Do cuttlefish change colour at night?

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We all know cuttlefish are capable of changing their colour pattern to mimic that of the substrate for camouflage, but can they do it at night?

This was the question Justine Allen and coauthors sought to answer in a study published in the most recent issue of the Journal of Experimental Biology.

Camouflage in cephalopods (the group to which cuttlefish belong) have traditionally been studied during the day, with very little recorded of their ability to utilise camouflage at night.

Because cuttlefish are thought to possess excellent night vision (either to detect prey or to avoid becoming prey), we might therefore expect their camouflage body patterns to be fine tuned and changeable, even at night. 

Using the Common cuttlefish (Sepia officinalis) as an experimental subject, the authors attempted to answer the following questions in their study:

(1) Do cuttlefish continue to camouflage as natural light levels change during the transition from daytime to night-time?

(2) In very dim light, is this camouflage behaviour adaptable, i.e. can the animal actively analyse visual information from its surroundings to choose an appropriate camouflage body pattern?

The authors began by monitoring the camouflage patterns of cuttlefishes during the transition from day to night time using a natural daylight cycle. They next used a dark room and simulated the following light regimes using artificial lighting, in gradual decreasing order: typical late afternoon, early evening, late evening, twilight, deep twilight, full moon, quarter moon and starlight.

They placed cuttlefish in arenas in which the walls and substrate were interchangeable and under the lowest light intensity (simulating starlight), the substrate and arena wall were changed to present visual cues known to stimulate a different body pattern. 

The authors switched among a combination of the following substrata and wall patterns: grey, small checks and large checks., and photographed each test animal after five minutes of acclimation.

They found that cuttlefish continue to camouflage themselves under light conditions comparable to night time levels.  This behaviour was found to be adaptive, i.e. the camouflage patterns are changeable as they are during daylight periods, and is attributed to the excellent night vision of the cuttlefish.

For more information, see the paper: Allen, JJ, LM Mäthger, KC Buresch, T Fetchko, M Gardner and RT Hanlon (2010) Night vision by cuttlefish enables changeable camouflage. Journal of Experimental Biology 213, pp. 3953–3960.