bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monoaminergic Systems in the Hypothalamus of the Acanthopterygian Chelon labrosus (Risso, 1826), with Special Reference to the Organon Vasculosum Hypothalami
Authors: Gómez‐Segade Pablo , Anadón Ramón , Gómez‐Segade Luis 
Published: April 2010

AbstractDistribution of biogenic amines in the diencephalon of the advanced teleost Chelon labrosus was investigated by formaldehyde‐induced fluorescence. We have found three closely interrelated bright yellow‐green fluorescent monoaminergic cell groups having numerous cerebrospinal fluid‐contacting cells with dendritic processes that protrude into the lumen of the third ventricle. The most rostral of them, the organon vasculosum hypothalami, located dorsally at the mid and caudal hypothalamus level, showed under electron microscopy some monoaminergic cells and others with an abundant smooth endoplasmic reticulum. The cerebrospinal fluid‐contacting processes of both cell types, in association with numerous fibres, terminal buttons and some capillaries, constitute a thick and complex intraventricular mat. The other two fluorescent regions, nucleus recessi lateralis and nucleus recessi posterioris, border the lateral and posterior recesses of the hypothalamus.The ultrastructural characteristics of the organon vasculosum hypothalami and its intraventricular mat suggest a function in the regulation of chemical changes in the cerebrospinal fluid. These monoaminergic regions probably represent three cell masses originated from a single region in primitive fish.
The Ulrastructure of the Gill of the Lugworm Arenicola marina (L.) (Annelida, Polychaeta)
Authors: Jouin Claude , Toulmond André 
Published: April 2010

AbstractArenicola marina gills are hollow, branched, body outgrowths with a central coelomic cavity and afferent and efferent vessels. The gill surface area per unit body weight is about 4 cm2/g wet weight. The blood vascular system anatomy differs from the tip to the base of the gill. In the distal branches of the gill the superficial afferent and efferent vessels are joined by connecting vessels. All vessels arise as spacings between the basal laminae of the thin epidermis and of the coelomic myoepithelium. The contractile part of this epithelium mainly borders the afferent and efferent vessels, whereas pedicel‐like cytoplasmic processes extend from the cell bodies and mainly line the connecting vessels. In the proximal branches of the gill the afferent and efferent vessels located in the coelomic cavity are surrounded by the coelomic myoepithelium, and a peripheral blood plexus is present below the epidermis. The gill epidermis is everywhere thin and does not exhibit the characters of a transporting epithelium. The gill coelomic myoepithelium has several functions: (i) periodic contractions of the gill, propelling blood and coelomic fluid toward the central vascular and coelomic compartments; (ii) blood ultrafilration toward the coelomic cavity; (iii) probably transport, suggested by the specialized structures of the lateral membranes of the cells.
Duplex Retina in the Mesopelagic Deep‐Sea Teleost Lestidiops affinis (Ege, 1930)
Authors: Munk Ole 
Published: April 2010

AbstractThe eye of the deep‐sea teleost Lestidiops affinis has been examined primarily by light microscopy and found to possess a duplex retina consisting of two main divisions, a pure‐cone and a pure‐rod region, with a narrow zone of transition, possessing both cones and rods, joining the two. The pure‐cone region is located in the temporal (caudal) part of the retina subserving binocular vision in the rostral direction. It has an area temporalis retinae with particularly long and densely packed single cones arranged in a regular hexagonal mosaic. Joined (double or twin) cones have not been recognized with certainty in the pure‐cone region. The pure‐rod region, comprising the larger part of the retina, contains rods grouped in bundles separated by retinal pigment epithelium (RPE) processes with pigmented cores. The synaptic endings of the rods are arranged in separate clusters in the outer plexiform layer, there being apparently a separate rod pedicle cluster beneath (vitread to) each rod bundle. Structural comparisons with certain other deep‐sea teleosts suggest the likely presence of a retinal tapetum in L. affinis, i.e. each single cone or rod bundle is situated in a reflecting pit formed by the RPE, with a discrete reflector apposed to the tip of each cone outer segment and the tips of the outer segments of each square‐cut rod bundle.
The Structure of a Sessile, Stalkless Crinoid (Holopus rangii)
Authors: Grimmer John C. , Holland Nicholas D. 
Published: April 2010

AbstractSpecimens of Holopus rangii (order Cyrtocrinida) were collected by submersible at depths of several hundred meters in the Caribbean and fixed for light and electron microscopy. The presence of an anus is confirmed. However, the chambered organ and glandular axial organ peculiar to crinoids are lacking. The gut lumen sometimes includes partially digested prey items up to several hundred micrometers in diameter, and we propose that Holopus may feed raptorially by rapidly closing its arms over demersal zooplankton. Electron microscopy of the arm reveals a radial nerve and a radial haemal channel, which light microscopy previously failed to demonstrate. The cuticle includes bacteria that are probably symbiotic. The ten brachial nerves of the aboral nervous system unite pairwise to form five calyx nerves. The calyx nerves, one in each radial position, are connected by a pentagonal, interradial commissure and then continue to the attached end of the body where they end blindly without forming an aboral nerve center. The absence of the aboral nerve center and related internal organs strengthens the argument that no basal ossicles are included in the skeleton of the calyx and suggests that Holopus may have evolved from stalked cyrtocrinid ancestors by saltatory loss of major body parts.
The Eyes of Mesostoma ehrenbergi (Focke, 1836) (Platyhelminthes, Rhabdocoela). Fine Structure and Photoreceptor Membrane Turnover
Authors: Bedini Celina , Lanfranchi Alberto 
Published: April 2010

Abstract Each pigment‐cup eye of Mesostoma ehrenbergi consists of two photoreceptor cells, the anterior cell being bilobate. the posterior almost linear, and of a multicellular pigment cup. The nuclei of the photoreceptor cells are located inside the medial region of the brain. Thin cytoplasmic photoreceptor projections provided with neurosecretory‐like granules are interposed between the inner surface of the eye cup and the distal extremity of the microvilli.The breakdown and renewal of microvillar membranes was analysed. Membrane turnover is a continuous process. At dusk and during the night abscission of photoreceptive membranes occurs. At dawn the membrane fragments are degraded to granular material, which is then endocytosed into the submicrovillar cytoplasm as coated vesicles. These vesicles form multivesicular bodies. The degradation of multivesicular body content occurs during the following light hours. The dark period is correlated with membrane synthesis for elongation of reticular membranes, which are converted into ellipsoid bodies. The formation of new microvillar membranes occurs at the base of the microvillar border, and involves the fusion with the old microvillar membranes of small vesicles detached from the tubular endoplasmic membranes and from the flattened concentric cisternae of ellipsoid bodies. The correlations with daily cycles of other invertebrates are discussed.
The Development of the Brachiopod Crania (Neocrania) anomala (O. F. Müller)and its Phylogenetic Significance
Authors: Nielsen Claus 
Published: April 2010

AbstractThe freely spawned eggs of Crania go through radial cleavage, embolic gastrulation, and the posteroventral part of the archenteron forms mesoderm through modified enterocoely. The blastopore closes in the posterior end of the larva. The ciliated, lecithotrophic larva has four pairs of coelomic pouches and three pairs of dorsal setal bundles. At metamorphosis, the larva curls ventrally by contraction of a pair of midventral muscles, which are extensions of the first pair of coelomic sacs; the larva attaches by the epithelium just behind the closed blastopore. The brachial valve is secreted by the middle part of the dorsal epithelium and the pedicle valve is secreted by the attachment epithelium. The second pair of coelomic sacs develop small attachment areas at the edge of the dorsal valve and become the lophophore coelom (mesocoel); the third pair of coelomic sacs become the body coelom (metacoel) with the adductor muscles. The posterior position of the closing blastopore is characteristic of deuterostomes. The ventral curving of the settling larva and the formation of both valves from dorsal epithelial areas indicate that the brachiopods have a very short ventral side as opposed to the phoronids. It is concluded that both groups have originated from a creeping ancestor with a straight gut.
Ultrastructural Study of Spermatogenesis in Gamasid Mites (Acari, Gamasida)
Authors: Witaliński W. , Dallai R. 
Published: April 2010

AbstractStructural alterations accompanying the development of germ cells in representatives of two families of gamasid mites: Pergamasidae (Pergumasus barbarus. P. truatellus) and Parasitidae (Porrhostaspis lunulata) were examined by scanning electron microscopy. Spermatogenesis occurs in cysts containing two (P. lunuluta) or four spermatogonia (P. barbarus and P. truatellus) prior to meiosis. later arranged in a tetrahedral pattern. Meiosis produces 8 and 16 spermatids per cyst, respectively. Spermatids are located radially and elongate synchronously. Dimples appear at their acrosomal ends, soon replaced by peg‐like structures surrounded by superficial ridges. The number of ridges which correspond to longitudinal ribbons can vary between and within species as well as between spermatids occupying one cyst. Our observations suggest some unknown mechanism which allows the spermatozoa to enter vasa deferentia in a unidirectional orientation.
Fine Structure of the Tentacles of Phoronis australis Haswell (Phoronida, Lophophorata)
Authors: Pardos F. , Roldán C. , Benito J. , Emig C. C. 
Published: April 2010

AbstractThe epidermis of the tentacles of Phoronis australis consists of six cell types: supporting cells, choanocyte‐like sensory cells, both types monociliated, secretory A‐cells with a mucous secretion, and three kinds of B‐cells with mucoprotein secretions. On cross‐sections of the tentacle, one can distinguish four faces: the frontal one, heavily ciliated and located between the two frontolateral rows of sensory cells, the lateral and the abfrontal ones. The orientation of the basal structures of the cilia is related to the direction of their beat. The basiepidermal nervous system is grouped mainly at the frontal and abfrontal faces. The basement membrane is thickest on the frontal face and consists of circular collagen fibrils near the epidermis and longitudinal ones near the peritoneum. All peritoneal cells surrounding the mesocoel are provided with smooth longitudinal myofibrils, and isolated axons are situated between these cells and the basement membrane. The wall of the single blood capillary in each tentacle consists of epitheliomuscular cells with circular myofilaments, lying on a thin internal basal lamina; there is no endothelium.
Ultrastructure of Spermatozoa and Spermatids in Bonellia viridis and Hamingia arctica (Echiura) With Some Phylogenetic Considerations
Authors: Franzén Åke , Ferraguti Marco 
Published: April 2010

AbstractSpermatozoa of the echiurans Bonellia viridis and Hamingia arctica show a similar ultrastructure. They are of a modified type. The head consists of a roughly cylindrical nucleus, which has a cover of electron‐dense material. The acrosome is very large and consists of an acrosomal vesicle and a rod‐shaped perforatorium or acrosomal rod. In close association with the nucleus, one or two mitochondria are found forming an irregular ring around the posterior tip of the nucleus and the centriolar apparatus. There are two centrioles, the proximal one with the conventional triplet microtubular structure. The tail flagellum is about 50 μm long and has the 9+2 axonemal structure. The oblique attachment of the acrosome to the anterior part of the nucleus gives the spermatozoon a bilateral symmetry. However, in the nuclear morphology, the arrangement of electron‐dense material around the nucleus, in the mitochondria, and in the attachment of the tail flagellum, the spermatozoon shows asymmetric organization. The sperm structure in bonelliids is unique but its genesis and the morphology of the mitochondrial midpiece support the theory that the echiurans are related to the annelids. The main results of the study are summarized in Fig. 11.
Ultrastructure of the Spermatozoa and Spermatophores of the Zuwai Crab, Chionoecetes opilio (Majidae, Brachyura)
Authors: Chiba A. , Kon T. , Honma Y. 
Published: April 2010

AbstractThe fine structure of the spermatozoa and spermatophores of the zuwai crab, Chionoecetes opilio, was examined electron microscopically. The spermatophores embedded in the secretory droplets within the vasa deferentia showed a spherical structure with an extremely wrinkled envelope and contained numerous spermatozoa. The mature spermatozoa of this crab, similar to those of other brachyurans, were stellate in shape and had a globular acrosome surrounded by a cup‐like nucleus with several radiating processes. The acrosome was ultrastructurally complex and its apical part was characterized by an electron‐dense discoid structure, whereas its innermost part was occupied by an electron‐lucent cylindrical structure containing assemblies of thin tubules and a reticular formation of electron‐dense material. The cytoplasm interposed between the nucleus and acrosome was remarkably reduced in volume and displayed a membranous lamellar complex, few mitochondria, and a centriole. The nuclear chromatin was not condensed but represented by finely flocculent material. The morphological aspects of the zuwai crab spermatozoa are discussed in comparison with those of other decapod crustaceans.
The Oldest Arthropods and the Origin of the Crustacea
Authors: Bergström Jan 
Published: April 2010

AbstractIn the last decade new finds in the Cambrian of well‐preserved faunas have given us a wealth of new material. This has meant a virtual explosion in our knowledge of the earliest arthropods, although only a fraction of the material has as yet been described. Most significantly, perhaps, the valuable descriptions of the Orsten material have shed some light on the origination of crustaceans through the sequential acquisition of crustacean characters in a group of ‘stemgroup crustaceans’ and even more basic forms. An attempt is made to outline an evolutionary tree leading on one side to trilobitomorphs and chelicerates, on the other to crustaceans and related forms. It involves numbers of synapomorphies added successively, and it appears unlikely that true crustaceans were present already in the earliest Cambrian.
Computerized Analysis of Crustacean Relationships
Authors: Wilson George D. F. 
Published: April 2010

AbstractThe strengths and weaknesses of phylogenetic analysis using computers are reviewed from the viewpoint of understanding crustacean evolution. Computerized methods require the explicit presentation of characters and character state homologies. New techniques allow investigators to design evolutionary models into a character data matrix, or to use evolutionary models that make minimal a priori assumptions. The computer analysis relieves the investigator from the highly repetitious testing of trees, allows the concentration on the character state data, and provides objective methods for comparing trees, primarily their length. These are regarded as the strengths of computerized methods. The weaknesses of these methods include the relatively inscrutable nature of the character data matrix compared with the overall ‘gestalt’ of resulting trees, the difficulties of defining discrete homologies within the Crustacea, especially for counts of segmentation, the lack of clear intermediate character states in some multistate segmental characters, and the inability to define evolutionary polarity. These difficulties may be overcome by analysing the data using the minimal assumption models of character evolution, and by a recognition that the trees are a result of the input data, and therefore the data should be criticized, rather than the trees themselves. A ‘consensus’ character data set, including most extant major groups of the Crustacea as well as several key fossils, was assembled and revised by the participants in the workshop. An artificial taxon, ‘ur‐crustacean characters’, was introduced to root the tree. Three observations may be made from parsimony analyses using several weighting and tree rooting methods. (1) The currently accepted large scale phylogeny and classification of the Crustacea is not corroborated. (2) The number of supposed plesiomorphic traits possessed by a taxon is not a good index for early derivation in crustacean evolution. (3) The taxon Maxillopoda is not supported by the arrangement of any of the trees.
F‐Actin and Tubulin During Spermatogenesis in Gamasid Mites (Acari: Parasitina)
Authors: Witaliñski W. , Dallai R. 
Published: April 2010

Abstract F‐actin and tubulin behaviour was investigated using fluorescence probes and electron microscopy in the course of spermatogenesis in two gamasid mites, Porrhostaspis lunulata Müller (Parasitidae) and Pergamasus truatellus Athias‐Henriot (Pergamasidae). In spermatogonia and primary spermatocytes of both species, the proteins were localized mainly in the intercellular bridges and, in lesser quantities, in the cytoplasm. Overall, actin was present along the plasma‐lemmal contact sites of the gonial cells.At the beginning of spermatid elongation, actin could be detected in two regions: in perinuclear cytoplasm and under the plasmalemma. Subplasmalemmal actin, visible as threads running along acrosome‐adhering protrusions of the nuclear envelope, is supposedly located within the electron‐dense material filling the subacrosomal gap. Tubulin was found on both sides of each actin thread; its location was consistent with two sets of microtubules adhering to the inner acrosomal membrane. Their involvement in acrosome shaping is suggested.As spermatid elongation terminated, the previous pattern of proteins disappeared. In Pergamasus, however, actin emerged briefly near the centrifugal ends of spermatids (granular bodies zone).In spermatocyte‐containing cysts, actin and tubulin fluorescence (more pronounced in Porrhostaspis) was associated with intercellular junctions between the cyst cells. In both species, diffuse actin fluorescence was also detected in the cytoplasm of cyst cells assembling elongated spermatids; the reaction was intensified at the end of the elongation process, when the cytoplasm of cyst cells aggregated around the centripetal ends of spermatids.
Ultrastructure of the Accessory Glands in Female Genitalia of Pholcus phalangioides(Fuesslin, 1775) (Pholcidae; Araneae)
Authors: Uhl Gabriele 
Published: April 2010

AbstractPholcus phalangioidesdoes not possess receptacular seminis. The uterus externus (genital cavity) itself functions as a sperm storage structure. Two accessory glands are situated in the dorsal part of the uterus externus; they discharge their secretory product into the genital cavity.The secretion is considered to serve primarily as a matrix for sperm storage, i.e. to keep the spermatozoa in a fixed position.The accessory glands consist of numerous glandular units, each being composed of four cells: two secretory cells are always joined and surrounded twice by an inner and an outer envelope cell. Both envelope cells take part in forming a cuticular ductule that leads from the secretory cells to the pore plates of the uterus externus. The inner envelope cell produces the proximal part of the canal close to the microvilli of the secretory cells, whereas the outer envelope cell produces the distal part of the canal leading to the pore plate. Close to the pore the latter exhibits prominent microvilli that might indicate additional secretory activity.
The Fine Structure of Trichobothria in Moss Mites with Special Emphasis onAcrogalumna longipluma(Berlese, 1904) (Oribatida, Acari, Arachnida)
Authors: Alberti Gerd , Moreno Ana I. , Kratzmann Markus 
Published: April 2010

AbstractUsing SEM and TEM techniques, the trichobothria ofAcrogalumna longipluma(Galumnidae, Pterogasterina) were studied in relation to a variety of other moss mites. Each sensillum is composed of a mostly solid bothridial seta and a very complex socket, the bothridium. The setal base bends sharply as it passes through the six chambers of the bothridium, which are arranged in an S‐shaped configuration. The proximal end of the seta is an elongated oval and inserted into a thin socket membrane provided with radiating suspension fibres. This peculiar shape of the setal base proper and probably also the existence of connecting pieces are assumed to provide directionality to the sensillum. Two differently shaped tubular bodies are found under the setal base, of which only one is in contact with the seta. The tubular bodies are surrounded by peculiar ‘dense tubes’, i.e. derivatives of the dendritic sheath. The rather thick, outer dendritic segments curve through an extensive receptor lymph cavity and terminate with ciliary regions. The inner dendritic segments are only short. Perikarya and axons as well as the enveloping cells do not show any peculiarities. The trichobothria of moss mites most probably represent vibration receptors reacting to substrate and/or air‐borne stimuli. The variety of shapes and the complexity, which is not found to this extent in any other arthropod group, are discussed in relation to ecophysiological demands.
Matrix Heterogeneity in the Radular Teeth of the Chiton Acanthopleura hirtosa
Authors: Evans L. A. , Macey D. J. , Webb J. 
Published: April 2010

AbstractThe structure and organization of the organic matrix of the cusps of the major lateral teeth of the chiton Acanthopleura hirtosahave been examined using conventional light and transmission electron microscopy techniques and by using the protein ferritin as an ultrastructural probe. The results show major structural differences in the organic matrix between the surface layers of the anterior (calcified) region and the posterior (magnetite‐mineralized) region and their respective underlying regions. In addition, the central (lepidocrocite‐mineralized) region of the tooth has been examined and shown to consist of bundles of fibres arranged such that they display a tightly interwoven pattern. It is suggested that while the structural organization of surface fibres readily permits the passage of ions required for mineralization, the architecturally discrete distribution of biominerals found in mature chiton teeth is due mostly to spatial delineation of the tooth by matrix macromolecules in the central region of the tooth.