黄鳝一种新的生殖腺发育状况报道

早在六十年前,刘建康就报道过黄鳝存在着自然性逆转现象[1]。在随后的几十年里,众多的学者对于黄鳝性逆转开展了较为广泛的研究[2—8]。目前一般认为黄鳝属于雌性先熟的雌雄同体鱼类,其性别发育为单方向进行,雌性发育阶段→间性发育阶段→雄性发育阶段。黄鳝雌性成熟发育第一次性周期内黄鳝个体全部表现为雌性发育,性成熟产卵后,卵巢内卵细胞败育,卵巢结构逐渐退化,与此同时雌性生殖细胞开始发育,通过雌雄间性发育过渡到雄性发育[2、3、7]。在这一发育程序中尚未有黄鳝同一个体生殖腺中精、卵巢结构均为成熟发育的报道。作者在对于黄鳝生殖…     

黄鳝“性逆转”一词小议

黄鳝Monopterus albus(Zuiew)属硬骨鱼纲合鳃目合鳃科,又名鳝鱼,鳝。在黄鳝的生活周期中,有一特殊的生物现象:生殖腺早期向雌性分化为卵巢,待卵巢中的卵母细胞发育成熟产卵后,卵巢转化为精巢,育成精子。一般认为,2龄前,平均体长为350毫米以下的黄鳝为雌性;3至5龄,平均体长450-600毫米为雌性、雌雄间性、雄性共存期;6龄,体长700毫米以上,则雄性个体可占95%以上。黄鳝的这一现象引起许多学者的兴趣。我国著名鱼类学家、黄鳝研究的先躯——伍献文与刘建康早在四十年代就进行了黄鳝性     

ERK/JNK在黄鳝雌、雄发育阶段生殖腺中的表达和定位

为探讨MAPK家族中ERK和JNK两个主要亚族在黄鳝雌、雄发育阶段生殖腺中的表达状况,应用蛋白质免疫印迹杂交技术和免疫组织化学法检测了ERK、JNK在黄鳝卵巢组织和精巢组织中的表达和定位。蛋白免疫印迹杂交显示:ERK在黄鳝雌、雄性腺组织中均有强的表达;JNK在性腺中的表达总体上弱于ERK,JNK1在精巢组织中的表达比卵巢组织显著降低,但JNK2在雌、雄性腺组织中的表达无明显差异。在免疫组织化学的观察中,ERK和JNK在卵原细胞和精原细胞中均为阳性反应,且定位相似:细胞质及细胞核核质呈阳性反应,核仁阴性。随着卵母细胞生长和成熟,ERK和JNK在卵母细胞胞质中阳性反应逐渐减弱。实验结果提示,ERK和JNK在黄鳝卵巢发育、凋亡退化以及雄性发育的启动过程中可能具有重要调控作用     

外源性甲基睾丸酮对雌性和间性黄鳝性腺发育的影响

本文研究了大剂量外源雄性激素（甲基睾丸酮,MT）对活检后的雌性和雌雄间性黄鳝发育的影响。我们应用色拉油溶解外源雄性激素对雌性和雌雄间性黄鳝进行腹腔注射,采用石蜡组织切片法,对MT对活检后的雌性和雌雄间性黄鳝性腺发育的影响进行组织学研究。试验未得到具有生殖能力的性逆转雄鱼,但发现了一些十分有趣的结构,将为进一步揭开黄鳝性逆转之谜奠定了一定的基础。结果如下：① MT可促进雌鳝卵母细胞退化,但不能使卵巢完全解体; ② MT可促进雌性和间性黄鳝性腺生殖板扩大、伸展,但不能使间质细胞增生;③ MT可促进雌性和间性黄鳝性腺生殖板上出现“中空小叶”,这种结构可以分成两种类型,即Ⅰ型“中空小叶”(“HL-Ⅰ”)和Ⅱ型“中空小叶”(“HL-Ⅱ”),Ⅱ型“中空小叶”可能是非正常发育下产生的生精小叶;④ MT对雌雄间体早期的黄鳝的雄性生殖细胞的发育有促进作用,对雌雄间性晚期的黄鳝可促进其生精小叶内的雄性生殖细胞外排,而形成另一类型的“中空小叶”。 ⑤ MT对雌雄间体黄鳝的作用强于对雌性黄鳝的作用。     

黄鳝减数分裂雌核发育及子代遗传纯合度分析

为了培育性状优良、遗传稳定的黄鳝(Monopterus albus)群体,研究探索了人工诱导黄鳝减数分裂雌核发育方法。针对养殖性状优良的深黄大斑鳝进行种质纯合,创制出3个深黄大斑鳝雌核发育群体。流式细胞术和染色体计数分析表明雌核发育黄鳝的细胞DNA含量、染色体数目均与野生型相同。性腺组织学切片观察表明雌核发育黄鳝卵巢发育正常。微卫星多样性分析表明雌核发育黄鳝群体的有效等位基因(N_e)、平均香农指数(I)、平均多态信息指数(PIC)、平均观测杂合度(H_o)及平均期望杂合度(H_e)等参数均极显著低于野生群体,雌核发育群体的遗传纯合度显著提高。雌核发育群体之间的遗传距离增大,遗传相似系数变小。深黄大斑鳝雌核发育群体为培育性状优良的黄鳝养殖品种提供了育种材料。     

黄鳝性腺自然逆转过程中vasa基因的表达分析

本研究采用RNA反义探针原位杂交技术,对vasa基因在黄鳝(Monopterusalbus)性腺发育过程中的表达情况进行了分析。结果表明:vasamRNA在Ⅰ、Ⅱ、Ⅲ期卵母细胞的胞质中均匀分布,在Ⅳ、Ⅴ期卵母细胞中vasamRNA有向胞质外周皮层迁移集中的趋势,但不明显;退化的卵粒也呈现vasamRNA阳性反应;在Ⅲ、Ⅳ期卵巢的被膜中检测到带有vasa阳性信号的细胞,这些细胞可能是待向精原细胞分化、迁移到卵巢被膜上的原始生殖细胞(Primordialgermcell,PGC),在性逆转过程中这些PGC可能由卵巢被膜迁移到精小叶中并发育成精子;在成熟精巢中,vasa在精原细胞和初级精母细胞中表达。进一步采用碱性磷酸酶染色法分析黄鳝卵巢及精巢后发现:在卵巢中,除了卵母细胞外,卵巢被膜中也检测到了带有碱性磷酸酶阳性信号的细胞;在成熟精巢中,只在生殖腺囊内的雄性生殖细胞中检测到碱性磷酸酶,而精巢被膜中没有检测到带有碱性磷酸酶阳性信号的细胞。本研究结果初步表明:黄鳝的雄性生殖细胞可能起源于雌性阶段卵巢被膜中的原始生殖细胞[动物学报51(3):469-475,2005]。     

棉铃虫卵巢形态与卵子发生过程观察

害虫发生高峰期、 发生量的准确预测和田间防治适期的确定与种群雌虫卵巢结构及卵子发生过程密切相关。为了明确棉铃虫Helicoverpa armigera卵巢结构及卵子发生过程, 本研究利用光学体视显微镜和透射电子显微镜, 对棉铃虫成虫卵巢管和卵子的超微结构进行了研究, 并确定了发育级别划分标准。结果表明: 根据卵巢的形状、 卵的产生过程、 卵黄沉积情况等将棉铃虫卵巢发育程度分为6个级别, 即发育初期(0级)、 卵黄沉积前期(Ⅰ级)、 卵黄沉积期(Ⅱ级)、 成熟待产期(Ⅲ级)、 产卵盛期(Ⅳ级)和产卵末期(Ⅴ级)。根据卵子发生过程中滋养细胞、 卵母细胞的变化, 将卵子发生期分为3个阶段： 卵黄发生前期、 卵黄发生期和卵黄成熟期。本研究首次对棉铃虫的卵子发生进行电子显微观察, 并完善了棉铃虫卵巢发育的分级标准, 为进一步研究棉铃虫的生殖发育机理提供了理论参考, 对田间棉铃虫种群发生期和发生量的预测预报也有重要的实践参考价值。     

黄鳝性逆转过程中Gsdf基因cDNA片段的克隆和表达分析

通过RT-PCR法从黄鳝性腺中首次克隆获得黄鳝Gsdf(gonadal soma-derived factor)基因的片段序列,该片段序列长218 bp,编码72个氨基酸。氨基酸序列分析表明黄鳝Gsdf基因片段与其他物种的相似性在61%~76%之间,其中与舌齿鲈(Dicentrarchus labrax)GsdfⅠ型、舌齿鲈GsdfⅡ型同源性最高,均为76%;系统进化树显示,黄鳝Gsdf与尼罗罗非鱼(Oreochromis niloticus)Gsdf基因聚成一支,与鲈形目鱼类亲缘关系较近。此外,不同性腺组织的基因检测结果显示,黄鳝Gsdf在卵巢和间期性腺的表达量很低,两者没有显著性差异(P0.05);在精巢组织中的表达量显著高于卵巢、间期性腺组织的表达量(P0.05)。上述结果表明Gsdf基因可能在黄鳝的性腺尤其是精巢的分化和发育过程中起着重要的作用。     

粗糙沼虾卵巢发育的组织学

利用组织切片技术,对粗糙沼虾的卵子发生和卵巢发育周期进行了组织学研究。根据细胞的大小、细胞核和核仁的大小形态及卵黄积累等情况,将卵子发生划分为4个时期,卵原细胞、卵黄合成期的卵母细胞、成熟前期和成熟期。卵黄合成期的卵母细胞又可细划分为3个时期。粗糙沼虾卵巢发育具有一定的规律性。根据卵巢的大小和颜色及每种雌性生殖细胞在卵巢中所占的比例,将卵巢发育划分为7个时期。并通过卵巢发育规律的探讨,对粗糙沼虾的人工养殖提出了合理的建议。     

未产卵雌性黄鳝的性转变

为探讨产卵是否为雌性黄鳝(Monopterus albus Zuiew)性转变的必经过程,研究分析了实验室内从受精卵或幼苗开始养殖至不同时间段的黄鳝性腺组织学状况,采用性腺活检技术跟踪了34月龄雌性黄鳝性腺发育变化,并以免疫组织化学方法探讨了黄鳝不同发育状态性腺中增殖细胞核抗原(PCNA)的分布.在养殖过程中,实验黄鳝...     

养殖鲥鱼性腺发育的研究

经激素处理和生态调控的养殖鲥鱼,能完成性腺发育的全过程,其可分为６个时期,卵细胞发育可相应分为６个时相。与其它鱼类不同,细胞中液泡最早出现在胞质的内缘而不是外缘。大、小核仁数随卵母细胞的发育而变化。成熟卵巢成熟系数为８５４％～１２６４％。成熟期卵径为６２８５～８３５３μｍ、精子头径为０７４～１５５μｍ。达性成熟的鲥鱼,冬季卵巢为Ⅱ期、精巢为Ⅱ～Ⅲ期。精、卵巢发育呈现出明显的不同步现象。前者５月底开始进入成熟期,后者７月初进入成熟期。初级卵母细胞由Ⅱ时相发育到Ⅳ时相基本上是同步的。第Ⅳ期卵巢卵径的频率仅出现１个高峰。养殖鲥鱼属１年１次产卵类型。     

Ovarian maturation and oogenesis in the blue swimmer crab,Portunus pelagicus (Decapoda: Portunidae)

The study was aimed at understanding the process of reproduction and the changes happening in the ovary of Portunus pelagicus during maturation, which would be useful for its broodstock development for hatchery purposes. For that, tissue samples from different regions of the ovary at various stages of maturation were subjected to light and electron microscopy, and based on the changes revealed and the differences in ovarian morphology, the ovary was divided into five stages such as immature (previtellogenic oocytes), early maturing (early vitellogenic oocytes), late maturing (late vitellogenic oocytes), mature (vitellogenic oocytes), and spent (resorbing oocytes). The ovarian wall comprised of an outermost thin pavement epithelium, a middle layer of connective tissue, and an innermost layer of germinal epithelium. The oocytes matured as they moved from the centrally placed germinal zone toward the ovarian wall. The peripheral arrangement of nucleolar materials and the high incidence of cell organelles during the initial stages indicated vitellogenesis I. Movement of follicle cells toward oocytes in the early maturing stage and low incidence of mitochondria and endoplasmic reticulum in the ooplasm during late vitellogenic stage marked the commencement and end of vitellogenesis II, respectively. Yolk granules at various stages of development were seen in the ooplasm from late vitellogenic stage onwards. The spent ovary had an area with resorbing oocytes and empty follicle cells denoting the end of one reproductive cycle and another area with oogonial cells and previtellogenic oocytes indicating the beginning of the next.     

拟目乌贼卵子发生与卵巢发育

为了丰富拟目乌贼(Sepia lycidas)生物学资料, 为人工育苗与养殖提供理论依据, 采用解剖学和组织学的方法, 对水泥池养殖条件下拟目乌贼卵子发生和卵巢发育进行了研究。结果表明: 经过6个月水泥池养殖, 平均体重为256.34 g, 最大体重达到457.08 g, 个别发育成熟, 绝大部分未达性成熟。卵子发生不同步, 根据细胞形态、细胞大小、滤泡细胞形态和卵黄形成情况可分为卵原细胞阶段(卵原细胞期)、原生质生长阶段(无滤泡期、单层滤泡期和双层滤泡期)、间质生长阶段(滤泡内折早期、滤泡内折中期和滤泡内折晚期)和营养质生长阶段(卵黄发生早期、卵黄发生晚期和成熟期), 共4个阶段10个时期。卵巢发育根据外观形态、性腺指数变化和切面上各期细胞所占的比例, 可分为形成前期、形成期、小生长期、大生长期、成熟前期和成熟期6个时期。拟目乌贼繁殖周期为一年。       

Morphology and ultrastructure of the adult ovarian cycle in Mithracidae (Crustacea,Decapoda, Brachyura,Majoidea)

The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.     

The stage of ovarian development affects organ expression of vitellogenin as well as the morphometry and ultrastructure of germ cells in the freshwater prawn Macrobrachium amazonicum (Heller, 1862)

The objective was to characterize vitellogenin expression in the ovary and hepatopancreas, and to describe the morphometry and ultrastructure of oocytes, in the freshwater prawn Macrobrachium amazonicum at various stages of ovarian development. Five ovarian stages were defined: (I) immature, (II) maturing, (III) mature, (IV) spawned, and (V) reorganized. Ovaries and hepatopancreas were analyzed by immunohistochemistry for vitellogenin expression. Vitellogenin expression in both ovary and hepatopancreas was predominantly widespread, beginning at Stage I, peaking at Stage III, and decreasing in Stages IV and V. Characterization of the ovary included measurement of the following germ cell types: oogonia (OG), and previtellogenic (PV), early vitellogenesis (EV), advanced vitellogenesis (AV), and mature (M) oocytes. Mean ± SD diameter of OG and EV oocytes in Stages I (14.2 ± 5.5 and 119.8 ± 15.7 μm) and II (17.9 ± 4.8 and 114.3 ± 34.6 μm), respectively, were significantly different from that in Stages IV (16.6 ± 4.7 and 107.0 ± 24.6 μm) and V (14.4 ± 4.1 and 101.0 ± 25.2 μm). Both scanning and transmission electron microscopy enabled identification of EV, AV and M oocytes based on the presence of a nucleus, and the organization and distribution of yolk in the cytoplasm. In summary, vitellogenesis occurred both in the hepatopancreas and ovary, with the ovary expressing vitellogenin starting as early as Stage I. This process promoted accumulation of yolk and growth of oocytes, thus favoring sexual maturation of females. This knowledge may be applied to improve production of farmed M. amazonicum.     

Ultrastructure of the ovary and oogenesis in the polychaete Capitella jonesi (Hartman, 1959)

Ultrastructural features of the ovary and oogenesis in the polychaete Capitella jonesi (Hartman, '59) have been described. The ovaries are paired, sac-like follicles suspended by mesenteries in the ventral coelom throughout the midbody region of the mature worm. Oogenesis is unsynchronized and occurs entirely within the ovary, where developing gametogenic stages are segregated spatially within a germinal and a growth zone. Multiplication of oogonia and differentiation of oocytes into the late stages of vitellogenesis occur in the germinal region of the ovary, whereas late-stage vitellogenic oocytes and mature eggs are located in a growth zone. Follicle cells envelop the oocytes in the germinal zone of the ovary and undergo hypertrophy and ultrastructural changes that correlate with the onset of vitellogenesis. These changes include the development of extensive arrays of rough ER and numerous Golgi complexes, formation of microvilli along the surface of the ovary, and the initiation of extensive endocytotic activity. Oocytes undergo similar, concomitant changes such as the differentiation of surface microvilli, the formation of abundant endocytotic pits and vesicles along the oolemma, and the appearance of numerous Golgi complexes, cisternae of rough ER, and yolk bodies. Yolk synthesis appears to occur by both autosynthetic and heterosynthetic processes involving the conjoined efforts of the Golgi complex and rough ER of the oocyte and the probable addition of extraovarian (heterosynthetic) yolk precursors. Evidence is presented that implicates the follicle cells in the synthesis of yolk precursors for transport to the oocytes. At ovulation, mature oocytes are released from the overy after the overlying follicle cells apparently withdraw. Bundles of microfilaments within the follicle cells may play a role in this withdrawal process.     

Ultrastructure of oogenesis in the bluefin tuna, Thunnus thynnus

Ovarian ultrastructure of the Atlantic bluefin tuna (Thunnus thynnus) was investigated during the reproductive season with the aim of improving our understanding of the reproductive biology in this species. The bluefin, like the other tunas, has an asynchronous mode of ovarian development; therefore, all developmental stages of the oocyte can be found in mature ovaries. The process of oocyte development can be divided into five distinct stages (formation of oocytes from oogonia, primary growth, lipid stage, vitellogenesis, and maturation). Although histological and ultrastructural features of most these stages are similar among all studied teleosts, the transitional period between primary growth and vitellogenesis exhibits interspecific morphological differences that depend on the egg physiology. Although the most remarkable feature of this stage in many teleosts is the occurrence of cortical alveoli, in the bluefin tuna, as is common in marine fishes, the predominant cytoplasmic inclusions are lipid droplets. Nests of early meiotic oocytes derive from the germinal epithelium that borders the ovarian lumen. Each oocyte in the nest becomes surrounded by extensions of prefollicle cells derived from somatic epithelial cells and these form the follicle that is located in the stromal tissue. The primary growth stage is characterized by intense RNA synthesis and the differentiation of the vitelline envelope. Secondary growth commences with the accumulation of lipid droplets in the oocyte cytoplasm (lipid stage), which is then followed by massive uptake and processing of proteins into yolk platelets (vitellogenic stage). During the maturation stage the lipid inclusions coalesce into a single oil droplet, and hydrolysis of the yolk platelets leads to the formation of a homogeneous mass of fluid yolk in mature eggs.