Underwater camouflage and mimicry
Encyclopedia
Underwater camouflage and mimicry is a technique of crypsis
—avoidance of observation—that allows an otherwise visible aquatic organism
to remain indiscernible from the surrounding environment, or pretend to be something else by mimicking another organism or object.
has produced some extraordinary methods of survival in the oceans. Camouflage and mimicry methods are very diverse and are found underwater in a range of animals from some of the smallest creatures to the largest fish in the world, from brainless organisms to animals with highly developed brains.
In ancient Greece, Aristotle
commented on the color-changing abilities, both for camouflage and for signalling, of cephalopod
s including the octopus, in his Historia animalium:
varies from green and red, to a ghostly white. The fish is almost flat and resembles a leaf in color and pattern, with a blotched skin. This fish has appendages around the mouth, and sometimes real algae
and hydroids grow on its skin. The fish molts periodically, and can change colors after the molt.
Leaf Scorpionfish not only look like leaves, but they mimic the movements of dead leaves that are rocked back and forth in the currents.
hunts during the day, hence the common name. This octopus can distinguish and match itself to the colors and textures of its surroundings, and thus it can if necessary perfectly resemble a rock or a coral it is hiding beside. And when necessary, in order to scare away a potential predator, the Day octopus can display markings which resemble very large eyes. Like many other octopus species, it uses both defensive and aggressive mimicry.
, the "Rockmover", also known as the "Dragon Wrasse", there is a striking difference in appearance between the adults and the juveniles. A juvenile Rockmover resembles a loose piece of sea weed or algae
. It swims in a vertical position with its head pointing downwards, and behaves in a way that perfectly resembles the movement of a piece of seaweed: moving back and forth in the surge, as if it was inanimate.
, Rhincodon typus has cryptic
coloration with Countershading
: it has a light-colored belly, and a darker back.
The Whale Shark also has disruptive coloration: from above its markings of stripes and spots visually break up the shape of the animal, creating an illusion of a school of fish swimming in the distance, a camouflage for the open ocean.
s have excellent adaptive camouflage
. They use cryptic coloration to avoid being detected by both prey and predators. Whenever possible rather than swim, they crawl on their fins along the bottom while constantly changing colors and patterns to match their background. In a study, some flounders demonstrated the ability to change color in eight seconds. They were able to match the pattern of checkerboards that they were placed on. Changing color is an extremely complex process involving the flounder's vision and hormone
s. If one of the fish's eyes is damaged, or covered by the sand, the flounder has difficulties in matching its color to its surroundings. Whenever the fish is hunting or hiding from predators, it buries itself into the sand, leaving only the eyes protruding.
s cannot change their colors nor their texture, yet some of them actively camouflage themselves. With their tube feet they pick up debris from the bottom and attach it to their upper surfaces. They use shells, rocks, algae and sometimes even sea anemone
s.
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
—avoidance of observation—that allows an otherwise visible aquatic organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
to remain indiscernible from the surrounding environment, or pretend to be something else by mimicking another organism or object.
Context
The ability to camouflage oneself can provide a survival advantage in the constant struggle between predators and prey. Natural selectionNatural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
has produced some extraordinary methods of survival in the oceans. Camouflage and mimicry methods are very diverse and are found underwater in a range of animals from some of the smallest creatures to the largest fish in the world, from brainless organisms to animals with highly developed brains.
In ancient Greece, Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
commented on the color-changing abilities, both for camouflage and for signalling, of cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s including the octopus, in his Historia animalium:
- "The octopus ... seeks its prey by so changing its colour as to render it like the colour of the stones adjacent to it; it does so also when alarmed."
Leaf scorpionfish, Taenianotus triacanthus
The color of the leaf scorpionfishTaenianotus triacanthus
Taenianotus triacanthus is a species of marine fish which is the sole member of the genus Taenianotus. It is commonly known as leaf scorpionfish or paperfish....
varies from green and red, to a ghostly white. The fish is almost flat and resembles a leaf in color and pattern, with a blotched skin. This fish has appendages around the mouth, and sometimes real algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and hydroids grow on its skin. The fish molts periodically, and can change colors after the molt.
Leaf Scorpionfish not only look like leaves, but they mimic the movements of dead leaves that are rocked back and forth in the currents.
Day Octopus, Octopus cyanea
Unlike many other octopuses, the Day octopusBig Blue Octopus
Octopus cyanea, also known as the big blue octopus, day octopus and Cyane's octopus, is an octopus in the family Octopodidae. It occurs in both the Pacific and Indian Oceans, from Hawaii to the eastern coast of Africa.O...
hunts during the day, hence the common name. This octopus can distinguish and match itself to the colors and textures of its surroundings, and thus it can if necessary perfectly resemble a rock or a coral it is hiding beside. And when necessary, in order to scare away a potential predator, the Day octopus can display markings which resemble very large eyes. Like many other octopus species, it uses both defensive and aggressive mimicry.
Juvenile rockmover, Novaculichthys taeniourus
In the fish species Novaculichthys taeniourusNovaculichthys taeniourus
Novaculichthys taeniourus is a wrasse that is mainly found in coral reefs and lagoons in the Indo-Pacific region. These include those of the Gulf of California to Panama; tropical Pacific Ocean islands including Hawaii; the Philippines, Indonesia and Australia; and the Indian Ocean to the east...
, the "Rockmover", also known as the "Dragon Wrasse", there is a striking difference in appearance between the adults and the juveniles. A juvenile Rockmover resembles a loose piece of sea weed or algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. It swims in a vertical position with its head pointing downwards, and behaves in a way that perfectly resembles the movement of a piece of seaweed: moving back and forth in the surge, as if it was inanimate.
Whale shark, Rhincodon typus
The whale sharkWhale shark
The whale shark, Rhincodon typus, is a slow-moving filter feeding shark, the largest extant fish species. The largest confirmed individual had a length of and a weight of more than , but unconfirmed claims report considerably larger whale sharks...
, Rhincodon typus has cryptic
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
coloration with Countershading
Countershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...
: it has a light-colored belly, and a darker back.
The Whale Shark also has disruptive coloration: from above its markings of stripes and spots visually break up the shape of the animal, creating an illusion of a school of fish swimming in the distance, a camouflage for the open ocean.
Peacock flounder, Bothus mancus
Like all flounders, Peacock flounderPeacock flounder
The Peacock flounder , also known as the Flowery flounder, is a species of fish in the family Bothidae...
s have excellent adaptive camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
. They use cryptic coloration to avoid being detected by both prey and predators. Whenever possible rather than swim, they crawl on their fins along the bottom while constantly changing colors and patterns to match their background. In a study, some flounders demonstrated the ability to change color in eight seconds. They were able to match the pattern of checkerboards that they were placed on. Changing color is an extremely complex process involving the flounder's vision and hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s. If one of the fish's eyes is damaged, or covered by the sand, the flounder has difficulties in matching its color to its surroundings. Whenever the fish is hunting or hiding from predators, it buries itself into the sand, leaving only the eyes protruding.
Sea urchins
Sea urchinSea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s cannot change their colors nor their texture, yet some of them actively camouflage themselves. With their tube feet they pick up debris from the bottom and attach it to their upper surfaces. They use shells, rocks, algae and sometimes even sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
s.