滇蛙多盘吸虫精子超微结构

利用透射电镜研究多盘吸虫精子的形态和结构。它属于单殖类中Ｐｏｌｙｏｐｉｓｔｈｏｃｏｔｙｌｅａ类型。精子细线形,含两根融入精子内的９＋１型轴丝,细长的细胞核,纤细的线粒体和微管。在第二根轴丝出现前的区段无微管的分布,具两根轴丝的主干段轴丝外无外侧管;细胞核消失后微管呈整圈排列;精子后部含糖原颗粒,背腹面中央向髓布内凹呈哑铃状并两侧向外突出形成波动膜;由精细胞则来的区段具外饰物。     

Ultrastructure of Spermiogenesis in Acanthocotyle and Myxinidocotyle (Platyhelminthes,Monogenea, Acanthocotylidae)

Abstract Spermiogenesis was studied by transmission electron microscopy in the acanthocotylid monogeneans Myxinidocotyle californica (from Eptatretus stoutii) and Acanthocotyle lobianchi (from Raja clavata). In Myxinidocotyle and Acanthocotyle, the zone of differentiation shows two 9+‘1’ axonemes, the elongating nucleus and mitochondrion, and a single cortical cytoplasmic microtubule. This single microtubule is found in the mature spermatozoon of both species and was also noted in capsalids. This requires a modified definition of ‘pattern 2’ of spermatozoa which becomes: ‘spermatozoa with two axonemes and no cortical microtubules, except one single element much shorter than the spermatozoon’. A very unusual structure was found in Myxinidocotyle, but not in Acanthocotyle: the centriolar derivative of one of the 9+‘1’ axonemes is made up of 18 diverging singlets of unequal length associated with electron-dense cytoplasm. This seems to be the first case of a centriolar derivative without nine-fold symmetry associated with an axoneme with nine-fold symmetry.     

Spermatogenesis and spermiogenesis in Didymocystis wedli Ariola, 1902 (Didymozoidae, Digenea).

The ultrastructure of the male reproductive system of Didymocystis wedli was studied for the first time, demonstrating spermiogenesis and spermatogenesis at different cell stages. The spermatozoa morphology was compared with that of other Digenea species. It was observed that the different cells of the spermatogenesis process follow the classic pattern reported for the majority of the parasitic platyhelminthes. During spermiogenesis, rootlet fibers, electrondense bodies and median cytoplasmic process were not observed. The mature spermatozoa of D. wedli were filiform, presenting nucleus, mitochondrion and two 9+1 axonemes, with a biflagellate distal extremity.     

Ultrastructural study of the male gamete of Pleurogonius truncatus Prudhoe, 1944 (Platyhelminthes, Digenea, Pronocephalidae) parasite of Eretmochelys imbricata (Linnaeus, 1766)

In Pronocephaloidea, the spermatozoa of only two species have been studied today. Because of this, we present in this work data concerning to a third specie, Pleurogonius truncatus Prudhoe, 1944. The mature spermatozoon of P. truncatus possesses two axonemes with the 9+"1" pattern typical of Trepaxonemata, mitochondrion, nucleus, parallel cortical microtubules, spinelike bodies, cytoplasmic expansion and an external ornamentation of the plasma membrane. A particularity of the spermatozoon of P. truncatus is in the ultrastructure of the anterior spermatozoon extremity with only cortical microtubules and ornamentation of the plasma membrane. This type of anterior extremity has never been described until today in Pronocephaloidea. On the other hand, the ultrastructure of the posterior extremity of the spermatozoon confirms that already described in Pronocephalidae.     

Investigation of the ultrastructure of Dendrocoelum constrictum (Platyhelminthes,Tricladida) spermatogenesis and mature spermatozoa

To add to our understanding of dendrocoelid spermatozoa and to describe additional phylogenetic characters, the ultrastructure of the testis was investigated in the subterranean freshwater planarian Dendrocoelum constrictum. This is the first study investigating spermatogenesis and spermatozoon ultrastructure in a subterranean freshwater planarian species. We found that the basic structure of spermatozoa in D. constrictum is similar to that of other Tricladida that have been studied previously. In fact, D. constrictum spermatozoa possess an elongated nucleus, one giant mitochondrion, and two subterminal flagella with a 9 + ‘1’ pattern. The flagella emerge together from one side of the spermatozoon. However, D. constrictum has some characteristics that have not yet been described for other freshwater planarians. In fact, the number of cortical microtubules reaches the maximum number in the anterior and middle part of region I, and then decrease until they disappear towards the posterior extremity of the spermatozoon. The extreme tip of the anterior region of the spermatozoon exhibits a specific external ornamentation of the plasma membrane.     

Ultrastructure of Pagrus major and Rhabdosargus sarba spermatozoa (Perciformes: Sparidae: Sparinae)

Transmission and scanning electron microscopy were used to investigate the ultrastructure of spermatozoa in two Sparinae species Pagrus major and Rhabdosargus sarba. Ultrastructurally, the spermatozoa of P. major and R. sarba both consist of a spherical, homogeneously electron-dense nucleus with a deep axial nuclear fossa, and an unusual notch, in the nuclear region. The midpiece contains two spherical mitochondria in R. sarba and one in P. major. The comparison of spermatozoal ultrastructure of these two species of Sparidae shows that they closely resemble one another and suggests that they are closely related. Variation in the geometry and dimensions of the mitochondrion and nucleus is substantial in these two Sparidae species. It is concluded that the spermatozoa of both species are of primitive type, and they are distinguished by several unique features which may provide useful systematic characteristics.     

峨眉髭蟾精子形态结构及分类学意义

应用透射电镜、扫描电镜和光学显微镜对峨眉髭蟾(Vibrissaphoraboringii)精子的形态和超微结构研究的结果表明:峨眉髭蟾的精子具角蟾科物种精子基本的形态和结构特征,即精子头部呈螺旋状,尾部呈弯曲状;精子具锥形的顶体、纤维束构成的穿孔器、平行排列的中心粒和双轴丝;线粒体位于尾部;精子核窝不明显、无轴纤维和波动膜等特征。此外,对已有报道的角蟾科和无尾类物种精子的特征进行分析比较表明:(1)角蟾科精子细胞核呈螺旋状,中心粒平行排列,尾部具双轴丝等结构不同于无尾类其他科精子的结构,具有明显的科间差别;(2)角蟾科精子各部的量度,尾部线粒体的分布和数量,以及轴丝的排列等特征在属间和种间表现出明显的差异;(3)峨眉髭蟾和东南亚拟髭蟾指名亚种精子的形态和超微结构存在明显的差异。     

Characteristics of Spermatozoa from Five Gall-Midge Species (Diptera, Cecidomyiidae)

The gall-midge family Cecidomyiidae is one of the largest within the animal kingdom. Its characteristics include, among others, a chromosome elimination during spermiogenesis and a bewildering diversity in sperm ultrastructure. The sperm tail, in particular, is unusual in that it deviates from the conventional 9+2 pattern of microtubules. We describe here the spermatozoa of five gall-midge species, all belonging to the same supertribe Cecidomyiidi. In Bremia more than 100 microtubular doublets form a tight spiral around a central mitochondrion. In an undetermined binomen many doublets form a spiral around the mitochondria in the distal end of the sperm tail, but a single row along a peripheral cistern in the main part of the tail. In Coquillettomyia caricis a peripheral row of doublets resides in the proximal part and tightly packed doublets distally. In Arthrocnodax sp. the many doublets also form a peripheral single or double row around a central mitochondrion. In Massalongia bachmaieri there are more than 500 doublets which form several rows around the nucleus and tightly packed doublets distally. The nuclear membrane forms bundles of extensive outpocketings. There is no acrosome. The nucleus consists of both condensed and dispersed material. Only outer dynein arms are present in all this species and the spermatozoa are motile. Cecidomyiidi species that have been examined for sperm structure fall into two groups: those where the mitochondria are confined to the centre of the tail and those in which the mitochondria lie in the head region and have a peripheral location. Most species belong to the first group, while Massalongia belongs to the second one.     

Spermatozoon ultrastructure and phylogenetic relationships in the monogeneans (platyhelminthes)

Justine J.-L., Lambert A. and Mattei X. 1985. Spermatozoon ultrastructure and phylogenetic relationships in the monogeneans (Platyhelminthes). International Journal for Parasitology15: 601–608. New observations reported in this study together with bibliographical data allow comparisons of spermatozoon ultrastructure in 28 genera of monogeneans, belonging to 19 families. The authors propose to compare and classify monogenean spermatozoa using two simple ultrastructural characteristics: (a) the number of axonemes, 1 or 2, (b) the presence or absence of cortical microtubules. These traits make it possible to group monogenean spermatozoa in four patterns. Pattern 1 (2 axonemes plus microtubules) is characteristic of the polyopisthocotyleans (9 families). The three other patterns are found in the monopisthocotyleans. Pattern 2 (2 axonemes without microtubules) is found in the Capsalidae and Dionchidae, which seem closely related, and also in the Udonellidae, Gyrodactylidae and Euzetrema. Pattern 3 (1 axoneme plus 1 altered axoneme plus microtubules) is found in the Monocotylidae and Loimoidae. Pattern 4 (1 axoneme without microtubules) is found in the Amphibdellatidae, Ancyrocephalidae, Calceostomatidae and Diplectanidae. A phylogeny of the monogeneans is drawn from the data of comparative spermatology; this scheme coincides in many points with the phylogeny of Lambert (1980) which was based on the study of chaetotaxy and ciliated cells of the oncomiracidium.     

Spermiogenesis and sperm ultrastructure in the monogenean parasite Acanthocotyle lobianchi

The ultrastructural events of spermiogenesis and the ultrastructure of the mature spermatozoon of an acanthocotylid monogenean, Acanthocotyle lobianchi, are described. The early zone of differentiation (ZD) contains two roughly perpendicular centrioles which become parallel and produce two free flagella, although these later become incorporated into the same body of cytoplasm. No cortical microtubules were found supporting the ZD at any stage of spermiogenesis. Much of the length of the thread-like sperm contains two axonemes of the 9 + '1' pattern together with a nuclear and mitochondrial profile but the 'posterior' region is occupied only by a single axoneme and the nucleus. A laterally situated electron-lucent vesicle with specialization of the adjacent surface membrane is found in the 'anterior' region of the sperm. The phylogenetic implications of these observations are discussed.     

滇蛙多盘吸虫精子发生的超微结构

利用透射电镜研究滇蛙多盘吸虫的精子发生。它属于典型的寄生扁形动物Ｃｅｒｃｏｍｅｒｉｄｅａ类型。本吸虫的特点是精子形成的早期,两根鞭毛轴丝相互生趣成９０℃,中央间体由三根带条带组成,不等长,中央带长于侧带;线粒体在融合前未观察到围核现象。     

Sperm ultrastructure of Helicometra epinepheli (Platyhelminthes, Digenea, Opecoelidae), parasite of Epinephelus fasciatus (Pisces, Teleostei)

This paper describes the ultrastructure of the mature spermatozoon of the digenean Helicometra epinepheli. The ultrastructural elements observed are: two axonemes with a 9+"1" pattern of Trepaxonemata, four attachment zones, a nucleus, two mitochondria, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. A particularity of this spermatozoon is the presence of an apical cone. However, the spermatozoon presents the general pattern of the Opecoelidae and thus differs from Helicometra fasciata (which appears as an exception in this family) by several ultrastructural features: the presence of external ornamentation and spine-like bodies and the arrangement of cortical microtubules around the first mitochondrion in the region of the ornamentation. Each ultrastructural feature is discussed and compared with the literature to highlight characters which could be useful for phylogeny.     

The ultrastructural characters of the mature spermatozoon of Opechona bacillaris (Molin, 1859) (Digenea,Lepocreadiidae) a parasite of Scomber colias Gmelin, 1789 (Scombridae) off the coast of Dakar (Senegal)

This study presents the ultrastructure of the mature spermatozoon of Opechona bacillaris, a digenean belonging to the family Lepocreadiidae. The sperm cell of O. bacillaris exhibits the general pattern described in most of the Lepocreadioidea: two axonemes of the 9 + ‘1’ pattern of the Trepaxonemata, mitochondria, a cortical mitochondrion, a nucleus, electron‐dense material in the anterior extremity of the spermatozoon, external ornamentation of the plasma membrane with associated spinelike bodies, and granules of glycogen. However, particularities of O. bacillaris are the simultaneous presence in the anterior extremity of the spermatozoon of the electron‐dense material, a mitochondrion, and the absence of cortical microtubules. In the Lepocreadiidae, we describe for the first time in O. bacillaris spinelike bodies associated with the external ornamentation of the plasma membrane and two mitochondria. The first mitochondrion is moniliform and composed of a mitochondrial cord with joined mitochondrial bulges. The second mitochondrion shows a regular form. The posterior tip of the spermatozoon has only singlets to owing to the disorganization of the second axoneme and granules of glycogen as occurs in Hypocreadium caputvadum, the other studied species of the family Lepocreadiidae.     

Spermatozoa and spermiogenesis in XyIopIax (Class Concentricycloidea): a new type of spermatozoon in the Echinodermata

In Xylopax turnerae Rowe et al ., 1988 (Class Concentricycloidea, Subphylum Asterozoa) from the Caribbean spermiogenesis culminates in the formation of a complex spermatozoon unlike that of any other echinoderm. Mature testicular spermatozoa are composed of: (1) an elongate, tapered acrosome, segmented internally; (2) a nucleus, finely tapered anteriorly, extremely elongate and rod-shaped posteriorly; (3) a single flagellum attached via a centriolar rootlet to the anterior portion of the nucleus; (4) a single elongate mitochondrion located posterior to the nucleus. Spermatozoa deposited in the ovary have acrosomes which are distinctly granular internally: otherwise these cells resemble testicular spermatozoa. Spermiogenesis differs substantially from the pattern observed in other echinoderms, especially in relation to acrosome development. Examination of alcohol-fixed testes from the New Zealand species Xyloplax medusiforrnis confirmed the presence of filiform spermatozoa, but no details could be established. In contrast to Xyloplax , spermatozoa of Caymanostella sp. (Asteroidea) from a similar habitat to Xyloplax are not modified from those of externally fertilizing Asteroidea, Ophiuroidea, Crinoidea and Holothuroidea. Results lend further support to the existence of a separate class of extant echinoderms (Concentricycloidea) for Xyloplax spp.     

Phylogenetic relationships between the families Capsalidae and Dionchidae (Platyhelminthes, Monogenea, Monopisthocotylea) indicated by the comparative ultrastructural study of spermiogenesis

Comparative ultrastructural observations were carried out on the spermiogenesis of the capsalid Caballerocotyla manteri Price and the dionchid Dionchus remorae MacCallum. At the beginning of spermiogenesis the zones of differentiation (ZD) jut out in all directions. A large mitochondrion shaped like a perforated bead, and through which the elongated nucleus passes, is found facing each ZD. Later the ZD become parallel and are embedded within the common cytoplasmic mass. Cortical longitudinal microtubules are present in the ZD at the outset of spermiogenesis, but they later disappear. The spermatozoon is long and filiform. It shows two parallel axonemes of the 9 +"1" flatworm pattern, the nucleus and mitochondrion, and no cortical microtubule. The ultrastructure of spermiogenesis and spermatozoon is remarkably similar in the two species studied, as in other capsalids previously described. Two characteristics, the perforated bead shape of the spermatid mitochondrion and the progressive disappearance of the microtubules of the ZD, may be considered as synapomorphies which indicate close phylogenetic relationships between the families Dionchidae and Capsalidae. This interpretation coincides with Llewellyn's (1971) scheme of the evolution of the monogeneans.     

The ultrastructure of the spermatozoon of the hoplonemertine,Emplectonema neesii

Summary Mature spermatozoa of the hoplonemertine, Emplectonema neesii were studied by light and electron microscopy. The spermatozoa are flagellate and motile, each gamete consisting of an elongate anterior head and a posterior flagellar tail. Three regions are identifiable in the head, the acrosome, a nuclear zone and a connecting piece containing two centrioles. The nuclear zone contains glycogen granules as well as an elongate, grooved nucleus and a large mitochondrion whose lobes interdigitate with the nuclear grooves. The flagellum has a typical 9 + 2 flagellar tubule organisation. Nemertine spermatozoan ultrastructure, as exemplified by that of E. neesii, is compared with that of platyhelminth male gametes and the supposed phylogenetic affinity of the two taxeis reexamined in the light of the results of this comparison.My thanks are due to Miss A. Harding and Miss J. Webb for collecting sexually mature E. neesii, and to Dr. R. G. Crump for laboratory facilities at the Orielton Field Centre, Pembrokeshire, Wales. The work was carried out during the tenure of a research grant from The Nuffield Foundation.     

Electron microscope study of spermatogenesis in two cestodes acanthobothrium filicolle benedenii Loennberg, 1889 and Onchobothrium uncinatum (Rud., 1819) (Tetraphyllidea, Onchobothriidae) (author's transl)]

The spermatogenesis, spermatozoon differentiation and fine structure of Acanthobothrium filicolle benedenii Loennberg, 1889 and Onchobothrium uncinatum (Rud., 1819) were studied by means of light and electron microscopy. Spermatogenesis in both species is of the rosette type. During sperm differentiation, the five following stages have been distinguished: (1) formation of arching membranes and differentiation zone; (2) nuclear elongation; (3) formation of two flagella with a median cytoplasmic process; (4) flagellar rotation; (5) fusion of two flagella with the median cytoplasmic process induced by the migration of nucleus into the latter. The mature spermatozoa of both species are threadlike structures about 250 mum long. They consist of two axonemes of the platyhelminth type (9+1 pattern), elongated nucleus and cortical microtubules embedded in a cytoplasmic matrix containing numerus beta-glycogen particles. The body which appears on cross-sections as crest, lateral with respect to the axoneme, is present in both species. Such a body is reported for the first time in Cestode spermatozoa. There is no mitochondrion in the two Onchobothriidae sperms studied.     

Spermatozoa in triploids of the rosy bitterling Rhodeus ocellatus ocellatus

Artificially induced triploid male Rhodeus ocellatus ocellatus showed typical nuptial colorations, irrespective of spermiation. In milt from triploids, abnormal spermatozoa (malformation of the head and mitochondrion, excessive formation of the head, mitochondrion and flagellum, and no flagellum) occurred at 78°4% frequency. Spermatozoa with multiflagella were most common, often with a saccate-like organ. Many triploid spermatozoa moved actively as long as those of diploids (10·92±0·91 min=mean±S.D., P >0·05), but did not advance like diploids, spinning around until movement ceased. The sperm density in triploids was < 2% of that from diploids. In triploid testes, deformed and variously sized spermatids were often observed, and normal spermatids and spermatozoa were seldom recognized. The DNA content of triploid spermatozoa varied greatly, compared with that of diploids. Peak of sperm DNA content differed slightly between two triploid samples with two peaks at 1·5 n and 1·9 n ( P <0·0001 in both), respectively. Triploids had the greatest average sperm head diameter of 2·25±0·67 μm (mean±S.D.), while that of diploids was 1·83±0·15 μm ( P =0·002). In the fertilization test using the eggs of diploids ( n =1500, 30 trials), only one egg developed. The embryo chromosome number was 60 (2·5 n) and the ploidy of spermatozoa contributing to fertilization appears to be 1·5 n. The extremely low fertility of triploid R. o. ocellatus spermatozoa seems to be caused by the reduced motility and large head size of spermatozoa, and the low sperm density of the milt. The ploidy of spermatozoa that are successful in fertilization is likely to be related to the distribution pattern in the DNA content of cells.     

Dimorphism of Spermatozoa in the Sea Urchin Strongylocentrotus nudus

A phenomenon of dimorphism in spermatozoa has been revealed for the sea urchin Strongylocentrotus nudus. The spermatozoa are different in the configuration of the circular mitochondrion. The bulk of male gametes (73.4%) have a symmetrical mitochondrion, whereas the remainder spermatozoa (26.6%) have an asymmetrical one. No other ultrastructural differences in the structure of spermatozoa have been revealed. The two types of spermatozoa are supposed to represent different kinds of normal gametes capable of fertilization.