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Iso-luminance counterillumination drove bioluminescent shark radiation.

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Author

  • Julien M Claes
  • Dan-E Nilsson
  • Nicolas Straube
  • Shaun P Collin
  • Jérôme Mallefet

Summary, in English

Counterilluminating animals use ventral photogenic organs (photophores) to mimic the residual downwelling light and cloak their silhouette from upward-looking predators. To cope with variable conditions of pelagic light environments they typically adjust their luminescence intensity. Here, we found evidence that bioluminescent sharks instead emit a constant light output and move up and down in the water column to remain cryptic at iso-luminance depth. We observed, across 21 globally distributed shark species, a correlation between capture depth and the proportion of a ventral area occupied by photophores. This information further allowed us, using visual modelling, to provide an adaptive explanation for shark photophore pattern diversity: in species facing moderate predation risk from below, counterilluminating photophores were partially co-opted for bioluminescent signalling, leading to complex patterns. In addition to increase our understanding of pelagic ecosystems our study emphasizes the importance of bioluminescence as a speciation driver.

Publishing year

2014

Language

English

Publication/Series

Scientific Reports

Volume

4

Document type

Journal article

Publisher

Nature Publishing Group

Topic

  • Zoology

Status

Published

Research group

  • Lund Vision Group

ISBN/ISSN/Other

  • ISSN: 2045-2322