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  • Melanin-concentrating hormone  (1)
  • Mesogastropoda  (1)
  • Springer  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Structural studies of nerve terminals containing melanin-concentrating hormone in the eel, Anguilla anguilla (1988)
    Springer
    Cell & tissue research 251 (1988), S. 433-439 
    Details
    ISSN: 1432-0878
    Keywords: Melanin-concentrating hormone ; Immunocytochemistry ; Pituitary gland ; White- and black-background adaptation ; Teleost, Anguilla anguilla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Eels were adapted to black- or white-coloured backgrounds and the pituitary glands were prepared for light and electron microscopy. Immunocytochemical staining was used to study the distribution of the neurohypophysial melanin-concentrating hormone in the neurointermediate lobe. The hormone was located in small, elliptical, electron-opaque neurosecretory granules, measuring approximately 120×90 nm. The neurones terminated on blood vessels in the centre of the neurohypophysis and on the basement membrane separating neural and intermediate lobe tissues. The results of both light and electron immunocytochemistry and of radioimmunoassay are consistent with a higher rate of hormone release from eels adapted to white backgrounds than from those adapted to black backgrounds. In addition to this, when fish that had been adapted to white tanks were transferred to black tanks, there was an accumulation of irMCH in the gland and an increased numerical density of secretory granules at nerve terminals. These results reinforce the proposal that MCH is released during adaptation to a white background, to cause melanin concentration and to inhibit MSH release, and that its release is halted in black-adapted fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215852
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  • 2
    Electronic Resource
    Electronic Resource
    Homarine as a feeding deterrent in common shallow-water antarctic lamellarian gastropodMarseniopsis mollis: A rare example of chemical defense in a marine prosobranch (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 2539-2549 
    Details
    ISSN: 1573-1561
    Keywords: Marseniopis mollis ; Mesogastropoda ; homarine ; defense ; sea star ; Odontaster validus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The common bright yellow antarctic lamellarian gastropodMarseniopsis mollis was examined for the presence of defensive chemistry. Proton nuclear magnetic resonance (NMR) spectroscopy indicated that a major component of ethanolic extracts purified by reversed-phase column chromatography was homarine. Further high-performance liquid chromatography (HPLC) analysis of the mantle, foot, and viscera verified the presence of homarine in all body tissues at concentrations ranging from 6 to 24 mg/g dry tissue. A conspicuous macroinvertebrate predator of the shallow antarctic benthos, the sea starOdontaster validus, always rejected live individuals ofM. mollis, while readily feeding on pieces of fish tail muscle. Filter paper disks treated with shrimp elicited a broad range of feeding behaviors in the sea starO. validus (movement of disc to mouth, extrusion of cardiac stomach, humped feeding posture). Shrimp disks treated with homarine (0.4 and 4 mg/disk) were rejected byO. validus significantly more frequently than control disks treated with solvent carrier and shrimp or shrimp alone. The highest concentration of homarine tested not only caused feeding deterrence, but in several sea stars a flight response was noted. Homarine was not detected in the tunic of the antarctic ascidianCnemidocarpa verrucosa, a presumed primary prey ofM. mollis. Nonetheless, crude extracts of the epizooites that foul the tunic (primarily the bryozoans and hydroids) contain homarine, suggestingM. mollis may ingest and derive its chemistry from these organisms. This appears to be only the third example of chemical defense in a member of the Order Mesogastropoda. As the vestigial internalized shell ofM. mollis is considered a primitive condition, the findings of this study lend support to the hypothesis that chemical defense evolved prior to shell loss in shell-less gastropods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02036190
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