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First published online July 20, 2007
Journal of Experimental Biology 210, 2657-2666 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.004382

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Disruptive coloration elicited on controlled natural substrates in cuttlefish, Sepia officinalis

Lydia M. Mäthger^1,*, Chuan-Chin Chiao^1,2, Alexandra Barbosa¹, Kendra C. Buresch¹, Sarrah Kaye¹ and Roger T. Hanlon¹

¹ Marine Biological Laboratory, Woods Hole, MA 02543, USA
² Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan

View larger version (69K): [in this window] [in a new window]   Fig. 1. Uniform and disruptive body patterns on artificial and natural backgrounds. (A) Uniform body pattern on a uniform artificial gray background and (B) uniform sand. (C) Cuttlefish showing disruptive coloration on a black and white checkerboard for which the white checks are roughly equal in size to the animal's White square component (component 2 in Fig. 1E). (D) Disruptive coloration on natural substrate with contrasting dark and light rocks. (E) Disruptive components that were graded (see text for detail on grading method). Light chromatic components: 1, White posterior triangle; 2, White square; 3, White mantle bar; 13, White head bar; 14, White arm triangle. Dark chromatic components: 17, Anterior transverse mantle line; 18, Posterior transverse mantle line; 19, Anterior mantle bar; 21, Paired mantle spots; 22, Median mantle stripe; 29, Anterior head bar. Components were originally described and numbered by Hanlon and Messenger (Hanlon and Messenger, 1988). For consistency, we have listed these numbers here.

View larger version (29K): [in this window] [in a new window]   Fig. 2. Spatial properties of six natural substrates (S1–S6) used in this study. Left column, images of substrates; right column, rock size distributions. Rock size scales (i.e. x-axis) of plots are kept the same to show shift towards the left (i.e. smaller size) of mean rock size. Red vertical line on the very left of each plot is truncated sand grain size. S1, rock substrate without any sand; S2, rock substrate with half a cup of the 0 sand spread over the substrate evenly; S3, one cup of sand; S4, two cups of sand; S5, four cups of sand; S6, full sand.

View larger version (10K): [in this window] [in a new window]   Fig. 3. (A) Mean rock size of S1–S6 as percentage of nine cuttlefish's average White square area (381.32 mm2). (B) Percentage of sand coverage of S1–S6. (C) Relative mean intensity of S1–S6. Unit represents percentage of average photon catch of each substrate relative to photon catch of a white surface (see text for photon catch calculation). (D) Root-mean-square (RMS) contrasts of S1–S6. (E) Number of lighter rocks of S1–S6. Lighter rocks are defined by Weber contrasts greater than 1 (see text for the Weber contrast calculation).

View larger version (20K): [in this window] [in a new window]   Fig. 4. Spectral properties and Weber contrast of selected rocks of S1. (A) Substrate S1 showing outline of three light rocks. (B) Reflectance spectra of three rocks marked in A, and the average reflectance spectrum of all rocks (black). (C) Weber contrast distribution of all rocks of S1.

View larger version (21K): [in this window] [in a new window]   Fig. 5. (A) Average grade of cuttlefish disruptive body patterning shown on substrates S1–S6. Cuttlefish were highly disruptive on S1 and their disruptive scores diminished as more sand was added to the substrate. Grading scores were low for S5 and S6. Images are representative body pattern shown on each substrate. Error bars are s.e.m.; N=9. (B) Number of dark and light rocks in animals' vicinity as a function of body patterning (disruptive and non-disruptive; see text for details). In the presence of dark rocks, animals showed disruptive or non-disruptive coloration, depending on whether or not light rocks were present. Light rocks consistently evoked disruptive coloration. Images are examples of body patterns shown. Data obtained from trial on S4 (total of 90 images). Error bars are s.e.m. (C) Average grade of disruptive body patterning shown on four substrates (SA–SD). Disruptive coloration was shown on sand with white rocks and sand with white and black rocks (SC and SD). Animals were non-disruptive on sand and sand with black rocks (SA and SB). Error bars are s.e.m.; N=12.

View larger version (65K): [in this window] [in a new window]   Fig. 6. Cuttlefish increase number of false edges or reduce visibility of true edges in response to different spatial properties of the substrate. (A–F) First column: original images of animals on substrates S1–S6. Second column: filtered images using edge-detection algorithm, Laplacian of Gaussian (LoG). Third column: the same LoG-filtered images of substrates only (i.e. S1–S6 in Fig. 2). Cuttlefish are difficult to detect, even with LoG operator.

View larger version (32K): [in this window] [in a new window]   Fig. 7. (A) Image of cuttlefish showing disruptive coloration on sand (i.e. no camouflage). (B) Filtered image using same LoG edge-detection algorithm as in Fig. 6. (C) LoG-filtered image of substrate only. This figure demonstrates that in addition to a human observer being able to discern the animal on the sand substrate easily, the LoG shows that the animal's false edges stand out conspicuously. This makes parts of the animal's body distinct objects on sand.