Characteristics of spermiogenesis and mature spermatozoa in Gyratrix hermaphroditus (Plathelminthes, Rhabdocoela, Kalyptorhynchia)

 Some events of spermiogenesis and the submicroscopic anatomy of male gametes in Gyratrix hermaphroditus are described. Special features occurring during the steps of sperm cell maturation are the development of delicate rootlet-like and spike-shaped structures attached to the basal bodies, an anchor apparatus of cilia staying near the tip of the outgrowing spermatids, the differentiation of a single mitochondrial rod, and the processes of compartmentalizing the chromatin resulting in the formation of extranuclear lamellar stacks. Mature spermatozoa are especially characterized by two incorporated axonemes, a string of large mushroom-shaped dense bodies in the anterior section of the cell, and two lateral rows of nuclear lamellar stacks in the median cell segment. Based on the present findings, the process of spermiogenesis and the organization of spermatozoa in the ground pattern of the monophylum Kalyptorhynchia are reconstructed. Apparently, the sister group of the Kalyptorhynchia can be found within the other free-living and symbiotic Rhabdocoela; the hypothesis of a sister group relationship with the Neodermata is not corroborated. Probably, spermatozoal characteristics can contribute to a discrimination between distinct populations of G. hermaphroditus which is proved to be a complex of several sibling species. Accepted: 25 June 1998     

Ultrastructure of the photoreceptors of Allostoma sp. (Plathelminthes,Prolecithophora)

The four eyes of the prolecithophoran Allostoma sp. are disposed in two pairs in a dorsolateral position at the periphery of the brain and beneath its capsule. They are rhabdomeric pigment-cup ocelli. Each eye in the anterior pair consists of one pigment cell and one receptor cell; each in the posterior pair is made up of a larger, single pigment cell and two photoreceptor cells. A lens in front of the pigment cell's aperture is formed by electron-dense, refractive, finger-like protrusions which arise from unpigmented cytoplasmic extensions of the pigment-cup margin. Degenerative signs are sometimes visible in the lens.     

Ultrastructure of spermatogenesis and sperm ofMulticotyle purvisi (Plathelminthes,Aspidogastrea)

Summary The ultrastructure of spermatogenesis is described for the first time in an aspidogastrean. The zone of differentiation which is usually formed during digenean spermiogenesis was not observed inMulticotyle purvisi. Instead, spermatid components are assembled within the common cytoplasmic mass before the outgrowth of spermatids. Microtubules, mitochondrion, nucleus and axonemes including their basal body regions, migrate from the cytoplasm into the spermatid which is pinched off at the level of the arching membrane. An unusual, complex structure of the basal body region is described. Intercentriolar bodies and striated rootlets are left behind and quickly disappear from the residual cytoplasm. Despite these atypical aspects, spermiogenesis results in the formation of mature sperm with the classical structure common to Digenea and Monogenea Polyopisthocotylea with the addition of some extra, non-cortical microtubules and a dense rod along part of the length of the sperm.Abbreviations used in the figures A cell type A, primary spermatogonium - AM arching membrane - AX axoneme - AZ attachment zone - B cell type B — spermatogonium - BB basal body region - C cell type C — spermatogonium - CEL central element - CI cisternae - CY cytophore - D cell type D — primary spermatocyte - DO doublet of microtubules - DR dark rod - E cell type E — multinucleate condensed cytophore - ER endoplasmic reticulum - G glycogen - GO Golgi body - I intercentriolar body - LB lamellate body - M mitochondrion - ME remnants of arching membranes - MT microtubules - N nucleus - R rootlet - S spermatid     

Ultrastructure of the protonephridial system of regenerating Stenostomum sp. (Plathelminthes,Catenulida)

Summary The ultrastructure of the flame bulbs, protonephridial capillaries and duct of fully developed and regenerating Stenostomum sp. is described. Flame bulbs are formed by a single cell whose nucleus is located basally or laterally to the weir. The weir is formed by a single row of transverse ribs connected by a thin membrane, apparently of extracellular matrix. Internal leptotriches arise from the proximal cytoplasm and extend in a (usually) single row along the weir and into the lumen of the distal cytoplasmic tube. Many or all leptotriches do not fuse with the distal cytoplasm. Two cilia are each anchored in the proximal cytoplasm by a cross-striated vertical and lateral rootlet, the latter bent forward and extending for some distance into one of the two cytoplasmic cords along the weir. Each cord contains the lateral rootlet in its proximal part, as well as many microtubules. The distal cytoplasmic tube contains two (longitudinal) junctions, i.e. lines of contact between cell processes of the same, terminal cell. Occasionally, more than two junctions were seen, apparently due to branches of the terminal cell in contact with each other. Flame bulbs join capillaries lined by several canal cells type I, containing few or no microvilli but lateral flames. Such capillaries join a duct (or ducts?) lined by canal cells type II with many long microvilli. The large protonephridial duct is lined by numerous cells with lateral flames and many long microvilli. In regenerating tissue (10.5 hours after cutting) some flame bulbs were free, i.e. not connected to capillaries, and some capillaries openly communicated with the surrounding intercellular space. In the presence of a single row of ribs in the weir, of internal leptotriches, and of vertical and lateral ciliary rootlets, the flame bulb of Stenostomum sp. resembles that of other Plathelminthes much more closely than hitherto thought. The species differs from non-catenulid plathelminths mainly in the large number of glandular cells lining the large protonephridial ducts, in the transverse orientation of the ribs in the weir and in the presence of only two cilia in the flame.     

Ultrastructure and formation of the bursa mouthpiece of Philocelis cellata (Plathelminthes,Acoela)

Philocelis cellata has a strengthened bursa mouthpiece which is arranged in front of the male copulatory organ. The main components of the bursa mouthpiece are numerous ring-shaped bursa mouthpiece cells whose central parts contain strengthened elements forming a tube around the sperm duct. Each of the peripheral areas of the bursa mouthpiece cells is separated by similarly ring-shaped gap cells. The end of the bursa mouthpiece towards the bursa is formed by a so-called sorting apparatus which consists of different cells; opposite the bursa the sperm duct ends in a globe-shaped sperm vestibule. The bursa mouthpiece is differentiated successively, beginning at the distal part at the bursa and proceeding proximally.     

Ultrastructure of the copulatory organ of Haplopharynx quadristimulus and its phylogenetic significance (Plathelminthes,Haplopharyngida)

Summary The male reproductive system in Haplopharynx quadristimulus consists of paired testes, sperm ducts, seminal vesicles, seminal ducts, a copulatory organ containing prostatic vesicle and stylet apparatus, and the male canal. By electron microscopy all components appeared to be regional specializations of a canal extending from the testes to the body wall and lined by a multiciliated epithelium. The epithelium of the stylet apparatus contained six different cell types. One cell type (matrix syncytium) formed the stylet and the other five were located distal to the stylet/prostatic-vesicle junction along the male system epithelium. Each cell type was attached to the supporting intercellular matrix at a different level along the stylet apparatus. All cell types extended to the distal end of the stylet apparatus regardless of where they originated along its length. The cells in the apparatus lacked cilia, but one of the cell types contained rootlets. Modified rootlets or rootlet derivatives were possibly present in another cell type in the form of rootlet-like ribbons. The findings support the monophyly of the Macrostomida Haplopharyngida (by common occurrence of a matrix syncytium) and at the same time suggest their separation as two distinct taxa (by differences in the structure of the prostatic vesicle and other parts of the stylet apparatus).Abbreviations a accessory spine - c circular muscle - ce centriole - ci cilium - di dictyosome - e epithelial cell - ed ejaculatory duct - ep epidermal cell - f rootlet-like ribbon - g prostatic gland cell neck - g1 type I gland cell granules - g2 type II gland cell granules - g3 type III gland cell granules - h hemidesmosome - i intercellular matrix - im internal muscle - j septate junction - l stylet apparatus lumen - le spine lateral extension - lm longitudinal muscle - m matrix syncytium - mc male-canal epithelial cell - me male canal - mp male pore - mt microtubules - mv microvilli - n nucleus - nc nerve cell body - np nerve process - om oblique muscle - p prostatic vesicle epithelial cell - pv prostatic vesicle - r rootlet - s stylet - sa stylet apparatus - sc sensory receptor - sd sperm duct - se seminal duct - sl stylet lumen - sp spot desmosome - sr sperm - sv seminal vesicle - t terminal web - te testis - u ultrarhabdite - z zonula adhaerens - 2 cell type 2 - 3 cell type 3 - 4 cell type 4 - 6 cell type 6     

Ultrastructure of flame cells and protonephridial capillaries of Craspedella and Didymorchis (Plathelminthes,Rhabdocoela)

Summary The ultrastructure of the flame cells and protonephridial capillaries of the Rhabdocoela Craspedella sp. and Didymorchis sp., ectocommensals on the freshwater crayfish Cherax destructor in eastern Australia is described. The flame cells of both species have variable numbers of cilia without distinct rootlets and with decreasing numbers of axonemal tubules towards the ciliary tips. Bundles of microtubules extend from the cytoplasm adjacent to the ciliary rootlets through the ribs of the weir apparatus into the distal cytoplasmic tube, where the numbers of microtubules gradually decrease. The weir apparatus is formed by a single row of longitudinal ribs connected by a membrane. In Craspedella, but not in Didymorchis, the ribs have external branched leptotriches. Mitochondria are common in the wall of the flame cell of both species. The protonephridial capillary just above the end of the ciliary tuft narrows in both species and bends sharply in Craspedella. The lumen of the flame cell and the capillary is lined by a dark layer of cytoplasm; there is no enlargement of the surface area by microvilli or lamellae. Centrioles were seen in the capillary wall of Craspedella, and in Didymorchis the cytoplasm around the capillaries has a very loose and light appearance. The ultrastructure of the flame cells and capillaries of both species corresponds closely to that of Temnocephala sp.Abbreviations in the figures BB basal body - CE centriole - L leptotrich - M microtubules - ME membrane of weir apparatus - MI mitochondrion - PC protonephridial capillary - R rib (rod) of weir apparatus     

Adhesive glands in the Pterastericolidae (Plathelminthes,Rhabdocoela)

Summary The ultrastructure of anteroventral gland cells with processes penetrating the epidermis inPterastericola bergensis, P. fedotovi, P. pellucida and the undescribedP. (sp. Rottnest) was studied with transmission and scanning electron microscopy. Specimens ofP. pellucida were shock frozen in situ in the epithelium of their asteroid host to study the function of the glands. Secretory products released from the gland cell processes fan out towards the host epithelium. The glands are concluded to have an adhesive function. They are compared with similar structures in Neodermata and other rhabdocoel taxa. The phylogenetic significance of the glands is discussed.Abbreviations b basal lamina - c cilium - cr ciliary rootlets - d septate desmosome - g gland cell process - gc gland cell - h host epithelium - m mitochondria - mc muscle cell - mv microvilli - mt microtubules - n nucleus - o ootype - pm plasma membrane - s secretory granule - sm secretory material released from dissolving secretory granules     

La famille des Cicerinidae (Turbellaria, Kalyptorhynchia)

The present study deals with 12 species of Cicerinidae. Further details are given for 6 species previously described: Toia ycia Marcus, Cicerina eucentrota Ax, Nan-norhynchides vividus Brunet, JV. harparius Brunet, N. corneus Brunet, Didiadema picardi Brunet. Two new species are described, Toia calceformis sp.n., different from T. ycia by half-boot shape of the cirrus, and Paracicerina globulosa sp.n., characterized by very short (4 μm) cuticular spermatic ducts and a spherical copulatory bulb provided with a spiny cirrus (35–40 μm long). Histological studies of Ptyalorhynchus coecus Ax confirm the generic separation of Ptyalorhynchus and Paracicerina; the main difference is the glandular girdle structure of the proboscis in Ptyalorhynchus which is split into two areas (inner and outer one) by basal circular muscles; the intensively stained secretion of the inner area is localized in 15 membranous canals. Pocillorhynchus gen.n., with two species, P. agilis sp.n. and P. minutus sp.n., is closely related to the genera Toia and Nannorhynchides , but differs from them by the following characters: proboscis with broad glandular girdle, devoid of circular muscle bulb, cuticular spermatic ducts long and thin (95–125 μm). From the comparison of their morphological and anatomical features, two groups of genera are distinguished in Cicerinidae; first group including Toia - Nannorhynchides - Pocillorhynchus , second group including Cicerina - Paracicerina - Etmorhynchus - Ptyalorhynchus - Zonorhynchus - Xenocicerina - Didiadema. Special attention is paid to proboscis structure. The study ends with an identification key for all known Cicerinidae.     

Identification of the Kalyptorhynchia (Plathelminthes) in Meixner's 'Turbellaria' 1938 with remarks on the morphology and distribution of the species in the North Sea and the Baltic Sea

Remarks arc given on taxonomy, structure and distribution of 38 species of Kalyptorhynchia, incompletely described (in part nomina nuda) in part I of 'Turbellaria (Strudclwürmer)' in Tierwelt der Nord-und Ostsee (Meixncr 1938). The remarks are based mainly on the existing parts of the basic material for Meixner's study in the collections of the Zoological Institution in Graz, Austria, including incomplete proof sheets of the unpublished part II. Available information on the species published after 1938 has been taken into account.     

Anatomy and evolution in Cylindrostomidae (Plathelminthes, Prolecithophora)

The following species of Cylindrostomidae are redescribed: Cylindrostoma lutheri Westblad, 1955, C. micropharynx Westblad, 1952, Monoophorum tubiferum Westblad, 1955, M. stiliferum Westblad, 1955 (transferred to Einarhelmins gen. n.), Allostoma crassicystiferurn (Westblad, 1952), A. uterinum (Westblad, 1955), and Euxinia baltica Meixner, 1938. Three new species are described: Cylindrostoma paralutheri, Allostoma neostiliferum and A. hopkinsi. A review is given on anatomy and evolutionary trends in Cylindrostomidae.     

Morphology and function of the proboscis in Bombyliidae (Diptera, Brachycera) and implications for proboscis evolution in Brachycera

Based on serial semithin sections and SEM photographs of representatives of European Bombyliinae and Anthracinae, the mouthparts of Bombyliidae are studied and compared with the relevant data from literature on other families of Diptera Brachycera. The three moving units of the proboscis (clypeo-cibarial region, haustellum-maxillary base region, and labella) and their structures and muscles are described. Functions and possible movements are inferred from the structures observed. Articulations both between the parts of the organ and to the head capsule enable the fly to retract its proboscis into a resting position. Proboscis movement from a resting to a feeding position encompasses the following submovements: rotating of the basal clypeo-cibarial region (= fulcrum) against the head capsule, folding of the haustellum-maxillary base region against the fulcrum, evagination and invagination of the labial base, and the labella movements. This is a novelty as compared to the rigid proboscis of Tabanidae and agrees largely with the conditions in the Cyclorrhapha. The evolution of these novelties and their functional significance are discussed. The fulcrum, as well as the haustellum-maxillary base, as the new moving units are deduced from the plesiomorphic state as present in Tabanidae by fusions of sclerites, shifts of musculature and formation of new articulations. Accepted: 5 April 2000     

Phylogeny of Paragnathorhynchus Meixner and Aculeorhynchus Schilke (Turbellaria, Kalyptorhynchia)

Paragnathorhynchus subterraneus Meixner is redescribed and identified with Prognathorhynchus stilofer Schilke. The paired tubular extracapsular secretory sacs in the proboscis apparatus of Aculeorhynchus glandulis Schilke are interpreted as evolutionary derivatives of intracapsular secretory vesicles in the proboscis of some Gnathorhynchidae. Aculeorhynchus Schilke is interpreted as an apomorph sister taxon of a group of taxa in the Gnathorhynchidae.     

Zur Morphologie und Phylogenie der Schizorhynchia (Turbellaria,Kalyptorhynchia)

The proboscis organs of 21 species of Schizorhynchia represent new characters. The meaning of apomorph characters of the proboscis organ and of certain parts of the genital apparatus is discussed. In the phylogenetic system the position of the four families of Schizorhynchia is considered.

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Gefördert durch eine Sachbeihilfe der Deutschen Forschungsgemeinschaft im Schwerpunktprogramm Litoralforschung — Abwassereinflüsse in Küstennahe.     

Photoreceptors with mitochondrial lenses inPogaina suecica (Plathelminthes,Rhabdocoela)

Summary The photoreceptors ofPogaina suecica correspond to the type of pigment cup ocelli. Each eye consists of one cup cell and three sensory cells. The most conspicuous differentiations of these eyes are lens elements formed by giant mitochondria densely filled with homogeneous electron-dense material. From electron microscopical findings available to date it is hypothesized that mitochondrial lensing might be an autapomorphy of a taxon comprising the Provorticidae Kirgisellinae, Dalyelliidae and Graffillidae groups which are ascribed to the paraphyletic Dalyellioida.Abbreviations l _1–3 lenses - npc nucleus of the pigment cell - pc pigment cell - pg pigment granule - rh rhabdomeres - sc _1–3 sensory cells     

Spermatozoa and spermatogenesis in Genostoma kozloffi (Plathelminthes, Rhabdocoela)

Genostoma kozloffi Hyra, 1993, is a symbiotic plathelminth living beneath the carapace of Nebalia pugettensis (Clark, 1932) (Leptostraca Crustacea). Because of similarities in the structure of its epidermis with that of the major group of parasitic flatworms, the Neodermata, and because of similarity in body form to a member of the Revertospermata, which includes the Neodermata and taxa that may be the sister group to the Neodermata, Genostoma was recently classified in the Revertospermata. By electron microscopy we found, however, that spermiogenesis in G. kozloffi does not occur in the manner characteristic of the Revertospermata. Instead, positioning of the axoneme and nucleus takes place as in free-living turbellarians in which the axoneme is fully incorporated, that is, in a distal-proximal fashion. Mature spermatozoa of G. kozloffi are filiform, possess an elongate rod-like nucleus, and one short single, fully incorporated axoneme. A rod of multiple, fused mitochondria accompanies the nucleus and axoneme, and an array of cortical microtubules with thickened walls runs the length of the sperm. Neither dense bodies nor acrosomal vesicles could be found. These features of its spermatozoa as well as the presence of a tunica surrounding its testes are reminiscent of the free-living group Kalyptorhynchia, specifically the Schizorhynchia. It is unlike the Kalyptorhynchia in other respects, however, and its systematic position remains uncertain, albeit removed from the Revertospermata.     

Fine structure of spermatozoa inAnthopharynx sacculipenis (Plathelminthes,Solenopharyngidae)

Summary The organisation of the spermatozoa ofAnthopharynx sacculipenis is described, based on electron-microscopical observations. The male gametes are fili-form in shape. They are totally enclosed by cortical microtubules and possess two free cilia. Special features are dot-like dense granules arranged in regular rows and terraced elaborations of the nuclear membrane. Such terraced elaborations are not known in any other species of flatworms whereas dot-like dense granules are described for some other taxa of the Rhabdocoela. Male gametes do not show synapomorphic correspondences between the Solenopharyngidae and the Prolecithiphora.Abbreviations ci cilia - ct cortical microtubules - db dense bodies - gl glycogen - mi mitochondrion - n nucleus - nt nuclear terraces     

小菜蛾成虫喙管感器的超微结构及其神经元中枢投射

【目的】明确小菜蛾Plutella xylostella成虫喙管感器的形态结构及感器神经元的投射。【方法】利用扫描电子显微镜观察小菜蛾成虫喙管结构和感器,利用神经回填技术和激光共聚焦显微镜观察喙管感器神经元在脑部的投射。【结果】小菜蛾成虫喙管上存在毛形感器(两种亚型)、腔锥形感器、锥形感器、刺形感器和栓锥形感器5种不同类型的感器。毛形感器表面光滑,分布于外颚叶外侧,可分为毛形感器Ⅰ型和Ⅱ型两种亚型,其中Ⅰ型比Ⅱ型长;锥形感器分布于喙管外表面,由一个感觉锥和一个短的圆形基座组成;腔锥形感器仅分布于食管内侧,只有一个粗短感觉锥而无基座;刺形感器由一个细长的感觉毛和一个圆形基座组成,表面无孔,分布于喙管的外表面;栓锥形感器是昆虫喙管上最典型的感受器,集中分布于喙管顶端区域,感器顶部凹腔伸出一个单感觉锥。此外,喙管上的感觉和运动神经元投射到初级味觉中枢咽下神经节。【结论】本研究阐明了小菜蛾成虫喙管感器的类型、分布和形态特征及其感器神经元在脑部的投射形态,为深入了解小菜蛾喙管感器的生理和功能奠定了基础。