Spermatogenesis and sperm structure of Acerella muscorum, (Ionescu, 1930) (Hexapoda, Protura)

The general organization of the male genital system, the spermatogenesis and the sperm structure of the proturan Acerella muscorum have been described. At the apex of testis apical huge cells are present; their cytoplasm contains a conventional centriole, a large amount of dense material and several less electron-dense masses surrounded by mitochondria. Spermatocytes have normal centrioles and are interconnected by cytoplasmic bridges. Such bridges seem to be absent between spermatid cells and justify the lack of synchronization of cell maturation. Spermatids are almost globular cells with a spheroidal nucleus and a large mass of dense material corresponding to the centriole adjunct. Within this mass a centriole is preserved. Mitochondria of normal structure are located between the nucleus and the plasma membrane. The spermatids are surrounded by a thick membrane. No flagellar structure is formed. Sperm have a compact spheroidal nucleus, a large cap of centriole adjunct material within which a centriole is still visible. A layer of mitochondria is located over the nucleus. The cytoplasm is reduced in comparison to spermatids; many dense bodies are interspersed with sperm in the testicular lumen. The sperm are small, immotile cells of about 2.5-3 μm in diameter.     

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.     

从弹尾纲和原尾纲的亲缘关系质疑缺尾纲（=近昆虫纲）的有效性

鉴于弹尾目（跳虫）和原尾目的尾部都没有尾须（cerci）,Brner于1910年就把这两类归并为一个类群缺尾纲（Ellipura）,这一分类阶元长期被许多昆虫学家沿用至今。Kukalová-Peck(1987 )在讨论化石双尾虫（?）附肢的总体结构（ground plan）时,认为跳虫和原尾虫的腹部侧板更原始,附肢无转节,将二者归纳成近昆虫纲（Parainsecta）。但是从形态特征、内部结构、比较精子学、变态类型和胚后发育等的特点以及线粒体DNA和核糖体DNA的测序分析结果,显示弹尾纲与原尾纲之间存在诸多重要差异,不具备较为密切的亲缘关系,我们不支持（弹尾纲+原尾纲）组成缺尾纲或近昆虫纲。据此建议取消缺尾纲（=近昆虫纲）这一分类阶元。     

The spermatogenesis and the sperm structure of Terebrantia (Thysanoptera, Insecta)

Spermatogenesis and the sperm structure of the terebrantian Aeolothrips intermedius Bagnall are described. Spermatogenesis consists of two mitotic divisions; the second is characterized by the loss of half of the spermatids, which have pyknotic nuclei. Early spermatids have two centrioles, but when spermiogenesis starts, a third centriole is produced. The three basal bodies give rise to three flagella; later these fuse into a single flagellum which contains three 9 + 0 axonemes. The basal bodies are surrounded by a large amount of centriole adjunct material. During spermiogenesis this material contributes to the shifting of the three axonemes towards the anterior sperm region parallel to the elongating nucleus, and it is transformed into a dense cylinder. In the mature spermatids the three axonemes amalgamate to create a bundle of 27 doublet microtubules. Near the end of spermiogenesis the dense cylinder of the centriole adjunct lies parallel to the nucleus and the axonemes. It ends where the mitochondrion appears at half-sperm length. We confirm that Terebrantia testes have a single sperm cyst; their sperm are characterized by a cylindrical nucleus, three axonemes fused into one, a small mitochondrion and a short cylindrical centriole adjunct which corresponds to the dense body described in a previous work. The acrosome is lacking. At the midpoint of the anterior half of the sperm the outline of the cross-section is bilobed, with the nucleus contained in a pocket evagination of the plasma membrane. These characters are discussed in light of a comparison between Tubulifera and Terebrantia.     

Gap junctions between oocyte and follicle cells in Acerentomon sp. (Insecta,Protura)

Each oocyte in the ovary of Acerentomon is surrounded by a layer of follicle cells (FC) and possesses a group of specialized, so-called chorion-producing cells (CPC). The FCs lying immediately under the CPCs form processes which make contact with the oocyte. Gap junctions occur at the points of contact between the oolemma and the membrane of the processes. A possible role of the heterocellular gap junctions in Acerentomon ovary is the coordination of development of the oocyte and CPCs.     

Ultrastructure of sensillum t1 on the foretarsus of Acerentomon majus berlese (Protura : Acerentomidae)

The shape and ultrastructure of sensillum t₁ on the foretarsus of the proturan, Acerentomon majus Berlese have been described by means of scanning and transmission electron microscopy. Sensillum t₁ is a club-shaped structure, innervated by 3 sensory cells. Each cell is bipolar, with a single dendrite whose ciliary region has a 9-doublet structure. The terminal parts of 2 of the 3 dentrites, filled with many single microtubules, penetrate the cuticular hair, and in the apical swollen region of the sensillum divide into several dendritic branches. The third dendrite terminates as a tubular body at the base of the peg. A sheath-producing cell, a trichogen cell, and one tormogen cell envelop the dendrites. The latter cell has abundant smooth endoplasmic reticulum and produces a very peculiar secretion that is discharged in the space between the cuticular sheath around the dendrites and the cuticle of the hair. A palisade of tubules, 14nm high, is present beneath the cuticle of the apical part of the sensillum; at this level, the cuticle is perforated by numerous pores through which passes a dense material, forming a continuous layer over the cuticle. An olfactory function of sensillum t₁ has been proposed.     

The sperm ultrastructure of Merluccius merluccius (Teleostei,Gadiformes): phylogenetic considerations

The anacrosomal aquasperm of the gadiform Merluccius merluccius is ultrastructurally similar to the advanced type II spermatozoa (perciform‐type sperm) typically found in most Perciformes. The perciform‐type spermatozoon is characterized by the lateral insertion of the flagellum and the location of the centrioles outside the nuclear fossa. Apart from these characteristics, the spermatozoon of M. merluccius is remarkable because of the mutually parallel arrangement of the centrioles, a rare feature among fishes, which is considered an apomorphic condition for animal sperm cells. Within the superorder Paracanthopterygii, which contains a large diversity of sperm patterns resulting from a high number of apomorphies, a perciform‐type sperm is present only in the order Gadiformes. The significance of the presence of perciform‐type spermatozoa in the three investigated gadiform families is discussed in a phylogenetic context.     

The presence of additional abdominal legs in Acerentomon gallicum Ionesco, 1933 (Protura, Acerentomidae)--a teratological case

A teratological specimen of Acerentomon gallicum Ionesco, 1933 having additional rudiments of abdominal appendages on segments IV and V is described. The hypothesis concerning the origin of seta P3 in the sternal chaetotaxy is discussed.     

The sperm pumps of Strepsiptera and Antliophora (Hexapoda)

Male genital structures of representatives of Strepsiptera, Siphonaptera and Diptera are described in detail, with special emphasis on sperm pumps. The parts involved in the apparatus are evaluated with respect to their homology. Functional interpretations are presented based on the morphological observations. The phylogenetic significance of characters related to the male genital apparatus is discussed. The sperm pumps differ strongly in Strepsiptera and Antliophora (s.s.) and are not homologous. The strepsipteran type, which lacks any sclerotized parts, has evolved independently. Autapomophies of the male genital apparatus are the compact testes, the large balloon‐shaped vesicula seminalis, the strongly developed musculature of the proximal ductus ejaculatorius, the strongly simplified copulatory organ, the unusual muscles of segments VIII and IX, and the complete absence of accessory glands. The median fusion and almost globular shape of the vesicula are potential autapomorphies of Corioxenidae. The absence of the furrow separating the testes from the vesicula seminalis is a derived condition found in Xenos and Myrmecolax. A sperm pump is absent in Boreus (Mecoptera) and Culicomorpha and the functionally relevant parts and their arrangement differ strongly in Siphonaptera, Pistillifera and Diptera (excl. Culicomorpha). The presence of a functional and homologous pumping apparatus does not belong to the groundplan of Antliophora, which implies that this alleged autapomorphy of the clade is invalid. A sperm pump belongs to the groundplan of Diptera and was secondarily reduced in Culicomorpha, many representatives of Bibionomorpha, and in Diopsidae. It was very likely primarily absent in Mecoptera. However, the precise reconstruction of the groundplan depends on the position of Nannochoristidae within Mecoptera and on the possible affinities of Siphonaptera and Boreidae. Sperm pumps should be considered as a functional term and not be used as a character for phylogenetic reconstruction, unless specific similarities are included in the character definition.     

The spermatogenesis and sperm structure of Timema poppensis (Insecta: Phasmatodea)

The ultrastructure of spermatogenesis and spermatozoa was studied in Timema poppensis Vickery & Sandoval, 1999, a putative basal taxon of Phasmatodea. The apical portion of testis follicles consists of spermatogonial cells with polymorphic nuclei. Primary spermatocytes display very short primary cilia originating from the peripheral centrosomes. Early spermatids develop a conspicuous “nebenkern” consisting of fused mitochondria. They have a single peripheral centriole with microtubular triplets, which expresses a 3.6-μm-long cilium featuring a 9?+?2 axonemal pattern. In a later stage, the centriole and the ciliary shaft displace toward the inner part of the cytoplasm by an infolding of the plasma membrane. Mature spermatids exhibit a derived centriole with microtubule doublets devoid of dynein arms, which is equipped with a dense arc-like outer structure. Ciliary degeneration was not observed during spermiogenesis. Spermatozoa are short flagellate cells about 55–60?μm in length. They are characterized by a three-layered acrosomal complex. The distinctive bell-shaped morphology of the acrosome vesicle is likely an autapomorphic trait of Timema. The flagellum has a 9?+?9?+?2 axoneme, two accessory bodies, two flattened cisterns, and two elongated mitochondrial derivatives. Results support the hypothesis that Phasmatodea, comprising Timema?+?Euphasmatodea, form a monophyletic group. The presence of 17 protofilaments in the wall of accessory microtubules and the flattened configuration of the flagellum are potential apomorphic groundplan features of the order. Within Phasmatodea, a key evolutionary divergence was from the conventional insect spermiogenesis and sperm structure of Timema, to the unusual spermiogenetic process and peculiar sperm structure of Euphasmatodea. As a result, Timema retains more sperm character states found in the polyneopteran ground pattern, while Euphasmatodea have evolved outstanding sperm autapomorphies, like the loss of mitochondria and flattened cisterns, and the presence of strongly expanded accessory bodies.     

Head structures of Karoophasma sp. (Hexapoda, Mantophasmatodea) with phylogenetic implications

External and internal head structures of adults of Karoophasma sp. were examined and described. The results are compared with conditions found in other representatives of Mantophasmatodea and members of other lower neopteran groups. The X-shaped apodeme of the frons, the unpigmented oval area enclosed by apical branches of the anterior tentorial arms, the oval sclerotisation at the base of the labrum, the sclerotized rounded apical part of the galea, and the loss of M. labroepipharyngalis are probably autapomorphic for Mantophasmatodea. Plesiomorphic features (groundplan of Neoptera) are the orthognathous condition, the absence of parietal ridges, the absence of a gula, the absence of a 'perforation of the corpotentorium', the multisegmented antennae inserted between the compound eyes, the general arrangement of the mouthparts, the shape and composition of the maxillae and labium, and the nearly complete set of muscles. The presence of a transverse muscle connecting the antennal ampullae is a potential synapomorphy of Orthoptera, Phasmatodea and Dictyoptera. Character states suggesting affinities with Grylloblattodea are the absence of ocelli, the elongation of the corpotentorium, and the very similar mandibles with widely separated bases and completely reduced molae. Whether predacious habits are a synapomorphic feature of Mantophasmatodea and Grylloblattodea is uncertain. The retained orthognathous condition in Mantophasmatodea and Mantodea is likely related with different specialized preying techniques in both groups, i.e. rapid forward pushes of the head–prothorax complex, and the use of raptorial legs, respectively.     

The phylogenetic position of the Prolecithophora (Rhabditophora, 'Platyhelminthes')

Complete 18S ribosomal DNA (rDNA) sequences and partial 28S rDNA sequences from a selection of rhabditophoran taxa were obtained and used in combination with literature data to determine the phylogenetic position of the Prolecithophora and of two families sometimes included in the Prolecithophora, the Urastomidae and the Genostomatidae. The results are largely compatible with earlier molecular studies when supported clades are considered, and adjusting for the denser taxonomic sampling of this study. The position of the Proseriata is not compatible with the taxon Seriata, which is rejected. The Rhabdocoela excluding the Fecampiida and the Neodermata is monophyletic. The phylogenetic position of the Neodermata cannot be determined, but its placement is not compatible with the proposed taxa Revertospermata and Mediofusata Kornakova & Joffe, 1999, which are rejected. The Urastomidae and the Genostomatidae in all analyses group with the Fecampiida, and it is our recommendation that these taxa be included in the Fecampiida. The amended Fecampiida always group separately from the Prolecithophora sensu stricto , the Rhabdocoela, and the Neodermata. Our analyses reveal the existence of a strongly supported clade consisting of Prolecithophora + Tricladida + the amended Fecampiida, and we propose the name Adiaphanida for this clade. Tentatively the sister group of the Prolecithophora is a clade consisting of the Tricladida + amended Fecampiida.     

The dipteran sperm tail: ultrastructural characteristics and phylogenetic considerations

The sperm tail from representatives of several families of Diptera has been examined by high resolution electron microscopy and a computer analysis that improved the visualization of recorded patterns. A considerable variability in sperm tail structure is found within Diptera, and is actually greater than that of any other insect order. The 'generalized insect sperm axoneme'. which is characterized as a 9+9+2 axoneme and by the accessory microtubules having 16 protofilaments, was found only in some dipterans; these are members of Mycetophilidae. From this fact we conclude that Mycetophilidae is likely to be the most primitive extant dipteran group. Another mycetophilid, Boletina , was seen to have accessory tubules with 15 protofilaments as have members of families Dixidae, Chironomidae, Culicidae, and Bibionidae. The last two families have spermatozoa of a type designated as 9+9+'1' there is a central rod rather than two microtubules. We regard this 9+9+'1'pattern with 15 protofilaments to represent a synapomorphic feature. Representatives of the neatoceran families Tipulidae and Trichoceridae have accessory tubules with 13 protofilaments as do examined members of several brachyceran families. Brachycera is hence likely to be derived from the vicinity of the tipulid family. The intertubular material is small in Mycetophilidae and most nematoceran groups, whereas in Tipulidae and Brachycera it is enlarged; here it bridges the space between the accessory tubules and contains various inclusions.     

First fossil record of stalked spermatophores with sperm (Collembola: Hexapoda)

Spermatozoa and stalked spermatophores in Baltic amber represent the first report of these reproductive structures in the fossil record. A comparison of this material with sperm and simple stalked spermatophores from extant invertebrates indicates that the fossil structures originated from a springtail (Collembola: Hexapoda). This conclusion is supported by the presence of a female springtail, Sminthurus longicornis Kock and Berendt (Sminthuridae: Symphypleona), in the same piece of amber. This specimen, which appears to have been molting at the time of death, is adjacent to objects interpreted as springtail eggs. The present find establishes the existence of the indirect method of sperm transfer by the late Eocene (40 Ma).     

The phylogenetic position of Aulotandra (Zingiberaceae)

The phylogenetic position ofAulotandra (Zingiberaceae).—Nord. J. Bot. 23 : 725–734. Copenhagen. ISSN 0107–055X.
Molecular data for 41 representatives of Zingiberaceae are analysed focusing on the phylogenetic position of Aulotandra and its relationship to Siphonochilus. Sequence divergences indicate that accessions of Aulotandra from Madagascar are closest to those of African Siphonochilus in both ITS and trnL-F data sets, indicating a close relationship. Together these genera form a highly supported monophyletic clade. This African-Madagascan lineage is sister to the rest of the family with African, Asian and South American members, showing that Aulotandra does not belong in the tribe Alpinieae, where it has been traditionally placed, but in the subfamily Siphonochiloideae with the genus Siphonochilus.