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  • 1
    Electronic Resource
    Electronic Resource
    Epidermal muscles and peristaltic burrowing in Carinoma tremaphoros (Nemertini): Correlates of effective burrowing without segmentation (1983)
    Springer
    Zoomorphology 103 (1983), S. 103-120 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A structural and ultrastructural investigation of epidermis in the esophageal region of Carinoma tremaphoros is correlated with analysis of burrowing locomotion. The pseudostratified epidermis contains multiciliated epidermal cells, gland cells and granule-containing basal or interstitial cells resting on a well-developed basement membrane. Both circular and longitudinal muscles are present within the epidermis, woven between the cells of this layer. These muscles are well-developed along the anterior region of the worm and, like the subepidermal muscles, are a variation of obliquely striated muscle without continuous Z-rods. Epidermal muscles originate as branches from the underlying mesodermal musculature and cross the basement membrane into the epidermis, confirming earlier observations. These muscles are unrelated to myoepithelial epidermal cells described in other metazoans. This condition is considered a secondary derivation consistent with the Gastraea-Enterocoel theory of bilateral metazoan evolution. Carinoma is a peristaltic burrower. Peristaltic waves are limited to the anterior region of the worm where the diameter of the rhynchocoel is maximal and the bilayered epidermal musculature is strongly developed. Following a consideration of burrowing mechanics in annelids, supernumerary epidermal muscles in Carinoma are interpreted as prerequisites to peristaltic burrowing effectiveness in a non-segmented coelomate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312241
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology of metazoan circulatory systems (1983)
    Springer
    Zoomorphology 103 (1983), S. 193-208 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The majority of large, bilaterally-symmetric animals possess two structurally distinct systems of internal fluid transport, the coelomic circulatory system and the blood vascular system (BVS). The coelomic circulatory system is generally situated laterally, lined by a continuous layer of mesodermally-derived cells and moves fluid with cilia or body wall muscles. The BVS occurs in extracellular matrix with the principal vessels situated dorsally and ventrally. The vessels are typically unlined by cells. Fluid is propelled by contraction of overlying muscle cells. Co-occurrence of two systems of internal fluid transport is explained by a segmentation hypothesis: Most large, triploblastic animals are segmented with at least two or three fluid-filled compartments separated by septal bulkheads. Because exchange surfaces (gas, nutrient) are regionally restricted, selective pressure favors a fluid transport system that bridges septal bulkheads. The BVS fulfills this requirement because it is situated in extracellular matrix that is non-cellular and continuous throughout organisms. A survey of animals indicates that all segmented taxa possess a BVS, except Sipuncula, where compensation sacs function as BVS analogues. Loss of the BVS in Hirudinea and other annelids is correlated with the disappearance of septa. Funicular vessels in Bryozoa are compared with BVS in other lophophorates. The fluid transport system of Nemertini and some platyhelminths is shown to conform to the definition of a coelomic circulatory system. This investigation supports Liwanow's proposition that the BVS evolved as the progressive modification of extracellular matrix in triploblastic animals. Evolution of coelomic circulatory systems is unresolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310477
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  • 3
    Electronic Resource
    Electronic Resource
    Hemoglobin-containing cells of Neodasys (Gastrotricha, Chaetonotida). I. Morphology and ultrastructure (1983)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 175 (1983), S. 57-64 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The overall anatomy of Neodasys as well as data for hemoglobin-containing cells are described. Hemoglobin-containing cells are shown to be mesodermal specializations constituting approximately 14% of the animal's total body volume (4.87 ± 104 μl). These globular cells (10-14 μm) are situated in two longitudinal rows, each dorsolateral to the straight gut. Branches from the cells enwrap perikarya of muscle and nerve cells whose mitochondria are found just below their respective plasmalemmata in intimate association with the hemoglobin-containing cells. The ground substance of the cytoplasm and nucleoplasm of these nearly organelle-free cells is extremely electron-dense and is presumed to represent the hemoglobin molecules. Locomotion analyses indicate that the cells can undergo a threefold change in linear dimension in 0.25 seconds, raising the possibility of convective mixing in these cells. Structural and ultrastructural comparisons with similar cells in adults of other species of Gastrotricha indicate that the hemoglobin-containing cells of Neodasys may be homologous to the socalled Y cells of other species, some of which contain myofilaments. A muscle-cell origin is considered for the evolution of hemoglobin-containing cells of Neodasys.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051750106
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