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  • 1
    Electronic Resource
    Electronic Resource
    Cell behavior during early development in the South American annual fishes of the genus Cynolebias (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 210 (1991), S. 247-266 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Living embryos of three species of South American annual fishes, Cynolebias constanciae, C. nigripinnis, and C. whitei, were observed from fertilization through the 10-somite stage. A description of normal stages of development applicable to all three species of Cynolebias is presented. Cleavage (stages 1-10) is meroblastic and produces a typical teleost blastoderm. Following cleavage (stages 11-13) blastomeres segregate into two populations, viz., (1) a population of deep blastomeres that will disperse as single motile cells, and (2) a hemispherical shell of outer blastomeres that flattens to form an enveloping cell layer (EVL). When epiboly of the EVL and the yolk syncytial layer (YSL) commences (stage 14), deep blastomeres clump together as a consolidation mass and then migrate outward as single cells on the YSL. When epiboly is concluded (stage 19), deep blastomeres have completely dispersed. If diapause does not intervene, the dispersed phase lasts only a few days. Subsequently, the dispersed cells come together to form a definitive aggregate (stage 27). Embryogenesis within the reaggregated mass of previously dispersed cells produces a typical teleost embryo.Early development in Cynolebias resembles that of other South American annual fishes, such as Austrofundulus, in that a phase of deep blastomere dispersion and reaggregation spatially and temporally separates epiboly from embryogenesis. Several features of development markedly differ from Austrofundulus. There are far fewer (250 vs. 2,500) deep blastomeres. Deep cells of Cynolebias are flattened rhomboids with filipodial extensions in contrast to the amoeboid cells of Austrofundulus. Blastomeres of dispersion and reaggregation stages in Cynolebias send out numerous cell surface extensions onto the YSL and in contact with one another, and often line up in rows as do some African annual fishes, e.g., Nothobranchius. During Dispersion II (stage 21), Reaggregation I (stage 22), and Reaggregation II (stage 23), deep cells move in an oriented pattern with respective mean velocities of 3.48 ± 0.91, 1.28 ± 0.46, and 1.31 ± 0.31 μm/minute. Cells move toward a granular mass of unknown composition, located at the YSL-yolk interface in the lower hemisphere of the egg. This mass appears to coincide with the site of cell reaggregation.
    Additional Material: 34 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052100305
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  • 2
    Electronic Resource
    Electronic Resource
    Naturally occurring diblastodermic eggs in the annual fish Cynolebias: Implications for developmental regulation and determination (1993)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 215 (1993), S. 301-312 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Annual fish development differs from that of other teleosts because a phase of blastomere dispersion-reaggregation spatially and temporally separates epiboly from embryogenesis. The fate of dispersed blastomeres was assessed in diblastodermic eggs of the annual fishes Cynolebias whitei and C. nigripinnis. In typical teleosts, blastomere determination and the events of primary embryonic induction occur prior to or during epiboly, so diblastodermic eggs produce partially or completely duplicated embryos. In the diblastodermic eggs of Cynolebias, the two blastoderms are completely separate from the one cell stage to the high blastula. Blastoderm fusion begins during midepiboly. By the end of epiboly, blastoderm fusion has been completed, and the deep, embryo-forming blastomeres of both blastoderms have completely dispersed and intermingled to form a single cell population. A typical annual fish dispersed blastomere phase ensues. Blastomeres reaggregate into a single mass, in which one embryo develops. When hatched, the young fish have no obvious structural or functional abnormalities. We suggest that the dispersed blastomeres of annual fish eggs are equivalent and that induction or determination takes place within the reaggregate. Alternatively, dispersed cells are partially determined but highly regulative, so that, when two populations fuse, the cells sort out according to tissue type and form a single embryo. In either instance, the formation of a single, normal embryo seems to corroborate the hypothesis that the dispersed cell phase of annual fishes is an adaptation that prevents environmentally induced developmental defects. © 1993 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052150309
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  • 3
    Electronic Resource
    Electronic Resource
    In vivo fluorescence imaging of the functional organization of trophotaenial placental cells of goodeid fishes (1994)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 219 (1994), S. 35-46 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Embryos of viviparous goodeid fishes undergo a 10 to 150 × increase in dry weight during gestation. Maternal nutrients are transferred across a trophotaenial placenta comprised of the ovarian lumenal epithelium and the trophotaeniae of the embryo. Trophotaeniae are externalized projections of the embryonic hindgut. Epithelial cells of the ribbon trophotaenia (Ameca splendens) resemble intestinal absorptive cells of suckling mammals and endocytose macromolecules. They possess an apical brush border, endocytotic complex, endosomal-lysosomal system, and apical and basal clusters of mitochondria. Cells of the rosette trophotaenia (Goodea atripinnis) lack an endocytotic apparatus, have small lysosomes, two mitochondrial clusters, and transport small molecules. Organelle-specific fluorescent probes were employed to characterize the functional organization of the two types of trophotaenial cells. In A. splendens, Lucifer Yellow, a membrane-impermeable tracer of vesicular transport, first appears in peripheral vesicles (15-45 sec), then passes into elongated tubular endosomes (1-3 min) and later appears in large central vacuoles (10-15 min). These vacuoles accumulate Acridine Orange, a classical probe for lysosomes, and have been shown to contain lysosomal enzymes. Endosomelysosome fusion was observed. In both A. splendens and G. atripinnis, Rhodamine 123 fluorescence was localized in two clusters of fine spots that corresponded to mitochondria. 4′,6-diaminido-2-phenyl-indole (DAPI) staining of nuclei established the positional relationships of cell organelles with respect to the nuclei. 3,3′-dihexyloxacarbo-cyanine iodide (DiOC6) revealed the perinuclear distribution of the endoplasmic reticulum. In order to compare in vivo fluorescence of Lucifer Yellow with previous ultrastructural observations, we employed fluorescence photoconversion and electron microscopy. © 1994 Wiley-Liss, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052190106
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  • 4
    Electronic Resource
    Electronic Resource
    An ultrastructural analysis of the dispersed cell phase during development of the annual fish, Cynolebias (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 204 (1990), S. 209-225 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell ultrastructure was investigated during the dispersion phase of development in the annual fish Cynolebias. Three cellular populations encompass the yolk mass during dispersion, namely, 1) the yolk syncytial layer (YSL) or periblast, which lies directly over the surface of the yolk; 2) the deep blastomeres of the blastoderm, which engage in morphogenetic movements on the surface of the YSL and beneath the enveloping layer prior to forming the future embryo; and 3) the enveloping layer (EVL) of the blastoderm, which is a cohesive epithelium that forms the outermost cell layer of the blastoderm. Deep blastomeres contain numerous mitochondria and scattered glycogen rosettes that appear to function in the utilization of energy reserves. These cells also possess surface extensions such as filopodia and ruffles. Numerous microfilaments running parallel to the plasma membrane occur in cell extensions and in the cortical cytoplasm of neighboring blastomeres. In bleb-like extensions such as ruffles, microfilamentous stress fibers run parallel to the plane of the plasma membrane and prevent cellular organelles from entering the hyaline cap of the ruffle. Deep blastomeres also have basal projections that contain glycogen as well as pits in the basal membrane. Blastomeres move about using the YSL as a substrate. The YSL possesses specializations for nutrient uptake, storage, and transport such as numerous multivesicular bodies and large amounts of glycogen. Glycogen, in the rosette form, occurs in extraordinary amounts, virtually occluding the cytoplasm. Glycogen reserves are postulated to serve as an energy source during diapause. Glycogen is sometimes contained within villous projections that extend from the apical surface of the YSL. This configuration suggests the possibility of glycogen transport to the overlying deep blastomeres. Specializations of the EVL include apical tight junctions and basal lateral zonulae adherentes that interdigitate with those of adjacent EVL cells. The EVL serves as an impermeable membrane that protects the developing egg from the vicissitudes of its environment.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052040209
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure and protein uptake of the embryonic trophotaeniae of four species of goodeid fishes (Teleostei: Atheriniformes) (1994)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 219 (1994), S. 105-129 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Embryos of most species within the viviparous teleost family Goodeidae develop characteristics perianal processes that are considered to be derivatives of the embryonic hindgut. These processes, termed trophotaeniae, are covered with an epithelium that is continuous with the absorptive epithelium lining the hindgut. Gestation is intraovarian, and trophotaeniae mediate the uptake of maternally provided nutrients into the embryo from the ovarian fluid. Ultrastructural examination of the trophotaeniae of four goodeid species reveals substantial diversity in the organization of the epithelium within the family. The trophotaeniae of Alloophorus robustus, Zoogoneticus quitzeoensis, and Ilyodon furcidens have morphological features associated with the endocytosis of macromolecules and can be shown to endocytose the exogenous protein tracer horseradish peroxidase (HRP) rapidly. The trophotaenial epithelia of these species differ from one another with respect to other morphological features such as cell height, organization of the brush border, and the complexity of the intercellular spaces. The trophotaeniae of Goodea atripinnis lack an endocytotic apparatus and do not endocytose HRP. However, the overall organization of G. atripinnis trophotaenial cells suggests a function as a transporting epithelium. The cells have a dense brush border, numerous mitochondria, and many mitochondria that are enveloped by lamellar sheets of intracellular membrane.Post-fixation with osmium and potassium ferrocyanide reveals a marked difference in the complexity of the subepithelial connective tissue. Alloophorus robustus and Z. quitzeoensis exhibit an extremely electron-dense ground substance containing many acellular components. Goodea atripinnis exhibits an electron-lucid ground substance with few acellular components. © 1994 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052190202
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