Polymorphism of spermatozoa in Largus rufipennis Laporte 1832 (Heteroptera: Pyrrhocoroidea: Largidae)

The production of polymorphic spermatozoa has been registered in various insect orders such as Diptera, Lepidoptera, and Hemiptera. In this work, morphology of two types of spermatozoa produced by Largus rufipennis was reported for the first time in the Largidae family. For this, techniques including optical and transmission electron microscopy were used. Spermatozoa measured, on the average, 260 and 200 μm, and both types possessed a nucleus measuring on the average 65 μm. No ultrastructural differences were observed between the two spermatozoa types from L. rufipennis. The head region is composed of an acrosome, a nucleus, and part of the centriolar adjunct. The centriolar adjunct is in parallel with the nucleus and followed by mitochondrial derivates. The flagellum consists of an axoneme (9 + 9 + 2 microtubules) and two mitochondrial derivatives; no other accessory bodies were observed. The mitochondrial derivatives are symmetric in size and diameter. A similar quantity of the two spermatozoa types was observed in the seminal vesicle (57% of the large type and 43% of the small type), while in the spermatheca of the female, the larger spermatozoa were preferentially stored (87%). These results permit discussions concerning of the species biology reproduction, most specifically sperm competition strategies.     

Sperm ultrastructure of the honey bee (Apis mellifera) (L) (Hymenoptera, Apidae) with emphasis on the nucleus-flagellum transition region

The flagellum of Apis mellifera (Hymenoptera, Apidae) consists of two mitochondrial derivatives, an axoneme and two accessory bodies. The mitochondrial derivatives are of unequal size and lie parallel to the axoneme. In the larger derivative four regions can be distinguished while in the smaller, only three. The region occurring only in the larger derivative consists of paracystalline material. The smaller mitochondrial derivative terminates anterior to the larger one. An extremely long centriolar adjunct is observed between the nucleus and the smaller mitochondrial derivative. This adjunct is compact, very electron dense and gradually tapers from base toward apex, finishing at the anterior extremity of the axonemal microtubules. In this flagellar region, there is only one accessory body present between the larger mitochondrial derivative and the axoneme. Anteriorly, the tips of the axonemal microtubules are inserted in a well developed mass of granular appearance. This material surrounds the nuclear base, separating it from the anterior end of the larger mitochondrial derivative. We believe that the structure identified here as a centriolar adjunct is homologous to that observed in Formicidae, Ichneumonoidea and Symphyta. Therefore, very probably, it is common to most Hymenoptera.     

Ultrastructural characterization of spermatozoa in euglossine bees (Hymenoptera, Apidae, Apinae)

Summary. Euglossine spermatozoa are the longest described to date for the Hymenoptera. This cell includes a head and a flagellar region. In transverse sections, the acrosome is circular at the tip but has an oval contour along most of its length. The perforatorium penetrates into a deep cavity in the nuclear tip. The flagellum consists in an axoneme, a pair of mitochondrial derivatives, a centriolar adjunct and a pair of accessory bodies. The axoneme has a 9+9+2 microtubule pattern which becomes gradually disorganized in the final portion, with the central microtubules and the nine doublets terminating simultaneously, followed by the accessory microtubules. The mitochondrial derivatives are asymmetric both in length and diameter. Sectioned transversally, the derivatives are ellipsoidal or have a pear shape. The larger one has a more obvious paracrystalline region. The centriolar adjunct begins at the nuclear base and extends parallel to the axoneme until it encounters the smaller mitochondrial derivative, on which it fits, making a concave groove. In addition to these consistent euglossine features, species-specific differences that might be useful in phylogenetic work on the group are also noted.Received 18 October 2003; revised 4 September 2004; accepted 4 October 2004.     

Ultrastructure of the Spermatozoon of an Opisthobranch, Tornatina sp. (Mollusca, Gastropoda, Retusidae)

The spermatozoon of Tornatina sp. has been studied with phase-contrast light microscopy and transmission electron microscopy. The head of the spermatozoon consists of an elongate acrosome which caps the apex of an unusually complex, helical nucleus. This elaborate nuclear morphology has not been previously reported, but possibly is found in other opisthobranch gastropod spermatozoa. An axoneme is inserted deeply into the base of the nucleus whilst posterior from the nucleus, the axoneme is ensheathed successively by the mitochondrial derivative (midpiece) and 'glycogen' granules (glycogen piece). The midpiece exhibits fine structure similar to that observed in other euthyneuran spermatozoa (paracrystalline and matrix materials) and possesses a single helical compartment filled with what are probably glycogen granules. A dense ring structure occurs at the junction of the midpiece and glycogen piece. The spermatozoon of Tornatina and other gastropods (prosobranch and euthyneuran) are compared.     

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.     

Structure and ultrastructure of spermatozoa and spermiogenesis in three species of Lucilia Robineau‐desvoidy, 1830 (Diptera: Calliphoridae)

Morphology of male internal reproductive organs, spermatozoa, and spermiogenesis of the blow‐flies Lucilia cuprina, Lucilia eximia, and Lucilia peruviana is first described here, using light and transmission electron microscopy. Spermiogenesis follows the characteristics described for others insect species. The spermatozoa of L. cuprina are similar to those described for other Brachycera. However, in L. eximia and L. peruviana, some differences were found. In L. cuprina and L. eximia species, the spermatozoa are long and thin, measuring about 211 μm and 146 μm in length, of which the head region measures approximately 19 μm and 17 μm, respectively. A polymorphism was observed in L. cuprina and L. eximia spermatozoa. In all three species, the head includes a monolayered acrosome with electron‐lucent material. The shape of the nucleus, in cross sections, varies from circular to oval with completely condensed chromatin. Implantation of the axoneme was observed in the middle region of the nucleus, known as the “peg” region. In the next region, the beginning of two mitochondrial derivatives of similar diameter and different lengths in L. cuprina and only one in L. eximia and L. peruviana was observed. In the overlap region, the following structures were observed: nucleus, centriolar adjunct, mitochondrial derivatives, and axoneme. The axoneme is of a conventional insectan type with a 9 + 9 + 2 microtubular arrangement. The male internal reproductive tract consists of testis, deferent ducts, a strongly developed seminal vesicle, accessory glands, and ejaculatory duct. These features are consistent with the structural diversity of the dipteran reproductive tract and spermatozoa, comprising an essential tool for understanding the complex variations found in the Diptera. J. Morphol. 2011. © 2011 Wiley Periodicals, Inc.     

The short spermatodesm of Arge pagana (Hymenoptera: symphyta)

In the seminal vesicle of the 'symphyta'Arge pagana the spermatozoa are stored in motile spermatodesm bundles, maintained by an anterior cap of extracellular material. This cap consists of a denser cortex and of an internal matrix, where part of the sperm heads are embedded. The number of spermatozoa per bundle is variable. The spermatozoa are short, only 30microm long, with a head region of about 23microm, and a very short flagellum of about 7microm. The head includes the acrosome, with a perforatorium, and the nucleus. The flagellum consists of an axoneme, with a 9+9+2 microtubule pattern, a centriolar adjunct, two mitochondrial derivatives and two accessory bodies. The mitochondrial derivatives are very slender and of different lengths. The longer begins at the base of the nucleus, while the shorter one starts just below the base of the centriolar adjunct. This latter is asymmetric and appears at the nuclear base, extending parallel to the axoneme up to the anterior end of the smaller mitochondrial derivative. The short spermatodesmata and the small mitochondrial derivatives characterize the A. pagana sperm. In addition, the centriolar adjunct asymmetry and the occurrence of spermatodesm bundles might be considered plesiomorphic states present in the basal Tenthredinoidea.     

Ultrastructure des spermatozoides des males haploides et diploides de Diadromus pulchellus wesmeal (Hymenoptera : Ichneumonidae)

The mature spermatozoa were described in the haploïd and diploïd males of Diadromus pulchellus Wesmeal (Hymenoptera : Ichneumonidae). Diploïd males produce spermatozoa, which do not seem to be different from those produced by haploïd males. The spermatozoon is about 100 μm long, and consists of a head, 0.8 μm in diameter, and a tail 0.3 μm in diameter. Its anterior part shows an acrosomal complex, including a perforatorium and a compact and electron-dense fusiform nucleus. The postnuclear region includes a longitudinal axoneme with 2 mitochondrial derivatives. The axoneme shows 2 typical central units, 9 peripheral doublet microtubules, 9 accessory internal tubules, and 9 external microtubules with dense contents. In the testes of diploïd males, a great number of abnormal spermatozoa were observed. These spermatozoa with degenerative structures are probably not implicated in egg fertilization.     

Sperm structure and spermiogenesis in Atelura formicaria Heyden (Zygentoma, Insecta)

The spermatozoon of Atelura formicaria (Zygentoma) shows several features that are typical of insects: an apical acrosome, an elongated dense nucleus, a centriole with expanded centriolar adjunct material, two large mitochondrial derivatives, and two thin accessory bodies located beneath the nucleus. The axoneme exhibits a 9 + 9 + 2 pattern with accessory tubules formed by 16 protofilaments and intertubular material. However, spermatozoa of A. formicaria show some remarkable features. The sperm cell is short for an insect, being only 50 µm in length. The nucleus is characterized by the presence of two lateral grooves which are filled with numerous infoldings of the nuclear envelope. In a cross-section the chromatin has the configuration of the Leonardo da Vinci's 'Vitruvian man'. Each mitochondrial derivative has a peculiar structure with peripheral cristae and four crystalline bodies in its matrix; two of these crystalline bodies are large and have differently orientated cristal planes. At the end of spermiogenesis, sperm bundles are stored in the proximal part of the testes. Secretions from the epithelial wall of this region give rise to large globular structures. These include sperm bundles intermingled with dense granules, forming the so called 'spermatolophids'. These formations descend along the deferent duct and are stored in the expanded seminal vesicle. Atelura spermatozoa do not pair as in some Lepismatidae, nor do they fuse as in Tricholepidion (Lepidotrichidae). Thus, sperm aggregation in Zygentoma is realized according to different modalities and can hardly be considered as a synapomorphic trait of its subtaxa.     

Morphology of the male reproductive system and sperm ultrastructure of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

The male reproductive tract of Leucoptera coffeella was processed for light and transmission electron microscopy. In the testis, the eupyrene cells are arranged in individual cysts, while the apyrene cysts form aggregates, never observed in other Lepidoptera. Both cysts contain 128 spermatozoa, which differ from the typical pattern. In the seminal vesicle, both types of spermatozoa are dispersed in the lumen, also different from other Lepidoptera. The apyrene spermatozoa are similar to those observed for other Lepidoptera. They present an anterior region covered by a dense cap and the flagellum is composed of a 9 + 9 + 2 axoneme and two mitochondrial derivatives. The eupyrene spermatozoa, however, differ from the typical pattern for Lepidoptera. Their anterior region contains a nucleus, an acrosome and a peculiar arc of eight accessory microtubules connected to the plasma membrane by dense bridges. In the nucleus–flagellum region, the ninth accessory microtubule is assembled between both mitochondrial derivatives, to participate in the axoneme. The flagellum comprises a 9 + 9 + 2 axoneme and two mitochondrial derivatives with paracrystalline cores. External to the plasma membrane and close to the accessory microtubules, there are tufts of an amorphous material, suggesting reduced lacinate appendages, while the reticular ones are absent. The reduction of lacinate appendages and the absence of sperm bundles in the seminal vesicle support the concept that the appendages of other Lepidoptera could be associated with the eupyrene aggregations. The characters ‘number of spermatozoa per cyst’ and ‘absence of bundles’ should be considered plesiomorphic, supporting the position of this taxon in the base of the Ditrysia.     

Structure and ultrastructure of the spermatozoa of Bephratelloides pomorum (Fabricius) (Hymenoptera: Eurytomidae)

The spermatozoa of Bephratelloides pomorum are very long and fine. Each spermatozoon measures about 620 μm in length by 0.38 μm in diameter and, when seen under the light microscope, appears to be wavy along its entire length. The head, which is approximately 105 μm, comprises a small acrosome and a nucleus. The acrosome is made up of a cone-shaped acrosomal vesicle surrounding the perforatorium and the anterior end of the nucleus. Innumerable filaments radiate from it. The perforatorium has a diameter equal to that of the nucleus at their junction, where it fits with a concave base onto the rounded nuclear tip. The nucleus is helicoidal and completely filled with homogeneous compact chromatin. It is attached to the tail by a very long and quite electron-dense centriolar adjunct that extends anteriorly from the centriole in a spiral around the nucleus for approximately 8.5 μm. The tail consists of an axoneme with the 9+9+2 microtubule arrangement pitched in a long helix, as well as a pair of spiraling mitochondrial derivatives (with regularly arranged cristae) that coil around the axoneme, and two small accessory bodies. As well as the spiraling of the nucleus, mitochondrial derivatives and axonemal microtubules, the sperm of B. pomorum present other very different morphological features. These features include the acrosome and centriolar adjunct, both of which differentiate the spermatozoa from the majority of sperm found in other Hymenoptera. In addition these structural variations demonstrate that the sperm of chalcidoids provide characteristics that can certainly prove useful for future phylogenetic analysis at the subfamily level and, possibly, the genus too.     

瘤背石磺的精子结构

用光学显微镜和透射电子显微镜技术研究了瘤背石磺精子的结构特点,分析了其生理生态适应性以及在肺螺亚纲系统演化中的意义。瘤背石磺的精子由头部、中段和末段组成。头部由奶嘴形的顶体和长圆筒状的细胞核构成。顶体包括顶体囊和顶体构架体两部分;两者的内含物都分布均匀,电子密度稍低于细胞核;顶体基部平整,与核前端之间有一空隙,内含物电子密度极低。细胞核由电子密度高的均匀颗粒物质组成,并出现核泡;核的后端有一"杯形"的凹陷,称为核后窝。中段结构复杂,主要包括一对位于核后窝内的中心粒、轴丝、质膜、线粒体及由线粒体衍生的糖原质螺旋体、基质层和类晶体层等。末段由"9 2"结构的轴丝及外包的质膜组成,无糖原质螺旋体和其它线粒体衍生物。比较瘤背石磺精子与肺螺亚纲其它物种的精子结构,我们认为该物种的精子属于"进化型",是一类在进化地位中比基眼目高等的动物。     

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.     

Structure and energy pathways of spermatozoa of the rove beetle Aleochara bilineata (Coleoptera, Staphylinidae)

The morphology of mature spermatozoa of the rove beetle Aleochara bilineata was examined by using scanning and transmission electron microscopy. They are about 1000 mum long and filiform. The acrosome and the nucleus are elongate and each about 20 mum long. A well-developed centriole adjunct region connects the nucleus with the sperm tail. The axoneme reveals the 9 + 9 + 2 pattern of the pterygote sperm flagellum. Two accessory bodies and two mitochondrial derivatives with paracrystalline inclusions are present. Cristae are reduced to the cortical zone of the derivatives. Cytochrome-c oxidase activity was detected within the cristae by DAB-reaction. The energy metabolism of the spermatozoa was investigated by using different inhibitors affecting the mitochondrial and cytoplasmic metabolic pathways. Sperm movement was used as an indicator for the utilization of ATP by the axoneme. In control experiments, the duration of motility was longer than 45 min. In the presence of atractyloside or potassium cyanide the motility duration was not affected. On the other hand, iodoacetic acid in the medium stopped sperm motility within 15 min. This indicates that sperm energy metabolism mainly depends on the glycolytic pathway.     

The ultrastructure of spermatozoa and spermiogenesis in pyramidellid gastropods,and its systematic importance

Ultrastructural observations on spermiogenesis and spermatozoa of selected pyramidellid gastropods (species ofTurbonilla, Pyrgulina, Cingulina andHinemoa) are presented. During spermatid developement, the condensing nucleus becomes initially anterio-posteriorly compressed or sometimes cup-shaped. Concurrently, the acrosomal complex attaches to an electrondense layer at the presumptive anterior pole of the nucleus, while at the opposite (posterior) pole of the nucleus a shallow invagination is formed to accommodate the centriolar derivative. Midpiece formation begins soon after these events have taken place, and involves the following processes: (1) the wrapping of individual mitochondria around the axoneme/coarse fibre complex; (2) later internal metamorphosis resulting in replacement of cristae by paracrystalline layers which envelope the matrix material; and (3) formation of a glycogen-filled helix within the mitochondrial derivative (via a secondary wrapping of mitochondria). Advanced stages of nuclear condensation (elongation, transformation of fibres into lamellae, subsequent compaction) and midpiece formation proceed within a microtubular sheath (‘manchette’). Pyramidellid spermatozoa consist of an acrosomal complex (round to ovoid apical vesicle; column-shaped acrosomal pedestal), helically-keeled nucleus (short, 7–10 μm long, shallow basal invagination for axoneme/coarse fibre attachment), elongate helical midpiece (composed of axoneme, coarse fibres, paracrystalline and matrix materials, glycogen-filled helix), glycogen piece (length variable, preceeded by a dense ring structure at junction with midpiece). The features of developing and mature spermatozoa observed in the Pyramidellidae are as observed in opisthobranch and pulmonate gastropods indicating that the Pyramidelloidea should be placed within the Euthyneura/Heterobranchia, most appropriately as a member group of the Opisthobranchia.