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  • Life and Medical Sciences  (2)
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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The choanocyte chambers of eight different haplosclerid sponge species have been investigated with regard to their histological structure, their relation to the mesohyl, and their arrangement between the canal systems. Two fundamentally different organizational types occur in the investigated sponge species. In Haliclona rosea, H. oculata, H. elegans, H. simulans, H. rava, H. fistulosa, and Acervochalina limbata the choanocytes are separated from the mesohylar tissue, being more or less covered over the outer surface by pinacocytes belonging to the incurrent canal walls. In Haliclona indistincta, on the other hand, the choanocytes are, as in most other Demospongiae, in contact with the mesohyl at their outer surfaces. This indicates that the present order Haplosclerida is polyphyletic and contains sponges of a presumably poecilosclerid origin.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 186 (1985), S. 343-359 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this astrophorid sponge, both intercellular fibrils and spongin microfibrils are elaborated with the former forming exceptionally dense arrangements throughout much of the matrix. Fibrils are very dense below the surface where they surround the small silica asters and throughout the cortex in the form of bundles that can form pseudo-plywood arangements. In the endosome, fibril bundles are isolated and fewer in number. The surfaces of the large silica spicules are uniquely encased by intercellular fibrils or compacted intercellular fibrils that form a type of “fibrillar spongin” or spongin microfibrils intermixed with fibrils. Well developed microfibrillar spongin, intermixed with some fibrils, encases larger spicules below the sponge surface within the tissue and extends above the tissue surrounding spicules that emerge from the sponge thus placing this fibrillar matrix in direct contact with the sea water. The results of other studies suggest that the fibrils and microfibrils of this species are collagenous. The elaboration of these special matrices indicates that the differentiation of spongocytes (which secrete microfibrils) is weak and that the activity of lophocytes (which secrete fibril bundles) is highly labile. The variability of the fibrillar arrangements in this species supports the view that astrophorid sponges are possibly important for understanding the phylogeny of the organic skeletal matrix of sponges.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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