黄侧异腹胡蜂线粒体基因组全序列测定和分析

【目的】测序和分析黄侧异腹胡蜂Parapolybia crocea线粒体基因组,并在线粒体基因组水平探讨异腹胡蜂属Parapolybia在胡蜂科中的系统发育地位。【方法】用Illumina二代测序技术测定黄侧异腹胡蜂线粒体基因组全序列,分析其结构特点和碱基组成;使用最大似然法(maximum likelihood,ML)构建胡蜂科7个种线粒体基因组的系统发育树,分析其在胡蜂科中的系统发育关系。【结果】黄侧异腹胡蜂线粒体基因组全长16 619 bp(Gen Bank登录号:KY679828),包含13个蛋白质编码基因,22个t RNA基因,2个r RNA基因(rrn S和rrn L)和1个控制区,基因排列顺序与推测的昆虫祖先序列不完全一致;全部蛋白质编码基因的起始密码子均为ATN,终止密码子除CYTB和ND1为TAG外,其余均为TAA;除t RNASer(AGN)的DHU臂缺失外,其他t RNA均能折叠成典型的三叶草结构;控制区中存在一个18 bp的T-stretch结构和2段串联重复序列。胡蜂科7个种基于线粒体基因组的系统发育关系表现为蜾蠃亚科+(胡蜂亚科+马蜂亚科),异腹胡蜂属与马蜂属Polistes同属于马蜂亚科。【结论】黄侧异腹胡蜂线粒体基因组存在基因重排现象。基于线粒体基因组的胡蜂科系统发育关系与传统的形态分类学结果一致:异腹胡蜂属隶属于马蜂亚科,马蜂亚科与胡蜂亚科的亲缘关系较其与蜾蠃亚科更近。     

雄性中华乌塘鳢贮精囊的结构与功能

应用组织学、透射电镜及酶联免疫吸附分析法研究了雄性中华乌塘鳢贮精囊的形态结构 ,并探讨其功能。结果表明 ,贮精囊是一对精巢的附属腺体 ,结缔组织隔膜将贮精囊分隔成为许多小室腔。被膜和隔膜中含有平滑肌纤维、毛细血管、成纤维和纤维细胞以及间质细胞。隔膜上排列单层上皮细胞 ,呈柱形、立方形或扁平形 ,生殖季节粗面内质网、管状嵴线粒体和高尔基复合体发达 ,上皮细胞顶部聚集许多无膜包裹的分泌颗粒 ,分泌后细胞器退化 ,胞质中出现大量的大空泡。成纤维细胞具有合成分泌胶原蛋白的结构特征。贮精囊中的间质细胞与精巢中的Leydig型间质细胞形态特征相似。在生殖高峰期不论贮精囊的近端、中央或远端均先后贮存大量的精子 ,混合在分泌物中 ,贮精囊不同小室的上皮细胞发育并不同步。精液加贮精囊液的实验表明 ,贮精囊液有助于增强精子活率和延长精子寿命 ,并能促进受精率的提高。贮精囊纤维丝状分泌物呈深紫红色的PAS阳性反应 ,提示分泌物为粘多糖蛋白 ,贮精囊液含有 17α羟孕酮、PGE2 和PGF2α,能体外诱发雌亲鱼产卵 ,具有性外激素的重要作用     

四种蝉科昆虫的精子形态(半翅目:蝉科)

【目的】为了明晰蝉科昆虫的精子形态及其在分类和系统发育分析方面的意义,本研究对蝉亚科的蒙古寒蝉Meimuna mongolica、黑蚱蝉Cryptotympana atrata、蛉蛄Pycna repanda及姬蝉亚科的蟋蝉Tettigetta sp.的精子进行了比较研究。【方法】分别通过光学显微镜和透射电子显微镜,观察这4种蝉科昆虫的精子形态特征。【结果】蒙古寒蝉、黑蚱蝉、蛉蛄和蟋蝉这4种蝉科昆虫精子形态基本相似,但精子长度在种内和种间都有明显不同,均表现出多态性。根据精子长度,蛉蛄精子可被分为长精子、中长精子和短精子3种类型;蒙古寒蝉、黑蚱蝉和蟋蝉的精子被分为长精子和短精子2种类型。4种蝉的精子结构也基本相似,头部包含顶体和细胞核,颈区由中心粒和中心粒侧体组成,尾部一般由一根轴丝和一对线粒体衍生物组成,轴丝微管为9+9+2模式。但蝉亚科3个物种的部分精子具有多个线粒体衍生物;首次在蛉蛄精子尾部发现一个电子致密的三角形区域,该结构在蝉科其他昆虫精子中未曾发现。蝉科不同类群的精子中心粒侧体存在显著差异,姬蝉亚科的蟋蝉精子中心粒侧体为片层状结构,蝉亚科昆虫则为鞘状结构。【结论】与蝉次目的角蝉总科和沫蝉总科昆虫精子相比,仅蝉科昆虫的精子表现出多态性,是该科的特有衍征。精子尾部可具多个线粒体衍生物的现象在蝉亚科物种中是否普遍存在有待进一步研究。蝉科不同类群在精子形态方面的差异,为蝉科昆虫分类及蝉次目系统发育分析提供了重要信息。     

斑衣蜡蝉雌性生殖系统超微结构

【目的】明确斑衣蜡蝉Lycorma delicatula雌成虫生殖系统整体形态及超微结构特征,为蜡蝉总科昆虫分类及系统发育探讨提供更多形态学证据。【方法】采用光学显微镜与透射电子显微镜,观察斑衣蜡蝉雌成虫生殖系统整体形态和各主要器官的超微结构。【结果】斑衣蜡蝉雌成虫生殖系统主要包括1对卵巢、1个中输卵管、1个交配囊、1个交配囊管、1个前阴道、1个后阴道、1个受精囊、1个受精管和2根受精囊附腺。卵巢为端滋式,由14根卵巢小管组成,卵室由固有膜、滤泡细胞和卵细胞组成,卵巢小管中的滋养细胞清晰可见;中输卵管位于前阴道基部,由中输卵管腔、上皮细胞、肌肉鞘和基膜组成;交配囊膨大呈圆球状,囊壁由上皮细胞、肌肉层和基膜组成;交配囊管呈圆柱状,连接交配囊和后阴道,由肌肉鞘、上皮细胞层和管腔组成;前、后阴道超微结构相似,主要由肌肉鞘、基膜、上皮细胞和管腔组成,但后阴道上皮细胞细胞核周围存在分泌颗粒,且管腔内有大量微绒毛,而前阴道壁内包含有大量囊泡结构;受精管从中输卵管末端延伸至受精囊,由基膜、厚层肌肉鞘和管腔组成;受精囊为受精管近末端略膨大的囊状结构,由肌肉鞘、基膜、上皮细胞和囊腔构成;雌性受精囊附腺着生于受精囊末端,为均匀的螺旋管状,主要由肌肉层、上皮细胞层和附腺中心管腔组成。【结论】斑衣蜡蝉雌性生殖系统与已报道的蜡蝉总科其他类群的雌性生殖系统结构相似,但卵巢小管数目有差异;蝉亚目中不同总科雌成虫雌性附腺与受精囊附腺的形态特征存在明显区别;斑衣蜡蝉雌性生殖系统超微结构与叶蝉总科和沫蝉总科昆虫也存在部分差异。这些差异是否可以作为头喙亚目高级阶元的划分依据仍有待于进一步研究。     

优雅蝈螽与暗褐蝈螽精子束的显微观察

本文应用微分干涉相衬法对优雅蝈螽Ｇampsocleis gratiosa Brunner von Wattenwyl和暗褐蝈螽G. sedakovii （Fischer von Waldheim） 雄性精巢管基部、输精管、贮精囊和精包,及雌性受精囊中精子束的形态变化进行了观察,对探讨螽斯近缘种的生殖隔离机制和生殖生物学具有重要意义.结果表明：这两种蝈螽的精子束通过精包转移到雌性受精囊后,精子束的形态发生了显著变化.精巢管基部的精子为游离的单个精子;输精管、贮精囊和精包中精子成束排列形成较分散的精子束,精子束头部包裹有粘液帽;雌性受精囊中的精子束的精子呈羽状排列,精子的头部汇集在中央轴上.两种蝈螽精子束形态差异不显著.     

透明疏广蜡蝉精子超微结构

【目的】昆虫精子的超微结构在昆虫种类鉴定和亲缘关系探讨方面具有重要意义。研究蜡蝉总科(Fulgoroidea)昆虫的精子超微结构,可以为目前仍存较大争议的该类群发育关系分析提供更多证据。【方法】采用超薄切片法并结合光学电子显微镜和透射电子显微镜,观察透明疏广蜡蝉Euricania clara Kato精子形态和超微结构。【结果】透明疏广蜡蝉的成熟精子聚集成束,单根精子无多态性,由头部、颈区和长鞭毛组成。头部包括双层顶体复合体和精子细胞核;颈区可见中心粒和中心粒侧体;长鞭毛主要由一对D形的线粒体衍生物、一对鱼钩状副体和典型的9+9+2微管型轴丝结构组成。【结论】透明疏广蜡蝉的鱼钩状副体与已报道的其他蜡蝉类群的该结构大体一致,但与头喙亚目其他类群的副体结构有显著差异;此外,透明疏广蜡蝉精子线粒体衍生物的数量、大小及横切形状与组成与其他昆虫类群有较大差异,而在头喙亚目内表现出一定的一致性,但也存在明显差异。本研究可以为蜡蝉总科昆虫系统发育分析提供科学资料。     

3种蛾类雄性内生殖系统形态学研究

为了探究蛾类昆虫新的有效分类特征,本研究对直脉青尺蛾Geometra valida、白雪灯蛾Chionarctia niveus和多斑豹蠹蛾Zeuzera multistrigata雄性内生殖系统进行了解剖观察和形态学比较。结果表明：3种蛾类雄性内生殖系统均由精巢、贮精囊（前贮精囊和后贮精囊）、输精管、复射精管、单射精管（单射精管原节和单射精管表皮节）和附腺组成;种间形态差异表现在贮精囊的形状及连接方式、复射精管的形状及长短、单射精管和附腺的长度等方面,这些鉴别特征可为蛾类分类及系统发育研究提供形态学借鉴。     

刘氏蝎蛉的精子发生和精子超微结构

【目的】精子超微结构在不同昆虫类群中变异较大,在昆虫种类鉴别和系统发育分析中具有重要意义。但截止目前,长翅目(Mecoptera)昆虫的精子发生和精子超微结构研究还很不充分。【方法】采用光学显微镜和透射电子显微镜技术,观察了刘氏蝎蛉Panorpa liui Hua的精子发生和精子超微结构。【结果】刘氏蝎蛉精原细胞在精囊内共分裂7次,产生128个精子细胞。这些精子细胞同步发育,成熟后结合形成数目略低于128的精子束。精子形成期,精子细胞内高尔基复合体产生的原顶体颗粒物质形成精子顶体;球状细胞核伸长、核内染色质凝集,形成致密的线形细胞核;分散的线粒体聚集、融合产生的副核转化形成2条线粒体衍生物。成熟精子由头部、颈区和长鞭毛组成。精子头部包括双层顶体和具有2条侧沟的细胞核两部分;颈区主要由中心粒和致密的鞘状中心粒侧体组成。鞭毛螺旋状,主要由1条9+2型轴丝、2条大小不等的线粒体衍生物和2条副体组成。【结论】刘氏蝎蛉精子束内精子数目略低于128,可能与精子复杂的形成过程及细胞的吞噬作用有关。线粒体衍生物在不同类群间差异显著,可为长翅目系统发育分析提供有用的特征。     

宽翅曲背蝗受精囊形态与超微结构观察（英文）

【目的】明确宽翅曲背蝗Pararcyptera microptera meridionalis雌虫受精囊的形态、组织结构与超微结构,为更好地认识昆虫受精囊的功能提供依据。【方法】本研究以宽翅曲背蝗已交配雌成虫为实验材料,利用光学显微镜和透射电子显微镜观察其受精囊的形态、组织结构和超微结构。【结果】宽翅曲背蝗受精囊由一个端囊和一条长的受精囊管组成,端囊用于储存精子。端囊和受精囊管有相似的组织学结构,由外到内依次为肌肉层、基膜、上皮层及表皮内膜。上皮层含上皮细胞、腺细胞和导管细胞3种细胞类型。腺细胞具有一个被有微绒毛的细胞外腔。腺细胞的分泌物经细胞外腔通过分泌导管进入到受精囊腔。分泌导管由导管细胞形成。【结论】在宽翅曲背蝗受精囊的端囊和受精囊管上,内膜和腺细胞的细胞外腔结构均存在差异,由此推测,端囊和受精囊管的功能存在一定差异。上皮细胞的超微结构特点显示上皮细胞具有支持、分泌和吸收的功能。     

宽翅曲背蝗受精囊形态与超微结构观察

[目的]明确宽翅曲背蝗Pararcyptera microptera meridionalis雌虫受精囊的形态、组织结构与超微结构,为更好地认识昆虫受精囊的功能提供依据.[方法]本研究以宽翅曲背蝗已交配雌成虫为实验材料,利用光学显微镜和透射电子显微镜观察其受精囊的形态、组织结构和超微结构.[结果]宽翅曲背蝗受精囊由一个端囊和一条长的受精囊管组成,端囊用于储存精子.端囊和受精囊管有相似的组织学结构,由外到内依次为肌肉层、基膜、上皮层及表皮内膜.上皮层含上皮细胞、腺细胞和导管细胞3种细胞类型.腺细胞具有一个被有微绒毛的细胞外腔.腺细胞的分泌物经细胞外腔通过分泌导管进入到受精囊腔.分泌导管由导管细胞形成.[结论]在宽翅曲背蝗受精囊的端囊和受精囊管上,内膜和腺细胞的细胞外腔结构均存在差异,由此推测,端囊和受精囊管的功能存在一定差异.上皮细胞的超微结构特点显示上皮细胞具有支持、分泌和吸收的功能.     

Ultrastructure and function of the seminal vesicle of Bittacidae (Insecta: Mecoptera)

The fine structure of the seminal vesicle and reproductive accessory glands was investigated in Bittacidae of Mecoptera using light and transmission electron microscopy. The male reproductive system of Bittacidae mainly consists of a pair of testes, a pair of vasa deferentia, and an ejaculatory sac. The vas deferens is greatly expanded for its middle and medio-posterior parts to form a well-developed seminal vesicle. The seminal vesicle is composed of layers of developed muscles and a mono-layered epithelium surrounding the small central lumen. The epithelium is rich in rough endoplasmic reticulum and mitochondria, and secretes vesicles and granules into the central lumen by merocrine mechanisms. A pair of elongate mesodermal accessory glands opens into the lateral side of the seminal vesicles. The accessory glands are similar to the seminal vesicle in structure, also consisting of layers of muscle fibres and a mono-layered elongated epithelium, the cells of which contain numerous cisterns of rough endoplasmic reticulum and mitochondria, and a few Golgi complexes. The epithelial cells of accessory glands extrude secretions via apocrine and merocrine processes. The seminal vesicles mainly serve the function of secretion rather than temporarily storing spermatozoa. The sperm instead are temporarily stored in the epididymis, the greatly coiled distal portion of the vas deferens.     

Sperm morphology of the neotropical harvestman Iporangaia pustulosa (Arachnida: Opiliones): comparative morphology and functional aspects

We describe herein the sperm morphology of the harvestman Iporangaia pustulosa. Adult males were dissected, the reproductive tract was schematized and the seminal vesicle was processed by light, transmission and scanning electron microscopy. The male reproductive tract is composed of a tubular testis, two deferent ducts, a seminal vesicle, a propulsive organ and a penis, similar to that observed in other Opiliones. The spermatozoa from the seminal vesicle are oval, aflagellate and immotile, presenting a nucleus surrounding an invagination of the cytoplasm, as well as a complex acrosome and projections on the cell surface. In the testis, spermatozoa are devoid of projections. In the seminal vesicle, they gradually acquire the projections with tufts adhering to it. Consequently, spermatozoa in various distinct stages of projection development can be found in the seminal vesicle. We believe that these projections (1) could help transport sperm along the male and perhaps female reproductive tracts; (2) are used to anchor the spermatozoa inside the female spermatheca in order to avoid mechanical displacement by the genitalia of other males and (3) may play a role in oocyte recognition. We propose that the evolution of aflagellarity in Opiliones is related to the unique morphology of the female reproductive tract. Since eggs are fertilized on the tip of the ovipositor just prior to being laid, there is no advantage favoring sperm mobility. Additionally, female sperm receptacles are small and males that produced small spermatozoa would have a higher chance of fertilizing more eggs.     

beta-N-acetylglucosaminidase in the reproductive organs and seminal plasma of the bull

The highest specific activity of beta-N-acetylglucosaminidase (beta-NAG) was found in the different parts of the epididymis, where the activity seemed to be partly in secretory and partly in non-secretory, tissue-bound form. Epididymal spermatozoa also contained moderate beta-NAG activity. The beta-NAG was separated by chromatofocussing and anion exchange chromatography with HPLC into multiple forms with distinct pI values (8.0-4.0). The cauda epididymidis, ampulla and the seminal vesicles formed the major secretory sources of the high beta-NAG activity in bull seminal plasma. The major secretory forms of beta-NAG in caput and cauda epididymidis showed distinct elution profiles. In the fractionation with gel filtration on Sepharose 6B, the beta-NAG activities derived from bull testis and caput epididymidis had smaller molecular weights than did the secretory enzymes in seminal plasma, seminal vesicle secretion and cauda epididymidis. Maximum activity of all beta-NAG isoenzymes was observed at pH 5.0. They were almost totally inactivated at 60 degrees C and about 75-80% of the activity was lost at 55 degrees C. All the isoenzymes were strongly inhibited by thiol reagents but not with other metal ions and chelating agents. Histochemical studies showed a strong granular (lysosomal) reaction for beta-NAG in basal cells and basal parts of the principal cells in all but the initial segment of the epididymis. An apical (secretory) reaction was prominent in the distal caput and corpus as well as in distal cauda. After the distal caput the luminal sperm mass became increasingly mixed with a beta-NAG-positive material. The epithelial cells of the ampulla and seminal vesicle displayed a moderate apical (secretory) reaction.     

Anatomy and ultrastructure of the male reproductive system in Pleioplana atomata (Platyhelminthes: Polycladida)

Abstract. The ultrastructure of the male reproductive system in the polyclad flatworm Pleioplana atomata is described. Numerous testes are scattered throughout the entire body but are heavily concentrated on the ventral side. All stages of differentiating sperm cells are present in all testes follicles. Intercellular bridges connect spermatocytes and spermatids derived from a single spermatogonium. In the distal part of spermatids, a zone of differentiation develops with a row of microtubules beneath the plasmalemma. Adjacent to these microtubules, an intercentriolar body is flanked by two basal bodies that give rise to two axonemes (each with a 9+“1” microtubular pattern) that face in opposite directions. The Golgi complex appears in the central portion of the spermatid and produces numerous small and large electron-dense bodies. The small bodies surround the nucleus, whereas the large bodies cluster along with the mitochondria in the central part of the spermatid. Development of the spermatid leads to cell elongation and formation of a filiform, biflagellate mature spermatozoon with cortical microtubules all along the sperm shaft. The male canal system consists of paired vasa deferentia that separately enter a single seminal vesicle. A single prostatic canal connects the seminal vesicle to the prostatic vesicle. Ultrastructurally, the seminal vesicle and prostatic canal are very similar, and along with the prostatic vesicle and stylet pocket, are lined by a ciliated epithelium. The ultrastructure of the prostatic vesicle indicates that it probably produces a large volume of seminal fluid that, along with spermatozoa, is transferred to the mating partner through a stylet. Some of the findings, particularly on sperm ultrastructure, may provide characters useful for phylogenetic analysis.     

Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera,Apidae)

Fiorillo, B. S., Zama, U., Lino‐Neto, J. and Báo, S. N. 2010. Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera, Apidae). —Acta Zoologica (Stockholm) 91 : 176–183. In Xylocopa frontalis the reproductive tract is composed of testes, deferent ducts, seminal vesicles, accessory glands and an ejaculatory duct. Each testis comprises four testicular tubules in which multiple cysts are present containing approximately 64 spermatozoa per cyst. The seminal vesicle consists of an epithelium, a thick basement lamina and a muscular external sheet. In the luminal region some vesicles can be observed; however, the epithelial cells of the seminal vesicle do not display morphological features associated with secretory functions. The spermatozoa, measuring approximately 260 µm long, are similar to the hymenopteran pattern. The head region consists of an acrosome with an inner perforatorium that penetrates an asymmetrical nuclear tip. The nucleus is linear, electron‐dense and its posterior tip projects into the beginning of the axoneme. The centriolar adjunct is asymmetric with many electron‐lucent lacunae interspersed throughout. The axoneme has the 9 + 9 + 2 pattern of microtubules and in the posterior region the central microtubules finish first, followed by the doublets and finally the accessory microtubules. The mitochondrial derivatives are asymmetric in both length and diameter with paracrystalline material present only in the larger one. These features may be useful characters for taxonomy and phylogenetic studies.     

Comparative studies of testicular structure and sperm morphology among copulatory and non-copulatory sculpins (Cottidae: Scorpaeniformes: Teleostei)

Testicular structure of 9 species and sperm head morphology of 19 species of Cottidae were observed in order to clarify relationships between morphological characteristics of the male reproductive organ and reproductive mode (copulation or non-copulation). Morphological structure of the testis was divided into the following five types based on the sperm transfer and reservoir system: (1) a non-duct type in which the sperm duct is not a distinct exterior structure, but the tube for sperm transport traverses along the testis as an interior structure; (2) an anterior duct type with distinct anterior sperm ducts traversing along the testis; (3) a posterior duct type with distinct anterior sperm ducts traversing along the dorsal hilus of testis and posterior sperm ducts extending to the rear of the testis; (4) an anterior duct posterior vesicle type with distinct anterior sperm ducts traversing along the testis, and the right and left sperm ducts fusing in the rear of testis, forming the seminal vesicle; (5) a non-duct posterior vesicle type in which sperm ducts do not accompany the testis, and the testis and seminal vesicle are connected directly or through posterior sperm ducts. It is thought that in Cottidae the non-duct type of reproductive organ is primitive, and the anterior duct type is common to all non-copulating species. The testes and accompanying seminal vesicle were seen only in copulating species. Sperm head morphology was divided into three types according to the length/width ratio: oval type ≤2, intermediate type >2 and ≤3, and slender type >3. The type of sperm head corresponded closely to the reproductive mode; non-copulating species had oval sperm head, and copulating species had intermediate or slender ones. These results suggest that the structure of the testis and the morphology of the sperm head evolved from testes with anterior sperm ducts and oval sperm heads to testes with an associated seminal vesicle and slender sperm heads in association with the evolution from non-copulatory to copulatory reproduction in Cottidae.     

Sperm structure and ultrastructure in the Hymenoptera (Insecta)

A light and electron microscopical survey of spermatozoan gross morphology and ultrastructure in the Hymenoptera is presented. Details are provided for the first time for members of the families Xyelidae, Argidae, Tenthredinidae, Diprionidae, Cephidae, Figitidae, Proctotrupidae, Diaprii- dae, Heloridae, Eurytomidae, Leucospidae, Perilampidae, Torymidae, Braconidae, Dryinidae, Sphecidae, Pompilidae and Vespidae. Spermatozoan length ranged from 8 μ m in some Braconidae to 500 μm in one chalcidoid. Considerable variation in gross morphology and ultrastructure were observed between taxa. Several phylogenetically informative characters were noted. Very small spermatozoa characterized most of the non-cyclostome subfamilies of Braconidae; spirally twisted axoneme and mitochondrial derivatives occur in the Eulophidae, Eurytomidae and Pteromalidae; spermatozoa with virtually indistinguishable head (nucleus and acrosome) regions characterized the Vespinae and Polistinae. The presence of well-developed spermatodesmata in the vas deferens and seminal vesicle characterize the Symphyta and were largely absent from other groups though they are occasionally present in some bees.     

平疣桑椹石磺生殖系统结构及精子储存场所

雌雄同体贝类精子的储存和利用规律一直是国内外贝类生物学研究的难点之一,本文利用活体解剖、显微观察、组织切片和扫描电镜技术,综合研究了平疣桑椹石磺(Platevindex mortoni)的生殖系统及精子储存场所。结果显示,其生殖系统包括生殖器本部、雌性生殖部分和雄性生殖部分。生殖器本部由两性腺、两性输送管、蛋白腺、黏液腺、支囊组成;雌性生殖部分包括输卵管、受精囊、阴道,位于身体中后方体腔内;雄性生殖部分包括输精管、刺激器、阴茎、阴茎鞘和阴茎牵引肌,位于身体前端右侧体腔内;其阴茎有阴茎鞘,阴茎表面布满倒刺。平疣桑椹石磺阴茎为直线状,无雄性附属腺。未交配的性成熟个体支囊内充满细长精子,受精囊内无精子;而交配后充当雌性个体的支囊内均为细长的自体精子,受精囊内有大量活力较强的粗短精子,其支囊为自体精子的存储场所,而受精囊为异体精子的存储场所。其精子储运情况为:两性腺内精子成熟后暂存于支囊,交配时通过输精管运输至阴茎,由阴茎输送精子至对方的阴道,异体精子进入受精囊内存储待用。     

Spermatozoa in the reproductive system of a hermaphroditic marine tardigrade,Orzeliscus belopus (Tardigrada: Arthrotardigrada)

Orzeliscus belopus has long been regarded as the only hermaphroditic marine tardigrade, yet there has been no published detailed information on its internal anatomy. Our study elucidates the ultrastructure of the ovotestis and the spermatozoa of Orzeliscus cf. belopus from Bermuda. The ovotestis had no septum to separate male and female germ cells and, while early stages of spermatogenesis were not observed, many spermatozoa were found at the periphery in both anterior and posterior areas of the gonad. The nucleus and the mitochondria of the spermatozoa in the ovotestis extend backward from the centriole region, forming a half-headed arrow-shape with the nucleus on the outer side of the ‘arrowhead’. The cross section of a long vesicular body (the paranuclear vesicle) is dumbbell- or horseshoe-shaped and attached to almost the entire length of the nucleus. In the seminal receptacle, we found both a complete spermatozoon and some which started to degrade. There is an indication that sperm is further modified after discharge as within the receptacle duct the sperm is no longer half-headed arrow-shaped but has a straight nucleus. This modification might be correlated with the degeneration of the paranuclear vesicle. Our observations clearly show that O. belopus is a simultaneous hermaphrodite, and suggests that the reproductive mode includes copulation and cross-fertilization.