Involvement of contractile elements in control of bioluminescence in Northern krill, <Emphasis Type="Italic">Meganyctiphanes norvegica</Emphasis> (M. Sars) |
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Authors: | Jenny Krönström Waldemar Karlsson Bengt R Johansson Susanne Holmgren |
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Institution: | 1.Department of Zoophysiology,University of Gothenburg,G?teborg,Sweden;2.Electron Microscopy Unit, Institute of Biomedicine,University of Gothenburg,G?teborg,Sweden |
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Abstract: | Inside the light organs of the bioluminescent (light-producing) crustacean Meganyctiphanes norvegica (krill), numerous capillaries drain haemolymph into the light-producing structure (lantern). We have investigated the arrangement
and function of filamentous material found around the opening of the capillaries. These have been suggested to work as sphincters,
controlling the haemolymph (i.e. oxygen) supply to the lantern and thereby the production of light. Electron microscopy shows
that the filamentous material consists of thick and thin muscle filaments arranged in perpendicular blocks around the opening
of each capillary. The actin probe rhodamine phalloidin has revealed that one component is filamentous actin. Clusters of
vesicle-dense nerve profiles surround the cells containing filamentous material and antibodies against 5-hydroxytryptamine
(5-HT) reveal that 5-HT containing nerves lead to the filamentous area. When exposed to the muscle-relaxing substances papaverine
and verapamil, krill respond with luminescence, suggesting that the sphincter structures are functionally involved in the
control of light production. Treatment with the muscle-contracting drugs Bay K8544 and thapsigargin gives no light response.
Thus, 5-HT stimulates light production in krill; however, a combination of 5-HT and the muscle-relaxing drugs or Bay K8544
potentiates the effect of 5-HT. Thapsigargin quenches the response to 5-HT. Our results corroborate speculations of earlier
authors who have suggested that the sphincter structures are of a muscular nature and important in controlling light production
in krill. However, other parameters in addition to the oxygen supply to the lantern are involved in controlling bioluminescence
in the light organs of M. norvegica.
We acknowledge financial support from the Biodiversity Program of the Swedish Science Research Council and from the Royal
Swedish Academy of Science for supporting work at the Kristineberg Marine Research Center. Electron microscopy equipment was
granted by the Lundberg Research Foundation. |
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Keywords: | Bioluminescence Sphincter Muscle filaments Krill Meganyctiphanes norvegica (Crustacea) |
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