The megamouth shark is a mysterious and rare shark species discovered in the 20th Century. It is known to be a filter feeder, however, the exact feeding mechanism is unclear. One group of researchers had hypothesized that the prominent white band on its upper jaw was a bioluminescent lure. Another group hypothesized that the white band reflected light emitted from bioluminescent prey. Neither theory was proven. This study, conducted in collaboration with a research team from the University of Louvain in Belgium, reexamined the theories on bioluminescence of megamouth sharks.

Researchers used different histological approaches (histological sections, fluorescent in situ hybridization (FISH) and scanning electron microscopy) and spectrophotometry. Researchers determined that the megamouth shark does not have functioning bioluminescent organs. Various forms of tiny placoid scales were found in the white band and in its mouth, which may reflect the bioluminescence produced by its planktonic prey.

Previous theories of the megamouth showing bioluminescence are probably due to the megamouth’s placoid scales reflecting the light from its bioluminescent planktonic prey, or even reflecting scuba diving lights.

Authors

Laurent Duchatelet, Victoria C. Moris, Taketeru Tomita, Jacques Mahillon, Keiichi Sato, Catherine Behets, Jerome Mallefet（太字：財団職員）

Title

The megamouth shark, Megachasma pelagios, is not a luminous species.

Journal

PLoS ONE

DOI

https://doi.org/10.1371/journal.pone.0242196