Cephalopod dynamic camouflage

نویسنده

  • Roger Hanlon
چکیده

Everyone knows what camouflage is and how it works. And many people (some scientists included) think chameleons are the masters of color change. Wrong on both counts. In this primer, I provide an overview of recent work on the mechanisms and principles of rapid adaptive camouflage of cephalopods — octopus, cuttlefish and squids. These strange but capable marine invertebrates can camouflage themselves against almost any background, a feat well appreciated by Aristotle, and one never mastered by any land animal. Yet their ability to quickly alter their body patterns on different visual backgrounds poses a vexing challenge: how to pick the correct pattern amongst their repertoire. The cephalopod ability to change appropriately requires a visual system that can rapidly assess complex visual scenes and produce the motor output — the neurally controlled body patterns — that achieves camouflage. The body patterns themselves must be well designed and Primer sophisticated enough to defeat the visual prowess of diverse predators — teleost fishes, diving birds and marine mammals. Curiously, the quantification and experimental testing of camouflage principles have scarcely been addressed by biologists. By studying the cephalopods, we may have stumbled onto some general principles of animal coloration. Most animals with a fixed or slowly changing body pattern must move to the correct visual background, at the right time and lighting conditions, to implement camouflage. Cephalopods have evolved a different life history tactic: with their keen vision and sophisticated skin — with direct neural control for rapid change and fine-tuned optical diversity — they move where they wish and can adapt their body pattern for appropriate camouflage against a staggering array of visual backgrounds: colorful coral reefs, temperate rock reefs, kelp forests, sand or mud plains, seagrass beds, and others. How they choose the appropriate pattern can tell us something about both cephalopod and predator vision, and will lend understanding to which visual cues are likely to play key roles in accomplishing camouflage. Figure 1 illustrates three features of cephalopod camouflage. First, the degree of background matching can be superb. This Octopus vulgaris in the Cayman Islands is mottled to match the overall pattern, intensity, color and three-dimensional physical texture of the algae on this rock. Background matching does not always require an exact match as in Figure 1; in fact, this octopus more often achieved a general background resemblance while I filmed it over 90 minutes as it foraged slowly throughout this backreef area. Second, the speed of change is rapid, as shown in the time lapse of 270 milliseconds between images one and two. The total body pattern change as the octopus switched from camouflaged to fully conspicuous took place in 2.02 seconds. Rapidity of visual change is accomplished by direct neural control of chromatophore organs, which are cytoelastic sacs of pigment with radial muscles attached around the periphery. Each muscle is innervated by motoneurons that originate in the lower motor centers of the brain, and they travel without any synapse to each chromatophore organ. Third, camouflage benefits from both optical and physical three-dimensional effects, the latter being due chiefly to the changeable skin papillae. Note in Figure 2 how the three-dimensionality of the skin is also under fine motor control. Curiously, although papillae expression is regulated by visual input, neither this nor the biomechanics of how the papillae operate as a muscular hydrostat in the skin has been studied in any detail.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Reconfigurable infrared camouflage coatings from a cephalopod protein.

In nature, cephalopods employ unique dynamic camouflage mechanisms. Herein, we draw inspiration from self-assembled structures found in cephalopods to fabricate tunable biomimetic camouflage coatings. The reflectance of these coatings is dynamically modulated between the visible and infrared regions of the electromagnetic spectrum in situ. Our studies represent a crucial step towards reconfigur...

متن کامل

Cephalopod dynamic camouflage: bridging the continuum between background matching and disruptive coloration.

Individual cuttlefish, octopus and squid have the versatile capability to use body patterns for background matching and disruptive coloration. We define--qualitatively and quantitatively--the chief characteristics of the three major body pattern types used for camouflage by cephalopods: uniform and mottle patterns for background matching, and disruptive patterns that primarily enhance disruptiv...

متن کامل

Cephalopod Experimental Projected Habitat (CEPH): Virtual Reality for Underwater Organisms

Cephalopods’ visually driven, dynamic, and diverse skin display makes them a key animal model in sensory ethology and camouflage research. Development of novel methods is critically important in order to monitor and objectively quantify cephalopod behavior. In this work, the development of Cephalopod Experimental Projected Habitat (CEPH) is described. This newly developed experimental design br...

متن کامل

Evidence for distributed light sensing in the skin of cuttlefish, Sepia officinalis.

We report that the skin of cuttlefish, Sepia officinalis, contains opsin transcripts suggesting a possible role of distributed light sensing for dynamic camouflage and signalling. The mRNA coding for opsin from various body regions was amplified and sequenced, and gene expression was detected in fin and ventral skin samples. The amino acid sequence of the opsin polypeptide that these transcript...

متن کامل

Cuttlefish camouflage: The effects of substrate contrast and size in evoking uniform, mottle or disruptive body patterns

Cuttlefish are cephalopod molluscs that achieve dynamic camouflage by rapidly extracting visual information from the background and neurally implementing an appropriate skin (or body) pattern. We investigated how cuttlefish body patterning responses are influenced by contrast and spatial scale by varying the contrast and the size of checkerboard backgrounds. We found that: (1) at high contrast ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Current Biology

دوره 17  شماره 

صفحات  -

تاریخ انتشار 2007