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  • 1
    Electronic Resource
    Electronic Resource
    Epidermal mucus and the reproduction of a crinoid echinoderm (1975)
    [s.l.] : Nature Publishing Group
    Nature 255 (1975), S. 223-224 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In both sexes the volume of the epidermal mucous cell population increases conspicuously in the weeks before spawn ing (Fig. 2). In the female (Fig. 20) this increase is about ten times as great as in the male (Fig. 2b). The volume of the mucous cell population decreases markedly around the time of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/255223a0
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  • 2
    Electronic Resource
    Electronic Resource
    ‘Lophenteropneust’ hypothesis refuted by collection and photos of new deep-sea hemichordates (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 374-376 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The deep ocean is home to a group of broad-collared hemichordates—the so-called ‘lophenteropneusts’—that have been photographed gliding on the sea floor but have not previously been collected. It has been claimed that these worms have collar tentacles and blend ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03382
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  • 3
    Electronic Resource
    Electronic Resource
    Annual Cycle in the Size of the Gut of the Purple Sea Urchin, Strongylocentrotus purpuratus (Stimpson) (1965)
    [s.l.] : Nature Publishing Group
    Nature 205 (1965), S. 1238-1239 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Twenty urchins were collected monthly from a tide pool near Yankee Point, California (36 33' N., 121 57' W.). The gut, exclusive of the pharynx, was dissected from each urchin, washed free of its contents, drained of free water, and weighed. The gonads were also removed, drained, and weighed. Both ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2051238a0
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  • 4
    Electronic Resource
    Electronic Resource
    Axial patterning in cephalochordates and the evolution of the organizer (2007)
    [s.l.] : Nature Publishing Group
    Nature 445 (2007), S. 613-617 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The organizer of the vertebrate gastrula is an important signalling centre that induces and patterns dorsal axial structures. Although a topic of long-standing interest, the evolutionary origin of the organizer remains unclear. Here we show that the gastrula of the cephalochordate amphioxus ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05472
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  • 5
    Electronic Resource
    Electronic Resource
    Sequence and developmental expression of amphioxus AmphiNk2–1: insights into the evolutionary origin of the vertebrate thyroid gland and forebrain (1999)
    Springer
    Development genes and evolution 209 (1999), S. 254-259 
    Details
    ISSN: 1432-041X
    Keywords: Key words NK2 homeobox ; Cephalochordata ; Lancelet ; Diencephalon ; Endostyle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We characterized an amphioxus NK-2 homeobox gene (AmphiNk2–1), a homologue of vertebrate Nkx2–1, which is involved in the development of the central nervous system and thyroid gland. At the early neurula stage of amphioxus, AmphiNk2–1 expression is first detected medially in the neural plate. By the mid-neurula stage, expression is localized ventrally in the nerve cord and also begins in the endoderm. During the late neurula stage, the ventral neural expression becomes transiently segmented posteriorly and is then down-regulated except in the cerebral vesicle at the anterior end of the central nervous system. Within the cerebral vesicle AmphiNk2–1 is expressed in a broad ventral domain, probably comprising both the floor plate and basal plate regions; this pattern is comparable to Nkx2–1 expression in the mouse diencephalon. In the anterior part of the gut, expression becomes intense in the endostyle (the right wall of the pharynx), which is the presumed homologue of the vertebrate thyroid gland. More posteriorly, there is transitory expression in the midgut and hindgut. In sum, the present results help to support homologies (1) between the amphioxus endostyle and the vertebrate thyroid gland and (2) between the amphioxus cerebral vesicle and the vertebrate diencephalic forebrain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050250
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  • 6
    Electronic Resource
    Electronic Resource
    Differential gene expression and intracellular mRNA localization of amphioxus actin isoforms throughout development: Implications for conserved mechanisms of chordate development (1997)
    Springer
    Development genes and evolution 207 (1997), S. 203-215 
    Details
    ISSN: 1432-041X
    Keywords: Key words Amphioxus ; Actin ; Tissue-specific gene expression ; Chordate evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The cephalochordate amphioxus is thought to share a common ancestor with vertebrates. To investigate the evolution of developmental mechanisms in chordates, cDNA clones for two amphioxus actin genes, BfCA1 and BfMA1, were isolated. BfCA1 encodes a cytoplasmic actin and is expressed in a variety of tissues during embryogenesis, beginning in the dorsolateral mesendoderm of the mid-gastrula. At the open neural plate stage, BfCA1 transcripts accumulate at the bases of the neuroectodermal cells adjacent the presumptive notochord. The 3’ untranslated region of BfCA1 contains a sequence that is similar to the ”zipcode” sequence of chicken β-cytoplasmic actin gene, which is thought to direct intracellular mRNA localization. BfCA1 is also expressed in the notochord through the early larval stage, in the pharynx and in the somites at the onset of muscle-cell differentiation. BfMA1 is a vertebrate-type muscle actin gene, although the deduced amino acid sequence is fairly divergent. Transcripts first appear in the early neurula in the somites as they begin to differentiate into axial muscle cells and persist into the adult stage. In young adults, transcripts are localized in the Z-discs of the muscle cells. Smooth muscle cells around the gill slits and striated muscle cells in the pterygeal muscle also express BfMA1; however, there is never any detectable expression in the notochord, which is a modified striated muscle. Together with the alkali myosin light chain gene AmphiMLC-alk, the sequence and muscle-specific expression of BfMA1 implies a conserved mechanism of muscle cell differentiation between amphioxus and vertebrates. Evolution of the chordate actin gene family is discussed based on molecular phylogenetic analysis and expression patterns of amphioxus actin genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050109
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  • 7
    Electronic Resource
    Electronic Resource
    Topographic changes in nascent and early mesoderm in amphioxus embryos studied by DiI labeling and by in situ hybridization for a Brachyury gene (1997)
    Springer
    Development genes and evolution 206 (1997), S. 532-535 
    Details
    ISSN: 1432-041X
    Keywords: Key words Mesoderm ; Notochord ; Brachyury ; Amphioxus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In amphioxus embryos, the nascent and early mesoderm (including chorda-mesoderm) was visualized by expression of a Brachyury gene (AmBra-2). A band of mesoderm is first detected encircling the earliest (vegetal plate stage) gastrula sub-equatorially. Soon thereafter, the vegetal plate invaginates, resulting in a cap-shaped gastrula with the mesoderm localized at the blastoporal lip and completely encircling the blastopore. As the gastrula stage progresses, DiI (a vital dye) labeling demonstrates that the entire mesoderm is internalized by a slight involution of the epiblast into the hypoblast all around the perimeter of the blastopore. Subsequently, during the early neurula stage, the internalized mesoderm undergoes anterior extension mid-dorsally (as notochord) and dorsolaterally (in paraxial regions where segments will later form). By the late neurula stage, AmBra-2 is no longer transcribed throughout the mesoderm as a whole; instead, expression is detectable only in the posterior mesoderm and in the notochord, but not in paraxial mesoderm where definitive somites have formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050083
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  • 8
    Electronic Resource
    Electronic Resource
    Cholinesterase in larvae of the ascidian,Ciona intestinalis, developing from fragments cut from centrifuged eggs (1974)
    Springer
    Development genes and evolution 175 (1974), S. 91-102 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary UnfertilizedCiona eggs were centrifuged, stratifying their mitochondria and some other cytoplasmic components. Each centrifuged egg had a mitochondria-free, centripetal clear layer that was contiguous with centrifugal layers containing mitochondria. By cutting centrifuged eggs in two at various levels along the centripetal-centrifugal axis, it was possible to obtain centripetal fragments including virtually no mitochondria, about one-tenth of the uncut egg's mitochondria or about one-fourth of the uncut egg's mitochondria. Most of these centripetal fragments, when fertilized, developed into larvae. However, only the centripetal fragments that included about one-fourth of the uncut egg's mitochondria developed into larvae giving the cytochemical reaction for cholinesterase, a convenient indicator of muscle cell differentiation inCiona. Therefore, the inclusion of a minimum number of mitochondria (more than one-tenth but less than one-fourth the number in the uncut egg) is correlated with muscle cell differentiation in larvae developing from the centripetal fragments. The possible influences of mitochondria and of other cytoplasmic components on muscle differentiation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00574295
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  • 9
    Electronic Resource
    Electronic Resource
    Fine structure of the stalk of an isocrinid sea lily (Metacrinus rotundus) (Echinodermata, Crinoidea) (1985)
    Springer
    Zoomorphology 105 (1985), S. 39-50 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sea lilies of the order Isocrinida (Metacrinus rotundus) were dredged from Sagami Bay, Japan, and their stalks were studied by transmission electron microscopy. New contributions to stalk histology are: an exact description of the different cell types in the stereom spaces; a demonstration of the haemal channel; and the discovery of (1) coelomic nerves, (2) collateral stalk nerves and (3) nerve tracts running with the aboral extension of the axial organ. Within the stalk, there is no structure derived from the axial sinus (=axocoel), and the widely accepted homology between the crinoid stalk and the larval asteroid stalk is thus open to serious question. The stalk has collagenous ligaments of two main types (intercolumnal ligaments and peripheral through-going ligaments); however, there are no central through-going ligaments comparable to those in stalks of larval feather stars and of bourgueticrinid sea lilies. The absence of muscles or other cells specialized for contractility indicates that the stalk of isocrinid sea lilies cannot bend actively. The cirri, which project from the stalk of M. rotundus, contain no muscle cells; however, the epithelial cells lining the oral and aboral coeloms of each cirrus contain a presumed contractile apparatus that is a bundle of 5 nm cytoplasmic filaments oriented parallel to each other and to the long axis of the cirrus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312072
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  • 10
    Electronic Resource
    Electronic Resource
    The structure of the sea lilyCalamocrinus diomedae, with special reference to the articulations, skeletal microstructure, symbiotic bacteria, axial organs, and stalk tissues (Crinoida, Millericrinida) (1991)
    Springer
    Zoomorphology 110 (1991), S. 115-132 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Calamocrinus diomedae was collected in deep water in the eastern Pacific. The skeleton and soft tissues were studied by light microscopy and by scanning and transmission electron microscopy. The skeleton of the arms and pinnules was unusual in lacking any galleried stereom; thus the ligaments as well as the muscles inserted on labyrinthic stereom. Therefore, the type of skeletal microstructure may not always be a sure guide to where the ligaments and muscles insert, and crinoid paleontologists should use caution when reconstructing soft parts from fossil skeletons. Contrary to the original species description, the skeleton of the theca apparently includes no infrabasal ossicles, andC. diomedae is monocyclic like other millericrinid sea lilies. Although many of the soft tissues resemble those of other crinoids, there are several exceptional features. The visceral mass within the theca includes not only a glandular axial organ typical of crinoids generally, but also what appears to be a second axial organ of the eleutherozoan type; dual axial organs have been seen before only in isocrinid sea lilies. The gut contents include partially digested crustacean prey, including some calanoid copepods. The soft tissues of the axial cord of the stalk comprise a haemal vessel, an aboral extension of the glandular axial organ, aboral coelomic extensions of the chambered organ, coelomic nerves, stalk nerves, an inconspicuous central through-going ligament, and aggregations of cells in each radial sector. Spherical bodies filled with rodshaped symbiotic bacteria are embedded in the soft connective tissues of the arms and pinnules. Possible chemosynthetic and bioluminescent roles for these bacteria are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01632868
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