温度对江黄颡鱼性分化的影响

通过组织学方法观察江黄颡鱼原始生殖细胞(PGCs)迁移、生殖嵴生成和性腺分化,并且探讨在不同温度培育下性腺分化的差异。实验结果显示:1日龄仔鱼PGCs位于鱼体中肠背方的脏壁中胚层中;5日龄时,PGCs迁移到背方的腹膜上皮;8日龄时,生殖嵴形成;14日龄时,原始性腺形成;23日龄时,性腺开始分化。从孵化后的第10天开始,分别用(20±0.5)、(24±1.0自然水温、对照组)、(30±0.5)和(34±0.5)℃4种水温培育仔鱼达25天。实验结束后统计结果显示:对照组和(20±0.5)℃组的雌、雄性比接近1∶1(分别为1∶1.09和1.22∶1);(30±0.5)℃组的为1∶4.89,雄性率达(83.3±0.7)%;(34±0.5)℃组的为2.85∶1,雄性率仅为(26.4±0.4)%。提示(30±0.5)℃可使幼鱼性腺发育趋向雄性,(34±0.5)℃则使幼鱼性腺发育趋向雌性。实验结果表明,江黄颡鱼的性分化是属于温度依赖型性别决定。     

泽蛙的性腺分化及温度对性别决定的影响

通过组织学方法观察了泽蛙(Rana limnocharis)原始生殖细胞(PGCs)的迁移、原始性腺的形成和性腺分化,并且探讨在不同的培育温度条件下性腺分化的差异。泽蛙的性腺分化有其特殊性:生殖嵴形成时,其中既有体细胞,又有原生殖细胞;无论原始性腺是分化成为精巢还是卵巢,其中都出现一个初生性腔。蝌蚪孵化后的17-34d(Gosner 26-38期)为性腺分化的敏感时期。在蝌蚪孵化后的第2d(Gosner 25期),分别用不同水温18℃±1℃、30℃±1℃、32℃±1℃、34℃±1℃培育蝌蚪,直至完成变态幼蛙(Gosner 46期)形成。自然水温23℃-25℃为对照。对照组的雌、雄性比接近1∶1(1∶1.06);18℃±1℃实验组的雌、雄比例为1.83∶1,雄性率仅35.1%(P<0.01);从30℃±1℃实验组起,雄性率提高,34℃±1℃实验组的雄性率达74.0%(P<0.01)。较高的培育温度可使泽蛙蝌蚪性别分化趋向雄性,而较低的培育温度则使蝌蚪雌性化。泽蛙的性别分化属于温度依赖型性决定(TSD)。当前全球性气候变暖对两栖类性比的稳定存在着威胁。     

温度对江黄颡鱼性分化的影响

通过组织学方法观察江黄颡鱼原始生殖细胞(PGCs)迁移、生殖嵴生成和性腺分化，并且探讨在不同温度培育下性腺分化的差异。实验结果显示：1日龄仔鱼PGCs位于鱼体中肠背方的脏壁中胚层中；5日龄时，PGCs迁移到背方的腹膜上皮；8日龄时，生殖嵴形成；14日龄时，原始性腺形成；23日龄时，性腺开始分化。从孵化后的第10天开始，分别用(20±0.5)、(24±1.0自然水温、对照组)、(30±0.5)和(34±0.5)℃4种水温培育仔鱼达25天。实验结束后统计结果显示：对照组和(20±0.5)℃组的雌、雄性比接近1∶1(分别为1∶1.09和1.22∶1)；(30±0.5)℃组的为1∶4.89，雄性率达(83.3±0.7)%；(34±0.5)℃组的为2.85∶1，雄性率仅为(26.4±0.4)%。提示(30±0.5)℃可使幼鱼性腺发育趋向雄性，(34±0.5)℃则使幼鱼性腺发育趋向雌性。实验结果表明，江黄颡鱼的性分化是属于温度依赖型性别决定。     

棘胸蛙的性腺分化及温度对其性别决定的影响

单性养殖在棘胸蛙(Quasipaa spinosa)养殖中意义显著。为了了解棘胸蛙性腺分化,并探讨在不同的培育温度条件下性腺分化的差异。通过组织切片观察了棘胸蛙原始性腺的形成和性腺分化。棘胸蛙的性腺分化有其特殊性:生殖嵴形成时,其中既有体细胞,又有原始生殖细胞(PGCs);无论原始性腺是分化成为精巢还是卵巢,其中都出现一个带有单层扁平上皮初生性腔,当单层扁平上皮逐渐消失后形成次生性腔。性腔周围的PGCs开始长大2—3倍时,性腺将分化成为卵巢;体细胞渗入性腔中,使腔隙变小直至消失,这种原始性腺分化成为精巢。棘胸蛙蝌蚪孵化后的l7—80 d(Gosner 25—26期)为性腺分化的敏感时期。实验选取同一批次刚孵出蝌蚪(Gosner 24期),分别用不同水温(16±1)℃、(27±1)℃、(31±1)℃3组实验组及自然水温(23±1)℃对照组条件下的培育蝌蚪。结果显示,对照组的雌、雄性比为26∶24,雄性率接近50%;(16±1)℃实验组的雌、雄比例为33∶17,雄性率仅34%(P0.05);从(27±1)℃实验组起,雄性率提高,(31±1)℃实验组的雄性率达70%(P0.05)。棘胸蛙的性别分化属于温度依赖型性决定(TSD)。较高的培育温度可使棘胸蛙蝌蚪性别分化趋向雄性,而较低的培育温度则使蝌蚪雌性化。     

南方鲶性腺分化的组织学观察

用芳香化酶抑制剂(Fadrozole)、雌激素受体拮抗剂(Tamoxifen)对人工孵化的南方鲶(Silurus meridionalis)幼鱼进行雄性化诱导处理(口服),获得雄鱼。对孵化后第5—130d的南方鲶幼鱼性腺进行组织学观察,结果表明,在实验条件下,南方鲶性腺分化发生在孵化后7d左右,雌雄性分化过程差异明显。雌鱼卵巢腔在孵化后12d左右形成,生殖细胞在孵化后35d左右快速增殖,成熟分裂最早发生在孵化后55d左右;雄鱼生殖细胞在孵化后130d左右快速增殖,成熟分裂最早发生在孵化后130d左右。雌性性腺分化早于雄性。     

环境因子对凡纳滨对虾性别分化的影响

通过外部形态观察和组织学连续切片,探讨温度(251)℃、(291)℃和(331)℃、光照周期(6L∶18D、12L∶12D、18L∶6D和24L∶0D)、光照强度(800、3000和5000 lx)、盐度(10、20、30和40)和环境雌激素壬基酚(40、80和120g/L)对凡纳滨对虾仔虾性别分化的影响。结果表明:温度和光照对凡纳滨对虾性别比例无显著影响(P0.05),但显著地影响性分化时间;10、20和40盐度组以及120g/L的壬基酚处理组的凡纳滨对虾雌雄比分别为0.81∶1,0.67∶1,1.29∶1和1.24∶1,显著偏离1∶1的性别比例,且盐度和壬基酚处理也影响性腺分化时间。此外,凡纳滨对虾触鞭长与体长之比1.0时与其性腺及外部形态分化时期相一致,提示可以将触鞭长与体长之比1.0作为判定凡纳滨对虾性分化开始的指标。       

黄颡鱼性腺分化的组织学观察

运用组织学方法,观察黄颡鱼(Pelteobagrus fulvidraco)性腺分化过程.结果表明,在水温(20±1)℃条件下,卵巢分化时间明显早于精巢.卵巢分化最早发生于孵出后13 d左右,其主要标志为原始性腺横切面上出现一个组织突起,进而形成卵巢腔;精巢分化的最早标志为精小叶和输精管的形成,开始于孵出后55 d.在发育早期,雌性生殖细胞的活动及分化明显早于雄性生殖细胞.孵出后25 d,卵原细胞开始通过有丝分裂快速增殖,孵出后34 d左右进入成熟分裂阶段;精原细胞在孵出后55 d时才开始大量增殖,成熟分裂最早发生于孵出后64 d.     

极端温度对海刺猬(Glyptocidaris crenularis)存活、摄食、生长和性腺的影响

在实验室条件下研究了极端温度对海刺猬的存活率、摄食率、生长以及组织器官等方面的影响。实验设置两个处理组温度为30°C和-2℃,对照组为自然水温(19~23℃),每组设置3个重复,每个重复60枚海刺猬,实验周期为56 d。结果表明:高温组海刺猬实验温度升到30℃后2 d内全部死亡,其平均摄食量(5.19±1.31 g·ind-1)极显著小于对照组(15.15±1.58 g·ind-1)(P0.01);低温组和对照组之间海刺猬存活率差异不显著(P0.05);但低温组海刺猬平均摄食量(0.18±0.04 g·ind-1)极显著小于对照组(10.90±0.33 g·ind-1)(P0.01);56 d内低温组海刺猬个体湿重极显著小于对照组(P0.01);低温组海刺猬口器湿重、壳湿重、性腺湿重、壳干重、口器指数、壳指数极显著小于对照组(P0.01),性腺干重、口器干重显著小于对照组(P0.05);但性腺指数与对照组无显著差别(P0.05);低温组海刺猬最大承受压力极显著小于对照组(P0.01);在实验室条件下,海刺猬(2~3 g·ind-1)无法长时间在高温环境(30℃)下存活,而能在低温环境(-2℃)下存活但其摄食、生长和性腺性状影响极显著。     

温度对中华鲟幼鱼血液生化指标的影响

分别在15℃、20℃、25℃和30℃水温养殖中华鲟幼鱼66d,研究温度对中华鲟幼鱼8项血液生化指标的影响。结果表明:中华鲟幼鱼血液中能源物质总蛋白、白蛋白、血糖、总胆固醇和高密度脂蛋白浓度变化规律相似,均呈现先升高后降低的趋势,而且均在20℃时达到最高值,分别为15.98g·L-1、5.6g·L-1、4.85mmol·L-1、2.44mmol·L-1和0.61U.L-1;在30℃时血液总蛋白、白蛋白、血糖、总胆固醇和甘油三酯浓度达到最低值,分别为8.93g·L-1、3.1g·L-1、2.26mmol·L-1、1.34mmol·L-1和3.35mmol·L-1;代谢产物总胆红素浓度呈现先降低后升高的趋势,在15℃组最高,在25℃组最低,分别为2.50±0.84和1.65±0.10mmol·L-1;尿素浓度随着温度升高而下降,在30℃时最低,为0.54±0.36mmol·L-1,显著低于15℃组和20℃组。综合不同温度组中华鲟幼鱼血液生化指标的变动规律表明,20℃时中华鲟幼鱼能量支出较少,是其较适宜的生长温度。     

温度和盐度对褐牙鲆幼鱼渗透生理及抗氧化水平的影响简

采用双因素析因实验设计方法,研究了温度(20℃、24℃、28℃)和盐度(10‰、30‰)急性应激对褐牙鲆(Paralichthys olivaceus)幼鱼渗透生理和抗氧化水平的影响。结果表明:盐度和温度变化对各实验组1d和6d时褐牙鲆幼鱼血浆皮质醇含量均无显著性差异。在高温低盐(28℃、10‰)环境中1d时渗透压显著高于其他各实验组,6d时无显著性差异。牙鲆幼鱼在28℃环境中1d时鳃Na+-K+-ATP酶活性显著高于20℃和24℃;6d时,温度和盐度对牙鲆幼鱼鳃Na+-K+-ATP酶活性有显著交互影响作用。1d时,随着温度的升高或盐度的降低牙鲆幼鱼肝脏超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性呈现上升趋势,并且高温低盐(28℃、盐度10‰)组褐牙鲆幼鱼肝脏丙二醛(MDA)含量显著高于其他各组;在3个实验温度下,10‰环境中牙鲆幼鱼肝脏脂质过氧化物(LPO)的含量高于30‰。在6d时,各实验组间肝脏SOD、CAT活性及MDA含量无显著性差异。因此,褐牙鲆能够耐受温度20—28℃和低至盐度10‰的环境条件,应激早期温度和盐度的变化可引起褐牙鲆幼鱼渗透生理和抗氧化水平的变化,高温低盐对褐牙鲆幼鱼抗氧化水平的影响最大,至6d可基本恢复稳定。     

Gonadal development and sex differentiation in the cichlid fish Cichlasoma dimerus (Teleostei, Perciformes): a light- and electron-microscopic study

Although the overall pattern and timing of gonadal sex differentiation have been established in a considerable number of teleosts, the ultrastructure of early stages of gonadal development is not well documented. In this study, gonads from larval and juvenile stages of laboratory-reared Cichlasoma dimerus were examined at the light-microscopic and ultrastructural levels. This freshwater species adapts easily to captivity and spawns with high frequency during 8 months of the year, providing an appropriate model for developmental studies. Larvae and juveniles were kept at a water temperature of 26.5 +/- 1 degrees C and a 12:12 hour photoperiod. Gonadal development was documented from 14-100 days postfertilization, covering the period of histologically discernible sex differentiation. Gonadal tissue was processed according to standard techniques for light and electron microscopy. C. dimerus, a perciform teleost, is classified as a differentiated gonochorist, in which an indifferent gonad develops directly into a testis or ovary. On day 14, the gonadal primordium consists of a few germ cells surrounded by enveloping somatic cells. Ovarian differentiation precedes testicular differentiation, as usual in teleost fishes. The earliest signs of differentiation, detected from day 42 onward, include the onset of meiotic activity in newly formed oocytes, which is soon accompanied by increased oogonial mitotic proliferation and the somatic reorganization of the presumptive ovary. The ovarian cavity is completely formed by day 65. Numerous follicles containing perinucleolar oocytes are observed by day 100. In contrast, signs of morphological differentiation in the presumptive testis are not observed until day 72. By day 100, the unrestricted lobular organization of the testis is evident. The latest stage of spermatogenesis observed by this time of testicular development is spermatocyte II.     

Gene expression during gonadal differentiation in the rat: A two-dimensional gel electrophoresis investigation

Gonadal protein patterns were studied during development in the rat by two-dimensional micro-gel electrophoresis. Specific proteins were detected in both the male and the female sex at the morphologically indifferent state (two female- and one male-specific) and during differentiation. At the onset of gonadal differentiation (day 14) two additional sex-specific proteins were discovered in the male and two in the female. These proteins remained expressed during further development. One testicular protein was restricted to the cytosol of the tunica albuginea. The other one was absent from the tunica. In the female gonad, the two proteins were membrane-specific, one present in germ cells, the other in somatic cells. In the testis, one additional protein was discovered at postnatal day 1. Thus according to biochemical criteria there is no indifferent state of gonadal development. The testis and ovary express sex-specific genes both before and after the onset of gonadal differentiation.     

Regulation of testicular differentiation and testosterone production in the fetal mouse gonad in vitro

The objective of the present study was to develop a chemically-defined medium in which early stages of testicular differentiation can be investigated in an organ culture system. Mouse gonadal primordia were explanted before and after initiation of morphological sex differentiation, i.e. 11 and 12 day of gestation (d.g.), respectively. We found that a combination of human albumin fraction, insulin (or IGF-I), and sodium pyruvate promoted testicular organization of gonadal explants of 11 d.g., but not those of 12 d.g. Insulin also increased the production of testosterone from testicular explants of 11 d.g., but not those of 12 d.g. For the younger explants, progesterone was more efficient than pregnenolone as a steroid precursor during the first day of culture, but the maximum effect of pregnenolone was much higher than that of progesterone in later stages. The responsiveness to human chorionic gonadotropin increased gradually along with testicular organization. The addition of either serum or pregnenolone prominently increased the activity of delta 5-3 beta hydroxysteroid dehydrogenase in testicular explants of 11 d.g., but not the number of positive cells as demonstrated by histochemical staining. These results suggest that insulin (or IGF-I) is required during the initial phase of testicular organization, which is reflected by an increase in testosterone production and sensitivity to gonadotropins.     

Estrogen-induced gonadal sex reversal in the tammar wallaby

Estrogens have a feminizing effect on gonadal differentiation in fish, amphibians, reptiles, and birds. However, the role of estrogen during gonadal differentiation in mammals is less clear. We investigated the effect of estrogen on gonadal differentiation of male tammar wallabies. Male pouch young were treated orally with estradiol benzoate or oil from the day of birth, before seminiferous cords develop, to Day 25 postpartum and were killed at Day 50 postpartum. In all estrogen-treated neonates, a decrease in gonadal volume, volume of the seminiferous cords, thickness of the tunica albuginea, and number of germ cells was found. The stage of treatment affected the magnitude of the response. Two of three male young born prematurely after 25 days of gestation and treated subsequently with estradiol had ovary-like gonads, with well-developed cortical and medullary regions and primordial follicle formation. Furthermore, at Day 50 postpartum, many (21%) of the germ cells in these sex-reversed ovaries were in the leptotene and zygotene stages of meiosis, similar to female germ cells at the same stage of development. In the other males born on Day 26 of gestation or later, estradiol treatment from the day of birth caused development of dysgenetic testes, with abnormal Sertoli cells, atrophy of the seminiferous tubules and tunica albuginea, and absence of meiotic germ cells. In this marsupial, therefore, estradiol can induce either partial or complete transformation of the male gonads into an ovary with meiotic germ cells. These results confirm that estrogen can inhibit early testicular development, and that testis determination occurs during a narrow window of time.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

Summary The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Functional maturation of the gonads of Turkish hamsters under various photoperiods

The golden hamster, Mesocricetus auratus, is the only photoperiodic rodent to date that has been shown to fail to respond to inhibitory (i.e., short, less than 12.5 h/day) photoperiods until after pubertal onset. In other photoperiodic hamsters, mice, and voles, short photoperiods greatly retard gonadal maturation. The Turkish hamster, Mesocricetus brandti, is a photoperiodic rodent that as an adult is reproductively competent only on photoperiods of 15-17 h of light per day; photoperiods of less than 15 or greater than 17 h of light promote gonadal regression. In this report we addressed two questions: a) are prepubertal M. brandti photoperiodic, and b) if so, is gonadal maturation enhanced or suppressed by exposure to photoperiods of greater than 17 h of light per day? Turkish hamsters were raised on photoperiods of 12, 16, 20, or 24 (= LL) h of light per day. Testicular growth was retarded for 16 wk by 12L:12D. Very long days, 20L:4D, or LL did not retard testicular development. In females, pubertal onset, as indicated by first vaginal estrus, was delayed in young raised on 12L:12D and in 2 of 18 and 4 of 19 young raised on 20L:4D and LL, respectively. These results demonstrate that prepubertal Turkish hamsters are photoperiodic, but respond differently from adults to photoperiods greater than 17 h of light per day.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Histological evaluation of gonadal differentiation in fathead minnows (Pimephales promelas)

The timing of sex determination and the pattern of sex differentiation have not been studied in fathead minnow even though this species of fish are commonly used as a research model for toxicological studies. In this study, the developmental histology of gonadal development was investigated. Fish were cultured in the laboratory conditions and spawning obtained at a photoperiod of 16 h-light and 8 h-dark. Samples were collected from day 7 fish post-spawning (day 7 fps) to day 150 fps and their gonads were processed for histological examination. Developmental histology was assessed by using a light microscopy. The results showed that ovarian differentiation normally occurs at around day 13 fps, while testicular differentiation normally occurs at around day 22 fps.