Search

In 1976, groups of rainbow trout (Salmo gairdneri) that were prepuberal males and adult females undergoing their second reproductive cycle were given methyltestosterone (MT) or estradiol (E) in pelleted feed at dosages of 50 or 500 µg/kg of feed (groups offish received each dosage of each hormone) during the period of spermatogenesis and full vitellogenesis between 17 May and 21 November. This treatment completely inhibited gametogenesis. Although vitellogenesis did not occur in the females, no major changes were observed in the ovaries, which remained at the previtellogenetic stage with apparently normal oocytes and oogonia. Drastic changes in the male testes were found, however, with disappearance of spermatogonia at the highest doses of MT and E. In sexually mature fish, MT did not appear to be a growth promoter. In both males and females, E inhibited growth and induced high mortality.

Des spécimens immatures ou pré-pubertaires de mâles et de femelles de truites arc-en-ciel de 2 ans, de 500 à 600 g, ont été exposés, à partir du 21 juin, à une lumière continue (groupe CL); un groupe de truites témoins (groupe C) ont été exposées à la photopériode naturelle de la région parisienne et ont subi les variations saisonnières de température. L'échantillonnage périodique des gonades, pour fin d'analyses quantitatives de la spermatogenèse et évaluation du diamètre des follicules, a permis de suivre la gamétogenèse. Des techniques radioimmunologiques ont été utilisées pour mesurer les variations des concentrations de l'hormone GTH dans l'hypophyse et dans le plasma. La quantité et la qualité des gamètes ont été évaluées au cours de la fraye. À la lumière continue, la gamétogenèse et la fraye sont retardées d'environ 2 mois par rapport aux poissons témoins gardés à la photopériode naturelle. De plus, la gamétogenèse ainsi retardée comporte certaines particularités. Chez les mâles, la proportion de cellules germinales dans le testicule est modifiée comparativement au groupe témoin; par exemple, il y a présence de spermatides dans les lobules testiculaires au moment où commence la spermiation. La production de sperme, telle que mesurée dans quatre échantillons, est plus faible chez les mâles soumis à la lumière continue que chez les poissons témoins. Chez les femelles, durant la gamétogenèse, le diamètre des follicules et l'indice gonadosomatique ont tendance à être plus faibles chez le groupe CL que chez les poissons témoins, mais le diamètre des follicules diminue éventuellement et la fécondité est la même chez les deux groupes. Les variations des concentrations de GTH ne montrent de particularités que dans le plasma, en décembre. Le contenu de GTH dans l'hypophyse est plus faible en décembre chez les deux groupes de poissons des deux sexes, quel que soit le stade de reproduction atteint et quelle que soit la photopériode. Il n'y a pas de différences entre les indices hépatosomatiques et viscérosomatiques des deux groupes de poissons.

The effects of bilateral castration on plasma gonadotropin (t-GtH), as measured by radioimmunoassay, were investigated in male rainbow trout at several stages in the reproductive cycle: at the start of spermatogenesis at the end of May, after its completion in September, and before and after the beginning of spermiation in October and December. Castration resulted in increased level of circulating immunoreactive t-GtH but the response varied with the season. The rise after castration was four times the initial value in May and September, and increased twofold in October and sevenfold in December. The duration of the response following castration was 4 months in May, 2 months in September, and less than 1 month in October and December.

The effects of injection of prostaglandin (PG) E1, PGE2, and PGF2? into the third ventricle on serum gonadotropin (GTH) concentrations in the goldfish were tested. Blood samples were taken at 30 min postinjection for radioimmunoassay of serum GTH. PG dosages of 0.5 and 1.0 ?g were ineffective. However, PGE2 and PGF2? at the 2.0-?g dosage significantly suppressed serum GTH. PGE1 at a 2.0-?g dosage had no effect. There were no effects on serum GTH when 2.0 ?g of PGE1, PGE2, or PGF2? were injected intraperitoneally. The results indicate that PGE2 and PGF2? suppress gonadotropin secretion by some action, presumably on the hypothalamus. However, action of PGE2 and PGF2? by diffusion from the site of injection to some other brain site or the pituitary cannot be eliminated in the present study.

In many male mammals and birds, exposure to sexual stimuli results in acute elevations of circulating luteinizing hormone (LH) and testosterone (T); a similar phenomemon has now been observed in the male goldfish (Carassius auratus). Mature males placed with either a receptive female or stimulus pairs of spawning goldfish had gonadotrophin (GtH) concentrations and expressible milt (sperm) volumes that were significantly greater than those of males kept in all-male groups. This stimulatory effect lasted from 20 min to at least 2 hr for GtH (20 degrees) and from less than or equal to 1 hr to greater than or equal to 24 hr for milt (14 degrees). When males were separated from the spawning pair by either a solid or perforated clear partition, no elevations of GtH or milt levels occurred. In contrast, these values increased in males placed in contact with a spawning pair, even when that pair contained no female, but a male induced to perform female sexual behavior by treatment with prostaglandin. These results suggest that, in goldfish, access to a spawning situation is necessary for rapid elevations in GtH and milt. Furthermore, it appears that the males must be sexually active in order for these physiological changes to occur, as males that failed to engage in courtship behavior with a spawning pair had GtH and milt values not different from isolated fish. This suggests that male sexual behavior and elevations in milt and GtH are concurrent events that share a common activation pathway in the brain. The increase in milt may be due to both neurally and hormonally mediated events that ensure milt availability for imminent spawning activity.

The author relates a visit to various experimental stations in the Nagano's Prefecture (Japan) and describes the attempt made since 1964 by professional fishermen, organized into cooperative societies, who decided to extend carp production by means of floating cages on lake Suwa. He gives a detailed description of cages, exact information on breeding and feeding, as well as on diseases which might affect young fish. This technique of production is now widely spread to lakes and irrigation basins; in 1973 it reached 5,749 tons, which represents 22% of total carp production in Japan. However, this type of production finds its own limits in its protein yield (4 kg of marine fish are necessary to produce 1 kg of carp) and also in the fact that it is a source of pollution for the lake.

L'objectif de la présente étude est d'étudier au Laboratoire et en conditions contrôlées le taux de fécondation et de survie embryonnaire d'oeufs de truite, placés dans des milieux de turbidité croissante avant et durant l'insémination., The aim of this paper is to determine whether clay sediments suspended in water can prevent trout eggs from being fertilized.

The pattern of spermatogenesis was studied during an annual reprodutive cycle in adult male brown trout. The part of the testicular volume occupied by the nuclei of germ cells and of Sertoli cells, the lobular lumen and the extra-lobular space were measured. The number of germ cells was estimated by the total volume occupied by each cell divided by the individual volume of each cell. The permanent number of spermatogonia A (spermatogonia isolated or in groups of 2) was about 50 million. Each GA cell produced several spermatogenetic waves during the same reprodutive cycle. Sperm production was about 25 X 10(9)/g of testis/year, or about 6.8 X 10(7)/g of body weight/year. Males stocked separately from females, thus presumably not releasing spermatozoa, were killed in December, January and February. Since these fish contained the same amount of spermatozoa it appears that the process of spermiation initiated in December did not continue in January and February. During this period, some spermatozoa were phagocytized by macrophages (spermatophages) in the lobular lumen and by Sertoli cells.

Male and female rainbow trout in their first reproductive cycle were subjected to long days (16L : 8D; 24L : 0D and 16L : 8D shifting progressively to 24L : 0D within 6 months). All the fish were maintained at ambient temperatures of between 3 and 16°C. Mean ovulation and spermiation times were 2 months later in the long-day group than in the control group, and ovulation and onset of spermiation were spread over a long period. The quantity and quality of the sexual products obtained were comparable in all groups. In subsequent experiments with the female groups, 50% of the females kept for the first time under permanent light ovulated or were about to ovulate 1–2 months later than the controls. All females initially kept in LD during the first cycle also showed delayed ovulation but only a few ovulated. In the ovaries of ovulated and non-ovulated females, small vitellogenetic oocytes were found, indicating abnormalities in recruitment. Fish exposed for the first time to long days showed a delay in spawning but had normal ovulation.

Short-term storage of rainbow trout gametes in vitro under oxygen. The storage of rainbow trout sperm, taken 1 1/2 months after the onset of spermiation, was tested in vitro in the air and under O2 at a room temperature of 9° C for 24 hrs. Fertilizing ability was assessed by the percentage of eyed-eggs at 300 degreesdays. Sperm was diluted to 1 / 1 000 (10–3 ) to inseminate ova, taken for each test, from a group of females. When the sperm was stored in the air, the fertility rate dropped more rapidly than when it was kept under O2 (P

Serum immunoreactive gonadotropin (GTH) levels were measured in sexually mature (gravid) female foldfish at 24 hr before and 24 and 72 hr after brain or pituitary stereotaxic implantation of either a blank pellet (cocoa butter only) or a pellet containing one of the anti-estrogens, clomiphene citrate or ICI 46474. Both pituitary implantation and implantation in the nucleus lateral tuberis (NLT) region of a pellet containing ICI 46474 caused a significant increase in serum GTH levels, with the former site having a more pronounced effect. Implantation of ICI 46474 in the nucleus preopticus (NPO) region, the posterodorsal hypothalamus, or the optic tectum (OT) had no significant effects on serum GTH. Implantation of clomiphene citrate in the pituitary caused a significant increase in serum GHT levels, but implantation in the NPO region or OT had no effects. The results demonstrate that the pituitary gland and, to a lesser extent, the NLT region are sites for negative feedback effects of estrogens in sexually mature (gravid) female goldfish.

Le pH du dilueur d'insémination pour Salmonidés peut être avantageusement stabilisé avec le système tampon Tris-glycocolle . Les molarités les plus favorables sont de 0,05 M pour le glycocolle et 0,02 M pour le Tris. Après dilution dans ce milieu (DIATG) le sperme conserve son pouvoir fécondant pendant 4 min. ( dilution 10-4 ) ou 8 min. (dilution 103 et 102) alors que la dilution dans un milieu tamponné par le système carbonate bicarbonate entraine une chute de la fécondance après une minute. Lorsque le DIATG est employé pour l'insémination d'ovules pollués par du vitellus provenant d'ovules écrasés, le taux de fécondation est significativement plus élevé que si l'insémination est pratiquée avec de l'eau., Use of the buffer system Tris-glycine to stabilize the pH of sperm diluent improves the effectiveness. The ideal concentration is 0.05 M glycine and 0 02 M Tris. Sperm diluted with this milieu ( DIATG) retain their a bility to fertilize for 4 min. (dilution 10-4) or 8 min. (dilution 10-3 and 10-2) compared to only one min. using a buffer system of carbonate/ bicarbonate. When DIATG is used for fertilization of eggs contaminated by yolk from damaged eggs, the fertilization success is significantly greater than that found using water.

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.

Rainbow trout sperm taken from males in spermiation for more than one month was diluted in modified Cortland or in a saline plus KCl (2g/l). Cryoprotectors were added : DMSO and Ethylene-Glycol (E.G.) at a rate of 10 %. After dilution (sperm 1 vol + diluant 1 vol) the mixture was taken in the dark at — 4 ° C in a non frozen state. In the Cortland medium motility was maintained for ten days at its initial value using either DMSO and E.G. (fig. 3). After 35 days storage motility decreased slightly. Fertilizing ability tested after 9 days storage was maintained at its initial value only with Cortland medium + DMSO. In the other combination Cortland + E.G. fertilizing ability dropped by nearly 50 % after 9 days storage.; Le sperme de truite arc-en-ciel prélevé sur des mâles plus d'un mois après le début de la spermiation a été dilué par moitié dans le milieu de Cortland modifié ou dans un milieu physiologique enrichi en KCl (2g/l) additionné de 10 % de DMSO ou d'éthylène-glycol (E.G.). Le sperme ainsi dilué (1 volume sperme + 1 volume dilueur) a été placé à l'obscurité à — 4 ° C à l'état non congelé. Il conserve une motilité voisine de la motilité initiale pendant 10 jours dans le milieu de Cortland. Après 35 jours de conservation dans les mêmes conditions, la motilité n'est que légèrement diminuée. Le pouvoir fécondant testé après 9 jours de conservation dans le milieu de Cortland se maintient à son niveau initial avec le DMSO, mais diminue notablement (environ 50 %) avec E.G.

International audience; L'administration de méthyltestostérone à raison de 4 0 wg par gramme d'aliment à des alevins de T. nilotica et T. macvochir pendant deux mois à partir de la fin de l'incubation buccale par la mère, a conduit aux résultats suivants :- Chez T. nilotica, nous avons obtenu l'induction complète et fonctionnelle du sexe mâle chez tous les animaux traités. Certains d'entre eux ont fourni une descendance entièrement femelle, révélant un génotype sexuel femelle, ainsi qu'une homogamétie femelle.- Chez T. macrochir, nous avons observé l'induction de la papille génitale de type mâle, et des modifications anormales dans la morphologie de la tête ; à une exception près, tous les animaux expérimentaux étaient stériles, avec disparition complète de la lignée germinale chez la plupart d'entre eux.

International audience; La production spermatogénétique de Poecilia reticulata est de 36 spermatozeugmes par jour soit environ 750 000 spermatozoïdes. Dans cette espèce, le canal testiculaire apparaît comme un véritable organe de stockage desspermatozoïdes qui n'assure pas une élimination régulière des spermatozeugmes ce qui conduit à une grande hétérogénéité dans l'âge des spermatozoïdes et pose le problème du vieillissement des gamètes et de ses conséquences.

International audience; La galvanonarcose de poissons d'aquariums tels que Xiphophores, Gambusies et Lebistes placés dans un champ électrique constitue un moyen d'immobilisation.

Collection Hydrobiologie et Aquaculture; National audience

Collection Hydrobiologie et Aquaculture; National audience

ISBN 2-85340-964-3; Les trente dernieres annees se caracterisent par un accroissement tres important du deficit du commerce exterieur francais en saumons, de 1727 tonnes en 1956 a 26937 tonnes en 1984 soit environ 1200 millions de francs. Les saumons frais, refrigeres ou congeles en constituent la part la plus elevee 23758 tonnes; viennent ensuite les preparations et conserves 3008 tonnes et les saumons fumes 176 tonnes. Les principaux pays fournisseurs en 1984 sont dans l'ordre, les Etats-Unis d'Amerique 9767 tonnes, le Canada 6489 tonnes, la Norvege 4969 tonnes, puis l'URSS 1527 tonnes et le Royaume Uni 1516 tonnes. Les saumons du Pacifique proviennent de peches faites en mer. Ils sont toujours majoritaires dans le marche 71 pour cent en 1984 mais depuis une decennie leur part respective baisse au profit du saumon altantique. Ceci est la consequence de la reussite de l'aquaculture en mer de cette espece en Norvege et en Ecosse.

Reproduction session. Concluding remarks