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  • Turbellaria  (37)
  • Springer  (37)
  • American Institute of Physics
  • Copernicus
  • 1985-1989  (37)
  • 1970-1974
  • 1986  (37)
Collection
Keywords
Publisher
  • Springer  (37)
  • American Institute of Physics
  • Copernicus
Years
  • 1985-1989  (37)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    Development of the reproductive apparatus of the land planarian Rhynchodemus sylvaticus (Turbellaria: Tricladida) and its significance for classification in the genus (1986)
    Springer
    Hydrobiologia 132 (1986), S. 175-180 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; land planarians ; copulatory organ development ; systematics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seven specimens of Rhynchodemus sylvaticus (Leidy) collected from a variety of localities in the US and having variously developed copulatory organs are believed to represent stages in the development of the copulatory apparatus. Four specimens were juveniles with under-developed male components, one specimen had a well-developed female atrium and small male component, and two specimens were mature with a male organ twice the size of the female part. In early stages, the male component had sperm ducts, seminal vesicle, and narrow atrium; more mature stages had a considerable elongated atrium with thick folds in its muscularized wall, a massive muscular bulbus; and a sigmoid ejaculatory duct opening into the large bulbar cavity. Morphological features of mature male copulatory organs in all species of the genus Rhynchodemus are basically similar whereas external body features (color and number of dorsal stripes) of these same species differ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046245
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative ultrastructure of copulatory organs having a stylet in the Proseriata (Turbellaria) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 165-173 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Proseriata ; ultrastructure ; copulatory organ ; hard structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructure of male copulatory organs having a stylet has been studied in some genera of the Proseriata. Within the Monocelididae there was a variety of stylet-like hard structures. The stylet in Monocelis fusca was a differentiation of the basement membrane of the epithelium lining a penis-like muscular papilla. The penis papilla in Ectocotyla consisted of circular muscles surrounded by a thickened basement membrane and an epithelium. Archilopsis sp. and Archilina sp. with a duplex copulatory bulb, had a stylet within a spiny cirrus. The stylet in Archilopsis sp. was a cylindrical muscular protrusion with a thickened basement lamina that lined the cirrus lumen. The stylet structure in Archilina sp. was composed of four long spines which were derivatives of the basement membrane. In Ectocotyla multitesticulata and Dupliminona corsicana, the accessory prostatoid organ was provided with a hook-shaped stylet that was differentiated in the basement membrane and of which the material was continuous with the fibrous matrix between the muscles of the prostatic bulb. The stylet and needles in the Archimonocelis species were intracellular differentiations. The copulatory organ in Carenscoilia biforamen consisted of a tubiform stylet and four needles, all of which were also intracellular specializations. I consider copulatory hard structures in the Turbellaria to be taxonomically significant in terms of structure, differentiation, and location (whether subcellular, in the basement membrane, or intracellular).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046244
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  • 3
    Electronic Resource
    Electronic Resource
    Cell migration and differentiation during wound healing and regeneration in Microstomum lineare (Turbellaria) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 181-188 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; wound healing ; regeneration ; [3H]T-autoradiography ; differentiation ; Macrostomida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using transmission electron microscopy and serial sections with light-microscopic autoradiography, I have investigated the ultrastructure of wound healing, the distribution of cells preparing for proliferation, and the fates of cells labelled with exogenous tritiated thymidine ([3H]T) in Microstomum lineare undergoing wound healing and regeneration. Immediately after decapitation the open wound was reduced to a minimum by strong contraction of circular muscle fibers. The wound epidermis was cellular, consisting of thin parts of epidermal cells from the epidermis around the wound. These epidermal cells maintained close adhesive contact with one another through zonulae adherentes and septate junctions. No proliferating cells were found in the old epidermis. The only cells taking up [3H]T were mesenchymal and gastrodermal neoblasts which proliferated and migrated towards the surface. The final epidermis was formed by conjunction of the wound epidermis and newly differentiated epidermal cells. Regeneration in Microstomum, in contrast to that of planarians, occurs mainly by morphallaxis, without the formation of a regeneration blastema, but also through continuous cell proliferation, migration, and differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046246
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  • 4
    Electronic Resource
    Electronic Resource
    Physiological regeneration of the digestive parenchyma in Convoluta convoluta and Oxyposthia praedator (Turbellaria, Acoela) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 189-193 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Acoela ; histology ; cell proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Autoradiography has been applied to two acoel turbellarians, Convoluta convoluta and Oxyposthia praedator, to determine the distribution and fate of proliferative cells. In C. convoluta, mitotic figures and nuclei that labelled with [3H]thymidine could be observed in the peripheral parenchyma but not in the middle zone of the central parenchyma. The time required for regeneration of physiologically competent digestive cells was about 10–15 days. In O. praedator, mitotic figures (in metaphase and telophase) were observed in the peripheral parenchyma while none were found in the epidermis either in untreated animals or after treatment with colchicine. Mitotic figures were found only rarely in the central parenchyma and only in its marginal zone. Autoradiographs of O. praedator demonstrated [3H]thymidine incorporation into both the nuclei and the cytoplasm of peripheral parenchymal cells. In the central parenchyma, no nuclei with primary labelling were observed. The digestive parenchyma of the acoels is regarded as a unique histological system involving both specialized cells of the central parenchyma and stem cells located in the peripheral parenchyma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046247
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  • 5
    Electronic Resource
    Electronic Resource
    Positional information and gonadal differentiation in the planarian Dugesia lugubris (Turbellaria) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 201-206 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia ; gonad ; transplantation ; regeneration ; positional information
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The planarian Dugesia lugubris is a balanced hermaphrodite, meaning that male genetic factors are in equilibrium with female factors. Differentiation of the gonads is controlled by the region in which they develop. According to the classical theory of germ cell formation, these cells stem from neoblasts that are induced to differentiate by factors specific to the gonadal regions, factors presumably due to gradients formed by neurosecretory activity of the cephalic ganglia and longitudinal nerve cords. A more recently proposed theory holds that germ cells in regenerates originate not from neoblasts but from dedifferentiated cells and that characteristics of the gonadal regions are determined by direct interactions of cells here. Results of our experiments with homo- and autoplastic grafst support the classical theory. Prepharyngeal portions grafted onto posterior body portions retained their ability to maintain or induce development of ovaries. Postpharyngeal portions grafted onto anterior portions produced only testes even though the brain developed normally in these regenerates. Under these experimental conditions, gonad regeneration took longer than it does in normal regeneration (i.e., that in which body regions are not displaced).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046249
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructural observations on gastrodermal regeneration in the planarian Dugesia japonica (Turbellaria) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 217-222 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Dugesia japonica ; regeneration ; gastrodermis ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The earliest detectable change during regeneration of the gastrodermis in Dugesia japonica was an aggregation of regenerative cells underneath the gastrodermis remaining at the wound margin. The gastrodermal cells in experimental regenerates retained some of their original characters and presented no indication of cell dedifferentiation. The regenerative cells came into contact with the basal surface of gastrodermal cells, forming stratified cell layers. Differentiation of these cells into gastrodermal cells was initiated by the development of synthetic organelles within their cytoplasm. These differentiating cells gave rise to two different types of gastrodermal cells, namely phagocytic cells and sphere cells. In later stages, there was an apparent movement of differentiated gastrodermal cells towards the parenchyma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046251
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  • 7
    Electronic Resource
    Electronic Resource
    Distribution, abundance, and size of rhabdoids in Dugesia polychroa. (Turbellaria: Tricladida) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 287-293 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Tricladida ; Dugesia ; rhabdoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ontogenetic changes in the distribution, abundance, and size of rhabdoids were examined in an undisturbed laboratory population of Dugesia polychroa. Irrespective of triclad age, rhabdoids in the epidermis and parenchyma were more abundant on the dorsal than the ventral side of the body. No significant differences were found in the abundance of epidermal or parenchymal rhabdoids among the anterior, medial, and posterior regions of the body. Rhabdoid number and size changed significantly with triclad age, with a marked depression coinciding with the onset of cocoon production. Rhabdoid discharge was correlated with physical and/or physiological disturbance and occurred in the absence of any overt environmental disturbance. Simple allometric relationships were observed between rhabdoid size and number on one hand and body plan area on the other. Different allometric trends were observed from field-collected individuals compared to the undisturbed laboratory population. The potential function of rhabdoids in the Tricladida is discussed in light of these findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046262
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  • 8
    Electronic Resource
    Electronic Resource
    Salinity-temperature tolerance of two closely related triclad species, Dugesia lugubris and D. polychroa (Turbellaria), in relation to their distribution in The Netherlands (1986)
    Springer
    Hydrobiologia 132 (1986), S. 279-286 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; triclads ; salinity ; temperature ; tolerance ; distribution ; habitat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The tolerance of adult specimens of Dugesia lugubris and D. polychroa for 13 different chlorinities ranging from 15.0–3.8‰ and for two temperatures, viz. 4 and 23 °C, was tested. At chlorinities of 7.5‰ and lower, the survival time of both species was considerably longer than at higher chlorinities (a few hours at 7.5‰, one to several days at 6.6‰ and lower concentrations). It is assumed that this is determined by the osmoregulatory capacity of the planarians. It was found that at low chlorinities combined with a high temperature D. polychroa survived longer than D. lugubris, while at the same chlorinities the opposite was true for a low temperature. The effect of temperature on survival at low chlorinities was more drastic for D. lugubris than for D. polychroa. The results correlate with data on the distribution of both species in The Netherlands. Outside areas with an average chlorinity below 2‰ the two species were rarely found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046261
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  • 9
    Electronic Resource
    Electronic Resource
    Initial morphological diversity as a criterion in deciphering turbellarian phylogeny (1986)
    Springer
    Hydrobiologia 132 (1986), S. 31-33 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; evolutionary morphology ; phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The most profound structural variety in morphofunctional systems and morphogenetic mechanisms, i.e. the highest morphological diversity, is observed in those groups where these systems and mechanisms are evolutionarily most primitive. Here, such variety can involve the basic body plan of a given phylum and the types of morphogenesis characteristic of it. This correlation provides a new criterion of evolutionary primitiveness, namely, the criterion of initial morphological diversity. The highest morphological diversity among turbellarian groups is observed in the order Acoela. Acoel turbellarians are archaic in most of their features, apparently being a group near the base of the turbellarian phylogenetic tree. Among other turbellarians there are a few groups that also are archaic in some few features (above all, the Catenulida), although on the whole they are more advanced than the Acoela. The Turbellaria as a whole is notable for its morphological diversity in comparison with other classes of the Scolecida.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046225
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrastructure of the copulatory stylet and accessory spines in Haplopharynx quadristimulus (Turbellaria) (1986)
    Springer
    Hydrobiologia 132 (1986), S. 157-163 
    Details
    ISSN: 1573-5117
    Keywords: Turbellaria ; Haplopharyngida ; ultrastructure ; reproductive system ; stylet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The copulatory organ of Haplopharynx quadristimulus Ax, 1971 (Carolina form, Rieger, 1977) consists of a proximal prostatic vesicle and a distal stylet apparatus comprising a central tubular stylet and four to five peripheral accessory spines. By electron microscopy it could be seen that the stylet and spines were intracellular specializations. The copulatory organ can be interpreted as a specialization of an epithelial canal extending from the testes to the body wall. In the complex stylet apparatus, the epithelium was differentiated into six cell types. The stylet, which was formed in a matrix syncytium next to the prostatic vesicle, extended into the lumen of the stylet canal. The interior of the stylet apparatus contained one group of cells that had thick ciliary rootlets and another that had rootlet-like ribbons. The cells that contain the rootlets enveloped bundles of longitudinally arranged muscles. The accessory spines were formed in cells which lay peripheral to the muscle bundles. The spines, stylet, rootlet-like ribbons, and rootlets had similar patterns of periodic cross striations. The similarity in striation patterns suggests that the accessory spines and stylet are composed of modified ciliary rootlets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046243
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