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1.
Nyuji M Selvaraj S Kitano H Ohga H Yoneda M Shimizu A Kaneko K Yamaguchi A Matsuyama M 《Fish physiology and biochemistry》2012,38(3):883-897
The endocrine regulation of reproduction in a multiple spawning fish with an asynchronous-type ovary remains largely unknown. The objectives of this study were to monitor changes in the mRNA expression of three gonadotropin (GtH) subunits (GPα, FSHβ, and LHβ) during the reproductive cycle of the female chub mackerel Scomber japonicus. Cloning and subsequent sequence analysis revealed that the cDNAs of chub mackerel GPα, FSHβ, and LHβ were 658, 535, and 599 nucleotides in length and encoded 117, 115, and 147 amino acids, respectively. We applied a quantitative real-time PCR assay to quantify the mRNA expression levels of these GtH subunits. During the seasonal reproductive cycle, FSHβ mRNA levels remained high during the vitellogenic stages, while GPα and LHβ mRNA levels peaked at the end of vitellogenesis. The expression of all three GtH subunits decreased during the post-spawning period. These results suggest that follicle-stimulating hormone (FSH) is involved in vitellogenesis, while luteinizing hormone (LH) functions during final oocyte maturation (FOM). Both GPα and FSHβ mRNA levels remained high during the FOM stages of the spawning cycle and increased further just after spawning. Thus, FSH synthesis may be strongly activated just after spawning to accelerate vitellogenesis in preparation for the next spawning. Alternatively, LHβ mRNA levels declined during hydration and then increased after ovulation. This study demonstrates that chub mackerel are a good model for investigating GtH functions in multiple spawning fish. 相似文献
2.
The duality of teleost gonadotropins 总被引：5，自引：0，他引：5
Hiroshi Kawauchi Kunimasa Suzuki Hiromichi Itoh Penny Swanson Nobuko Naito Yoshitaka Nagahama Masumi Nozaki Yasumitu Nakai Seiga Itoh 《Fish physiology and biochemistry》1989,7(1-6):29-38
The duality of salmon gonadotropins has been proved by biochemical, biological, and immunological characterization of two
chemically distinc gonadotropins. GTH I and GTH II were equipotent in stimulating estradiol production, whereas GTH II appears
to be more potent in stimulating maturational steroid synthesis. The ratio of plasma levels and pituitary contents of GTHs
and the secretory control by a GnRH suggest that GTH I is the predominant GTH during vitellogenesis and early stages of spermatogenesis
in salmonids, whereas GTH II is predominant at the time of spermiation and ovulation. GTH I and GTH II are found in distinctly
separate cells. In trout, GTH I is expressed first in ontogeny, whereas GTH II cells appear coincident with the onset of spermatogenesis
and vitellogenesis, and increase dramatically at the time of final reproductive maturation. Comparison of the amino acid sequences
of polypeptides and the base sequences of cDNA revealed that salmon GTH I β is more similar to bovine FSHβ than bovine LHβ
and salmon GTH II β shows higher homology to bovine LHβ than to bovine FSHβ. The existence of two pituitary gonadotropins
in teleosts as well as tetrapods suggests that the divergence of the GTH gene took place earlier than the time of divergence
of teleosts from the main line of evolution leading to tetrapods. 相似文献
3.
Follicle-stimulating hormone beta subunit (FSHβ) and luteinizing hormone beta subunit (LHβ) have been cloned and characterized
from the pituitary of grass carp (Ctenopharyngodon idella). The full length of FSHβ and LHβ cDNA was 393 bp and 441 bp, with open reading frame encoding proteins of 130 and 146 amino
acids, respectively. Phylogenetic analysis of the proteins of FSHβ and LHβ showed a high homology with other fishes. Homology
analysis also indicated that LHβ has higher conservation than FSHβ. The expression analysis of grass carp FSHβ and LHβ by
RT-PCR suggested that they were only expressed in the pituitary. Real-time quantitative PCR protocols were developed and validated
to measure FSHβ and LHβ mRNAs during ovarian development. The FSHβ and LHβ mRNA level was very low in the pituitaries of early-pubertal
fish and significantly increased during the ovulation period. These results suggested that in grass carp the gonadotropins
synthesized synchronously in order for asynchronous oogenesis to take place. 相似文献
4.
Tetsuro Shiraishi Suvarna D Ketkar Hajime Kitano Mitsuo Nyuji Akihiko Yamaguchi Michiya Matsuyama 《Fisheries Science》2008,74(4):764-769
Abstract: The question of whether the ovulation and spawning time in chub mackerel Scomber japonicus is entrained by a circadian rhythm was raised by our previous experiments. Further questions were also raised about whether the time course of human chorionic gonadotropin (hCG)-induced final oocyte maturation (FOM) and ovulation reflected the natural time course induced by endogeneous pituitary gonadotropin (GtH). To address these questions, hCG and gonadotropin-releasing hormone analog (GnRHa) were administered at two 'opposite' times, 14:00 and 02:00 hours, and the time courses of FOM and ovulation were compared. When hCG was injected, ovulation occurred 33 h post-injection in both groups, regardless of the timing of the hCG injection. The timing of ovulation in chub mackerel depends on the timing of hCG injection, but apparently not on circadian rhythms. When GnRHa was injected, ovulation began at 36 h post-injection of GnRHa, regardless of the timing of injection. These results indicate that the time course of FOM and ovulation in the chub mackerel followed a similar pattern whether stimulated by hCG injection or spontaneous luteinizing hormone (LH) surge because GnRHa induces the secretion of endogenous GtH (primarily LH) from the fish pituitary. Thus, it is concluded that the time course of hCG-induced FOM and ovulation in chub mackerel follows the natural time course induced by endogenous pituitary LH. 相似文献
5.
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
6.
Jan Bogerd 《Fish physiology and biochemistry》2005,31(2-3):247-254
In mammals, the specificity of FSH–FSH receptor (FSHR), LH–LH receptor (LHR) and TSH–TSH receptor couples is such that no
cross-activation occurs under normal physiological conditions. The interactions between fish gonadotropins and their receptors,
however, appear to be less discriminatory. For example, the catfish FSHR is highly responsive to both catfish LH and catfish
FSH, while the catfish LHR is specific for its cognate LH. Comparative structure–function studies aimed at elucidating the
molecular basis of ligand promiscuity (in fish) and ligand selectivity (in mammals) are described in this paper. 相似文献
7.
Pham KX Amano M Kurita Y Shimizu A Fujinami Y Amiya N Yamamori K 《Fish physiology and biochemistry》2008,34(4):357-365
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
8.
ABSTRACT: Final oocyte maturation and ovulation of captive chub mackerel Scomber japonicus with fully yolk-accumulated oocytes were induced by a single injection of human chorionic gonadotropin. Reproductive parameters, including spawning frequency and batch fecundity, which are required to estimate spawning biomass in pelagic fish by the daily egg production method, were analyzed. Germinal vesicle migration (GVM) occurred at 18–24 h post-injection, and the hydration and ovulation of oocytes were completed at 30 and 36 h post-injection, respectively. The results of the maturation process suggest that fish with GVM-stage ovaries captured in the daytime from the field are capable of spawning on the night following their capture. The oocytes used in the oocyte size-frequency distribution method for batch fecundity estimates should be at late GVM and more advanced stages. The results of sequential artificial insemination showed that the quality of ovulated eggs held in the ovarian lumen rapidly deteriorated as time progressed after ovulation. This indicates that the fertilization window for the ovulated eggs of chub mackerel lasts only a few hours, and spawning behavior should be performed within a few hours after ovulation in the wild population. 相似文献
9.
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
10.
The spawning grounds of the chub mackerel (Scomber japonicus) and spotted mackerel (Scomber australasicus) in the East China Sea were estimated based on catch statistics of the Japanese large- and medium-type purse seine fishery
from 1992 to 2006. Biometric data were obtained from specimens caught by purse seiners in the East China Sea from 1998 to
2006. Gonadosomatic index (GSI) at 50% sexual maturity of chub mackerel and spotted mackerel females was 2.5 and 2.6, respectively.
Using this criterion for GSI, chub mackerel larger than 275 mm and spotted mackerel larger than 310 mm in fork length were
considered to be mature. Mature chub mackerel was observed in the area of 15–22°C sea surface temperature (SST), and mature
spotted mackerel was observed in the area of 17–25°C SST. The spawning period of chub mackerel ranged from February to June,
and that of spotted mackerel ranged from February to May in the East China Sea. The spawning grounds were estimated from the
distributions of catch per unit effort (CPUE) of spawners and SST. As a result, the spawning ground of chub mackerel was estimated
to be in the central and southern part of the East China Sea and the area west of Kyushu in February, March, and April, and
in the central part of the East China Sea, the area west of Kyushu and Tsushima Straight in May, and in Tsushima Straight
and western part of the Sea of Japan in June. The spawning ground of spotted mackerel was estimated to be in the central and
southern part of the East China Sea and southern coastal area of Kyushu in February, March, and April, and the central and
southern part of the East China Sea and the area west of Kyushu in May. 相似文献
11.
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
12.
Tetsuro Shiraishi Suvarna D. Ketkar Yoshiki Katoh Mitsuo Nyuji Akihiko Yamaguchi Michiya Matsuyama 《Fisheries Science》2009,75(3):649-655
Female Japanese chub mackerel Scomber japonicus of the Tsushima Current subpopulation were collected during the spawning season from March to May 2001. A total of 137 adult
females were caught between midnight and daybreak. A considerable number of fish displayed new postovulatory follicles (POF),
whereas there was no evidence of germinal vesicle breakdown or hydrated oocytes in any of the fish collected. This suggests
a daily spawning synchronicity toward midnight. To estimate the spawning frequency (S), the female reproductive state was classified into four criteria based on the degenerative stage of the POFs and the developmental
stage of the oocytes. To stage the POFs according to age and determine the stage duration, ovaries from S. japonicus were induced to spawn in the laboratory and were sampled 0–72 h after ovulation at appropriate intervals. The average S, which is evaluated from four different indices, was 16.9%, corresponding to the average female chub mackerel spawned every
5.9 days (8.5 times) during the 50 days. 相似文献
13.
Koichiro Gen Sonoko Yamaguchi Koichi Okuzawa Naoki Kumakura Hideki Tanaka Hirohiko Kagawa 《Fish physiology and biochemistry》2003,28(1-4):77-80
The duality of gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), has been confirmed in most teleost species, but very little is known about their biological functions. To elucidate the physiological roles of FSH and LH in fish reproduction, the expression profiles of GTH subunit genes during gonadal development were analyzed in both male and female red seabream. Furthermore, in vitro studies were carried out to examine the effects of GTHs on steroid hormone production and cytochrome P450 aromatase (P450arom) expression in red seabream gonads. In both sexes, LHβ mRNA was maintained at high levels from the early gametogenesis until spawning season, and declined with gonadal regression. Interestingly, FSHβ mRNA levels in males increased in parallel with testicular development, whereas those in female were remained low throughout oocyte development. From in vitro studies using purified red seabream FSH and LH, both GTHs had a similar potency in stimulating 11-ketotestosterone production by testicular slices, while the biological activity of FSH was much lower than that of LH in stimulating production of estradiol-17β by vitellogenic follicles. Moreover, expression of P450arom mRNA was induced by LH, but not FSH, in ovarian follicles in vitro. FSH was also ineffective in inducing maturational competence and final oocyte maturation. These results suggest that, unlike salmonids, FSH may play an important role during gametogenesis in male, but not female, red seabream, whereas LH may be involved in regulation of both early and late gametogenesis in both sexes. 相似文献
14.
M. P. García Hernndez A. García Ayala B. Agulleiro A. García W. van Dijk R. W. Schulz 《Aquaculture (Amsterdam, Netherlands)》2002,210(1-4):203-218
Purified Mediterranean (M.) yellowtail luteinizing hormone-like gonadotropin (MyLH) and its β-subunit (MyLHβ) served to develop a radioimmunoassay (RIA) for MyLH. The rabbit antisera against MyLH and MyLHβ used for this purpose were tested on pituitary sections by immunocytochemistry. Anti-MyLHβ specifically detected a single type of cells, which were located at the periphery of the proximal pars distalis (PPD) and surrounding the pars intermedia (PI). Anti-MyLH, however, also recognized two other cell types, thyrotropin β-immunoreactive (ir) cells and putative follicle-stimulating hormone-like (MyFSH)-producing cells. Labeling of the two latter cell types was prevented by preabsorption of anti-MyLH with M. yellowtail pituitary glycoprotein -subunit. The standard curve for the RIA was generated using purified MyLH, 125I-labeled MyLHβ and anti-MyLHβ at a dilution of 1:70,000, which resulted in the binding of 30% of the tracer added. The standard curve ranged from 0.25 to 50 ng/ml. The midrange of the assay (ED50) was obtained with 5.48–7.87 ng LH/ml. The variation between assays was less than 15%. An average cross-reactivity of FSH in the LH RIA of 8.4% was found. Serial dilutions of M. yellowtail pituitary extracts displaced radiolabelled MyLHβ parallel to the MyLH standard. Application of the LH RIA to blood samples and pituitary cell culture medium provided physiological validation of the assay. Significant increases in LH levels were recorded after salmon GnRH treatments in vivo and in vitro. Serum LH levels from wild fish sampled at the spawning season were significantly higher than those from captive fish sampled in the same period. 相似文献
15.
16.
1999—2011年东、黄海鲐资源丰度年间变化分析 总被引：4，自引：1，他引：3
根据1999—2011年我国鲐大型灯光围网渔业数据,使用广义线性模型(generalized linear model,GLM)和广义加性模型(generalized additive model,GAM)估算了影响CPUE的时间(年、月)、空间(经度、纬度)、捕捞性能和环境效应[海表面温度(sea surface temperature,SST)、海表面高度、海表面叶绿素浓度],并以年效应作为资源丰度指数,分析了东、黄海鲐资源丰度的年间变化,东、黄海鲐资源丰度指数的年间变化与产卵场海表面温度以及捕捞强度间的关系。GAM结果表明,时间、空间、捕捞和环境变量对CPUE偏差的解释率为11.69%,其中变量年的解释率最大,占总解释率的38%。结果显示,1999—2011年东、黄海鲐鱼资源丰度指数(abundance index,AI)总体上呈下降趋势,2008年以来更是持续下降,丰度指数由2008年的1.22降至2011年的0.82。东、黄海鲐资源丰度指数年间与产卵场呈正相关,关系式为AI=-3.51+0.23SST(P0.05),这表明较高的产卵场SST对鲐资源量增加有利。过高的渔获量以及我国群众围网渔业渔船数量的快速增长是导致近年来鲐鱼资源下降的重要原因。 相似文献
17.
Effects of synthetic kisspeptin peptides and GnRH analogue on oocyte growth and circulating sex steroids in prepubertal female chub mackerel (Scomber japonicus) 
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下载免费PDF全文 Sethu Selvaraj Hirofumi Ohga Mitsuo Nyuji Hajime Kitano Naoki Nagano Akihiko Yamaguchi Michiya Matsuyama 《Aquaculture Research》2015,46(8):1866-1877
In recent years, kisspeptin peptides, encoded by kiss genes have been used to manipulate reproductive processes in farmed animals, including fish. Our previous studies demonstrated that the chub mackerel brain expresses kiss1 and kiss2 and intramuscular injection of synthetic Kiss1 pentadecapeptide (Kiss1‐15) but not Kiss2 dodecapeptide (Kiss2‐12) accelerates spermatogenesis in prepubertal male chub mackerel (Scomber japonicus). In the present study, we evaluated their effects in prepubertal female chub mackerel. The gonadosomatic index (GSI) values of experimental fish did not show any significant changes. Condition factor (CF) values increased significantly in Kiss1‐15 treated fish, in comparison with control and GnRH analogue (GnRHa) injected fish. Histologically, only perinucleolar oocytes were found in all experimental fish. However, Kiss and GnRHa treated fish showed a significant increase in the perinucleolar oocyte diameter, in comparison with the control fish. Gene expression analyses revealed decreased expression of gnrh1 in the telencephalon‐preoptic region of the brain of Kiss2‐12 and GnRHa injected fish, in comparison with control fish. In contrast, GnRHa injected fish exhibited higher levels of fshβ in the pituitary, with no changes in the levels of lhβ among different treatments. Levels of circulating sex steroids, testosterone, and estradiol‐17β were significantly higher in Kiss1‐15 injected fish, in comparison with control fish. These results indicate that synthetic kisspeptin peptides and GnRHa can induce oocyte growth in prepubertal female chub mackerel. 相似文献
18.
东海南部鲐鱼生物学特性的初步研究 总被引：1，自引：0，他引：1
本文对东海南部的鲐鲹鱼类的叉长、体重及性腺成熟度等进行了初步分析,认为1999年5月份东海南部鲐鱼优势叉长组为26～28cm,优势体重组为200～300g;7、8月份优势叉长组为24～26cm,优势体重组为100～200g。蓝圆鲹优势叉长组为20～21cm。2000年7、8月份鲐鱼优势叉长组为24～26cm。1999年鲐鱼叉长组成基本呈正态分布,2000年鲐鱼叉长组成明显存在两个峰值。2000年相同叉长的鲐鱼体重要略低于1999年,认为跟1999年、2000年海洋环境因子变化有关。从相关系数来看,2000年的曲线更贴近实际情况。并认为5月份北上参加产卵洄游的鲐鱼群体、其性腺已开始发育成熟,并沿途产卵。 相似文献
19.
Michiya Matsuyama Shinji Adachi Yoshitaka Nagahama Katsuhiko Maruyama Shuhei Matsura 《Fish physiology and biochemistry》1990,8(4):329-338
Ovarian developmental stages and serum steroid hormone levels were examined at six different times of day (0100, 0600, 1000,
1300, 1600, 2000 h) in a marine teleost, the Japanese whiting Sillago japonica, which has an asynchronous-type ovary containing oocytes at various stages of development and spawns every day during a period
ranging up to three months. The largest oocytes in the ovaries at the active vitellogenic or post-vitellogenic stages were
found between 0100 and 1300 h. Oocyte maturation indicated by germinal vesicle breakdown (GVBD) occurred at 1600 h, and ovulated
oocytes were observed in the ovaries collected at 2000 h. These processes were accompanied by a significant daily change in
serum steroid hormone levels. The serum level of estradiol-17β showed a peak in fish with mature oocytes sampled at 1600 h.
In these fish, the second-largest oocytes in the ovaries were at the initial stage of vigorous vitellogenesis, the secondary
yolk stage. Therefore the highest level of serum estradiol-17β was considered to be due to the second-largest oocytes. Testosterone
levels remained low and constant throughout the experimental period. The serum levels of 17α,20β-dihydroxy-4-pregnen-3-one
(17α,20β-diOHprog) peaked at 1600 h at which time all fish had mature oocytes. These results indicate that the Japanese whiting
possesses a diurnal rhythm of oocyte development including vitellogenesis, oocyte maturation and ovulation, and further suggest
that daily cycles in oocyte growth and maturation which simultaneously take place in an ovary are regulated by diurnal secretions
of estradiol-17β and the maturation-inducing steroid, 17α,20β-diOHprog. 相似文献
20.
东、黄海日本鲭种群鉴定和划分的研究进展 总被引：1，自引：0，他引：1
分布于东、黄海的日本鲭(Scomber japoncus)在我国海洋渔业中具有重要的地位,随着中韩、中日渔业协定的生效,开展日本鲭等重要经济鱼类的种群归属研究显得尤为重要。关于东、黄海日本鲭种群划分,20世纪中日两国学者利用标志放流和渔业调查数据分别进行了研判,但中日间以及国内对其种群划分存在不同见解。21世纪以来,中国一些研究者利用形态框架法和分子遗传学方法对前辈的种群划分进行了验证并提供了一些证据,但分析结果值得商榷。总结相关研究结果,多数中国学者将分布于东、黄海的日本鲭划分为东海西部种群、五岛西部种群和闽南—粤东地方种群,也有中国学者将其划分为东海群系和闽南—粤东地方种群;日本学者将分布于东海不同越冬场日本鲭归属为对马暖流群系,也有日本学者将分布于东、黄海和日本海西部的日本鲭划分为九州西部群系和东海西部群系。针对东、黄海日本鲭种群划分存在的不同观点,今后研究者应同时利用目前较为先进的、相对可操作的鱼类框架形态和分子遗传等判别技术,增加产卵场样本采集覆盖面,以获得判别东、黄海日本鲭种群相对最为科学的证据。 相似文献