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The energetics of sperm motility in fish must take into account both the energy necessary for survival in the genital tract and the energy required for motility. Spermatozoa are transferred directly into the female genital tract via modified anal fin of various morphologies. The mature oocytes are probably fertilized at this time, but oocyte maturation may occur during several days after parturition, and it is possible that spermatozoa are then freed from the ovarian seminal receptacle under a mechanism presently unknown. The sperm production of many species of oviparous fish is high and large amounts of seminal plasma are available for biochemical analysis. A glycolytic system exists during spermatogenesis and is in great part lost in the final product, the spermatozoa. Gardiner suggested that this was due to a change in the plasma membrane in the spermatozoa which will have to face a hostile environment once released in water.

Sturgeon sperm was cryopreserved in liquid nitrogen or stored at 1–4 °C on a short-term basis. The objective was to establish reliable technologies for the conservation of certain endangered sturgeon species and for artificial reproduction in sturgeon farms. Cryopreseved sperm was diluted in buffered extenders (pH between 8 and 8.5) containing intracellular (dimethyl-sulfoxide (DMSO), methanol, ethylene glycol) or extracellular (saccharose, egg yolk) cryoprotectants. The concentration of intracellular cryoprotectants ranged from 5% to 20%. Tested freezing rates were in a range of 0.5–18.5 °C/min and the thawing rate between 15 and 40 °C/min for 5 to 6 s. Ten to eight percent of the sperm were motile after thawing. Fertilization rates up to 73–94% were reported for thawed sperm but in most cases, average values were 20%. The motility of non-frozen sperm was activated after few days of in vitro storage. Motility declined with time depending on oxygen availability in the milt, temperature (optimum near 0 °C) and pH; though some spermatozoa were still motile after several weeks of storage.

The effects of ageing oocytes for 6 h before fertilization in the European catfish Silurus glanis are compared with the same experiment under normal conditions (stripping and fertilization immediately after ovulation). Fertilization rate and hatching rate are lower in the aged groups, while the percentages of malformed larvae and chromosomal abnormalities are significantly higher. Several kinds of abnormalities are described in detail.

Des ovules de truites Arc-en-Ciel ont été fécondés par des spermatozoïdes de la même espèce traités par l'iode suivant différents protocoles afin de couper la transmission de la nécrose pancréatique infectieuse (NPI) des salmonidés. L'efficacité de l'iode a été évaluée en parallèle par neutralisation du virus en 1 mn. Le protocole conseillé pour la solution d'iode disponible dans le commerce (ovules égouttés, puis recouverts de solution- iodée et sperme ajouté immédiatement) a d'abord été utilisé. A pH compris entre 5 et 8 et pour des concentrations en iode de 15, 25 et 35 mg/l, le pourcentage de fécondation est inférieur à 10 et ne remonte qu'à pH 9 (69 % pour 25 mg/l). Par contre, l'efficacité contre le virus décroît rapidement pour des pH supérieurs à 7, et aucun pH n'a permis de concilier efficacité et innocuité. Le même protocole'utilisé avec 10 spermes individuels a montré des différences de sensibilité individuelle marquées (pourcentages de fécondation de 1,6 à 37 % pour 25 mg/l d'iode à pH8), qui ne sont pas en corrélation avec la qualité des spermes appréciée par la concentration de la protéine de membrane 42 kDa dans le liquide séminal. Les différents essais de préincubation du sperme (de quelques secondes à 1 minute) ont donné des rendements de fécondation nuls, sauf pour un large excès de sperme, qui entraînait aussi la perte de l'efficacité de l'iode contre le virus. Deux expériences de transmission expérimentale ont été réalisées en incubant les spermatozoïdes avec du virus concentré. L'élimination systématique des oeufs morts et anormaux suivie d'une désinfection externe des oeufs (50 mg/l d'iode, 15 mn) avant l'éclosion n'a pas permis dé couper la transmission, ce qui laisse supposer que le virus peut être transmis sans infecter l'embryon de façon létale.

Summary Spermiation was stimulated in the European catfish Silurus glanis L. by injection of carp pituitary preparation (5 mg kg-1 of body weight) and mammalian GnRH [(D-Ala6) en-RH ProNHEt] implanted at a dose of 75 μg and 150 μg per male, respectively. The total number of spermatozoa collected by daily sampling during 7 days post-stimulation and expressed in millions per kg of body weight was 3.29 with carp pituitaries, 0.872 and 0.780 with 75 μg and 150 μg GnRH anjoue implant, respectively, and 0.387 in the control group treated with Ringer solution. In all groups, after sperm stripping there was a spontaneous activation by urine of the sermatozoa motility which was revented by collection of the sperm in an immobilizing solution (NaCl 200 mM, Tris 30 mM, pH 7). The percentage of motile spermatozoa ranged from 80 to 65% at days 1 to 5, and less than 50% at day 6 and 7. A similar decline of quality was observed with time for mass progressive movement (55 to 65 s on day 1, and 28 to 35 s on day 7) and total duration of displacement (66 to 77 s on day 1, and 45 to 53 on day 7).

Resume Au cours des quinze dernieres annees, les spermatozoides et le liquide seminal des poissons teliosteens ont fait l'objet de nombreux travaux dans le but de comprendre les processus mecaniques et chimiqes regulateurs de la motilite. Les spermatozoides de truite et de carpe ont ete plus articulierement etujies; leur flagelle est du type classique “9 + 2” doublets de microtubules auquels sont associes des bras internes et externes de dyneine. Les battements flaellaires sont engendres par des cycles d' accrochage/ decrochage des bras de dyneine d'un microtubufe au microtubule adjacent, l'energie provenant de I'hydrolyse de l'ATP. Une protease couplee a une ligase interviendrait egalement. Les spermatozoides subissent une alteration structurale lors de l'emission dam l'eau douce qui ne se produit pas dans la solution saline d'activation; cependant, dans les deux cas, la mobilite des spermatozoides est breve, 30sec. chez la truite et une minute chez la carpe. Leur trajectoire est circulaire; la frequence des battements flagellaires, elevee lors du declenchement de la mobilite (50–60 Hz), decroit ensuite jusqu'a 10–20 Hz: on constate alors l'arret du deplacement des tetes spermatiques bien que les flagelles des sermatozoides de carpe continuent leurs battements a une frequence faible (< 10 Hz). La vitesse de deplacement diminue parallelement a la frequence et la distance moyenne parcourue est de 3 mm chez la truite et 5 mm chez la carpe. La mobilite des spermatozoides de truite et de carpe est influencee par l'environnement ionique. Une forte concentration en ion K+ chez la truite et une pression osmotique elevee chez la carpe, inhibent la mobilite. D'autres ions tels que H+ Ca2+ Mg2+ interviennent egalement dans la regulation du mouvement. Lors de l'initiation du mouvement des spermatozoides de truite, I'activite de l'adenylate cyclase et la concentration en AMPc augmentent. L'AMPc serait donc un facteur du declenchement de la mobilite, il entrainerait la phosphorylation d'une proteine 15 Kd par l'intermediaire d'une Tyrosine proteine kinase et interviendrait aussi in vivo dans l'acquisition de la mobilite. Lorsque les spermatozoides de carpe ne sont pas mobiles dans la solution d'activation, ils peuvent subir une “maturation in vitro” par incubation dans un milieu riche en potassium et de pression osmotique elevee. Apres l' initiation du mouvement dans une solution d'activation, la quantite d'ATP diminue raidement dans les deux especes. L'ATP se regenere spontanement dans les uinze minutes qui suivent l' arret du mouvement chez la truite. Chez la carpe il n'y a pas de restauration de l'ATP dans la solution saline d'activation mais elle est possible en replasant les spermatozoides en condition d'immo-bilisation (forte pression osmotique). II a ete montre que des spermatozoides de truite demembranes sont reactivables en presence d'ATPMg2+ et d' AMPc, alors que chez la carpe l'AMPc n'est pas neces-saire. Summary Spermatozoa motility of trout (Oncorhynchus mykiss) and carp (Cyprinus carpio) In the past fifteen years, teleost spermatozoa and seminal plasma were studied with the aim of understanding the mechanical and chemical processes which regulate motility. Trout and carp spermatozoa were particularly studied; their flaella are classic, with “9+2” microtubule doublets and outer and inner associated dynein arms. Flagellar beating results from hooking/unhooking cycles from the dynein arms of one microtubule to the one adjacent through ATP hydrolysis. A protease coupled to a ligase is probably also involved. Spermatozoa undergo drastic structural change when shed in freshwater but not in an activating saline solution; however, in both cases, motility is short, 30 sec. in trout and one minute in carp. Trajectories are circular; flagellar beat frequencies are high at the beginning of the motility (50–60Hz), and decrease to 10–20Hz: one observes that sperm head stop, whereas flagella of carp spermatozoa continue beating at low frequency (< 10 Hz). The velocity decreases with frequency; the mean duration of displacement is 3 mm in trout and 5 mm in carp. Trout and carp spermatozoa motility are influenced by the ionic external environment. A high concentration of K+ ions in trout and a high osmotic pressure in carp inhibit motility. Other ions like H+ Ca2+ Mg2+ also interfere with the motility regulation. At the time of trout spermatozoa movement initiation, adenylate cyclase activit and cAMP concentration increase. cAMP is likely a factor involved in the initiation of motility, which may also involve the phosphorylation of a protein 15 Kd through a Tyrosine protein kinase activity. cAMP may also be involved in the acquisition of sperm motility in vivo When carp spermatozoa are immotile in the activating solution, they can undergo a “maturation in vitro” (i.e. the acquisition of the capacity to move) by incubation in a medium with high concentration of K+ and with a high osmotic pressure (400 m Osm/kg). After initiation of movement in the activating solution, intracellular ATP decreases rapidly in the spermatozoa of the two species. ATP regeneration occurs spontaneously within fifteen minutes following the arrest of movement in trout. In carp there is no ATP regeneration in activating saline solution, but replacing sermatozoa in an immobilizing solution (high osmotic pressure) results in a recovery of the intracellular ATP content. It was shown that demembranated trout spermatozoa can be reactivated with ATPMg2+ and CAMP; in contrast, cAMP was not necessary in carp.

Endocrinology has considerably expanded its field in recent years and many mechanisms of regulation in biology involve hormone related factors (biochemical mediators) which can be found in all living organisms. Endocrinology has provided powerful tools to understanding the regulation of many functions in fish and other animals. The various models seen in the composite group of fish permit fruitful comparisons with those in other groups of vertebrates and allow these to be placed into an evolutionary perspective. Applications to medical sciences have been derived from work originally carried on in fish endocrinology and several concepts developed on mammals and higher vertebrates were useful for research on fish. Endocrinology has had a major impact on the knowledge of many aspects of fish biology, such as reproduction, osmoregulation, stress, growth, and pathology, with application to fish farming. It has provided conceptual and technical tools for the control of several functions of some cultivated species and has contributed to the efficient domestication of several fish species.

The world’s oceans produce about 100 million metric tons of living resources, 85,000 metric tons of which is caught by the fisheries (a kind of hunting-gathering activity) of the world. Impressively, this harvest is half of the meat produced by domestic animals in the world (170 million tons). The world aquaculture production is significantly lower. Only 16 million tons, not including 10 million tons of algae, is produced annually (Table 1). In general, the total harvest over the past 15 years has increased in part due to a steady rise in aquaculture production (Figure 1).

The aim of this study was to develop a method for cryopreserving turbot semen and to compare sperm motility characteristics, metabolic status and fertilization capacity of frozenthawed and fresh semen. The best results were obtained when spermatozoa were diluted at a 1:2 ratio with a modified Mounib extender, supplemented with 10% BSA and 10% DMSO. For freezing sperm samples, straws were placed at 6.5 cm above the surface of liquid nitrogen (LN) and plunged in LN. The straws were thawed in water bath at 30 degrees C for 5 sec. Use of this simple method resulted in a 60 to 80% reactivation rate of the thawed spermatozoa. Although the percentage of motile spermatozoa in the frozen-thawed semen samples was significantly lower than in fresh semen, spermatozoa velocity and respiratory rate remained unchanged. The process of cryopreservation significantly decreased intracellular ATP content. The fertilization rate of frozen-thawed spermatozoa was significantly lower than that of fresh spermatozoa, but it increased with sperm concentration.

Pike, Esox lucius, is a well-studied fish species and general observations on its biology were published early in this century (reviews: Toner, 1966; Toner and Lawler, 1969). Until the 1960s most investigations were devoted to wild populations and their management. More recently there has been increasing interest in pike culture (Chapter 9). Information on reproduction is reported in some conference proceedings (Dube and Gravel, 1979; Billard, 1983a, 1985) and in monographs or general papers (Huet, 1976; Steffens, 1976; Souchon, 1977; Montalembert et al., 1978a; Pouvreau, 1980; Marcel, 1981; Louche, 1985). Details are also given in textbooks on pike culture (Schaperclaus, 1962; Arrignon, 1976; Piper et al., 1982; Huet, 1986; Westers, 1986). This chapter reviews data on reproduction, especially in the pike, with some references to other Esox species on the North American and Asian continents. Limited information is available on puberty and gametogenesis and no consistent work is known on endocrinology. Several studies have been carried out on the final stages of gametogenesis, spermiation, oocyte maturation—ovulation and on gamete biology, mostly for the purpose of induced spawning and artificial reproduction.

Carp spermatozoa are immotile in seminal plasma or in saline solution of high osmolality (> 400 mosmol kg-1). These ‘quiescent’ spermatozoa initiate a progressive forward motility when transferred in freshwater or in saline solution with low osmolality (< 160 mosmol kg-1). In this study we investigated ‘in vitro’ the relationship between sperm ATP content (measured by bioluminescence) and sperm motility (analysed by videomicroscopy). Sperm ATP content remained high in the immobilizing medium (200 mM KCl, Tris 30 mM, pH 8.0) where no flagellar movement occurs. Dilution of these spermatozoa in the activating medium (45 mM NaCl, 5 mM KCl, Tris 30 mM, pH 8.0) triggered forward motility which varied with temperature. At 20 degrees C, sperm ATP content decreased rapidly during the progressive forward motility phase from 12 to 4 nmol/10(8) spermatozoa, concomitantly with decreases in velocity (130 to 10 microns s-1) and the beat frequency (50 to 7 Hz). An inhibitor of mitochondrial respiration (KCN 10 mM) produced a drop in sperm ATP content irrespective of the incubation medium (activating or immobilizing). A second phase of sperm motility in the activating medium was induced following a previous transfer of spermatozoa into a medium of high osmolality for a few minutes prior to the second phase. Within 10 minutes, spermatozoa recover 90% of the initial ATP level as well as forward motility. These results suggest that motility of carp spermatozoa depends on sperm ATP synthesized by mitochondrial respiration mainly stored before activation. In low osmolality conditions, the mitochondrial oxidative phosphorylation is unable to compensate for the ATP hydrolysis required to sustain motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Live trout spermatozoa initiate flagellar motility for only a short period (30 sec at 18 degrees C) during which their mean beat frequency decreases steadily from 60 to 20 Hz. Motility then stops abruptly. Investigations of the activation of movement in demembranated sperm points to cyclic-AMP being necessary for reactivation (half effect at 0.5 microM) in some conditions. cAMP acts mainly by increasing the percentage of motile cells and not the beat frequency (BF) of the flagellar axoneme. Dibutyryl cAMP does not initiate movement or prolong motility of live sperm. The initiation of movement of demembranated trout sperm was investigated in various incubation conditions relative to previous phases of in vivo movement and to ATP concentration. In the absence of cAMP and in the presence of ATP lower than 25 microM, all sperm cell models were active with BF up to 15-20 Hz whatever their previous physiological conditions. In contrast, at ATP concentrations above 100 microM, the fraction of active spermatozoa decreased proportionally but the BF of the active ones increased so that, at 1 mM ATP, only 5% were active but with a BF of 65 Hz: the addition of cAMP up to 20 microM restored activity to 100% sperm models with a similar BF of 65 Hz. At ATP concentrations higher than 25 microM, cAMP was necessary in a concentration dependent manner in the reactivation, but not in the demembranation medium. This dependence was found to be unrelated to a previous in vivo phase of movement. The antagonistic effects of ATP vs. cAMP were tested at various concentrations of both nucleotides: the apparent affinity for cAMP, measured as the concentration restoring movement of 50% cell models, was decreased from 15 nM at 0.1 mM ATP to 0.5 microM at 1 mM ATP; conversely, the affinity for ATP, measured as the concentration giving rise to the half maximal beat frequency, was not significantly affected when the concentration of cAMP was raised to 0.5 mM. Preincubation with phosphodiesterase (PDE) resulted in motility of 100% of sperm models even at low ATP concentration. This tends to show that cAMP must be constantly present to sustain motility.

Carp semen obtained from isolated fish after hormonal stimulation was highly variable in terms of volume of semen, osmotic pressure of the seminal plasma, and sperm capacity to move. Moreover, this last parameter was unstable when the spermatozoa were kept within the seminal plasma, and the present work was designed to investigate and possibly correct this phenomenon. Sperm potential movement was the major parameter studied and was measured by the percentage of motile cells in a final 3.000-fold dilution in a medium of low osmotic pressure in which sperm movement is known to occur (Morisawa and Suzuki, Science 210:1145-1147, 1980). This was completed with occasional measurements of flagellar beat frequencies and demembranation-reactivation of axonemal movement. The results showed that sperm potential movement was preserved upon dilution of the semen into cold 200 mM KCl medium and that semen of initially "poor" quality or spermatozoa that had lost their capacity to move during storage in the semen recovered gradually their potential movement during incubation at 2 degrees C in the same medium. The K+ dependence for both the conservation and the regeneration of sperm capacity to move showed a minimal requirement of 50 mM KCl in media of high osmotic pressure. Na+ ions had similar properties but not divalent cations. The K+ activation was not pH dependent between pH 9.03 and 6.04. Whatever the functional state of live spermatozoa, demembranation-reactivation occurred in ATP-Mg2+. It is concluded that, with dilution of the semen in appropriate conditions, carp spermatozoa retain or acquire potential movement and therefore are a lower vertebrate spermatozoa model available year-round. In addition, obtaining potentially nonmotile sperm and reversion in vitro might be useful to study the control of in vitro maturation.

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.

An automatic recorder has been developed to study the dynamics of fish pond biocenosis by a modeling of the ecosystem. In order to be flexible and portable, the system is composed of independent and autonomous modules including four or five probes (respectively for aquatic and meteorological modules), an analogical converter and a data recorder. Paramete rs are measured on the surface (air temperature, sunshine, pluviometry, wind force and direction, atmospheric pressure) and in the water (temperature, dissolved oxygen, pH, conductivity and redox potential). Aquatic probes are simply immersed in the pond water so as to save energy, eliminate moving parts and not disturb the water layer. A portable computer is used to collect the recorded data once a week and to program the different recorders: input format, rhythm of measurement, threshold values etc… Due to the extensive use of CMOS, particularly for the RAM (Random Access Memories), a set of 1.5 V alkaline batteries provides the desired 2-weeks autonomy. A model of pond dissolved oxygen dynamics (in progress) can use to advantage the numerous measurements taken by this equipment to monitor indirectly the biological activity of the pond.

Summary Cryo-preservation of carp, Cyprinus carpio, sperm Deep-freezing trials of carp sperm were carried out by varying several factors such as the basic saline solution, the cryoprotectors added (glycerol, propanediol, ethylene glycol and DMSO), the media (Menezo-INRA B2, egg yolk, urea) and the deep-freezing and dilution rates. The success of deepfreezing was judged by the percentage of motile spermatozoa, intensity of motility, fertilizing ability and morphological integrity of the spermatozoa studied under the scanning electron microscope. DMSO was the best cryoprotector and the mineral composition of the dilution medium the least important factor, but there was noticeable improvement after organic compounds were added. The following mixture has been proposed: NaCl 100 mM + KC1100 mM, Tris 20 mM, pH 8: 37%, Menezo medium B2 INRA: 15%, urea 5%, DMSO: 10%, fresh sperm: 33%. Optimal deep-freezing rate was: 5°C/min from 2 to-7°C and 25°C/min from-7 to-70°C. In these conditions, about 70 to 80% of the spermatozoa were motile after thawing compared to fresh control sperm, but fertilizing ability was not more than 30 to 40% of that with fresh sperm. The percentage of spermatozoa considered intact was 66% after thawing as against 83% for fresh control sperm. The motility and fertilizing ability of deep-frozen sperm were significantly improved when the dilution rate at insemination was reduced from 1/100 to 1/2.

International audience; Changes in the maturational gonadotropin (c‐GtH) levels during 24 h in carp males, as a result of the presence or absence of other carp specimens, were investigated. Carp males were cannulated to ventral aortae. Gonadotropin levels were radioimmunologically determined. It has been found that in males two peaks of c‐GtH occur strictly in 2 periods during the day in which spawning takes place under natural conditions (early morning and late evening). Being in contact or not with another male or hypophysed female did not affect circadian changes in c‐GtH levels in investigated males.

International audience; Long-term (annual and seasonal) variations in plasma concentration of reproductive hormones (maturational gonadotropin GTH and sex steroids) have been studied in relation to the gonad cycle in some teleosts. Plasma GTH concentrations are low and increase only gradually during the major part of gonad development (vitellogenesis, spermatogenesis) but increase sharply towards the end of gametogenesis–that is, around the time of oocyte maturation and ovulation and before the start of spermiation. In females, plasma concentrations of 17β-estradiol and estrone rise continuously during vitellogenesis. In salmonids, after a decrease in 17β-estradiol concentration starting at the end of the vitellogenesis, there is a small peak in testosterone concentration followed by a strong transient rise in 17α-hydroxy-20β-dihydroprogesterone, which induces oocyte maturation. The concentrations of testosterone and 11-ketotestosterone rise during spermatogenesis. Maximal concentrations of 11-ketotestosterone were recorded in rainbow trout Salmo gairdneri just prior to the start of spermiation. Plasma concentrations of both androgens in this species dropped during spermiation, whereas that of 17α-hydroxy-20β-dihydroprogesterone showed an important rise. Short-term (circadian and ultradian) variations in concentrations of reproductive hormones in teleosts have been less studied. Daily fluctuations in plasma GTH and in sex steroid concentrations, the pattern of which depends on the development stage of the gonads, have been demonstrated in a few fish species. Pulsed gonadotropin secretion occurs in some phases of gametogenesis in rainbow trout and common carp Cyprinus carpio.

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.

Goldfish serum gonadotropin (GTH) concentrations were determined by radioimmunoassay 20 min after injection of goldfish brain extracts or synthetic luteinizing hormone-releasing hormone (LH-RH) into the third ventricle in the ventrobasal hypothalamic region. Extracts of the cerebellum and medulla were ineffective. Synthetic LH-RH, and extract of the lateral hypothalamus each significantly increased plasma GTH levels. The results indicate that the hypothalamus of the sexually mature female goldfish contains gonadotropin releasing hormone activity, and that releasing hormone is effective when administered via the intrahypothalamic route.

To test the antifertility effect of various steroids, fish were fed a diet containing steroids at two stages of the reproductive cycle: during spermatogenesis (June to November, experiment A) and during spermiation (November to February, experiment B). The fish in experiment A were given testosterone (T), methyltestosterone (MT), estradiol-17β (E2), hexestrol (H), progesterone (Pg), and FGA (Fluorogestone acetate) at doses of 0.05 and (or) 0.5 mg/kg of food. In experiment B, T, MT, and E2 were given at a dose of 0.5 mg/kg of food. The fish received a daily ration amounting to 1% of their body weight. In experiment A, inhibition of testicular growth was total with 0.5 mg MT and 0.5 mg E2 and partial with 0.5 mg T/kg of food. In these groups, there was no noticeable change in plasma gonadotropin (GTH) compared with the controls, except that the GTH rise observed in the other groups in September was prevented. This suggests that steroids act directly at the level of the gonad. In experiment B, no noticeable regression of the gonad occurred after steroid treatment. A big GTH rise was seen in the E2-treated group, but this was not followed by stimulation of spermiation. The total amount of sperm (50%) and spermatozoa collected during the experiment tended to be lower in the steroid-treated fish than in the controls. Spermatozoal fertilizing ability was significantly decreased (P < 0.005) by the testosterone treatment.

Testes of Esox lucius and Esox niger were investigated histologically, cytochemically, and ultrastructurally in reproductive fish. Intralobular Sertoli cells possessed numerous lipid droplets in Esox lucius, but not in Esox niger. In both species, interlobular cell types included myoid cells and lipid-negative Leydig cells within the extravascular space. Evidence is presented for a contractile network of myoid cells within the testes of these teleosts. The presence of Leydig cells and myoid boundary cells in the testis of Esox lucius refutes the reported homology between lobule boundary cells and Leydig cells in this species.

Une revue sommaire de la bibliographie portant sur quelques aspects de la biologie et de l'élevage du corégone fait l'objet de cet article Les problèmes de systématique sont brièvement exposés. La présentation de la biologie de l'espèce (gamétogenèse, fécondité, embryogenèse, croissance, exigences de l'environnement, etc.) est développée en relation avec les problèmes d'élevage posés par ces espèces : stockage des géniteurs, reproduction, insémination artificielle, incubation, élevage larvaire dans diverses conditions, élevage des estivaux, etc. Les possibilités d'utiliser ces espèces pour l'élevage en étang ou pour le pacage lacustre sont examinées.

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.

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.

The postcastration increase of gonadotropin secretion in the rainbow trout, was partially inhibited by charcoal treated seminal liquid. Protein testicular extract did not have any effect. This result demonstrates the probable existence of an inhibitory factor of gonadotropin secretion in the seminal plasma of the Trout.

Bilateral castration of male rainbow Trout resulted in increased levels of circulating gonadotropin, as measured by radioimmunoassay, but the response varied depending on the season. In early May the increase was 12 ng/ml after 30 days, when compared to the intact control but later in the month at the time when a peak of gonadotropin level is observed in normal fish, the increase was 25 ng/ml after 13 days. At the beginning of August, when spermatogenesis commences, the increase was 9 ng/ml after 12 days. In September, when spermatogenesis is ending, an increase of 20 ng/ml was found after 7 days, but only 50% of the animals responded. In December, during spermiation, an increase of 90 ng/ml was found after 7 days.

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.

Free and peptidic amino acids were measured in the seminal plasma of carp. Some acids such as glutamic acid and glutamine, taurine, glycine and proline were exceptionally abundant, while others like lysine, arginine and histidine were found in small amounts. Generally, the amino acid level was higher in carp seminal plasma than in that of other Vertebrate species. As this level was systematically higher than in the blood plasma, it is supposed that there was neoformation of an original fluid in the genital tract.

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.

Female brown trout were sacrificed every month or twice a month during the reproductive season. Plasma gonadotropin (GtH) and estradiol-17 beta (E2-17 beta) 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), lipidoprotéique (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 17 beta. 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 E2-17 beta 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 E2-17 beta 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, E2-17 beta, and the diameters of eggs had been calculated. There was a positive correlation among GtH, E2-17 beta levels, and the diameters of eggs during exogenous vitellogenesis, and a negative between GtH and E2-17 beta at the end of the reproductive cycle. These results were discussed, in relation to the existence of a pulsatile mode of GtH secretion.

10 In the rainbow trout and the tench, at the time of spermatogonia divisions a rise in the plasma gonadotropin levels was observed. Just before or during the spawning period, E217 beta and plasma gonadotropin reach their maximum levels. 20 When the effects of raising the natural cycle temperature of the tench were studied (deltat + 3 degrees C and + 6 degrees C), in conditions where nycthemeral and seasonal rythmicity were maintained, a significant increase in fertility was observed with the increase in temperature (the first spawning period was earlier and there was a rise in the number of spawnings). This effect of temperature seems to act at the level of the hypothalamo-pituitary system.

After rainbow Trout sperm were diluted in 0.01 and 0.001 M theophylline media, motility and fertilizing ability were prolonged as compared to the control media without theophylline. However, the motility observed was lower and of a different type than normal motility. This suggests that other factors besides cyclic nucleotides intervene in the motility of Trout spermatozoa.