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1.
Jeffrey A. Malison Lynne S. Procarione Terence P. Barry Anne R. Kapuscinski Terrence B. Kayes 《Fish physiology and biochemistry》1994,13(6):473-484
The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from
upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early-
to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte
diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior
to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E2 levels in females increased rapidly from low values in October (< 0.1 ng ml−1) to peak levels of 3.7 ng ml−1 in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E2 levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml−1 in November, and peaking again at 3.3 ng ml−1 just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml−1, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In
males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells)
with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn)
to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml−1 by November, remained elevated throughout the winter, and peaked at 2.8 ng ml−1 I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml−1, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml−1. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and
suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting
fish to relatively simple environmental and hormonal treatments. 相似文献
2.
The relationship between plasma and ovarian levels of gonadal steroids was examined in two New Zealand fish species with multiple
spawning cycles of differing length. Snapper (Pagrus auratus) have a daily cycle of oocyte development, ovulation and spawning, whereas demoiselles (Chromis dispilus) spawn over 2–3 days during a repeat spawning cycle of 7–9 days. Ovarian and plasma levels of the gonadal steroids 17β-estradiol
(E2), testosterone (T), 17-hydroxyprogesterone (17P) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in reproductively
active fish captured from the wild. Ovarian levels of E2, T and 17P changed in relation to spawning cycle and gonad stage in both snapper and demoiselles. E2 and T levels were detectable at all times, but highest during vitellogenesis in both species. Cyclic changes of 17P occurred
in both species, and levels appeared to depend on the rate of conversion of 17P to other hormones. No changes in ovarian levels
of 17,20βP were detected in relation to stage of the spawning cycle in snapper; however, ovarian levels of 17,20βP were highest
in demoiselles before spawning when fish undergoing final oocyte maturation predominated. Plasma levels of E2 and T were strongly correlated with ovarian concentrations (r=0.850 and r=0.819 for E2 and T respectively) in demoiselles but there was poor correlation between ovarian and plasma levels of 17P and 17,20βP (r=0.004
and 0.273 respectively), or between ovarian and plasma levels of E2, T, 17P or 17,20βP of snapper (r=0.135, 0.277, 0.131 and 0.279). The poor correlation between plasma and ovarian levels of
some steroid hormones suggests that plasma concentrations of steroids may not adequately reflect the reproductive status of
the fish during short-term cyclic ovarian changes. It is suggested that this disparity is likely to be most marked in species
with ovulatory periodicity of short duration. 相似文献
3.
M.L. Pinillos A.I. Guijarro M.J. Delgado P.C. Hubbard A.V.M. Canário A.P. Scott 《Fish physiology and biochemistry》2002,26(2):197-210
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
4.
This study examined the changes in plasma steroids during natural (Experiment 1) and induced (Experiment 2) final maturation
in yellow perch Perca flavescens. In experiment 1, ovulating yellow perch were stripped of eggs and blood samples collected to determine the concentrations
of testosterone (T), estradiol-17β (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Eggs from individual females were
weighed and fertilized. Fertilization rate was determined at the embryo eyed stage. In experiment 2, females were randomly
assigned to one of the following treatment groups: (1) saline (0.7% NaCl), (2) des-Gly10[D-Ala6] LHRH-ethylamide (100 μg LHRHa/kg), and (3) LHRHa plus 17,20βP (100 μg LHRHa/kg + 2 mg 17,20βP/kg). Fish were injected intraperitoneally
with two doses at a two-day interval. Blood was collected prior to injections and at the time of ovulation/spawning and concentrations
of T, E2, and 17,20βP (free and conjugated) were determined. In experiment 1, low concentrations of 17,20βP were recorded
at spawning. In experiment 2, all surviving fish injected with LHRHa (5 of 5) released their eggs spontaneously during the
week following injections. None of the surviving control fish (0 of 5) ovulated during this period, whereas only 1 of 3 surviving
fish injected with LHRHa + 17,20βP released eggs. In the control group, concentrations of E2 and 17,20βP did not show significant
differences over the experimental period, whereas plasma T concentrations increased significantly. In fish injected with LHRHa,
the concentrations of T and 17,20βP increased significantly after the first injection but then declined at ovulation/spawning.
It also appears that 17,20βP was conjugated to its sulfated form. Mortality reached 62.5% in the group injected with LHRHa
+ 17,20βP indicating that this treatment was severe. Thus, LHRHa alone appears highly effective in inducing ovulation in yellow
perch.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
The present study was undertaken to develop a comprehensive understanding of how environmental cues and sex steroids relate with cyclic changes in spermatogenesis in freshwater spotted snakehead Channa punctatus that is nutritious and economically important. The seasonal histological changes in testis and annual profile of gonadosomatic index (GSI) of C. punctatus delineated the testicular cycle into four phases: regressed (December–March), preparatory (April–June), spawning (July and August) and postspawning (September–November). Among environmental variables, correlation and regression analyses exhibited an important relationship between photoperiod and testicular weight while role of rainfall was seen confined to spawning. The seasonal profile of plasma sex steroids when correlated with cyclic changes in spermatogenesis in spotted snakehead, testosterone (T) seems to be involved in controlling the major events of spermatogenesis from renewal of stem cells to spawning of spermatozoa. Another important androgen prevalent in teleosts, 11-ketotestosterone (11-KT), was high during preparatory phase, suggesting that 11-KT in addition to T plays an important role in progression of spermatogenesis and spermiation in C. punctatus. However, 11-KT was not seen to be associated with milt production and release of spermatozoa during spawning. Plasma profile of estradiol-17β (E2) during different reproductive phases revealed the involvement of E2 in repopulation of stem cells during postspawning phase and in maintaining quiescence of testis during regressed phase. 相似文献
6.
J.K. Sundaray K. Ohta A. Yamaguchi K. Suzuki M. Matsuyama 《Fish physiology and biochemistry》2003,28(1-4):193-195
The wrasse, Pseudolabrus sieboldi, is a diandric protogynous labrid fish. Spawning is performed by a terminal phase (TP) male and an initial phase (IP) female between 6:00 and 9:00 h daily during two-month-long spawning season. In the present study, to investigate the roles of steroid hormones in the diurnal spermatogenesis of the P. sieboldi TP male, all steroid hormones produced in the testis were identified and the synthetic pathways of these steroids were determined. Furthermore, the circulating levels of the major steroids produced were analyzed throughout a day at 3-hour intervals during spawning season. In the testis, 11-ketotestosterone (11-KT), estradiol-17β (E2), 17,20β-dihydoxy-4-pregnane-3-one (17,20β-P) and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) were synthesized as the major metabolites. In vitro steroid biosynthesis experiments showed similar results to the circulation profiles of the major steroids. This study is the first to clarify the complete steroidogenic pathways in the gonads of a diandric protogynous species throughout its life, when combined with the results of the steroidogenesis in the ovarian follicles. This is also the first report of a clear diurnal rhythm of the steroid production corresponding to the spermatogenic process in the testis of a male teleost. 相似文献
7.
In order to study the possible homeostatic regulation of gonadal steroids in fishes, plasma steroid levels were measured in
hemi-castrated and sham-operated nesting male three-spined sticklebacks, Gasterosteus aculeatus, and in mature 2-year old male Atlantic salmon, Salmo salar. Hemi-castration significantly suppressed androgen levels in both species. In sticklebacks, plasma levels of 11-ketotestosterone
(11KT) were 56% and levels of testosterone (T) 55% of those found in sham-operated males. In hemi-castrated salmon the levels
of 11KT were 63%, and the levels of T were 75% of the levels in sham-operated males. In contrast, levels of 17α,20β-dihydroxy-4-pregnen-3-one
(17,20-P) in salmon (not measured in sticklebacks) were not different between hemi-castrated and sham-operated males. The
results suggest that, although levels of the steroid 17,20-P were compensated in hemi-castrated salmon, the androgen levels
in fish males in full spawning condition are not closely regulated by negative feedbacks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Arimune Munakata Masafumi Amano Kazumasa Ikuta Shoji Kitamura Katsumi Aida 《Fisheries Science》2012,78(1):81-90
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
9.
Skjæraasen J.E. Salvanes A.G.V. Karlsen Ø. Dahle R. Nilsen T. Norberg B. 《Fish physiology and biochemistry》2004,30(2):163-174
An experiment was conducted to examine (a) the effects of photoperiod on timing of sexual maturation (b) the relationship between plasma steroid levels, appetite and growth in male and female Atlantic cod (Gadus morhua L.). Wild caught Norwegian coastal cod were subjected to either a 6L/18D photoperiod typical of January at 60° N-(Short day group) or a simulated natural photoperiod (Normal day group) from June 2000 until spawning started. Appetite of individual fish were measured twice weekly, while weight, length and plasma levels of the sex steroids testosterone (T), 11 keto-testosterone (11-KT) and estradiol-17β (E2) were monitored bimonthly. Cod in the Short day group matured 3 months ahead of the cod in the Normal day group and started spawning in early November. Appetite decreased in both sexes 2–3 months prior to spawning in both groups, but this reduction was stronger among males. In both sexes, length growth was reduced concurrently with the appetite loss. Overall, females had significantly higher somatic growth, put relatively less energy into length growth and had developed larger livers compared to males at the time of spawning in the Short day group. Plasma steroid levels increased in both groups throughout the experiment, reaching peak levels of ca 10 ng ml−1 (T) and 15–20 ng ml−1 (11-KT) in males, and 1.5–2 ng ml−1 (T) and 12–18 ng ml−1 (E2) in females at the onset of spawning. Steroid levels increased more rapidly among Short day cod verifying the earlier onset of maturation. These results confirm that photoperiod is a major cue to maturation in cod and imply that the high cost of spawning for females incur differences in appetite between the sexes. 相似文献
10.
Ismael Hachero-Cruzado Asunción Forniés Marcelino Herrera Juan Miguel Mancera Gonzalo Martínez-Rodríguez 《Fish physiology and biochemistry》2013,39(2):215-220
The aims of the present study were to characterize sperm quality and to quantify seasonal changes in sexual hormone (testosterone [T], 11-ketotestosterone [11-KT] and 17,20β-dihydroxypregn-4-en-3-one [17,20β-P]) levels in male brill (Scophthalmus rhombus) plasma, as well as to test a more intensive sampling strategy to establish relationships between sex steroid levels and sperm production parameters. Sperm concentration ranged from 0.5 to 3.1 × 109 spermatozoa mL?1, and changes in sperm quality parameters depending on sampling date were observed. Plasma sexual steroid levels remained high and changed in parallel during the spawning season and afterwards decreased to very low levels in summer. The analysis of annual changes of 11-KT and T ratios suggests that 11-KT can be the main circulating androgen for stimulating spermatogenesis in S. rhombus and that T could be involved in the beginning of spermatogenesis through the positive feedback on brain-pituitary-gonad axis. Finally, daily 11-KT and T levels showed similar patterns of variation in males sampled, whereas 17,20β-P amounts showed somewhat opposite trends. These differences could be related with the different role of androgens and progestin during the spermatogenesis. 相似文献
11.
In order to gain a better understanding of the reproductive cycles of male and female tench (Tinca tinca), gonadosomatic index, gonad histology and plasma concentrations of estradiol‐17β (E2), testosterone, an drostenedione, 11‐ketotestosterone (11‐KT), 17,20β, 21‐trihydroxy‐4‐pregnen‐3‐one (17,20β,21‐P), 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and 17,20α‐dihydroxy‐4‐pregnen‐3‐one (17,20α‐P) were measured at the four seasons of the year, plus a further sampling coincident with the peak of spawning in early July. As expected, in both males and females, the plasma concentrations of androgens (excluding 11‐KT in females – undetectable) and C21 steroids were significantly more elevated in the spring and summer (when most gonadal development took place) than in the autumn and winter. The only unexpected finding was that 17,20β‐P and 17,20β,21‐P, the steroids that are normally associated with oocyte final maturation in females and spermiation in males, were found in substantial amounts in both pre‐vitellogenic, pre‐spermatogenic and post‐spawning fish. This suggests that these steroids may have other as yet unidentified roles in this species. 相似文献
12.
Erik Vikingstad Eva Andersson Tom Johnny Hansen Birgitta Norberg Ian Mayer Sigurd Olav Stefansson Per Gunnar Fjelldal Geir Lasse Taranger 《Fish physiology and biochemistry》2016,42(3):895-907
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
13.
Unal G Erdoğan E Oğuz AR Kaptaner B Kankaya E Elp M 《Fish physiology and biochemistry》2008,34(4):447-454
Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken
to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17α,20β,21-trihydroxyprogesterone (20β-S), progesterone (P), 17α-hydroxyprogesterone (17α-HOP), 11-deoxycortisol
(11-DOC), and 17α-hydroxy-20β-dihydroprogesterone (17,20β-P) were measured in fish caught from Lake Van and the Karasu River,
and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated
in vitro with different doses (50, 200, and 1,000 ng/ml) of 20β-S, 17α-HOP, 11-DOC, and 17,20β-P. 11-DOC was found to be the
most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20β-P could not be determined
in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels
(P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte
culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion,
11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this
species. 相似文献
14.
ABSTRACT: In order to clarify the roles of androgen and gonadotropin-releasing hormone (GnRH) on gonadotropin (GTH; luteinizing hormone [LH] and follicle stimulating hormone [FSH]) synthesis, effects of castration and implantation of GnRH analog (GnRHa) or 11-ketotestosterone (11-KT) on expression of GTH subunit, α-glycoprotein subunit (αGSU), FSHβ, and LHβ genes, during the early spermatogenic stage in male red seabream Pagrus major were examined. Male red seabream underwent castration or sham-operation and were subsequently implanted with cholesterol pellets containing GnRHa, silicone capsules filled with 11-KT, or blank capsules (control). FSHβ mRNA levels increased due to castration, and it was reversed by treatment with 11-KT. 11-ketotestosterone treatment also decreased FSHβ mRNA levels in sham-operated fish. These results suggest that 11-KT acts on the pituitary to suppress FSH synthesis in male red seabream. On the other hand, neither castration nor replacement of 11-KT in castrated fish had effects on LHβ mRNA levels, whereas 11-KT treatment had slightly but significantly decreased LHβ mRNA in sham-operated fish. αGSU mRNA levels were not changed by castration or 11-KT treatment in both sham-operated and castrated fish. Meanwhile, treatment with GnRHa significantly decreased FSHβ mRNA levels in sham-operated fish, but not in castrated fish. This suggests that GnRHa may down-regulate expression of FSHβ mRNA through the production of 11-KT in testis. LHβ and αGSU mRNA levels in sham-operated fish, but not in castrated fish, were significantly elevated by treatment with GnRHa. 相似文献
15.
Dorts J Grenouillet G Douxfils J Mandiki SN Milla S Silvestre F Kestemont P 《Fish physiology and biochemistry》2012,38(2):389-399
Climate change is predicted to increase the average water temperature and alter the ecology and physiology of several organisms
including fish species. To examine the effects of increased water temperature on freshwater fish reproduction, adult European
bullhead Cottus gobio of both genders were maintained under three temperature regimes (T1: 6–10, T2: 10–14 and T3: 14–18°C) and assessed for gonad
development (gonadosomatic index—GSI and gonad histology), sex steroids (testosterone—T, 17β-estradiol—E2 and 11-ketotestosterone—11-KT)
and vitellogenin (alkali-labile phosphoprotein phosphorus—ALP) dynamics in December, January, February and March. The results
indicate that a 8°C rise in water temperature (T3) deeply disrupted the gonadal maturation in both genders. This observation
was associated with the absence of GSI peak from January to March, and low levels of plasma sex steroids compared with T1-exposed
fish. Nevertheless, exposure to an increasing temperature of 4°C (T2) appeared to accelerate oogenesis with an early peak
value in GSI and level of plasma T recorded in January relative to T1-exposed females. In males, the low GSI, reduced level
of plasma 11-KT and the absence of GSI increase from January to March support the deleterious effects of increasing water
temperature on spermatogenesis. The findings of the present study suggest that exposure to elevated temperatures within the
context of climate warming might affect the reproductive success of C. gobio. Specifically, a 4°C rise in water temperature affects gametogenesis by advancing the spawning, and a complete reproductive
failure is observed at an elevated temperature of 8°C. 相似文献
16.
Ryusuke Sudo Ryota Tosaka Shigeho Ijiri Shinji Adachi Hiroaki Suetake Yuzuru Suzuki Noriyuki Horie Satoru Tanaka Jun Aoyama Katsumi Tsukamoto 《Fisheries Science》2011,77(4):575-582
To improve understanding of the mechanism of early ovarian development in eels, the effects of water temperature decrease
on oocyte development, plasma levels of sex steroids [estradiol 17β (E2), testosterone (T), 11-ketotestosterone (11-KT)],
and gonadotropin β-subunit [follicle-stimulating hormone (FSHβ), luteinizing hormone (LHβ)] messenger RNA (mRNA) expression
levels were investigated. A total of 27 female Japanese eels Anguilla japonica were divided into initial, control, and test (water temperature decrease) groups. Starting on 22 September 2009, eels in
the test group were reared in a tank with gradual temperature decrease from 25°C to 15°C over 39 days, while the control group
was maintained at 25°C. The test group accumulated more oil droplets in their oocytes than did the other groups. Levels of
sex steroids, especially 11-KT, were higher in the test group. In contrast, FSHβ and LHβ mRNA expression levels were lower
in the test group. These results suggest that water temperature decrease only induced an early stage of ovarian development
that was partly affected by an 11-KT increase. For further maturation, other environmental factors related to induction of
gonadotropin increase appear to be needed. 相似文献
17.
Makito Kobayashi Peter W. Sorensen Norm E. Stacey 《Fish physiology and biochemistry》2002,26(1):71-84
Species that employ sexual reproduction must synchronize gamete maturity with behavior within and between genders. Teleost
fishes solve this challenge by using reproductive hormones both as endogenous signals to synchronize sexual behavior with
gamete maturation, and as exogenous signals (pheromones) to synchronize spawning interactions between fish. This dual role
of hormonal products is best understood in the goldfish, an external fertilizer with a promiscuous mating system. Female gonadal
growth and vitellogenesis is stimulated by 17β-estradiol (E2) which also evokes release of a recrudescent pheromone. At the
completion of vitellogenesis, ovarian E2 production drops and plasma testosterone increases, sensitizing the female gonadotropin
II (luteinizing hormone; LH) system to environmental cues (temperature, spawning substrate, pheromones). These cues eventually
trigger a LH surge that alters steroidogenesic pathways to favor the production of progestins including 17,20β-dihydroxy-4-pregnen-3-one
(17,20β-P). Plasma 17,20β-P stimulates oocyte maturation but is also released to the water along with sulfated 17,20β-P and
androstenedione to serve as a preovulatory pheromone. This pheromone stimulates male behavior, LH release, and sperm production.
At the time of ovulation, females become sexually active in response to prostaglandin F2α (PGF2α) synthesized in the oviduct.
PGF2α and its metabolites are released as a postovulatory pheromone that induces male spawning behavior which further increases
male LH and sperm production. Androgenic hormones are required for male behavior and LH release. Although goldfish are gonochorists,
hormone treatments can induce heterotypical functions in adults. Similar findings in other fish demonstrate that a sexually
bipotential brain is not restricted to hermaphroditic fishes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
YASUNORI KOYA KIYOSHI SOYANO KAZUHISA YAMAMOTO HIROYUKI OBANA TAKAHIRO MATSUBARA 《Fisheries Science》2002,68(5):1099-1105
The present study investigates the relationship between testicular development and serum steroid hormone levels in captive Pacific herring Clupea pallasii during the first reproductive cycle. The maturity of the testis was divided into five periods based on histological observation. These are early spermatogenic stage (April to July), mid-spermatogenic stage (August to November), late spermatogenic stage (December to March), functional maturation stage (early April) and spent stage (late April). The pattern of seasonal change in gonadosomatic index (GSI) clearly reflected testicular maturity. 11-Ketotestosterone (11-KT) levels increased from October to a peak level (6.58 ± 1.87 ng/mL) in January, and were maintained at this level until March. In contrast, testosterone levels were consistently low, less than 1 ng/mL, at all times. These results suggest that 11-KT is the predominant androgen that controls spermatogenesis in this species. 17,20β-Dihydroxy-4-pregnen-3-one (DHP) showed a single sharp peak (3.38 ± 0.35 ng/mL) in early April of the second year, suggesting that milt production is induced by DHP as in some other teleost species. 相似文献
19.
David E. Kime Shelley Bhattacharya Malgorzata Koldras Krzysztof Bieniarz 《Fish physiology and biochemistry》1993,10(5):389-398
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
20.
Peter Thomas Paul A. Copeland John A. Prentice 《Journal of the World Aquaculture Society》1994,25(2):214-224
Seasonal changes In oocyte growth and plasma estradiol, testosterone, thyroid hormones and vitellogenin levels were monitored in three captive adult female orangemouth corvina Cynoscion xanthulus subjected to a condensed (8 mo) seasonal cycle of photoperiod and water temperature. Plasma concentrations of estradiol and testosterone began to rise when temperature increased to 28 C and photoperiod to 15 h light (midsummer conditions). This was accompanied by elevated circulating levels of vitellogenin and the appearance of vitellogenic oocytes (diameter > 100 μm). Estradiol concentrations and mean oocyte size increased concurrently during late summer conditions and were maximum during fall conditions, approximately 8 wk after the beginning of ovarian recrudescence. In contrast, plasma levels of thyroid hormones did not show any distinct seasonal changes. Gonadally recrudesced females contained several size classes of vitellogenic oocytes. Injection of these fish with a luteinizing hormone-releasing hormone analog (LHRHa) caused maturation and spawning of the largest oocytes (mean diameter of follicles × 2500 μm). Another group of vitellogenic oocytes had been recruited into this size class by 2 wk after the end of spawning, which suggests that this species is capable of repeated spawning during the reproductive season. Injection of LHRHa resulted in increased plasma levels of gonadotropin and repeated spawning over several days. LHRHa-induced final oocyte maturation, ovulation and spawning were preceded by increases in plasma levels of two teleostean maturation-inducing steroids, 17α,20β, 21-trihydroxy-4-pregnen-3-one (20β-S) and 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P4). The results provide preliminary evidence that oocyte growth is stimulated in orangemouth corvina subjected to an abbreviated seasonal cycle in captivity under midsummer photoperiod and temperature conditions and is associated with seasonal increases in plasma estradiol concentrations and vitellogenin production. However, the relative importance of 20β-S versus 17α, 20β-P4 in the control of final oocyte maturation in this species could not be determined from the results of the present study. 相似文献