Spermatozoa from the supertribes Lasiopteridi and Stomatosematidi (Insecta, Diptera, Cecidomyiidae): ultrastructure data and phylogeny of the subfamily Cecidomyiinae

Spermatozoa from seven gall-midge species, representing the supertribes Lasiopteridi and Stomatosematidi, have been examined by electron microscopy and compared to the spermatozoa of 30 previously examined gall-midge species of the subfamily Cecidomyiinae. Derived characteristics of all examined representatives of this subfamily are the lack of acrosome and the absence of accessory tubules in their axoneme. The sperm axoneme of Didactylomyia has a unique '9 + 5 pattern', i.e. with 9 outer doublets and 5 inner singlet microtubules. Unlike other members of Cecidomyiinae, Didactylomyia has retained some plesiomorphic traits, namely crystal containing mitochondria and a homogeneously condensed nucleus. Stomatosema has a 10 + 0 axoneme and an irregular nuclear condensation. Thus, Didactylomyia may serve as an useful outgroup for phylogenetic analysis within the subfamily Cecidomyiinae. The supertribe Stomatosematidi is a paraphyletic assemblage. Nearly all members of Lasiopteridi, Ozirhincus, Arnoldiola, Brachineura and Ledomyia , have a synapomorphic character in the great number of microtubules in parallel to the axoneme. A notable exception is Rhizomyia , which shares certain apomorphic traits with several genera that have previously been classified within the Cecidomyiidi, i.e. Contarinia, Allocontarinia, Lestodiplosis and Myricomyia. Moreover, these genera have a flat sperm tail and microtubular doublets located close to the cell membrane, both characteristics that differ markedly from the very peculiar sperm tail found in other members of Cecidomyiidi.
Cladistic analysis of sperm characters suggests that the supertribe Cecidomyiidi is a polyphyletic taxon and supports the existence of a sister-group relationship between the supertribe Lasiopteridi and the genera Rhizomyia, Contarinia, Allocontarinia, Lestodiplosis and Myricomyia.     

Ultrastructure of sperm and spermatogenesis of Lobatostoma manteri (Trematoda, Aspidogastrea)

Mature sperm has two axonemes of the 9 + '1' pattern incorporated in the sperm body, a row of peripheral microtubules interrupted along part of the sperm by the axonemes, some microtubules in the interior of the sperm and a long lateral extension (lobe) of the sperm body, an elongate nucleus and mitochondrion, and many dense rod-like structures. A supporting rod extends underneath a specialized region consisting of alternating thin and thick transverse rows of irregular dense patches, and with surface ridges around (all or) most of the surface of the sperm. Primary spermatocytes in the prophase of the first meiotic division have synaptonemal complex(es), and are rich in mitochondria. In early spermiogenesis, mitochondria are arranged around the surface of the nucleus, a dense layer appears at one pole of the nucleus, close to an apposed dense layer at the cell membrane in which a row of microtubules develops. The intercentriolar (= central) body develops close to the nucleus. The fully developed intercentriolar body has a regular striation and is located perpendicular and close to the surface of the nucleus. Two flagella extend into the space surrounding the outgoing median process, their basal bodies are located perpendicular to the intercentriolar body and their cross-striated rootlets extend along the surface of the rounded nucleus. At a later stage, rootlets and flagella become more parallel with the intercentriolar body, the nucleus and the fused mitochondria migrate into the median process, and the flagella become incorporated into the median process (= sperm body). The outgrowing spermatozoa are connected to the cytoplasm of the cytophore by dense arching membranes. Finally, rootlets of flagella are resorbed and the spermatozoa are pinched off close to the basal bodies. Two species (Lobatostoma and Multicotyle) of the same family differ strongly in the type of spermiogenesis, although their mature sperm is of the same basic type, i.e. spermiogenesis is not necessarily more useful for phylogenetic considerations than sperm structure.     

Morphogenesis of the giant sperm axoneme in Asphondylia ruebsaameni Kertesz (Diptera, Cecidomyiidae)

The formation of the sperm giant axoneme of the gall-midge fly Asphondylia ruebsaameni is described here. The axoneme consists of a great number of microtubular doublets (up to 2,500) arranged in a double spiral wrapping around an axial cluster of mitochondria. Each microtubular doublet is provided with an outer arm only. In the early spermatid the occurrence of a large system of curved multi-layered filamentous material associated with membranous cisternae has been observed in the perinuclear region. Such a system extends throughout the cytoplasm to contact the plasma membrane. The filamentous material appears to act as a nucleating centre for the assembly of the microtubular doublets, which initially have a submembranous location and later are distributed in the interior of the cell. After their assembly, microtubular doublets are associated pairwise and are arranged in a single microtubular row with a zig-zag configuration. This configuration changes during spermiogenesis as a consequence both of a rotation of the microtubular doublet pairs and a compaction of the axonemal complex due to the elimination of the excess cytoplasm. As a result of this process, a double parallel spiral of microtubular doublets is formed.     

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。     

Two sperm types in the spermatozeugmata of Tubifex tubifex (annelida,oligochaeta)

The spermatozeugmata (sperm bundles lacking a distinct wall) from the spermathecae of Tubifex tubifex are composed of two different zones: an internal axial cylinder containing conventional spermatozoa and an external cortex composed of modified spermatozoa, tightly packed together. The conventional spermatozoa conform to the classical clitellate scheme: very long and thin with a complex acrosome, a filiform nucleus, small mitochondria, and a flagellum with Y links and β glycogen granules as accessory structures. The modified spermatozoa show “empty” acrosomes, degenerating nuclei, and tails which contain γ glycogen granules. The tails are helically wound around the spermatozeugma and are connected to each other by junctional complexes. The tips of the cortical tails are free and move with a metachronal wave. The presence of two sperm types in tubificids is discussed and a protective function for the modified cortical spermatozoa is proposed.     

Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy

Fürböck, S., Patzner, R.A. and Lahnsteiner, F. 2008. Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy. — Acta Zoologica (Stockholm) 91 : 88–95
The fine structure of spermatozoa of sneep or nase, Chondrostoma nasus , and lake chub, Rutilus meidingerii , was investigated by means of scanning and transmission electron microscopy. The uniflagellate spermatozoa of C. nasus lacked an acrosome. The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) and lacked lateral fins. The uniflagellate spermatozoa of R. meidingerii were made up of a head, also without an acrosome. For both species the sperm tail was covered by a plasma membrane. The midpiece of C. nasus contained five or six mitochondria on average, vesicles and glycogen granules, whereas the midpiece of R. meidingerii had seven mitochondria of a spherical or ovoid shape. The centriolar complex was located caudolaterally with respect to the nucleus. In C. nasus , the centrioles were orientated at an angle of 125° to each other, whereas the centrioles of R. meidingerii were at an angle of 110°. The fine structure of C. nasus and R. meidingerii spermatozoa showed species-specific differences in the position of the proximal centriole relative to the distal centriole, the position and number of mitochondria, size of the head and the length of the flagellum. (Correction added on 11 June 2009, after first online publication: The word 'axoneme' was deleted from the sentence 'The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) axoneme and lacked lateral fins.')     

Umsatz von Lymphozyten in Blut und Lymphknoten der Ratte

Summary Mature spermatozoa from the seminal vesicles of adult Agriolimax reticulatus have been studied by means of phase contrast and electron microscopy; sperm were either live, or sectioned or mounted whole and shadowed with gold. The cell is of the typical pulmonate sperm type with a simple acrosome and a spiral nucleus comprising the head, and a tail which is ensheathed along its entire length by mitochondrion. The 9 peripheral fibrils of the axial complex show no indication of a double nature. Within the spermatheca or gametolytic gland breakdown of sperm occurs; the nucleus and axial fibre bundle of the flagellum survive the longest. The complexity of the flagellum and the relative simplicity of the acrosome are discussed in light of the ecology of the spermatozoa. Many problems concerning the functional physiology of the sperm organelles remain to be investigated.     

Ultrastructural abnormalities of boar spermatozoa

Described here are the main ultrastructural malformations observed in spermatozoa of ejaculates collected from healthy, adult Landrace boars following 2 days of sexual abstinence. Previously semen had been collected 3 times per week. Sperm concentration in the cell-rich fraction of ejaculates was approximately 700,000 sperm/mm(3). The aberrant gamete forms did not exceed 2% of the total number of spermatozoa. Ultrastructural anomalies of spermatozoa were classified into 2 groups: head malformations and tail malformations. These consisted of: 1) spermatozoa with expanded and vacuolated acrosomes, 2) spermatozoa with myelin figures within the perinuclear space, 3) macrocephalic spermatozoa with 2 nuclei and a deformed acrosomal vesicle, 4) spermatozoa with an expanded acrosomal apex, 5) spermatozoa with nuclear vacuoles, 6) macrocephalic spermatozoa with a roundish head, 7) spermatozoa with swollen mitochondria, 8) spermatozoa with additional mitochondria over the mitochondrial sheath, 9) spermatozoa without the central microtubular pair, 10) spermatozoa without some peripheral doublets, 11) spermatozoa with 1 or 2 coiled tails, 12) spermatozoa with a folded tail and a disorganized connecting piece, 13) spermatozoa with a vesiculated tail, and 14) spermatozoa with 2 tails fused by their respective mitochondrial sheaths.     

Spermatozoa and sperm aggregates in the vestimentiferan Lamellibrachia luymesi compared with those of Riftia pachyptila (Polychaeta: Siboglinidae: Vestimentifera)

The spermatozoa and the sperm bundles of the vestimentiferans Riftia pachyptila and Lamellibrachia luymesi (Annelida: Siboglinidae) were studied using several microscopical techniques (transmission and scanning electron microscopy, and confocal microscopy) and compared with some other annelid sperm. The spermatozoa and sperm bundles of both species show a similar structure, but they differ in the dimensions of the components of individual cells and in the number of spermatozoa forming each sperm bundle. The spermatozoa of R. pachyptila and L. luymesi are filiform cells composed, in sequence, by an acrosome in the form of a thread-like helical vesicle, an elongated coiled nucleus surrounded by two helical mitochondria, and a long flagellum. In the spermatozoa of both species, the apical portion of the nucleus is completely devoid of chromatin and is delimited by a thickened nuclear envelope with a fibrillar appearance. Both species have sperm bundles that resemble buds, having a calyx-like portion formed by the helical heads, and a stalk-like portion formed by the tightly packed flagella. A parsimony analysis based on spermatozoal characters showed monophyly of the Siboglinidae and the Vestimentifera. We propose a new set of autapomorphies characterizing vestimentiferan spermatozoa. Our analysis suggests that spermatozoal characters are useful to the understanding of the phylogeny of the group.     

Living without mitochondria: spermatozoa and spermatogenesis in two species of Urodasys (Gastrotricha, Macrodasyida) from dysoxic sediments

Abstract. The spermatozoa of two species of Macrodasyida (Gastrotricha), Urodasys anorektoxys and U. acanthostylis , show an ultrastructural organization diverging from one another and from other gastrotrichs: their main peculiarity is in the absence of mitochondria. In U. anorektoxys , the acrosome is a long, twisted column inserted into the nucleus, which is basally cylindrical, and the flagellum shows rows of peculiar, large globules parallel to the axonemal doublets. In U. acanthostylis , the acrosome is completely cork-screwed and surrounds the nucleus, and the tail shows columnar accessory fibers. At present, the absence of mitochondria in the mature sperm, and the peculiar fingerprint aspect of condensed chromatin are the only traits shared by the two species. The features of the spermatozoa of these two species of Urodasys widen the range of different models of gastrotrich spermatozoa, and place the genus in a peculiar position, from the spermatological point of view, within the Macrodasyida. The loss of mitochondria in mature spermatozoa is possibly related to either the dysoxic habitat of the two species or a peculiar fertilization mechanism.     

ELECTRON MICROSCOPE STUDIES ON SPERM DIFFERENTIATION IN MARINE ANNELID WORMS. I. SPERM FORMATION IN IKEDOSOMA GOGOSHIMENSE

The ultrastructur of spermatozoa and the changes through which they are differentiated during sperm formation in an echiuroid were observed under the electron microscope. Many spermatids are connected to one central cytoplasmic mass and the sperm differentiation proceeds synchronously in one sperm-ball. Dense plate-like structures appear in the cytoplasm of early spermatids and disappear soon. In the process of nuclear condensation, many electron-dense aggregates appear in homogeneously textured chromonema and the aggregates are packed together to form a uniformly dense nucleus. Near the centriole at the opposite side from the central mass, the mitochondria fuse together to form one large middle-piece mitochondrion and the acrosomal vesicle is formed from the Golgi-complex. The differentiating acrosome in the late spermatid moves to the anterior tip of the head. In the completed acrosome, a flocculent substance accumulates in the conspicuously expanded invaginated pocket of the acrosomal vesicle and two kinds of material of different electron density fill the inside of the acrosomal vesicle. The spermatozoa remain connected to the central mass at the lateral side of the head until they become fully mature and are packed into the nephridia before spawning.     

The role of actin and myosin in ascidian sperm mitochondrial translocation

Fertilization-related sperm mitochondrial movement occurs at a rate comparable to other actin-myosin-driven movements and is inhibited by cytochalasin B and N-ethyl maleimide in Ascidia ceratodes sperm. F-actin was demonstrated in the tails and mitochondria using NBD-phallacidin fluorescence. Both actin and myosin were also detected on the mitochondrion and in the tail by indirect immunofluorescence. Western blot analysis verified the presence of these proteins. Boltenia villosa and Cnemidocarpa finmarkiensis also have mitochondrion and tail localized actin and myosin. In the tails of all 3 species the fluorescence takes the form of discrete spots 0.25-0.5 micron apart. Boltenia and Cnemidocarpa sperm have additional actin at the tip of the head and additional myosin at the base of the head. The presence of actin and myosin on the mitochondrion and in the tail supports a means by which the force for mitochondrial movement is generated.     

The Spermatozoon of Siboglinum (Pogonophora)

The spermatozoon and some spermatid stages of Siboglinum (Pogonophora) have been examined by light and electron microscopy. In the spermatozoon a helical acrosome, a helical nucleus and a “body” with axonema follow each other in normal sequence. Head and tail are joined by a very short neck region containing two modified centrioles. The posterior portion of the nucleus is surrounded by a mitochondrial sheath consisting of three tightly wound mitochondrial helices. In the main portion of the tail the 9+2 unit is sorrounded by a granular sheath of dense material. In the neck region a centriole adjunct develops into a dense substance containing about nine rods. At an early stage, when the centriolar apparatus and flagellum become associated with the nucleus, three large mitochondria with fairly regular cristae are seen at the base of the nucleus. A well developed Golgi apparatus is present in early stages. Rows of microtubules are observed encircling the spermatid nucleus. Compared with the primitive type of spermatozoon the pogonophore sperm shows elongated and specialized nucleus, acrosome and mitochondria. It is concluded that the ancestral form must have had a fairly primitive spermatozoon and that evolution has proceeded towards a modified sperm with complicated spiral structure in connection with the evolution of a modified biology of fertilization, viz. specialized spermatophores. It is not known how the spermatophore discharges the spermatozoa nor how the spermatozoa find their way to the eggs. Two kinds of sperms are produced in the gonads of Siboglinum. The atypical sperm is smaller than the typical one.     

Ultrastructure of spermatogenesis and spermatozoa of Cephalodasys maximus (Gastrotricha,Macrodasyida)

Summary Spermatogenesis and sperm ultrastructure of the macrodasyidan gastrotrich Cephalodasys maximus are described by means of transmission electron microscopy. The filiform sperm consists of an acrosomal accessory structure and an acrosomal vesicle, both being surrounded by spiralled material. The successive nuclear helix encloses the spiral-shaped mitochondrion and the axoneme of the flagellum is accompanied by dense strings, three helical elements and peripheral microtubules. During spermiogenesis the acrosomal accessory structure develops first and moves into a cell projection, where the spiral around this acrosomal rod forms. A nuclear section with condensed chromatin and one single fused large mitochondrion follow into the extension, becoming helical. A connecting clasp between nucleus and flagellum shortens to a cap-like structure. Parallel to the acrosomal and nuclear projection the flagellum develops where the spiralled elements and the basal plate form in succession, while the basal body shrinks.     

Ultrastructure of the sperm of blue sprat, Spratelloides gracilis; Teleostei, Clupeiformes, Clupeidae

The general sperm structure of the investigated clupeoids possess an oliviform head with a distinct deep nuclear fossa, a midpiece with one mitochondrion and a posterior flagellum. They are characterized by two apomorphies: an annular or C-shaped mitochondrion and ITDs (intratubular differentiation) in the A tubules of the axonemal doublets. The fine structure of the spermatozoa of blue sprat, Spratelloides gracilis, was investigated to see if resulting data conformed to the current hypotheses of the taxonomy of the Clupeidae. The mature sperm is characterized by the following features: (1) the nucleus is oliviform; its prominent deep nuclear fossa encloses the initial portion of flagellum, (2) a proximal centriole has not been identified, (3) a single spherical mitochondrion is located laterally in relation to the flagellum and (4) no cytoplasmic canal is present. Our blue sprat-spermatozoan morphology data suggest that the blue sprat has Clupeomorpha affinities, while indicating no close affinity with Elopomorpha. Clupeoid sperm exhibit morphological variations with the nucleus and mitochondrion being particularly variable. This study provides useful systematic characters to the existing knowledge of comparative spermatology and may provide additional clue to Euteleost phylogeny.     

The sperm structure of the gall-midges Anaretella and Lestremia (Insecta, Diptera, Cecidomyiidae)

The sperm structure of some dipteran flies belonging to the Lestremiini tribe have been examined. Anaretella cincta was shown to have an axoneme made of 20-21 microtubular doublets, disposed in a circle in a cross section and surrounding a mitochondrion. Other crystal-containing mitochondria flank the axoneme; a second species (Anaretella sp.) was provided with 21-22 axonemal doublets. Lestremia is characterized by a flattened axoneme, consisting of about 150 doublets arranged in 2 antiparallel rows and surrounding a few mitochondria. These mitochondria, in Lestremia sp., have a crystalline core that is missing in Lestremia cinerea. The structure of microtubular doublets is quite similar in the 2 related genera and a derivation of the flattened axoneme found in Lestremia from that circular of Anaretella is suggested. Sperm structure suggests that Lestremia cinerea is not a uniform species.     

Ultrastructural Observations on the Spermatozoa of Two Temnocephalids (Platyhelminthes)

The spermatozoa of two Temnocephalidae collected in Uruguay, Temnocephala iheringi Haswell, 1893 (Host: Pomacea canaliculata) and Temnocephala axenos Monticelli, 1899 (Host: Parastacus varicosus), were studied with a transmission electron microscope. In both species the spermatozoon is made up of a long sperm body which bears at one extremity two free flagella of the 9+‘1’ flatworm pattern. The sperm body contains the nucleus, mitochondria, dense bodies and parallel, cortical, longitudinal singlet microtubules. Along a part of the sperm body the palissade of the microtubules displays a spiral pattern in transverse sections. A part of the perimeter of the cell is thus lined by two overlapping rows of microtubules. This spiral pattern of the singlets is considered as a synapomorphy of the family Temnocephalidae. The singlet microtubules are interconnected by two kinds of links: tangential links between neighbouring singlets in the same row and radial links between singlets belonging to two rows. The presence of these links suggests that this structure could be a motile system of singlets.     

Cauda epididymal spermatozoa of the rufous hare wallaby, Lagorchestes hirsutus (Metatheria, Mammalia) imaged by electron and confocal microscopy

The ultrastructure of mature Lagorchestes hirsutus spermatozoa is described for the first time, revealing unusual aspects of sperm structure in macropodid species. The sperm head is ovoid rather than cuneiform, lacks a ventral nuclear groove and has an acrosomal distribution over approximately 85–90% of its dorsal surface. Immediately adjacent to the nuclear membrane the peripheral nucleoplasm in most spermatozoa form an irregular series of distinctive evaginations previously not described in the spermatozoa of any other marsupial. The midpiece is extremely thickened and short, containing no helical network or peripheral plasma membrane specializations. Axonemal structure is unspecialized with no connecting lamellae; dense outer fibres are closely adherent to axonemal doublets. The sperm morphology of this species is highly aberrant in comparison to other macropod taxa and supports the retention of Lagorchestes as a distinctive genus. In light of this new information, skeletal and serological data should be re‐evaluated to determine the true taxonomic and phylogenetic position of this species.     

Ultrastructure of spermatids and spermatozoa in the cyclostomatous bryozoan Tubulipora (Bryozoa,Cyclostomata)

Summary Differentiation of spermatids to mature spermatozoa in the bryozoan Tubulipora liliacea was studied by transmission electron microscopy. The spermatozoon of Tubulipora is of a filiform, modified type, and has evolved from the primitive type as an adaptation to a specialized biology of fertilization. The head of the spermatozoon consists of a small, conical acrosome capping an elongated, cylindrical, anteriorly tapering nucleus. A basal invagination in the nucleus contains the proximal portion of the axoneme and a dense attachment matrix. The flagellar axoneme has the typical 9+2 structure. Four elongated rodshaped mitochondria with typical cristae surround the axoneme in the cylindrical middle piece. Granular electron-dense material is accumulated in the form of four columns alternating with four long cylindrical mitochondria. The mitochondrial middle piece is separated externally from the tail region by an involution of the plasma membrane. The tail region contains a cytoplasmic sheath with accessory fibers surrounding the axoneme. Nine outer, coarse fibers extend posteriorly paralleling the nine doublets of the axoneme. The coarse fibers develop from electron-dense plate-like structures associated with the doublets of the axoneme. A characteristic feature in spermiogenesis is that spermatozoa develop in tetrads. There seem to be significant differences in spermatozoan ultrastructure between the three bryozoan classes Stenolaemata, Gymnolaemata, and Phylactolaemata. The differences indicate different lines of evolution of fertilization biology in these groups.Abbreviations used in the figures a acrosome - av acrosomal vesicles - ax axoneme - c coarse fiber - d electron dense rod - m mitochondrion - mp middle piece - Scale bars=0.5 m - mt microtubule - n nucleus - ne nuclear envelope - p nuclear protrusion - pm plasma membrane - t tail     

Characteristics of the sperm tail of the velvet worm, Euperipatoides leuckarti (Onychophora)

The onychophoran sperm tail contains several kinds of microtubulcs; probably more than that of any other animal group. There are thus a peripheral manchette consisting of many tightly spaced microtubules, a ring of nine 'peripheral singlets' and a central axoneme of the classical 9 + 2 type (nine doublets and two central singlets). The protofilament organization of these various microtubules was examined and compared to the structure and mode of formation of the peripheral singlets with that of its analogues in other animal groups. The onychophoran peripheral singlets were found to differ in two respects from those in insects: they are formed from the manchette rather than from the axonemal doublets and their transient connection to the axoneme is to the A-subtubules of the doublet rather than to the B-subtubules. The manchette microtubules as well as the peripheral singlets consist of 13 protoh'laments. The manchette may serve a mechanical function (to strengthen the unusually thick sperm tail) hut the role of the peripheral singlets remains unknown.