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1.
SUMMARY: Behavioral experiments concerning a releaser pheromone in the urine of female rainbow trout were performed using immature fish administered orally with 17α-methyltestosterone (MT) during the non-spawning season. The urine was collected by catheter. The frequency of entries of test fish was recorded in each channel scented by test and control solutions in a Y-maze trough. The behavior of both MT-treated and control fish demonstrated that they could not discriminate the differences between distilled and environmental water as control solutions. There was also no difference between MT-treated and control fish when distilled and environmental water were introduced. The MT-treated immature fish were attracted to the channel scented by ovulated female urine. Neither coelomic fluid nor the immature female urine had any effect on the behavioral responses of MT-treated fish, while immature control fish had no preference for the urine of ovulated females. These results suggest in rainbow trout that ovulated female urine contains a releaser pheromone to attract mature males, and that androgens are involved in the sensory mechanisms detecting the releaser pheromone in fish.  相似文献   

2.
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3.
The involvement of testosterone (T), estradiol-17β (E2), 11-ketotestosterone (11-KT), 17,20β-dihydroxy-4-pregnene-3-one (DHP), luteinizing hormone (LH), thyroxine (T4), and triiodothyronine (T3) in the regulation of downstream and upstream movement (swimming behavior) was investigated in land-locked sockeye salmon Oncorhynchus nerka, using an artificial raceway. During the downstream migratory period, T implant resulted in high plasma T levels and inhibited the occurrence of downstream swimming behavior (negative rheotaxis) in yearling (1+) immature smolts. In terms of upstream behavior, 2-year-old (2+) males exhibited high plasma T and 11-KT levels, while 2+ females had elevated T and DHP levels. In 1+ immature fish, a T implant induced upstream swimming behavior (positive rheotaxis). In experiments 1 and 3, the plasma T4 and T3 levels of non-migrants tended to be higher than those of migrants. In contrast, no marked changes in plasma and pituitary LH were found in both downstream and upstream migrants. These results suggest that sex steroids, such as T, play significant roles in the regulation of downstream and upstream swimming behaviors in land-locked sockeye salmon.  相似文献   

4.
This study investigated the in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU) in masu salmon Oncorhynchus masou Brevoort. Underyearling fish were fed with RU for 16 months. Monthly changes in body growth, gonadal maturation and serum levels of sex steroids were monitored. Gonads were also incubated at 0, 1, 10, 100 and 1000 μg RU mL−1 Leibovitz's L‐15 medium for 18 h. The levels of steroids in serum and cultured medium were measured. It was determined that RU‐fed immature and mature males, when compared with control groups, showed significantly higher body growth during spring, summer and the spawning period. Similarly, immature RU‐fed females showed significantly higher fork length and body weight in autumn, spring and summer. Furthermore, RU‐fed males showed significantly higher levels of serum testosterone (T) and 11‐ketotestosterone (11‐KT) levels in the pre‐spawning season, and 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) in the spawning season. In vitro RU incubation of gonads showed a dose‐dependent and significant increase in T, 11‐KT, oestradiol‐17β and DHP release in the medium. It appears that the causes of enhanced body growth and increased steroid production herein observed in salmonids are the physiologically active substances that may be present in the mycelium of the fungus.  相似文献   

5.
Maintaining high-quality fish eggs stably and efficiently is important for aquaculture. We developed a label-free immunosensor system for measuring 17,20β-dihydroxy-4-pregnen-3-one (DHP). DHP is suddenly secreted before ovulation as a maturation-inducing hormone in fish, and therefore, DHP levels are an indicator for predicting ovulation. The method is based on immunologic reactions and amperometric measurement using cyclic voltammetry (CV). For biomolecular immobilization on the surface of sensing electrode, Au electrode, we used self-assembled monolayers of thiol-containing compounds to fix anti-DHP immunoglobulin. In addition, we used a single-walled carbon nanotube to improve sensitivity. Using this electrode, we were able to determine the CV signal change caused by the antigen–antibody complex. The proposed immunosensor system showed a linear correlation (correlation coefficient: 0.9827) between the anodic peak current of the CV and the DHP level in range from 15.6 to 50,000 pg ml?1. The sensor system was then applied to monitor DHP of goldfish (Carassius auratus). Blood plasma of fish was collected every 3 h after administering a DHP inducer. In the measurement, the anodic peak current of the CV showed distinct changes depending on DHP levels in the blood plasma. A good relationship was observed between DHP levels determined by our proposed system and the conventional method (correlation coefficient: 0.9351).  相似文献   

6.
River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodus argenteus, from the S?o Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34?km of the river after the dam (site 1) and the second 34–54?km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17β-estradiol and 17α-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions.  相似文献   

7.
Repeated injections of salmon pituitary extract (20 mg per fish per week) induced vitellogenesis in feminized, cultivated Japanese eels (Anguilla japonica). Oocytes were attained at the migratory nucleus stage after 11 or 12 injections. Addition of 17,20-dihydroxy-4-pregnen-3-one (DHP) into the incubation medium induced germinal vesicle breakdown (GVBD) in the oocytes at the migratory nucleus stage. An injection of DHP (2 µg g-1 BW), given 24h after an injection of salmon pituitary extract (20 mg fish-1), succeeded in inducing maturation and ovulation in females which contained occytes at the migratory nucleus stage. Most fish ovulated 15–18h following the DHP injection. Eggs that were ovulated within 15h after the DHP injection showed high fertility and hatchability, but eggs ovulated 18 or 21h after the DHP injection, showed considerably lower fertility and hatchability. A delay between ovulation and stripping of the eggs rapidly decreased both the fertility and hatchability within 6–9h after ovulation, indicating that artificial fertilization must be carried out immediately after ovulation. Repeated injections of human chorionic gonadotropin (hCG) at a concentration of 1 IU g-1 BW week-1 induced spermatogenesis, spermiation, and the acquisition of potential for sperm motility in cultivated males. Most males spermiated after the fifth or sixth injection of hCG, and the milt weight gradually increased and remained constant (1–2 g) from the 11th to 31th injection. Sperm motility peaked 24h after each weekly injection, and decreased from the 3rd day after the injection. Potassium ions are an essential constituent for the maintenance of motility in the eel spermatozoa. Artificial seminal plasma containing 15.2 mM KCl is applicable as a milt diluent. Using these techniques developed for female and male eels, we have succeeded in obtaining many fertilized eggs from cultivated eels.  相似文献   

8.
Exposure of fish to stressors can elicit biochemical and organismal changes at multiple levels of biological organization collectively known as stress responses. The organismal (plasma glucose and cortisol levels) and cellular (hepatic hsp70) stress responses in fish have been studied in several species, but little is known about sex-related differences in these responses. In this study, we exposed sexually immature juvenile chinook salmon (Oncorhynchus tshawytscha) to bleached kraft mill effluent (BKME: 0%, 1%, and 10% v/v) for 30 days and then measured components of their organismal and cellular stress responses. Males exposed to 1% BKME had higher levels of plasma glucose than females. Plasma cortisol levels were unaffected in females exposed to BKME, but males exposed to 10% BKME had significantly higher levels of plasma cortisol relative to non-exposed males. While exposure to BKME did not affect hsp70 levels in males, females exposed to 1% BKME had higher levels of hsp70 relative to non-exposed and 10% BKME groups. Within any given treatment, females had higher levels of hsp70 relative to males. This study demonstrates that sex-related differences exist in commonly used indicators of stress in fish, and points out the importance of considering the sex of the fish in stress research. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
Wild striped bass,Morone saxatilis, were collected from coastal waters and spawning areas to describe the endocrine correlates of oocyte development in non-captive, migratory fish. The fish were classified according to their most advanced oocytes. Serum levels of estradiol (E2), testosterone (T) and 17-20-dihydroxyprogesterone (DHP) were measured by radioimmunoassay (RIA). Females in the primary growth phase and early secondary growth phase (pre-vitellogenic) had low levels of plasma steroids, ovarian lipid content and gonadosomatic indices (GSIs). Significant increases in E2, T, ovarian lipid content and GSIs occurred during the vitellogenic phase. Maximum levels of all reproductive parameters were found in prespawning fish sampled in the Hudson River. Mean levels of E2, T, ovarian lipids and GSIs for these fish were 2.0±0.5 ng/ml, 3.0±0.3 ng/ml, 24±1 mg/g, and 5.6±0.3% (mean±SEM), respectively. In fish induced to spawn with human chorionic gonadotropin (HCG), DHP levels (1.9±0.4 ng/ml) were significantly elevated. Similar levels were found in two fish captured during the spawning season, suggesting that DHP may serve as the maturation-inducing steroid in this species.  相似文献   

10.
Gonadal steroid and prostaglandin F2α (PGF2α) plasma levels were evaluated in successfully (SP) and unsuccessfully ovulated (UN) female Piaractus mesopotamicus. Forty-one females were injected with crude carp pituitary extract (0.6 and 5.4 mg kg?1 with a 24-h interval between the doses) and sampled to determine the plasma concentration of 17β-estradiol (E2), 17α-hydroxyprogesterone (17α-OHP), 17α,20β-dihydroxy-4-pregnen-3-one (DHP), PGF2α, and testosterone (T) after each injection (first—A1 and second—A2), and at the time of ovulation for SP and UN. Two clusters were obtained using multivariate analysis: 1—composed of all A1, all A2, and some UN; and 2—composed of all SP and some UN. Median values of E2 plasma levels were similar between clusters; however, plasma levels of T, 17α-OHP, DHP, and PGF2α of cluster 2 (predominantly formed by SP) were higher than those of cluster 1. Since cluster 2 contained all SP and females of this cluster presented higher levels of PGF2α, T, 17α-OHP, and DHP, here we evidently shown in an unprecedented manner that concomitant increased levels of these substances were associated with successful ovulation in this species, but such an increase was not determinant for successful ovulation due to the presence of some UN females in the same cluster 2. These findings highlight the unexplored potential of PGF2α to be used as an accessory tool for inducing successful ovulation for fish farming purposes.  相似文献   

11.
This study was designed to determine the effects of hormonal manipulation on stress responses in female and male pikeperch. Two-year-old cultured female and male broodstocks with an average weight of 337.4 ± 20.1 (mean ± SE; n = 16) and 318.7 ± 15.1 g (n = 16), respectively, were randomly allocated into four hormonal treatments each containing 4 fish. Two sexual groups of 16 fish for each gender were considered. Sexually mature male and female pikeperch were injected with either physiological saline solution (as control group), common carp pituitary extract (CPE), human chorionic gonadotropin (hCG) and or luteinizing hormone-releasing hormone analog (LHRHa2). The blood samples were taken before hormonal injection and after ovulation and spermiation. Then the plasma levels of stress indices (cortisol, glucose, and lactate) were determined. The results showed that all CPE-, HCG-, and LHRHa2- injected males produced sperm. In females treated with CPE and hCG, three of four ovulated, but none of LHRHa2- and saline-injected fish spawned. Significant changes in cortisol, glucose, and lactate levels were observed among the females injected with different hormones. Plasma cortisol and glucose levels increased significantly in males injected with CPE and females injected with hCG, but no significant change was observed in lactate levels before and after hormonal induction. Comparison of two sexes revealed significant differences in glucose levels for females in some groups before injection, while CPE-injected sexes showed significant changes in cortisol and lactate concentrations. The results indicated that the induction of ovulation or spermiation stimulated stress responses especially in female pikeperch, and therefore, all the procedures should be made to minimize the disturbance during the artificial spawning.  相似文献   

12.
In teleost, sex steroid hormones are critical for reproduction. Progestin is known to promote spermiation. To further understand the functions of progestin via its receptors during the annual reproductive cycle in male turbot (Scophthalmus maximus), we observed testicular development, quantified several sex steroid hormones, detected the expression of progestin receptors, and measured various sperm parameters. Results showed that the turbot testicular structure was of the lobular type. During breeding season, a number of spermatocytes (stage III) developed into spermatids (stage IV), then differentiated into sperm during spermiogenesis (stage V), and finally regressed to spermatocytes (stage VI). Concomitant with testicular development, serum progesterone (P4) and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) exhibited higher levels from stage IV to V than other stages. Furthermore, males with higher motility sperm showed higher levels of P4 and DHP compared with fish with lower motility sperm. These results indicated that P4 and DHP might induce spermatogenesis due to seasonal changes. Concurrently, in testes, the nuclear progesterone receptor (pgr) was expressed throughout the reproductive cycle and its level peaked during spermiogenesis while expression of membrane progestin receptor alpha (mPRα) did not change significantly. However, in sperm, mPRα expression was higher than in testes and had a significant positive correlation with curvilinear velocities (VCL), sperm motility, and motility duration. In conclusion, progestin appears to exert a direct pgr-mediated effect on spermiogenesis and improve sperm motility characteristics depending on the abundance of mPRα protein in sperm during spermiation.  相似文献   

13.
Impact of osmoregulation on plasma sex steroid levels and gonadal histo‐architecture was monitored to elucidate the effects of deviation from habitat salinity on gonadal recrudescence in an active reproductive season of an euryhaline fish Etroplus suratensis (pearlspot). Fish were maintained in three different salinities of 0 ppt Fresh Water (FW), 15 ppt Brackish Water (BW) and 30 ppt Sea Water (SW) for a period of 60 days. Plasma osmolality values were found to be significantly highest in SW‐acclimated fish accompanied by highest levels of plasma K? and Cl¯ ions. The progress of gonadal recrudescence was higher in BW followed by FW and SW as evident from the cellular features of gonads and increased level of plasma sex steroids, such as, in case of female and 11‐keto Testosterone and Testosterone in case of males. Plasma cortisol levels were comparatively higher in fish of both sexes in SW group. Significantly high levels of cortisol in SW suggest its role in hypo‐osmoregulation and associated stress. This study clearly reveals that salinity changes during the active reproductive phase can suppress the steroid‐mediated gonad recrudescence maximally under hypo‐osmoregulation in an euryhaline fish.  相似文献   

14.
Atlantic salmon (Salmo salar L.) females (2 SW), maturing for the first time, were reared under one of three temperature regimes (high: 14.3 ± 0.5°C; natural: 10.6 ± 1.0°C; and cold: 6.9 ± 1.0°C) in combination with one of two experimental treatments; an injection of GnRH analogue (GnRHa) contained in biodegradable microspheres, or a sham injection (microspheres only). The six experimental groups were then reared under simulated natural photoperiod for 4 weeks. Blood samples were drawn for analysis of plasma steroid levels and the fish were inspected for ovulation weekly. Batches of stripped eggs were incubated in triplicate incubators in raceways until the eyed stage. Treatment with GnRHa resulted in a substantial advancement and synchronization of ovulation at all temperatures, while exposure to cold water also appeared to advance ovulation slightly. While 75% (warm and cold) to 90% (natural) of GnRHa fish ovulated during the 4-week trial, only 30% of sham-treated females exposed to cold water, and none of the sham-treated fish held at higher temperatures, ovulated during this period. Survival rates of embryos to the eyed-stage were significantly higher for broodstock exposed to cold water. Plasma levels of testosterone (T), 17β-oestradiol (E2), and 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) were all significantly affected by treatment with GnRHa and, to a lesser extent, temperature. The efficiency of GnRHa in counteracting the negative effects of high temperature on ovulation and the associated changes in circulating sex steroids suggest that temperature inhibition operates at least in part at the brain or pituitary.  相似文献   

15.
Seasonal changes in plasma levels of insulin-like growth factor I (IGF-I) in precociously maturing amago salmon (Oncorhynchus masou ishikawai), which matured as 1-year-olds, have been investigated. Profiles of plasma IGF-I levels were compared with changes in growth and maturity, and plasma growth hormone (GH) and thyroxine (T4) concentrations. The maturity of the fish was determined by calculating the gonadosomatic index; in November, 100% of males and 89% females matured. In both males and females, plasma IGF-I levels increased from March to August, and subsequently, plasma IGF-I levels in the early maturing males and females declined gradually and were maintained at lower levels during the spawning period in November. Plasma GH levels were high in April, and then declined gradually through September. Thereafter, in early maturing fish, a slight increase in plasma GH levels was observed in October and November. No significant changes in plasma T4 levels were found in the precociously maturing fish. In sharp contrast, plasma IGF-I levels in immature fish remained elevated through September, reaching a peak in October, and then gradually declined in November. In immature females, plasma T4 and GH levels were elevated in August, reached their maximum in September and then gradually declined until November.  相似文献   

16.
The role of gonadotropin (GTH) in the reproduction of the Japanese flounder, Paralichthys olivaceus, was studied by assessing the changes in the apparent activity of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the pituitary gland during gonadal maturation by immunohistochemical analyses. Corresponding changes in plasma levels of testosterone (T), estradiol-17β (E2), and 17α,20β-dihydroxy-4–pregnen-3-one (DHP) were also studied. Reared fish at the early spawning to termination stages were sampled from May to August and wild fish at the previtellogenic to termination stages were caught at 3- to 4-week intervals between April and September offshore from the northern mainland of Japan by gill nets. The gonadosomatic index of the reared fish decreased from the early spawning stage to the termination stage, while that of the wild fish increased significantly from the previtellogenic stage to the early spawning stage and decreased thereafter. In the reared fish, the immunostaining intensities of FSH and LH were high during the spawning period, accompanied by high plasma levels of T, E2, and DHP. In the wild fish, the immunostaining intensities of FSH and LH were low during the previtellogenic stage but increased during the maturing and spawning stages. These results indicate that both FSH and LH are likely associated with oocyte maturation in the Japanese flounder.  相似文献   

17.
Triploid fish have under-developed gonads due to altered reproductive endocrinology. Triploids of Indian catfish (H. fossilis) showed significantly reduced plasma levels of gonadotropin (GtH-II), testosterone (T) and estradiol-17 (E2) than that of diploids throughout the year, except for the resting phase, irrespective of sex. Plasma levels of GtH-II were significantly different (p<0.001) between diploid and triploid fish during preparatory, prespawning and spawning phase. The plasma testosterone contents in triploids were significantly less (p<0.001) than that of diploids, except during the resting phase. Triploid females showed very low titres of estradiol-17 (<1 ng ml–1) throughout the annual reproductive cycle in contrast to highly fluctuating levels in diploid females. Thus, this study for the first time provides information on reduced levels of GtH-II and sex steroids in plasma of male triploid fish and additional information on species-specific alteration of sex hormones in female triploids.  相似文献   

18.
A label-free immunosensor for detecting the oocyte maturation-inducing hormone 17, 20β-dihydroxy-4-pregnen-3-one (DHP), was developed. A principle of the sensor system was based on differences in electrochemical activity changed by an immunoreaction in the absence and presence of DHP. For preparation of the immunosensor, anti-DHP IgG was immobilized on an Au working electrode modified with a self-assembled monolayer of 3-mercaptopropionic acid. The sensor was immersed into a sample solution containing DHP. DHP was determined by cyclic voltammetry. The immunosensor showed a specific response to DHP, and the oxidation peak current linearly decreased in the range of 7.8–500 pg ml−1 with a correlation coefficient of 0.996. The sensor system was applied to determine the DHP levels in plasma of goldfish and was compared with the DHP levels of the same samples determined using an ELISA as the conventional method. Good correlation was obtained between values determined using both methods in the range of 0.1–7.7 ng ml−1 (correlation coefficient 0.876). These findings suggest that the proposed label-free immunosensor can be used to analyze DHP levels in fish plasma samples.  相似文献   

19.
Blood samples were collected from captive Pacific halibut, Hippoglossus stenolepis , at intervals of about six weeks from early December 1986 to late November 1987. Concentrations of plasma androgen and estradiol-17β were determined by radioimmunoassay. The plasma concentrations of steroid were highest during autumn and winter in halibut that matured during late winter. The concentrations of steroids in samples collected in December were above 2 ng/mL (estradiol) or 1 ng/mL (androgen) in maturing females and below 0.5 ng/mL for both steroids in non-maturing females. The levels of steroids decreased rapidly about one month before spawning. In a mature male, androgen began to rise in August and November, and reached a peak of 7 ng/mL in early December. One month before spawning, the androgen concentration fell to 0.16 ng/mL. Estradiol concentrations were detectable in the male and varied little during the year. In immature fish, neither androgen nor estradiol changed significantly throughout the year. These results suggest that the concentrations of estradiol or androgen measured in blood samples taken during December may be used to determine the sex and state of maturation of Pacific halibut.  相似文献   

20.
Abstract. Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17-α methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT-treated tilapia was evaluated during consecutive treatment, nursery, and grow-out phases under conditions approximating commercial, semi-intensive tilapia farms in Central America. Oreochromis niloticus (L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT-treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0·1 g/fry for both treatments. Fry were subsequently stocked into 0·2-ha nursery ponds for 94 days growth. Slopes of control and MT-treated fish growth curves were not significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate significantly from the1:1 male: female ratio, but MT-treated fish were 97% males. Control male and MT-treated male fingerlings were stocked for grow-out into 0·1-ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT-treated fish. Mean gross yields after 150 days and mean final individual weights were similar for both treatments.  相似文献   

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