Modular organization of adaptive colouration in flounder and cuttlefish revealed by independent component analysis

Abstract

Flounders and cuttlefish have an impressive ability to change colouration, for camouflage and, in the case of cuttlefish, for communication. We pursue the hypothesis that these diverse patterns are created by combining a small number of distinct pattern modules. Independent component analysis (ICA) is a powerful tool for identifying independent sources of variation in linear mixtures of signals. Two versions of ICA are used, one assuming that sources have independence over time, and the other over space. These reveal the modularity of the skin colouration system, and suggest how the pattern modules are combined in specific behavioural contexts. ICA may therefore be a useful tool for studying animal camouflage and communication.

Cuttlefish camouflage: a quantitative study of patterning

“…Moreover cuttlefish can stretch and shift their skin, introducing additional complications. These difficulties are solved by warping the images as described elsewhere (Anderson et al ., 2003). Second, as in conventional fMRI, it is necessary to filter the images before processing to remove high‐frequency noise.…”

“…The combined effects of these distortions mean that the raw images cannot be directly compared. To allow direct comparison, images were warped using specially designed computer software to discount perspective and other distortions (Anderson et al ., 2003). Warping was conducted by selecting a mesh of 14 reference points on the body of the cuttlefish that could be accurately identified by an experienced observer.…”

A physiological interpretation of pattern changes in a flatfish

“…Little is known about central processing of the visual chromatic stimuli. Theoretical relationships between retinal stimulation, central processing and possible neural pathways to localized areas of the skin have been discussed (Ramachandran et al, 1996;Anderson et al, 2003). Observations on a cyprinid fish, the European minnow Phoxinus phoxinus (L.) indicate that spinal cord dorsomedial pigmentomotor neural pathways within the substantia gelatinosa Rolandi and corpus commune posterius (Burton, 1964(Burton, , 1966(Burton, , 1969 (Whitear, 1952;Gray, 1955Gray, , 1956Burton, 1964Burton, , 1966Burton, , 1969.…”

Using image analysis on the ventral colour pattern in Salamandrina perspicillata (Amphibia: Salamandridae) to discriminate among populations

“…To our knowledge, there are few studies that have analysed the elements of the colour pattern (i.e. the 'patches') on the basis of their number (Endler, 1978(Endler, , 1980(Endler, , 1984Aparicio et al, 2005) and shape (Bosch & López-Bueis, 1994), and fewer still that have employed quantitative image analysis (Anderson et al, 2003;Todd et al, 2005).…”

“…In the present study, we use for the first time an approach based on geometric morphometrics (Bookstein, 1991;Rohlf & Marcus, 1993;Marcus et al, 1996;Dryden & Mardia, 1998;Zelditch et al, 2004), which is similar to warping (Anderson et al, 2003), to standardize ventral shapes. This technique is useful for eliminating form distortions.…”