Ultrastructural studies on euspermatozoa and paraspermatozoa in Mantispidae (Insecta, Neuroptera)

Previous studies have demonstrated the presence of sperm dimorphism in the Mantispidae Perlamantispa perla. We extended the study on several other mantidflies. In all the examined species the occurrence of euspermatozoa (typical) and paraspermatozoa (atypical) was established. The euspermatozoa are characterized by the presence of a cylindrical nucleus surrounded by an envelope that fans out laterally into two thin wings of different length. The acrosome seems to be missing. The nucleus is surrounded by extracellular material. The flagellum is provided with a 9 + 9 + 2 axonemal pattern; the accessory tubules contain 16 protofilaments and the intertubular material has the distribution typical of the taxon. Two elongated accessory bodies flank partially the axoneme and connect this structure with the mitochondrial derivatives. The flagellar axoneme of paraspermatozoa consists of an axoneme and two giant mitochondrial derivatives filled with large globular units. The axoneme exhibits a 9 + 9 + 2 pattern, in which the central 9 + 2 units have a normal structure, in that the microtubular doublets are provided with both dynein arms and radial links. On the contrary, the nine accessory microtubules have a large diameter and their tubular wall consists of 40 protofilaments. This comparative study provided evidences about the uniformity of sperm ultrastructure in Mantispidae. The function of non-fertilizing giant sperm in mantidflies is discussed.     

Sperm ultrastructure and spermiogenesis of Coniopterygidae (Neuroptera, Insecta)

The spermiogenesis and the sperm ultrastructure of several species of Coniopterygidae have been examined. The spermatozoa consist of a three-layered acrosome, an elongated elliptical nucleus, a long flagellum provided with a 9+9+3 axoneme and two mitochondrial derivatives. No accessory bodies were observed. The axoneme exhibits accessory microtubules provided with 13, rather than 16, protofilaments in their tubular wall; the intertubular material is reduced and distributed differently from that observed in other Neuropterida. Sperm axoneme organization supports the isolated position of the family previously proposed on the basis of morphological data.     

The sperm structure of Cryptocercus punctulatus Scudder (Blattodea) and sperm evolution in Dictyoptera

Sperm of the dictyopteran key taxon Cryptocercus punctulatus was examined. It has largely maintained a blattodean groundplan condition, with a three‐layered acrosome, an elongate nucleus, a single centriole, a conspicuous centriole adjunct material, two connecting bands (=accessory bodies), and a long functional flagellum with a 9+9+2 axoneme provided with accessory tubules with 16 protofilaments and intertubular material. These sperm characters are shared with several other polyneopterans. The sperm of C. punctulatus is very similar to what is found in Periplaneta americana and species of other groups of roaches, including the sperm of Loboptera decipiens described here for the first time. The general sperm organization here described can be assumed for the groundplan of Insecta and Pterygota. The following evolutionary path can be suggested: after the split between Cryptocercidae and the common ancestor of Isoptera, the typical pattern of sperm formation was altered very distinctly, resulting in a duplication or multiplication (Mastotermitidae) of the centrioles. Mastotermes has maintained a certain sperm motility, but with a very unusual apparatus of multiple flagella with a 9+0 axoneme pattern. After the split into Mastotermitidae and the remaining Isoptera, sperm motility was completely abandoned, and different modifications of sperm components occurred, and even the loss of the sperm flagellum. J. Morphol. 276:361–369, 2015. © 2014 Wiley Periodicals, Inc.     

Sperm structure of Mecoptera and Siphonaptera (Insecta) and the phylogenetic position of<Emphasis Type="Italic"> Boreus hyemalis</Emphasis>

Sperm ultrastructure has been studied in three species of the taxa Mecoptera and Siphonaptera. The spermatozoon of the scorpion fly Panorpa germanica shows an apical bilayered acrosome, a helicoidal nucleus, a centriolar region and a 9+2 flagellar axoneme helicoidally arranged around a long mitochondrial derivative. A second mitochondrial derivative is very short and present only in the centriolar region. A single accessory body is present and it is clearly formed as a prolongation of the centriole adjunct material. Two lateral lamellae run parallel to the nucleus. The snow fly Boreus hyemalis has a conventional sperm structure and shows a bilayered acrosome, a long nucleus, a centriolar region, two mitochondrial derivatives and two accessory bodies. The axoneme is of the 9+2 type and is flattened at the tail tip. Both P. germanica and B. hyemalis have two longitudinal extra-axonemal rods and have a glycocalyx consisting of longitudinal parallel ridges or filaments. The spermatozoon of the flea Ctenocephalides canis has a long apical bilayered acrosome, a nucleus, a centriolar region, a 9+2 axoneme wound around two unequally sized mitochondrial derivatives, and two triangular accessory bodies. In the posterior tail end the flagellar axoneme disorganises and a few microtubular doublets run helicoidally around the remnant mitochondrial derivative. The glycocalyx consists of fine transverse striations. In all three species, the posterior tail tip is characterised by a dense matrix embedding the disorganised axoneme. From this comparative analysis of the sperm structure it is concluded that Mecoptera, as traditionally defined, is monophyletic and that B. hyemalis is a member of Mecoptera rather than of Siphonaptera.     

Sperm structure of Limoniidae and their phylogenetic relationship with Tipulidae (Diptera, Nematocera)

The sperm ultrastructure of a few species of Limoniidae (Limonia nigropunctata; L. nubeculosa; Chionea n. sp.; C. alpina; C. lutescens) was studied. The two species of Limonia have a monolayered acrosome with crystallized material, a three-lobed nucleus in cross section, a ring of centriole adjunct material and a flagellum which consists of a 9+9+1 axoneme and a single mitochondrial derivative. The central axonemal tubule is provided with 15 protofilaments in its tubular wall, while the accessory tubules have 13 protofilaments and are flanked by the electron-dense intertubular material. The three species of Chionea share a monolayered acrosome, a nucleus with two longitudinal grooves, a centriole adjunct material which surrounds the centriole and the initial part of the axoneme. The axoneme is of conventional type, with 9+9+2 microtubular pattern, with accessory tubules provided with 13 protofilaments and intertubular material. However, in C. lutescens the accessory tubules start with 15 protofilaments and transform into a tubule with 13 protofilaments. These data are discussed in the light of the phylogenetic relationship between Limoniidae and Tipulidae. For this purpose, the sperm ultrastructure of Nephrotoma appendiculata was also considered comparatively.     

New findings on sperm ultrastructure of Xenos vesparum (Rossi) (Strepsiptera,Insecta)

The systematic position of insect order Strepsiptera is still under debate. It was, therefore, thought of interest to examine the ultrastructure of a strepsipteran in a search for synapomorphies shared with Coleoptera, Diptera, or any other insect order. The fine structure of spermatozoa and the spermatid from Xenos vesparum (Rossi) was re-examined using scanning and transmission electron microscopy and a fixation technique that permits the visualization of the macromolecular organization of the organelles. The spermatozoon was shown to possess several traits that are characteristics of insects in general, such as a 9 + 9 + 2 axoneme, two mitochondrial derivatives containing a crystalline material and two 'zipper lines' present along the sperm tail. Seventeen protofilaments occurred along most of the accessory tubules, which reduced to 16 posteriorly. An acrosome is absent. The neck region contains a prominent centriolar adjunct, which gives rise to two accessory bodies which adhere to the mitochondrial derivatives, and to slender strands of the so-called intertubular material found between the accessory tubules. Of interest is the finding that the glycocalyx consists of prominent filamentous strands, similar to those found in siphonapterans, mecopterans and basal dipterans.     

日本纺织娘的精子超微结构（直翅目：螽斯总科，纺织娘科）

对日本纺织娘Mecopoda nipponensis的精子超微结构进行了透射电镜观察。结果表明：其顶体复合体侧生于细胞核上且包裹了核顶端的部分;细胞核致密,横切面多为新月形或半月形;2蚕豆形副体位于9+9+2轴丝的两侧;线粒体衍生体横切面为椭圆形,其基质几乎完全晶状化;线粒体衍生体一侧的2扁平膜池横切面近S形;轴丝与线粒体衍生体之间有3条连接带,其中中央的一条呈环状;在有些尾部横切面中,质膜之内又有一双层膜把尾部的细胞器围绕起来。     

The sperm structure of <Emphasis Type="Italic">Galloisiana yuasai</Emphasis> (Insecta,Grylloblattodea) and implications for the phylogenetic position of Grylloblattodea

The sperm ultrastructure of the Grylloblattodea Galloisiana yuasai was described and the sperm characters were comparatively examined in several orthopteroid insect orders for inferring the phylogenetic placement of the Grylloblattodea. The spermatozoa of G. yuasai are joined in bundles (spermatodesms) containing 200 units. Major features of these spermatozoa include a monolayered acrosome, a 9+9+2 axoneme with 16-pfs accessory microtubules and expanded intertubular material, and an evident “centriole adjunct”. The diffused material observed between the axoneme and the mitochondrial derivatives is considered to be an extension of the three connecting bands observed in other orthopteroid taxa, similar to what happens in some orthopteran lineages. The presence of the connecting bands, even though modified in G. yuasai, suggests that the Grylloblattodea are to be placed in a clade with Mantophasmatodea, Mantodea and Orthoptera.     

Sperm structure and spermiogenesis in Coletinia sp. (Nicoletiidae, Zygentoma, Insecta) with a comparative analysis of sperm structure in Zygentoma

The spermatozoon of Coletinia sp. has a bilayered acrosome, a short nucleus (4 microm) and a relatively short sperm tail with two mitochondrial derivatives. The chromatin is uniformly dense except for several electron-lucid channels or strands which permeate the nucleus and which originate in the spermatid as invaginations of the nuclear envelope. The invaginations occur mostly or exclusively along two meridians of the spermatid that are also characterized by the presence of a longitudinal rod of medium electron density. The two rods (designated as 'mid-spermatid rods') evidently are instrumental in the formation of the electron-lucid channels. The significance of this elaborate system of intranuclear channels is not understood. The sperm tail has a 9 + 9 + 2 axoneme with each of the nine microtubular doublets accompanied by an accessory microtubule; scant intertubular material can also be distinguished. Hence, the tail axoneme resembles that of many pterygote insects. Each of the two mitochondrial derivatives contains a crystalline inclusion that has periodically spaced layers going in different directions on either side of the midline. Two synapomorphic traits appear to be shared by Ateluridae and Nicoletiidae, namely the invaginations of the nuclear membrane along two meridians of the nucleus and the shape of the crystalline inclusions of the mitochondrial derivatives. Four species from the family Lepismatidae were also examined as to their sperm ultrastructure. Three of them, Allacrotelsa kraepelini, Ctenolepisma longicaudata and Ctenolepisma sp., were found to be very similar to the two previously examined lepismatids, Thermobia domestica and Lepisma saccharina. On the other hand, spermatozoa of Tricholepisma aurea were aggregated in small groups rather than pairwise joined as seen in the other lepismatids. Sperm characters are also used to reconstruct a phylogenetic hypothesis which suggests a close relationship between Ateluridae and Nicoletiidae.     

Fine structure of the ladybird spermatozoa (Insecta,Coleoptera, Coccinellidae)

The sperm structure of several ladybird species belonging to different subfamilies of Coccinellidae was studied. Three main sperm types were clearly recognized, and were characterized by differences in acrosomal length, the presence of a dense coat around the acrosome, the length of the basal body, the amount of the centriole adjunct material, and the diameter of the mitochondrial derivatives. However, the whole group shares a pattern of the posterior sperm region uncommon for insects, in which the axoneme and other flagellar components are running parallel with the nucleus. As a general conclusion, this study has revealed an inconsistency between the sperm structure and the systematics of the group, indicating that the generic concepts within the group do not reflect a natural classification, a statement also shared by molecular studies.     

Characteristics of the sperm flagellum in fungus gnats (Insecta,Diptera, Mycetophiloidea)

Spermatozoa from several members of the closely related Mycetophilidae and Keroplatidae were examined by electron microscopy using a fixative that contains glutaraldehyde and tannic acid, followed by a post-fixative that consists of uranyl acetate rather than osmium tetroxide. With this fixative, the detailed architecture of the flagellar axoneme and its various microtubules could be resolved. The so-called accessory tubules, which surround the central 9+2 unit of the sperm axoneme, were found to have 16 protofilaments in several examined Mycetophiloidea, but in no other Diptera. As 16 is the common number in holometabolic insects, it is presumably the plesiomorphic condition in Diptera. Other fungus gnats have accessory tubules with 15 or 14 protofilaments. The intertubular material situated between the accessory tubules is smaller in the examined members of the Mycetophilidae than in the Keroplatidae. The acrosome consists of an apical vesicle, which in one species, Macrorhyncha ancae, has three microtubular doublets in its anterior part and two large and three small extensions which extend posteriorly along the sperm axoneme.     

Giant sperm cells with accessory macrotubules in a neuropteran insect

The flagellar axoneme of the atypical spermatozoa (paraspermatozoa) of Mantispa perla (Neuroptera, Planipennia) contains accessory microtubules or rather macrotubules that are 55 nm in diameter and that has a wall consisting of about 40 protofilaments. The sperm tail further contains two giant mitochondrial derivatives, which during spermiogenesis store an electron dense material. The mature spermatozoon has a flattened acrosome and a elliptical nucleus. These giant spermatozoa may furnish nutrients to the functional spermatozoa (euspermatozoa) when they reach the female genital tracts or/and they function in sperm competition filling the spermatheca.     

两种草螽精子超微结构比较研究(直翅目,螽斯总科)

比较研究了长翅草螽Conocephalus longipennis与鼻优草螽Euconocephalus nasutus精子的超微结构。两种精子的顶体复合体侧生于核上且包裹了核的一部分;轴丝为典型的9 9 2型;轴丝两侧的副纤维结构前者为2副体,后者为2副微管;线粒体衍生体横切面前者为鞋履形,后者卵圆形;轴丝与线粒体衍生体之间的连接带前者为5条,后者3条;近线粒体衍生体的两扁平膜池在长翅草螽中连接在一起呈飞燕形。     

The spermatozoon of Mengenilla moldrzyki (Strepsiptera,Mengenillidae): Ultrastructure and phylogenetic considerations

Even though the spermatozoa of several strepsipteran species were described earlier, no data were available for the basal family Mengenillidae. Well-fixed material of the recently described Tunisian species Mengenilla moldrzyki was used for a detailed examination of the sperm ultrastructure. The total length is c. 30 μm. The head region contains a conical acrosome vesicle (0.3-0.35 μm) and an elongated nucleus (7.3 μm) with dense chromatin. Some granular material along with a uniformely dense centriole adjunct and two mitochondrial derivatives are visible at the posterior end of the nucleus. The material of the centriole adjunct does not extend along the flagellum and accessory bodies are absent. The mitochondrial derivatives are elongated structures crossed by a longitudinal crista but lacking parallel transverse cristae and paracrystalline material in the dense matrix. The mitochondrial derivatives gradually reduce their size and end at the most posterior tail region. The flagellar axoneme has a 9 + 9 + 2 pattern and originates beneath the nucleus. In the terminal tail region the axoneme gradually disintegrates. Despite the extreme specialization of the endoparasitc group, strepsipteran spermatozoa are mostly characterized by plesiomorphies. The pattern within the order is largely uniform, but Mengenilla displays several apomorphic features compared to the presumptive strepsipteran groundplan (e.g., absence of crystallizations and cristae in the mitochondrial derivatives). The subdivision of the intertubular material into two compartments with a dense beak-like structure adhering to the tubular wall supports a clade Coleopterida (=Strepsiptera + Coleoptera) + Neuropterida.     

Substructure of the axoneme of pterygote insect spermatozoa: Phylogenetic considerations

Spermatozoa from a great number of insect species were fixed in a tannic acid-containing fixative and the ultrastructure of the flagellar axoneme was examined in a search for apomorphies. Most of the examined species, representing a majority of insect orders. have accessory tubules outside the axoneme (hence a 9 + 9 + 2 pattern), and these consist of 16 protofilaments. Some important apomorphies concern the number of protofilaments in the accessory tubules: 13 (plus 7 inner elements) in Ephemeroptera, 13 in the (elliptic) tubules of Psocoptera + Anoplura + Mallophaga (thus a synapomorphy), 13 in Tipulidae + Brachycera, 15 in the dipteran families Dixidae + Chironomidae (with a 9 + 9 + 2 axoneme) and Culicidae + Bibionidae (with a 9 + 9 + “1” axoneme), 17 in Phasmatodea, and 17–20 in Trichoptera. Other apomorphies concern the appearance of the so-called intertubular material outside the microtubular doublets, the appearance of the interior of the various microtubules, and the loss, in some taxa, of outer or inner dynein arms of both dynein arms. In some cases, the flagellum is completely abnormal; the sperm tail of Thysanoptera, for example, consists of 27 elements of 3 different kinds. The different taxa within orders Diptera and Trichoptera have sperm tail axonemes of different appearances, where those from other orders have a rather uniform appearance. The conclusions that can be drawn from this spermatological study, generally agree with data from classical studies, except with some variations, in some cases.     

Effect of rapid freezing and thawing on cellular integrity of honey bee sperm

Abstract. Direct observations on the effect of rapid freezing and thawing on honey bee ( Apis mellifera L.) sperm were made by light, scanning and transmission electron microscopy. Rapid freezing of honey bee ejaculated sperm, suspended in freezing diluent, in liquid nitrogen followed by rapid thawing can cause cellular injuries which lead to the death of the sperm. The frozen-thawed sperm, supravitally stained, showed a significant decrease in cell viability compared with that of the control fresh sperm ( P <0.001). Significant uptake of the stain in the dead sperm resulted from damage in the cell membrane. The scanning electron micrographs of frozen-thawed sperm further demonstrated that the injury of cell membrane can lead to the splitting of mitochondrial derivatives from the flagellar axoneme. More cellular injuries including the release of acrosomal content and membrane damage at the acrosome, nucleus and the tail regions were further revealed by transmission electron microscopy. The impact of cellular injuries on the quality of honey bee sperm cryopreserved for artificial insemination of honey bee queens is discussed.     

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.     

The sperm structure of Embioptera (Insecta) and phylogenetic considerations

The sperm structure of two species of Embioptera, Embia savignyi Westwood 1837 and Aposthonia japonica (Okajima 1926), was studied. Spermatozoa of both species exhibit a monolayered acrosome and a layer of material surrounding the sperm cells for most of their length. The presence of a 9+9+2 axoneme provided with accessory microtubules with 16 protofilaments, two accessory bodies and two crystallized mitochondrial derivatives are characters shared with other polyneopteran taxa. The supposed close relationship between Embioptera and Phasmatodea is not supported by characters of the sperm ultrastructure.     

Characteristics of the flagellar axoneme in Neuroptera,Coleoptera, and Strepsiptera

Spermatozoa from representatives of the five insect orders in superorder Neuropteroidea were examined by electron microscopy following a new fixation method that includes tannic acid in the primary fixative but has uranyl acetate rather than osmium tetroxide as the secondary fixative. The sperm axoneme was found to be similar in the four orders Megaloptera, Raphidioptera, Neuroptera, and Coleoptera, and is characterized above all by its so-called intertubular material being divided into two portions, one located outside, but in contact with the doublet, and the other projecting from the accessory tubule and having a beak-like shape. These features have not been seen in insects from other orders and may be a synapomorphy for these neuropteroid orders. The accessory tubules in these four orders have 16 protofilaments. The shape of the accessory bodies adjacent to the mitochondrial derivatives is nearly the same in insects from the more primitive neuropteroid orders and in Coleoptera. The sperm tail of the examined strepsipteran deviates in several respects from that of other neuropteroids: the particle row in the wall of accessory tubules is incomplete, an intertubular material is missing, and the mitochondria contain no crystal. © 1994 Wiley-Liss, Inc.