Study
Bioluminescent countershading in midwater animals: evidence from living squid
Young, Richard E.; Roper, Clyde F. E.
Science, 1976
Held living midwater squid in a tank illuminated from above at controlled intensities, and measured the light the animals produced from their ventral photophores as the overhead illumination was varied.
- Studied in
- Teuthida
- Sample size
- living midwater squid under controlled downwelling light
The squid adjusted the intensity of their downward-directed light to match the downwelling illumination, so that their silhouette against the light from above was reduced or eliminated. The matching tracked changes in overhead intensity.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Ventral light production functions as counterillumination — camouflage against being seen in silhouette from below — and is actively regulated rather than emitted at a fixed intensity.
How NatureHQ reads it
The experiment that turned counterillumination from a plausible idea into a measured behaviour. The regulation is what makes it convincing: the animals are not simply glowing, they are matching, and the match changes when the experimenter changes the light.
- Laboratory conditions with artificial downwelling light rather than the real water column.
- A small number of animals, since midwater squid are difficult to keep alive.
Turning the light up, and watching the squid follow
Midwater squid produce light from their undersides. Is that camouflage against being seen in silhouette, or simply a glow?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Counterillumination
Midwater animals cancel their own silhouette by lighting their undersides to match the daylight filtering down — and they adjust the brightness as the light above changes.
Counterillumination
The strategy only works in a narrow band of the ocean — deep enough that a silhouette is what gives you away, shallow enough that there is still light above to match. Below that, there is nothing to match.
Published by: American Association for the Advancement of SciencePublished in Science or Science Advances (AAAS).
doi.org/10.1126/science.1251214
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.