes. Brief exposure to GtH evoked increases in plasma androgens and significantly increased pituitary GtH in males; the accumulation of pituitary GtH was not observed in female trout which showed significant but smaller increases in plasma androgen resulting from GtH administration. There was no evidence of gonadal negative feedback in intact immature fish since pituitary GtH and plasma androgens remained at basal levels in castrate juvenile trout. Since the castrate male trout failed to respond to GtH injections, the data suggest that the immature gonad produces a steroid capable of triggering pituitary GtH production by hypothalmo-pituitary feedback in males.

Experiments were carried out to test the possibilities of using plastic bags inflated with oxygen to preserve and to transport rainbow trout sperm. Sperm survival is improved after storage in an O2 atmosphere in comparison with storage in air. After storage for 5 days (Exp. 1) fertilizing ability was similar under O2 to that of the controls (freshly collected sperm) but under air it was significantly lower (P < 0.001). In another experiment (Exp. 2), fertilizing capacity depended on the rate of dilution and the quality of the eggs. With some females high levels of fertilization were recorded after 14 days of sperm storage and with other females fertilizing capacity of the same sperm drops within one day. This variability in the response still limits the practical application of short-term preservation of rainbow trout sperm.

Steroid binding in female trout plasma has been studied. 2 thermolabile binding systems are detected by saturation analysis and competitive assays. One is a 'sex binding protein' with high affinity for testosterone (K Sub(4{degree}C) = 3.8 x 10 Super(8) M Super(-1)) and oestradiol-17{beta} (K Sub(4{degree}C) = 1.8 x 10 Super(8) M Super(-1)).The 2nd is a 'transcortin type' system binding testosterone (K Sub(4{degree}C=3.7 x 10 Super(7) M Super(-1)), progesterone (K Sub(4{degree}C=2.2 x 10 Super(7) M Super(-1)), oestradiol-17{beta} (K Sub(4{degree}C=1.4 x 10 Super(7) M Super(-1)) and corticosteroids. Association constants and capacities determined by gel filtration or by equilibrium dialysis are compared. As in other fish, measured capacities are higher than for mammalian bin ding systems. Whether the 2 kinds of sites are on a single or 2 proteins is discussed. Competitive assays performed with fractions of a DEAE-cellulose chromatography of plasma show a partial separation. But only one peak of radioactivity sediments in the 5-6S zone when plasma is ultracentrifuged with tritiated steroids in a sucrose gradient. To test the steroid inactivation by binding, the induction of maturation of trout oocytes in vitro by 17{alpha}-hydroxy-20{beta}-dihydroprogesterone has been used as biological assay. 17{alpha}-Hydroxy-20{beta}-dihydroprogesterone activity is suppressed by plasma binding. Biochemical and biological results are compared and discussed.

Temperatures susceptibility of rainbow trout gametes was defined following in vitro experimentation. Brood stock reared at 10-12 °C were handstripped and gametes were diluted and submitted to various temperatures (1 to 20 °C for ova and 0 to 30 °C for sperm) for 20 or 40 min. before insemination. Effects of various temperatures at the time of artificial insemination were also investigated. When spermatozoa are diluted in the Diluent for Insemination (DI) (in which they are motile) fertilizing ability is better maintained at 0 and 5 °C than at 10 and 15°C. If spermatozoa are kept immobile (after dilution in MMLS enriched in K+) fertilizing ability is significantly decreased at 20 °C (fig. 1) and sometimes at 15 °C (fig. 3). Following 40 min. exposure to the experimental temperature fertilization of ova was maximally maintained only at 1 and 5 °C. At the time of insemination, the most favourable temperatures are located between 5 and 15 °C. At 1 °C, 20 °C and higher the percentage of fertilization is reduced especially when the rate of dilution is high.; Les températures supportables par les gamètes de truites arc-en-ciel ont été définies par expérimentation in vitro. Après prélèvement sur des géniteurs élevés à la température de 10-12° C, les gamètes ont été dilués et exposés à différentes températures (1 à 20 °C pour les ovules et 0 à 30 °C pour le sperme) pendant 20 ou 40 minutes avant insémination. Les effets de différents niveaux thermiques appliqués au moment de l'insémination ont aussi été testés. Lorsque les spermatozoïdes sont mis en mouvement après dilution dans le dilueur d'insémination (D.l) ils conservent leur pouvoir fécondant plus longtemps à 0 et 5 °C qu'à 10 et 15 °C. Si les spermatozoïdes sont maintenus immobiles après dilution dans le Milieu Minéral de Liquide Séminal (MMLS) riche en K+, le pouvoir fécondant est significativement diminué à 20 °C et dans certains cas à 15 °C (Figures 1 et 3). En ce qui concerne les ovules, après 40 minutes d'exposition la fécondabilité n'est bien conservée qu'à 1 et 5° C. Au moment de l'insémination les températures les plus favorables se situent entre 5 et 15 °C. A 1° C, 20 °C et au-delà, le taux de fécondation est diminué d'autant plus que la dilution est plus forte.

The influence of testosterone on plasma and pituitary levels of gonadotrophin (GTH) as well as on gonadal development was studied in immature rainbow trout. Among the animals receiving a testosterone-cocoa butter implant (200 micrograms) at the age of 5 months, gonadal puberty occurred 8 months later in half of the males (opposite to the controls which remained immature) and the beginning of oocyte maturation was observed in only one female. These animals were characterized by a higher pituitary GTH level. Owing to the multivariate statistical analyses made, it was possible to provide evidence for the presence of two populations with different reactions to the same steroid treatment. They also confirmed the existence of a positive testosterone feedback, in the male, leading to a precocious gonadal development. The pituitary GTH load obtained with 200 micrograms of testosterone seemed to be related to the age of first maturation. The secretion of an appropriate level of GTH resulting in the stimulation of gametogenesis required the availability of a relatively large pituitary GTH level and seemed to be possible because the animals were already in the pubertal period. The fact that the highest pituitary GTH level of the treated lot was found in the only female showing a beginning of sexual maturation suggests that testosterone may also act in females.

Eggs provided by several rainbow trout (Salmo gairdneri) were placed in freshwater after insemination and agitated mechanically for one hour. Usually agitation for more than 30 minutes significantly reduced the percentage of eggs found developing at 100 degree-days (P < 0.001 and P < 0.05). In one case no significant reduction was found. If agitation occurs between 30 and 60 minutes after egg transfer to freshwater no reduction of developing eggs was found. Therefore there is no particularly sensitive stage. during hardening ; total duration of agitation is the most important factor. These results show that embryonic development of eggs for some females may be reduced by prolonged agitation of eggs during the phase of hardening. The manipulation of fertilized eggs should be avoided after the first hour in freshwater.; Des œufs de Truite arc-en-ciel en provenance de plusieurs femelles ont été transférés en eau douce après insémination et soumis à une agitation mécanique pendant une heure. Généralement on observe après 30 mn d'agitation une diminution du pourcentage d'œufs embryonnés qui est significative (P < 0,001 et P < 0,05). Cependant dans le cas d'une femelle la diminution n'était pas significative (fig. 1). Si l'agitation est appliquée seulement entre la 30e et la 60e minute après le transfert en eau douce, il n'y a pas de diminution du pourcentage d'œufs embryonnés (fig. 3). Il n'y a donc pas de phases plus sensibles que d'autres ; la durée totale d'agitation étant le facteur le plus important. La manipulation des œufs pendant une heure après leur transfert en eau douce apparaît au moins dans certains cas préjudiciable au développement embryonnaire et doit donc être évitée.

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.

1. 1. The development of an in vitro brain-pituitary perfusion technique allowed both the measurement of gonadotropin release and the recording of electrical activity in various brain areas of the rainbow trout. 2. 2. GnRH sensitive neurons were found in the nucleus preopticus (NPO). 3. 3. Gonadotropin release was evoked after microinjections of LHRH-A into the pituitary or into the NPO. 4. 4. Norepinephrine has been demonstrated to have a stimulatory effect on gonadotropin release.

International audience; The present study investigates the effects of seasonally changing photoperiod regimes on the levels of serum gonadotropin, oestradiol-17/3, and vitellogenin (as indicated by phosphoprotein phosphorus and calcium measurements) on the time of spawning of female rainbow trout (Salmo gairdneri). This included a control regime and also seasonal cycles in which the increasing and decreasing components of the photoperiod were maintained but compressed into 6- and 9-month periods. Spawning in the control fish occurred in mid- January at the same time as fish in outside ponds under ambient conditions, whereas under the 6- and 9-month cycles it was advanced by approximately 12 and 6 weeks, respectively. Under both the control and experimental regimes, the primary change was an increase in serum levels of gonadotropin during the early stages of ovarian development, after which levels were reduced. This was followed by increased oestradiol-17β levels which became particularly pronounced during the period of exogenous vitellogenesis. These changes in oestradioL17β appeared to stimulate vitellogenin production and release by the liver as evidenced by increases in serum calcium and phosphoprotein phosphorus levels. Subsequently, vitelogenin levels remained high until after spawning was complete. During the later stages of ovarian development oestradiol levels fell, thus signalhng, probably by a negative feedback mechanism, a further and larger increase in gonadotropin levels presumably required for the control of fmal oocyte maturation and ovulation. This sequence of endocrine changes was similar under the shortened photoperiod cycles, although modifications were apparent in both their timing and duration, resulting in earlier spawning times.

International audience; In this study, I attempted to induce tetraploidy in the rainbow trout by means of 28 °C-heat shocks applied to fertilized eggs. Variations in the parameters of treatment resulted in large differences in survival rates between the batches, and varying proportions of tetraploid, diplotetraploid and diploid embryos were obtained with shocks beginning between 6 h 30 min and 9 h after fertilization and lasting more than 14 min. Tetraploidy was always associated with high mortality rates.

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.

Individual free-swimming female rainbow trout in which oocytes underwent final stages of germinal vesicle migration, maturation, or ovulation were bled via a dorsal-aortic catheter at frequencies of once every 1, 3, or 4 hr over periods of 9 to 36 hr. Gonadotropin (GtH) and 17 alpha-hydroxy,20 beta-dihydroprogesterone (17 alpha,20 beta-OHP) levels were measured in the plasma samples. GtH levels were elevated and showed wide and progressive daily variations. A high degree of synchronization appeared among the GtH profiles of individual fish. Two distinct daily GtH surges were observed, one at early photophase and the other during the mid-scotophase. The onset of the GtH increases was closely related to the beginning of the photophase and the scotophase, respectively. In females undergoing oocyte maturation or in ovulated females, 17 alpha,20 beta-OHP levels were increasing or high, showing progressive daily fluctuations that were either synchronized with the GtH changes or somewhat phase-shifted in relation to them. These data are discussed in relation to the seasonal changes in the short-term profiles of reproductive hormones in the trout.

International audience; A testicular feed back on the hypothalamo-pituitary system was studied in male rainbow trout (Salmo gairdneri) after bilateral castration and steroid or testicular supplementation. Experiments were carried out at various periods of the spermatogenetic cycle ; in March-April (resting stage), June (initiation of spermatogenesis), October (end of spermatogenesis and before spermiation), and December (running stage). In March and April, plasma t-GTH is low in intact males (< 2 ng/mi) and castration induced a threefold rise of GTH. Testosterone (T) given by a silastic capsule inserted in the body cavity of the castrate did not change plasma t-GTH in comparison with the intact control. When T is given in the same manner in intact males GTH is significantly increased. In June, a significant t-GTH rise was observed after castration (P < 0.05), this rise was prevented by injection of T and estradiol ()2.E When 2E and T were given to intact males plasma t-GTH was significantly decreased. In October plasma t-GTH was high (13 ng/ml) and was not modified by castration ; injected T or E2 had no effects on plasma t-GTH either in intacts or castrates. In December, a sevenfold increase of t-GTH is observed after castration. This was partly suppressed by intraperitoneal injection of T and E2 and declined after stereotaxic implantation of 11-ketotestosterone into the pituitary. It was not significantly suppressed by intraperitoneal injection of testicular extracts. It is suggested that at this period steroids are the main gonadal factors involved in the feed back at the hypothalamo-pituitary system level.

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.

Trout ovaries were processed in vitro to determine relationships between the following parameters — oocyte sensitivity to the maturational steroid 17α-hydroxy-20β-dihydroprogesterone (17α,20β-OH-P); follicular sensitivity to the maturational gonadotropin s-GtH; inhibitory potency of exogenous oestradiol-17β (E2) during s-GtH-induced maturation; and level of E2 in the plasma. The sensitivity to hormones was estimated by the median efficient dose (MED) for oocyte maturation in vitro. The peripheral migration of the germinal vesicle coincided with an increase in oocyte sensitivity to 17α,20β-OH-P. A significant correlation was observed between plasma E2 level and the follicular sensitivity to s-GtH, but not between plasma E2 and the oocyte sensitivity to 17α,20β-OH-P. It was concluded that the peripheral migration of the GV is a morphological event which coincides with an increase in oocyte sensitivity, and that E2 is a physiological regulator of follicular sensitivity to GtH.

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

International audience; In this work, we tried to optimize y-treatment of sperm to obtain large numbers of haploid gynogenetic embryos after fertilization. The analysis of increasing doses showed a typical « Hertwig effect)) in all cases, but we found wide between-male variations in the most efficient dose. This variability was reduced by mixing several irradiated samples collected from different males or given different efficient doses.

The changes in cAMP were followed in trout oocytes incubated in vitro after defolliculation performed by either enzymatic or manual dissection. Both defolliculation methods induced a highly significant rise in oocyte cAMP level (4.5 times the basal level of control [follicle-enclosed oocytes], after 6 h). Treatment of defolliculated oocytes with 17 alpha-hydroxy, 20 beta-dihydroprogesterone (17 alpha, 20 beta-OH-P) (10(-6) M), which induced oocyte maturation (germinal vesicle breakdown [GVBD]) was able, first, to interrupt the increase of oocyte cAMP level promoted by defolliculation and then to lower this level significantly down to values that still remained higher than folliculated controls. Very low concentrations of 17 alpha, 20 beta-OH-P (1.38-55.6 10(-9) M), or physiological doses of testosterone (0.35 10(-6) M, in the range found in vivo before ovulation) were able to induce a similar decrease of oocyte cAMP level without inducing GVBD. Under the same experimental conditions estradiol (0.35 10(-6) M) exhibited no action. These results suggest that some factor(s) originating in the follicle (FIF), inhibit the oocytes' tendency to accumulate cAMP before the final surge of 17 alpha, 20 beta-OH-P. This factor might be a follicular steroid such as testosterone or nonmaturing concentrations of 17 alpha, 20 beta-OH-P. Moreover our data favour the hypothesis that the final surge of 17 alpha, 20 beta-OH-P could induce distinct intraoocyte mechanisms: the first induces an irreversible blockage of cAMP level before the inhibitory action of the FIF is suppressed by ovulation, and the second mechanism leads to GVBD.

Responses of eggs of the rainbow trout Salmo gairdneri to a series of temperature and salinity combinations were measured for percentages of total-and viable-hatch and time to 50% hatch. Hatch occurred at the combinations of temperature range of 8.0 to 16.0℃ and chlorinity range of 0 to 6.0‰. Response surface analysis suggests that the maximum percentages of total-and viable-hatch (i.e.,optimum) may be found at 10.0℃ combined with 0‰. Time required to 50% hatch varied 18.5 and 44.6 days after fertilization,and was inversely and exponentially related to the temperature. The effect of chlorinity on the time was statistically insignificant within the hatchable range of eggs.

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.

International audience; An in vitro method is presented for investigation of protein incorporation into the ovarian follicles of rainbow trout (Salmo gairdneri). A protein induced into serum of S, gairdneri, after estrogen treatment, was incorporated into vitellogenic follicles to a greater extent than other serum proteins of S. gairdneri or bovine serum albumin (BSA) which served as controls. A large proportion of the incorporated BSA and other non-vitellogenic proteins is probably associated with follicular tissues other than the oocyte. These results offer further evidence that the estradiol-induced serum protein found in teleosts is vitellogenin, the precursor of oocyte yolk proteins.

International audience; A dual cannulation of free-swimming rainbow trout is used to estimate the metabolic clearance rate (MCR) of Estradiol-17β (E2-17β) by both single injection and constant infusion methods. It is shown that E2-17β MCR changes significantly during the progress of oogenesis, mainly at the end of the sexual cycle. The same changes in MCR and very similar values are found with both single injection and constant infusion methods: MCR is stable (28.8 ml/hr/kg) from the postovulation period (throughout endogenous vitellogenesis) to early exogenous vitellogenesis. It decreases significantly during advanced exogenous vitellogenesis (18.7 ml/hr/kg) and increases clearly at the onset of oocyte maturation (40.9 ml/hr/ kg). A direct relationship between MCR and plasma E2-17β occurs: Plasma E2-17β levels increase (advanced exogenous vitellogenesis) when MCR decreases. Then estradiol decline takes place at the same time that MCR reaches its highest values (oocyte maturation). An increase in MCR is probably one event required to allow the establishment of an appropriate hormonal environment for oocyte maturation.

When trout (Salmo gairdneri) spermatozoa were diluted in coelomic fluid or saline diluents at high dilution rates of 10(-3) and 10(-2) for increasing periods of time before insemination, there was a rapid decline and loss of fertilizing ability. At a lower dilution rate of 10(-1), there was partial or no loss of fertility. Dilution in a KCl-enriched saline diluent to inhibit sperm motility produced a slight decrease in fertility at a 10(-3) dilution rate, indicating that the spermatozoa, although sensitive to dilution, were less so when they were kept immotile. A partial loss of fertility was observed after the spermatozoa or eggs had been washed with saline diluents. The loss of fertility was total when both gametes were washed. Removing the seminal fluid by centrifugation led to a significant decrease in the fertilizing ability of the spermatozoa when insemination was carried out in saline diluent but not in coelomic fluid. Adding BSA at high doses (10 mg BSA/ml) into the diluent led to longer survival of the diluted spermatozoa. We conclude that (1) sperm dilution rate is a major factor in the maintenance of fertilizing ability of diluted salmonid spermatozoa, (2) as reported in the literature, coelomic fluid is superior to mineral diluents only when the gametes have been washed, and (3) some substances (possibly proteins) present in seminal and coelomic fluids play a role in gamete protection. These findings may explain the discrepancies in the literature concerning the duration of motility and fertilizing ability of salmonid spermatozoa.