Fine Structural Observations on the Turbellarians <i>Stenostomum</i> sp. and <i>Microstomum lineare</i> with Special Reference to the Extracellular Matrix and Connective Tissue Systems

Pedersen, Knud Jørgen

doi:10.1111/j.1463-6395.1983.tb00799.x

Cited by 19 publications

(37 citation statements)

References 34 publications

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“…The oogenesis is highly specialized with a complicated system of nurse cells which empty their cytoplasm into the oocyte (Pianka, 1974). The cleavage is biradial and highly determined already at the two-cell stage.…”

Section: Pro Tornaeozoamentioning

confidence: 99%

Animal phylogeny in the light of the trochaea theory

Nielsen¹

1985

Biological Journal of the Linnean Society

128

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Ultrastructural similarities unite Choanoflagellata and Metazoa as the Kingdom Animalia.Metazoa (Porifera + Placozoa + Gastraeozoa) are characterized by the presence of collagen, septate/tight junctions and spermatozoa. Porifera and Placozoa lack basal lamina, nerve cells and synapses, which characterize Gastraeozoa (Cnidaria + Trochaeozoa). Cnidaria have cnidoblasts and lack the multiciliate cells found in almost all Trochaeozoa (Gastroneuralia + Protornaeozoa). Gastroneuralia (Spiralia + Aschelminthes) have an apical brain and a pair of ventral nerves, a blastopore which becomes mouth and anus, a mouth surrounded by a downstream collecting system of compound cilia, and a mesoderm formed from the blastopore lips. Spiralia (Articulata + Parenchymia + Bryozoa) have spiral cleavage and 4d-cell mesoderm, whereas these characters are lacking in Aschelminthes, which all lack primary larvae. Protornaeozoa (Ctenophora + Notoneuralia) have mesoderm from vegetal cells. Ctenophores have colloblasts. Notoneuralia have a dorsal nervous system behind the apical area and form a new mouth surrounded by an upstream collecting system of single cilia on monociliate cells; the blastopore becomes the anus surrounded by a ring of compound cilia.These features fit the trochaea theory, which proposes that Gastroneuralia and Notoneuralia evolved independently from the trochaea, a blastaea with the blastopore surrounded by a ring of rompound cilia, which were both locomotory and particle collecting.

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Section: Pro Tornaeozoamentioning

confidence: 99%

Animal phylogeny in the light of the trochaea theory

Nielsen¹

1985

Biological Journal of the Linnean Society

128

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“…All these genera are rather different from other macrostomorphans (the Microstomidae, Dolichomacrostomidae, and Haplopharyngida) which have a complete matrix layer beneath the epidermis at least. A distinct limiting layer seems absent, however, in all of the Macrostomorpha (Rieger, 1981;Pedersen, 1983;Tyler, 1984).…”

Section: Arrangement Of Ecmmentioning

confidence: 99%

Organization and differentiation of the body-wall musculature in Macrostomum (Turbellaria, Macrostomidae)

et al. 1991

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We studied the body-wall musculature, its ECM (extracellular matrix), and the junctional complexes between muscle cells and between muscle cells and ECM in Macrostomum hystricinum marinum Rieger, 1977, using Nomarski-contrast and electron microscopy. Differentiation of these body-wall components was followed by monitoring embryonic stages at 52%) 64%) and 82% of the time between egg-laying and hatching and with study of the hatchling and adult stages. For comparison, the body-wall musculature of other macrostomidans has been examined in conventional light-histological sections. Muscles form a grid of longitudinally, diagonally, and circularly oriented fibers beneath the epidermis in M. hystricinum marinum and this orientation of cells can be found already in embryos at 64% development. Younger embryos at 52% development show no muscle differentiation. The ECM forms a net-like arrangement that apparently envelops the individual muscle cells. Characteristic knob-like thickenings of the ECM occur at the base of the epidermis. Muscle cells attach to each other, to the epidermis, and to other cell types through hemidesmosome-like junctions at thickenings of the ECM in the adult and hatchling stages; no true desmosomes exist between muscle cells. Gap junctions occur commonly between longitudinal muscles of adult specimens and between perikarya of muscle cells in embryos at 64% and 82% development.More comparative studies are needed to determine the systematic value of presence or absence of the diagonal muscle fibers in the body wall of turbellarians.

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“…Turbellarians have an ECM (extracellular matrix) that ranges in robustness depending on the species: some have just enough to separate cells from each other, others have discrete basement membranes and collagen skeletons (Pedersen, 1983;Tyler, 1984). As the ratio of ECM to cellular tissue varies greatly among species and even among different regions of the same worm, its degree of differentiation is not assumed to reflect phylogenetic relationships but rather to relate only to body size and mode of locomotion (Ehlers, 1985;Smith & Tyler, 1985).…”

Section: Introductionmentioning

confidence: 99%

“…ECM's are mainly composed of macromolecules such as collagens, adhesive glycoproteins, and proteoglycans that interact with each other and with cell-surface receptors through specific binding sites (Kornblihtt & Gutmann, 1988). The small amount of ECM present in turbellarians makes histochemical studies at the light microscopical level difficult (Pedersen, 1983;Lindroos & Wikgren, 1987). Ul-trastructurally, ECM is known to consist of an amorphous ground substance and non-striated collagenous fibrils, 8-10 nm in diameter (Pedersen, 1983;Rieger, 1985).…”

Section: Introductionmentioning

confidence: 99%

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Extracellular matrix in some microturbellarians

Lindroos

Reuter

1991

Hydrobiologia

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Electron microscopy was used to study the ECM (extracellular matrix) in the epidermis, brain, and parenchyma of the catenulid turbellarians Stenostomum leucops leucops (Dugits) and Stenostomum leucops aquariorum Luther and of the proseriates Archiloa unipunctata (Fabricius) and Promonotus schultzei Meixner. Specimens were fixed with a tannic-acid fixation that enhances staining of extracellular proteins (TAR1 method) or a conventional electron microscopical method. Differences between species were found in the amount of matrix and extracellular fibrils. In S. leucops leucops the ECM was very sparse, consisting of only a thin electron-dense sheath beneath the epidermis and surrounding neuropil. These sheaths were not found in S. leucops aquariorum which had only rarely encountered extracellular spaces. In P. schultzei and A. unipunctata ECM was more abundant. A. unipunctata had a distinct sheath surrounding the neuropil and a fibrillar subepidermal membrane; the same membranes in P. schultzei appeared only as patches of ECM. In A. unipunctata hemidesmosome-like structures attached the epidermal cells to the underlying membrane, and from these attachments, fibrils projected to the underlying muscle layer. The TAR1 method revealed exocytotic activity in the brain. The morphology of ECM in these and other flatworms indicate that it could be an internal medium for transport and exchange of substances among cells. Variability in the structure of ECM among species probably does not reflect evolutionary relationships.

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Fine Structural Observations on the Turbellarians Stenostomum sp. and Microstomum lineare with Special Reference to the Extracellular Matrix and Connective Tissue Systems

Cited by 19 publications

References 34 publications

Animal phylogeny in the light of the trochaea theory

Animal phylogeny in the light of the trochaea theory

Organization and differentiation of the body-wall musculature in Macrostomum (Turbellaria, Macrostomidae)

Extracellular matrix in some microturbellarians

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