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1.
In broodstocks of Atlantic halibut, Hippoglossus hippoglossus, male and female gamete production often becomes unsynchronised towards the end of the spawning season—milt becomes very viscous and difficult to express while the females are still producing batches of good quality eggs. Gonadotrophin-releasing hormone agonist (GnRHa) has been shown to stimulate spermiation in a number of fish species. Therefore, we conducted two experiments where male halibut were implanted intramuscularly with pellets containing GnRHa. The effect of the pellets was tested at three periods: before, at the height of and at the end of spermiation. In the middle period, GnRHa was tested at two doses (5 and 25 μg/kg bodyweight). Measurements were made of milt hydration, sperm motility and fertilisation rate. Implanted males began spermiation at least 4 weeks before control males. Both doses of GnRHa increased the fluidity of the milt. This effect lasted for at least 20 days in the low dose group and for 40 days in the high dose group. When applied at the end of the season, GnRHa reversed the normal trend for the milt to become more viscous. GnRHa treatments did not affect fertilisation rates obtained with the sperm. However, towards the end of the spawning season, sperm motility was enhanced in males treated with the high dose of GnRHa (25 μg/kg) compared to controls. As described previously, plasma concentrations of the gonadal steroids, 5β-pregnane-3β,17,20β-triol 20-sulphate and 17,20-dihydroxy-4-pregnen-3-one, were significantly enhanced by GnRHa treatment. Concentrations of testosterone on the other hand decreased when spermiating males were treated with GnRHa. Our data suggest that 17,20β-dihydroxy-4-pregnen-3-one or its metabolites are involved in milt hydration, possibly through affecting ion transport.  相似文献   

2.
Spermiated male greenback flounder (Rhombosolea tapirina) were implanted with gonadotropin releasing hormone analog (GnRHa) pellets at different dosages to examine their effects on milt characteristics and plasma levels of testosterone (T), 11-ketotestosterone (11KT) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Milt and blood samples were collected for up to 28 or 42 days post-implantation (p.i.) in two separate experiments using fish that were slightly or moderately spermiated, respectively. In both experiments, fish treated with GnRHa pellets showed a consistent and significant increase in milt volume relative to controls, and the increase of milt volume was more rapid than the increase in numbers of spermatozoa. Spermatocrit (Sct) was significantly lower in GnRHa-treated fish than in controls. Plasma levels of T and 11KT were elevated at 7 and 14 days p.i. in slightly spermiated fish treated with GnRHa and elevated plasma T and 11KT levels were accompanied by increased milt volume early in the spermiation period. In contrast, there was no significant difference in plasma T levels between GnRHa-treated and control fish in fish that were moderately spermiated at the time of implant. Treatment with GnRHa tended to result in lower plasma levels of 11KT and higher levels of 17,20βP relative to controls, and there was a positive relationship between the elevation of plasma 17,20βP and the increase in milt volume in response to implantation of GnRHa pellet. Slow release GnRHa administration had no effect on sperm activity or pH and osmolality of seminal plasma in either experiment.  相似文献   

3.
In two separate spawning seasons, spermiating male Atlantic halibut were implanted with pellets containing gonadotrophin-releasing hormone agonist (GnRHa). Males were bled repeatedly, and milt samples were collected. Blood samples were assayed for free and conjugated steroids: testosterone, 11-ketotestosterone, 17,20-dihydroxy-4-pregnen-3-one (17,20-P), 17,20-dihydroxy-4-pregnen-3-one (17,20-P), 17,20,21-trihydroxy-4-pregnen-3-one and steroids with a 17,20 configuration. Towards the end of the first season, pellets were implanted into three wild-caught and three hatchery-reared males. No control fish were available. The major progestogen in plasma was identified as sulphated 5-pregnane-3,17,20-triol (3,17,20-P-5-S). Concentrations of this steroid were stimulated by the GnRHa. Sulphated 17,20-P was also identified in the plasma, but at 10-fold lower concentrations than 3,17,20-P-5-S. In the middle of the second season, pellets were implanted into five hatchery-reared males; five unimplanted males were used as controls. Levels of androgens fell following GnRHa treatment, levels of progestogens rose briefly, and there was a significant increase in the fluidity of the milt. Of all the measured steroids, free and sulphated 17,20-P showed the best correlation with milt fluidity.  相似文献   

4.
Testes from spermiating goldfish were incubated with [3H]17-hydroxyprogesterone. The major products in the unconjugated fraction were identified as androstenedione, androstenetrione, 11-β-hydroxyandrostenedione, 11-ketotestosterone, 17,20α-dihydroxy-4-pregnen-3-one (17,20αP) and 11-deoxycortisol. Testosterone was present predominantly in the glucuronide fraction, but yields were low (1–3%). The major components of the sulfate fraction were 17,20αP and 11-deoxycortisol. The identification of cortisone in low yield (< 2.5010) in both the free and sulfate fractions is the first report of corticosteroid biosynthesis by a teleost testis. The high yields of 17,20αP and 11-deoxycortisol and their sulphates suggests that their possible role in spermiation of the goldfish should be further investigated.  相似文献   

5.
The present study was designed to examine the potential for inducing ovulation in starry flounder (Platichthys stellatus) using gonadotropin-releasing hormone analog (GnRHa) and human chorionic gonadotropin (hCG) to assess whether starry flounder are differentially responsive to GnRHa and hCG. Female starry flounder were injected or implanted with different doses of hCG or GnRHa pellets to examine their ovulation-inducing potential and effects on plasma levels of testosterone (T), 17β-estradiol (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Blood samples were collected for up to 10 or 25 days post-injection or post-implantation in two separate experiments designed to mimic the early and middle stages of spawning, respectively. Fish treated with the GnRHa pellets (100 µg) showed a significant increase in the total number of stripped eggs relative to the controls. GnRHa administration had no effect on the floating rate or fertilization rate of ovulated eggs in the both experiments, whereas hCG injection affected both of these rates. Plasma T levels were not significantly different between the exogenous hormone-treated and control fish. In contrast, the plasma E2 level was elevated in those fish treated with GnRHa, regardless of injection or implantation, and was accompanied by increased numbers of stripped eggs in both experiments. Treatment with GnRHa resulted in higher 17,20βP levels compared to the controls, and there was a positive relationship between elevated plasma 17,20βP and an increase in ovulated eggs in response to GnRHa treatment. The implantation of starry flounder with GnRHa-containing pellets was effective at inducing sustained ovulation compared to hCG treatment.  相似文献   

6.
Maturing male and female Atlantic salmon (Salmo salar L.) were held under three temperature regimes for 10 weeks between September and December: warm (constant 14–16 °C), ambient (decreasing from 11 to 5 °C), and cold (decreasing from 7 to 3 °C). Blood samples were analyzed for plasma steroid levels, and the fish were inspected for the presence of expressible milt (total volume and spermatocrit) and ovulation weekly. Samples of eggs were dry-fertilized with milt stripped from three males held at the same temperatures and incubated until the eyed stage. In females, levels of plasma testosterone (T) and 17β-oestradiol (E2) dropped as ovulation approached, concurrent with a rapid increase in levels of plasma 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P). In males, levels of T and 11-ketotestosterone (11-KT) peaked 2–3 weeks after the first appearance of expressible milt, while levels of 17,20β-P increased steadily and did not exhibit a definite peak. Exposure of females to cold water amplified and advanced the profiles of all three steroids compared with the ambient group, and increased the survival rates to the eyed egg stage. Cold water had no immediate effect on the male steroid profiles, but later, higher levels of 17,20β-P were evident compared with both the ambient controls and the warm water group, while the effects on 11-KT and T were more variable. Exposure to warm water completely inhibited both milt production and ovulation. Moreover, warm water modulated the steroid profiles of the males with lower 11-KT levels compared with ambient controls and lower 17,20β-P level compared with cold-water-treated males. In females, warm water resulted in total inhibition of the peri-ovulatory peak in 17,20β-P and prevented the normal decline of T and E2 levels associated with ovulation. The findings of the present study are highly relevant for broodstock management in aquaculture, as well in understanding the impact of climate change/temperature variability on wild salmon spawning.  相似文献   

7.
Compared to control fish, gonadotropin releasing hormone-analogue (GnRHa) treatment delivered either by microspheres or cholesterol pellets successfully increased sperm production (cells kg–1) and milt volume (ml kg–1) in mature yellowtail flounder Pleuronectes ferrugineus during the spawning season. Spermatocrit decreased in both treated and control groups between 12 and 29 days post-implantation, indicating a seasonal decrease in sperm concentration, rather than an effect of the GnRHa treatments.Plasma levels of testosterone, 11-ketotestoterone and 17,20dihydroxy-4-pregnen-3-one (1720P) showed no clear pattern either across treatments or over days, however this does not exclude the possiblity that GnRHa had its effect on milt volumes via the stimulation of steroid production since the sampling protocol did not allow for the rapid clearance of steroids from the plasma. GnRHa treatment did not have a negative effect on sperm fertilizing ability, percentage hatch or larval morphology. Sperm motility and seminal plasma pH were increased by GnRHa treatment.  相似文献   

8.
Goldfish,Carassius auratus, spawn several times within a spawning season. A gonadotropin (GtH) surge occurs at the time of ovulation in this cyprinid species. This ovulatory GtH surge mediates the processes of final oocyte maturation and ovulation, and occurs at the end of each spawning cycle. Within a cycle, there is a shift in the predominant plasma steroid from estradiol to testosterone, and finally 17α, 20β-dihydroxy-4-pregnen-3-one at the time of the ovulatory GtH surge. High levels of testosterone were always observed before ovulation. When ovariectomized or sexually regressed female goldfish were implanted with testosterone, they exhibited a GtH surge which was similar to those normally observed at ovulation. These results strongly suggest that elevated plasma testosterone is an important physiological requirement for the occurrence of the GtH surge.  相似文献   

9.
The present study is concerned with pheromone communication in tench (Tinca tinca L.), establishing firstly whether males have a high olfactory sensitivity to some typical teleost sex steroids and prostaglandins; and secondly whether males and females might be able to synthesise and release some of these steroids into the water. The C21 steroid, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was found to give large electro-olfactogram responses with an estimated threshold of detection of 10−12 M. The male tench were equally sensitive to glucuronidated 17,20β-P (10−11.6 M) but 100 times less sensitive to sulphated 17,20β-P (11−9.7 M). Preliminary data from cross-adaptation studies suggest that both the free and conjugated forms are detected by the same olfactory receptor(s). Male tench also had high olfactory sensitivity to prostaglandin F2α (PGF2α) and 15-keto PGF2α (11−11.5 and 10−11.4 M). They were relatively insensitive, however, to testosterone (T), androstenedione (AD), 11-ketotestosterone (11-KT), 17β-oestradiol (E2), 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P) and 17,20α-dihydroxy-4-pregnen-3-one (17,20α-P). Radioimmunoassays were used to measure the steroids in plasma and water and all samples were processed for the measurement of free, sulphated and glucuronidated fractions. In females, free 17,20β-P, 17,20α-P, free and glucuronidated T, and AD in plasma showed the largest increases in response to injection with mammalian gonadotropin-releasing hormone analogue (GnRHa) or Ovaprim (a mixture of GnRHa and a dopamine inhibitor). Free 17,20β-P was released into the water at the greatest rate. Plasma concentrations of the two conjugated forms of 17,20β-P were also elevated 18 h after the administration of GnRHa, but not by as much as the free steroid. In males, AD and 11-KT showed the greatest increase in response to GnRHa and were moreover released into the water at a higher rate in the treated group than in the control. The data support a possible pheromonal role for free and glucuronidated 17,20β-P. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

10.
Plasma levels of 17,20-dihydroxy-4-pregnen-3-one (17,20OHP), which is involved in the regulation of spermiation in male salmonid fish, increase dramatically at the time of spermiation. To advance the understanding of the regulation of 17,20OHP production during the spermatogenetic cycle in trout, we have studied the in vitro effect of gonadotropin type II (GtH II) and the precursor 17-hydroxy-4-pregnene-3,20-dione (17OHP) on the production of 17,20OHP. The sensitivity with which testes secreted 17,20OHP following stimulation with GtH II was maximum during spermatogenesis. The addition of 17OHP (10 to 1600 ng ml-1) to the culture medium of testes fragments induced a significant and dose-related increase in 17,20OHP secretion. Although the capacity to produce 17,20OHP was not saturated by the 17OHP concentrations used, the conversion rate was highest for tested at an immature stage. As to the regulation of 17OHP, in vivo, a single injection of partially purified salmon gonadotropin (50 ng g-1 body weight) induced a significant increase in the circulating levels of 17OHP of immature males. In conclusion, the maximum sensitivity to GtH II stimulation and the highest conversion rate of 17OHP to 17,20OHP in vitro, occurred before the dramatic increase in the 17,20OHP secretion observed in rainbow trout at the time of spermiation.  相似文献   

11.
Incubation of follicular cells from postvitellogenic spotted wolffish ovaries with tritiated steroid precursors revealed that granulosa cells were able to convert 17-hydroxyprogesterone (17-P) to 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and androstenedione. Theca cells had limited ability to synthesise additional steroids from 17-P but converted 17,20β-P to 17,20β-P sulphate. Neither of the two cell layers was able to synthesise 5β-pregnane-3α,17,20β-triol-20-sulphate (3α,17,20β-P-5β-S) which is found in high concentrations in plasma. 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P), 17,20β-dihydroxy-5β-pregnan-3-one (17,20β-P-5β) and 17,20β-P were most potent in inducing germinal vesicle breakdown (GVBD). Sulphation of 17,20β-P resulted in loss of GVBD inducing activity.  相似文献   

12.
Abstract.— Captive-reared, 10-mo-old, male striped bass Morone saxatilis were sampled monthly for testicular development between February and June 1994. One of the five males sampled in February showed precocious testicular development and had a gonado-somatic index (GSI) of 1.26%. while the other four fish had immature testes with a mean GSI ± sx, of 0.17 ± 0.03%. Spermiating individuals were present from April to June. In April the average body weight (BW) of spermiating males was 65 ± 4 g and their GSI reached a mean value of 4.75 ± 0.52%. In June, milt collected from ten precocious males contained motile spermatozoa with a mean of 31 ± 7% of the sperm showing forward movement. Mean milt volume and sperm concentration were 1.67 ± 0.41 mL/kg BW and 92.3 ± 1.8 ± 109 spermatozoa/mL. respectively. These data show that male striped bass reared in captivity can reach sexual maturity during their first year. This is one year earlier than previously reported for striped bass in mid-Atlantic regions.  相似文献   

13.
The present study demonstrates that acceleratedphotoperiod advances ovulation in Atlantic salmon, and that exposure to cold water prior to spawning further advances and synchronizes this process while improving egg-survival. High water temperature inhibited both sperm release and ovulation, whereas a GnRHa treatment overrode this temperature effect in most individuals. A decrease in water temperature seemed to accelerate both ovulation and sperm release, and water temperature modulated the plasma 17,20βP profiles around ovulation and sperm release. The GnRHa treatment markedly increased the volume of strippable milt and the plasma 17,20βP levels in males.  相似文献   

14.
The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na+ (measured as the short-circuit current, Isc) and secretes K+ (measured using86Rb+ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na+ uptake and K+ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.  相似文献   

15.
The main steroids produced by three stages ovarian fragments (post-vitellogenic PV, oocytes in GV migration phase Mtg and mature oocytes M) of white croaker were compared. In Mtg and M stages 17,20β-dihydroxy-4-pregnen-3-one (17,20βP), 17,21-dihydroxy-4-pregnene-3,20-dione (17,21P) and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) were synthesised. The specific synthesis of 20βS in Mtg oocytes suggests a MIS role for this steroid.  相似文献   

16.
Cultured red porgy Pagrus pagrus (L.) males (n=6) were sampled every 2 weeks for milt, in order to monitor changes in sperm quality parameters during a whole spawning period. On 11 January 2001, 60% of the fish were spermiating, increasing to 100% in mid‐February and dropping to 30% by mid‐April. Sperm density showed a slight increasing trend, with mean values ranging between 8.6 and 23.7×109 spermatozoa mL?1. Sperm motility percentage exhibited a significant improvement during the spawning season (analysis of variance (anova ) P=0.0001). The duration of forward motility for the major part of the monitoring period ranged between 2 and 4 min. Red porgy spermatozoa maintained their viability for many days after whole storage of milt at 4°C. During the monitoring period there were significant changes in the mean duration of sperm survival after cold storage, ranging from 5 to 12 days. The total volume of expressible milt was maximal on 28 March, increasing from a mean value of 1.7 mL to 5.3 mL kg?1. Milt production of captive‐reared red porgy does not appear to be limiting, when compared with the volume of expressible milt produced by other cultured marine fishes.  相似文献   

17.
The silver perch (Bidyanus bidyanus Mitchell) (Teraponidae), is a native Australian freshwater fish that, due to its high potential for aquaculture, was introduced to Israeli fish farming. The objective of this study was to find an optimal method for inducing spawning of silver perch. The agents tested for this purpose were: human chorionic gonadotropin (hCG; 150 or 200 IU/kg BW); salmon gonadotropin releasing hormone analogue (sGnRHa at 10, 20, 30, or 40 μg/kg BW); mammalian GnRH analogue (mGnRHa at 30 μg/kg) and the combination of sGnRHa at 20 μg/kg and domperidone at 5 mg/kg BW. Based on spawning success and relative fecundity, sGnRHa at the dose of 30 μg/kg was found to be more efficient than hCG, mGnRHa or sGnRHa with domperidone. Since domperidone does not improve the GnRHa effect on final oocyte maturation (FOM) and spawning, it is suggested that the dopaminergic inhibition during the stages of FOM in the silver perch is weak. Therefore, the use of GnRHa alone is sufficient to induce spawning in this fish. Immunoreactive gonadotropin (IR-GtH) and estradiol levels increased after a single injection of sGnRHa, and peaked after 24 h. Plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P) also increased significantly 24 h after the injection of mGnRHa, 12 h before spawning, suggesting that 17,20-P is the maturation-inducing steroid in silver perch. In order to reveal whether the heterologous gonadotropin may elicit an immunological reaction, silver perch was subjected to prolonged treatment with hCG. This treatment resulted in no detectable titer of antibodies against the mammalian gonadotropin. In conclusion, although hCG has no deleterious effects in this fish, and is the more commonly used for spawning induction, sGnRHa at 30 μg/kg is the recommended treatment for spawning induction of female silver perch under the conditions prevailing in Israeli aquaculture.  相似文献   

18.
Two year old black porgy (Acanthopagrus schlegeli) fed a diet containing 4.0 mg kg–1 of estradiol-17 (E2) for 5 months had significantly lower GSI than the control group during the spawning season. E2 suppressed testicular development, spermiation and plasma testosterone (T) and 11-ketotestosterone (11-KT) and stimulated ovarian development, vitellogenesis and sex reversal. Spermiation in the control group occurred in January and February with the concentrations of 1.08–1.36 × 1010 sperm ml–1 of milt. Higher plasma T and 11-KT, but lower E2 levels were detected in the spermiating fish (control group). Higher plasma E2 levels were detected in the sex reversing black porgy during the pre-spawning season. A sharp rise in plasma 11-KT and a drop in T levels were detected in spermiating fish (control group) from January to February. Plasma 11-KT levels correlated with the testicular development and spermiation. The data suggest that E2 plays an important role in controlling the sex reversal of black porgy.to whom correspondence should be addressed.  相似文献   

19.
Weekly injections of salmon pituitary extracts (SPE) were administered to female Japanese eel, Anguilla japonica at a dose of 20 mg/fish. This induced vitellogenesis and caused oocytes to reach the migratory nucleus stage. Later, a majority of the females that received an injection of SPE at a priming dose, followed 24 h later by 17,20β-dihydroxy-4-pregnen-3-one (DHP), ovulated 15 to 18 h after the final injection. In cultivated males, repeated injections of human chorionic gonadotropin (hCG) at a dose of 1 IU/g BW/week induced spermatogenesis and spermiation. Since potassium ions were revealed to be an essential constituent for the maintenance of motility in the eel spermatozoa, artificial seminal plasma containing KCl was designed as a diluent of milt, and enabled the preservation of milt for several weeks in refrigeration. As a result, artificial fertilization performed immediately after ovulation with pre-diluted and stocked milt consistently resulted in the production of high-quality gametes. Recently, a slurry-type diet made from shark egg yolk has been found to be a suitable feed for captive-bred eel larvae. Although preleptocephalus larvae can be reared with this diet beyond the depletion of their yolk and oil droplet stores, it remains inadequate because larvae reared under this way cannot be raised to the following stage. Therefore, the diet was improved by supplements of krill hydrolysate, soybean peptide, vitamins and minerals. Larvae fed on this new diet have grown to 50 to 60 mm in total length (TL), and have begun to metamorphose into glass eels approximately 250 days after hatching.  相似文献   

20.
Testosterone, 3,17-dihydroxy-5-pregnen-20-one, 17,20-dihydroxy-4-pregnen-3-one (17,20P) and 5-pregnane-3,17,20-triol were identified as the major metabolites of [3H] 17-hydroxyprogesterone in ovarian incubations of the European catfish Silurus glanis. 17,20P and the reduced triol were present only in ovaries from fish primed with carp hypophysial homogenate (chh) while testosterone yields were significantly higher in controls than in treated fish. 11-Ketotestosterone, 11-hydroxytestosterone and 17,20-dihydroxy-4-pregnen-3-one (17,20P) were identified as the major metabolites of [3H]17-hydroxyprogesterone in in vitro incubations of testes of a spermiating catfish. There was no significant production of conjugates or other water soluble metabolites by either sex. The stimulation of plasma 17,20P, 17,20P and 11-hydroxytestosterone by chh in primed but not control males suggests that the role of these steroids in spermiation should be further examined.  相似文献   

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