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  • 1
    Digitale Medien
    Digitale Medien
    Southern stingray (Dasyatis americana) feeding on lancelets (Branchiostoma floridae) (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 41 (1992), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: A southern stingray from the shallow sand flats of Tampa Bay, Florida, had its gut filled almost exclusively with lancelets. The absence of small lancelets from the gut contents indicated a pharyngeal sieving mechanism by the ray.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1992.tb02732.x
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  • 2
    Digitale Medien
    Digitale Medien
    Time-lapse cinematography of feather stars (Echinodermata: Crinoidea) on the Great Barrier Reef, Australia: demonstrations of posture changes, locomotion, spawning and possible predation by fish (1984)
    Springer
    Marine biology 78 (1984), S. 179-184 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Aspects of feather star behavior and ecology were recorded by time-lapse cinematography approximately 1 frame min-1 on the Great Barrier Reef, Australia over a 1 mo period in 1983. The current regime influenced body postures of most species studied, whether nocturnal or not. Moreover, feather stars of several species crawled on the substratum with their arms; each crawling episode lasted roughly 10 min, and the maximum speed attained was about 1 arm length min-1. Nocturnal feather stars crawled to their nighttime feeding perches around dusk and crawled back to their daytime hiding places around dawn. Surprisingly, some species of feather stars living on the reef surface both day and night also crawled around at dawn and dusk for reasons that are not known. In the time-lapse films, and individual of Comanthus bennetti (sex undetermined) spawned for about 2 min just after dark on 5 July 1983. Another film showed possible predation on a feather star (Himerometra robustipinna) by a saddled coralfish (Chaetodon ephippium).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00394698
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Particle interception, transport and rejection by the feather star Oligometra serripinna (Echinodermata: Crinoidea), studied by frame analysis of videotapes (1986)
    Springer
    Marine biology 93 (1986), S. 111-126 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Suspension feeding by a stalkless crinoid (Oligometra serripinna) was studied at Lizard Island, Australia, in 1985. The crinoids were placed in a laboratory flume with a slow, unidirectional current of seawater. Nutritive and non-nutritive particles (15 to 180 μm) were introduced upstream from the crinoid, and feeding behavior was recorded at high magnifications on videotape for frame analysis. These direct observations showed that each intercepted particle (whether a dejellied clam egg, Sephadex bead or latex sphere) contacts a single, evidently adhesive tube foot and is rapidly transferred to the pinnular food groove by a bend of the tube foot. The tube foot bends in about 0.1 s and returns to its extended position in 1 to 2 s. Spheres less than 20 μm in diameter cause only the intercepting tube foot to bend. In contrast, larger spheres cause the coordinated bending of the intercepting tube foot plus many of the neighboring tube feet: the stimulus spreads through the reacting group of tube feet at about 1 cm s-1. After transfer to the pinnular food groove, the nutritive particles (dejellied clam eggs) travel at about 1 cm min-1 to the arm axis and thence down the arm food groove at about 4 cm min-1 to the mouth; in contrast, non-nutritive particles (Sephadex beads and latex spheres) are discarded from the pinnular food groove between 1 and 30 s after capture. Tube-foot bending is presumably triggered when arriving particles (whether nutritive or non-nutritive) are detected by sensory cells in the tubefoot epithelium: mechanoreception by itself appears sufficient to initiate bending, although chemoreception may modify the reaction. Then, soon after captured particles have been transferred to the pinnular food groove, the crinoid discards those judged unsuitable (probably by contact chemoreceptors in the food-groove epithelium). Clam eggs with intact jelly layers temporarily hang up on tube feet they contact and then float away in the curent: the jelly evidently interferes with mechanoreception and/or chemoreception by the tube-foot epithelium. Some previous studies of crinoid feeding have suggested that particles are trapped in extensive nets or strands of mucus: we found no evidence for this in O. serripinna, which captures particles predominantly be the direct interception method of the aerosol filtration model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00428660
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Fine structure of the stalk of the bourgueticrinid sea lily Democrinus conifer (Echinodermata: Crinoidea) (1984)
    Springer
    Marine biology 81 (1984), S. 163-176 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Specimens of Democrinus conifer (A. H. Clark, 1909) dredged from about 280 m were fixed aboard ship for transmission electron microscopy. The most important new contributions to stalk histology are the following: an exact description of the different cell types of the stereom spaces; a demonstration of the haemal channel; description of the radial aggregations of cells in the central canal; discovery of coelomic nerves; and discovery of nerve tracts running in association with the aboral extension of the axial organ. The collagenous ligaments of the stalk are separated into three types anatomically (and possibly also functionally). The stalk contains no trace of an axial sinus derived during ontogeny from the anterior coelom (=axocoel). In the roots, the central canal contains a root nerve, but no extensions of the haemal channel or of the coelomic tubes; therefore, roots of bourgueticrinid sea lilies are not homologous to cirri of isocrinid sea lilies or feather stars. The chambered organ and axial organ of D. conifer closely resemble the same organs in feather stars that have previously been described by electron microscopy. The functional implications of our structural results are: (1) cells in the stereom space appear to be a major site of nutrient reserves, (2) the abundant cells with lipid-rich organelles could make the sea lily body more buoyant, and (3) the absence of muscles or other cells specialized for contractility indicates that the stalk of bourgueticrinid sea lilies cannot bend actively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00393115
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of current speed on filtration during suspension feeding in Oligometra serripinna (Echinodermata: Crinoidea) (1988)
    Springer
    Marine biology 97 (1988), S. 111-125 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Suspension feeding by the crinod Oligometra serripinna was studied at Lizard Island, Australia, in 1986. Video recordings were made of 90-μm particles interacting with the filter of the crinoid in a laboratory flow chamber. A complete census of particles was possible because both the capture event and the filter area could be defined unequivocally. Also, because O. serripinna is a passive suspension feeder, a census of partcles could be made at different ambient current speeds without interference due to active pumping by the crinoid. Experiments were run at seven current speeds from 0.9 to 13.3 cm s-1. Particles approaching the filter: (1) were captured, (2) passed through the filter without triggering a capture event, (3) passed through the filter after escaping from an unsuccessful capture event, or (4) were deflected around the filter. With increasing current speed, the proportion of deflections declined and the proportion of particles passing through rose: these results could be partially explained by the progressive widening of the spaces within the filter due to distortion of filter parts by the current. The proportion of captures (normalized to approaches) was comparatively low at 0.9 cm s-1, rose to a relatively constant maximum from 1.7 to 6.4 cm s-1, and then declined progressively at 9.5 and 13.3 cm s-1. These proportions were translated into capture rates for whole crinoids by taking into consideration both the encounters with particles and the reduction of filter area by distortion of body parts at higher speeds. When plotted against current speed, capture rate peaked at 6.4 cm s-1, which was close to the mean current speed that we measured on the reef in the microhabitat of O. serripinna.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00391251
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  • 6
    Digitale Medien
    Digitale Medien
    A brominated secondary metabolite synthesized by the cyanobacterial symbiont of a marine sponge and accumulation of the crystalline metabolite in the sponge tissue (1994)
    Springer
    Marine biology 119 (1994), S. 1-11 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The dictyoceratid marine sponge Dysidea herbacea (Keller, 1889) is common in shallow waters of the tropical Pacific Ocean. Polybrominated biphenyl ethers such as 2-(2′,4′-dibromophenyl)-4,6-dibromophenol (1) are characteristic secondary metabolites of some specimens of this sponge and may represent as much as 12% of the dry weight. We have found 1 to be deposited as conspicuous crystals throughout the sponge tissue. The dominant prokaryotic endosymbiont in the mesohyl of the sponge is a filamentous cyanobacterium (Oscillatoria spongeliae), although a vacuole-containing, heterotrophic bacterium is also present. The cyanobacteria were separated from the sponge cells and heterotrophic bacteria by flow cytometry. Coupled gas chromatography—mass spectrometry and proton nuclear magnetic-resonance spectroscopy revealed that the major brominated Compound 1 isolated from the intact symbiotic association is found in the cyanobacteria and not in the sponge cells or heterotrophic bacteria. This suggests that the production of the compound is due to the cyanobacterium, and not to the sponge or symbiotic heterotrophic bacteria, as had been suggested earlier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00350100
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Ovulation in an echinoderm (Comanthus japonica) (1975)
    Springer
    Cellular and molecular life sciences 31 (1975), S. 1078-1080 
    Details
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An invertebrate type of ovulation is described for the first time for an echinoderm. In this echinoderm, which is a crinoid, ovulation is the passage of maturing oocytes through temporary openings in the epithelium lining the ovary. After ovulation, which takes about 1 h, the oocytes lie free in the ovarian lumen; there they quickly finish maturing into ova which are spawned into the sea water.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02326971
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  • 8
    Digitale Medien
    Digitale Medien
    Two classes of metabolites fromTheonella swinhoei are localized in distinct populations of bacterial symbionts (1996)
    Springer
    Cellular and molecular life sciences 52 (1996), S. 716-722 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Aphanocapsa feldmanni ; Beggiatoa ; cyanobacteria ; lithistid sponge ; Theonella swinhoei ; secondary metabolites ; swinholide A ; symbiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The marine spongeTheonella swinhoei (lithistid Family Theonellidae, Order Astrophorida) has yielded many important, bioactive natural products, most of which share structural features with bacterial natural products. The presence of microbial symbionts inT. swinhoei has been reported, and it was originally suggested that the cytotoxic macrolide swinholide A and many of the bioactive cyclic peptides fromT. swinhoei were all produced by symbiotic cyanobacteria. By transmission electron microscopy, we found four distinct cell populations to be consistently present inT. swinhoei: eukaryotic sponge cells, unicellular heterotrophic bacteria, unicellular cyanobacteria and filamentous heterotrophic bacteria. Purification and chemical analyses of each cell type showed the macrolide swinholide A to be limited to the mixed population of unicellular heterotrophic bacteria, and an anti-fungal cyclic peptide occurred only in the filamentous heterotrophic bacteria. Contrary to prior speculation, no major metabolites were located in the cyanobacteria or sponge cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01925581
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  • 9
    Digitale Medien
    Digitale Medien
    Developmental expression of AmphiWnt1, an amphioxus gene in the Wnt1/wingless subfamily (2000)
    Springer
    Development genes and evolution 210 (2000), S. 522-524 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Blastopore ; Cephalochordate ; Lancelet ; Neurenteric canal ; Wnt gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  A full-length Wnt1 gene (AmphiWnt1) was isolated from amphioxus. Expression is first detectable in the gastrula around the lip of the blastopore. By the early neurula, transcription is in the mesendoderm near the closed blastopore, but is down-regulated in the overlying ectoderm. In the late neurula, expression is limited to the posterior wall of the neurenteric canal. Later in development, AmphiWnt1 transcripts can no longer be detected. AmphiWnt1 has no counterpart of the predominant expression domains of vertebrate Wnt1 genes in the neural tube, but its expression may be more comparable to that of wingless in the invaginating hindgut primordium of insects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270000089
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  • 10
    Digitale Medien
    Digitale Medien
    Characterization and developmental expression of AmphiNk2-2, an NK2 class homeobox gene from amphioxus (Phylum Chordata; Subphylum Cephalochordata) (1998)
    Springer
    Development genes and evolution 208 (1998), S. 100-105 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words NK2 homeobox ; Amphioxus ; Brain ; Gut
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The genome of amphioxus includes AmphiNk2-2, the first gene of the NK2 homeobox class to be demonstrated in any invertebrate deuterostome. AmphiNk2-2 encodes a protein with a TN domain, homeodomain, and NK2-specific domain; on the basis of amino acid identities in these conserved regions, AmphiNk2-2 is a homolog of Drosophila vnd and vertebrate Nkx2–2. During amphioxus development, expression of Amph- iNk2-2 is first detected ventrally in the endoderm of late gastrulae. In neurulae, endodermal expression divides into three domains (the pharynx, midgut, and hindgut), and neural expression commences in two longitudinal bands of cells in the anterior neural tube. These neural tube cells occupy a ventrolateral position on either side of the cerebral vesicle (the probable homolog of the vertebrate diencephalic forebrain). The dynamic expression patterns of AmphiNkx2-2 suggest successive roles, first in regionalizing the endoderm and nervous system and later during differentiation of specific cell types in the gut (possibly peptide endocrine cells) and brain (possibly including axon outgrowth and guidance).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050159
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