Living on the reef must be tough! There is nowhere else on Earth where life is found in such an abundance and diversity as it is on a coral reef. Thousands of different species are competing against each other for food and space, and in a constant struggle to survive and prosper, some marine animals have evolved in the most bizarre ways.
What is Mimicry?
Mimicry involves at least two species, however it can me more. One of the species involved is known as the model. The model has a specific desirable trait that aids in its survival, whether it is for hunting or for defence. The other species involved –let’s call them the copycats – have evolved over time to look like the model species. This way, other animals will confuse the two and the copycat species can be left alone. This is known as Batesian Mimicry.
An example of Batesian mimicry that you will probably know well is the hoverfly. These little guys look and move in a very similar way to wasps, however, they do not have the sting that we all fear. They have evolved to look the same in hope that other creatures will fear them and leave them alone. This form of mimicry is quite common underwater because many species have powerful defence techniques such as venomous spines, poisonous flesh or a powerful bite.
One of the best underwater examples of Batesian mimicry is the black saddled toby and the mimic filefish. The black saddled toby is actually a species of pufferfish, and its flesh is among the most poisonous on the planet. They are not the best swimmers, and they can’t really bite any attackers, however, nothing will touch them because doing so would almost certainly result in death. The copycat mimic filefish looks almost identical to the toby, and the further blend in, it will follow the toby around the reef. Now the mimic filefish is almost guaranteed safety because of its appearance.
This mimicry is so effective, even most people cannot tell the two species apart. Hint: Look at the dorsal fins…
There is another form of marine mimicry which is quite common; Müllerian mimicry is where two or more species have evolved to look similar to one another. A nice example of this is wasps and bees. Both of these yellow and black striped insects have stings that are capable of inflicting painful wounds. By sharing attributes, most animals know they should stay clear of any animal that looks the same.
It is not only venomous animals that mimic each other either. Animals with sharp spines, poisonous flesh, or simply a foul taste may allow Müllerian mimicry to develop. Müllerian mimicry is not always visual mimicry either. Several species of venomous snakes give out similar auditory warnings, and different species that look nothing alike might share similar, bright colour patterns.
Underwater, Müllerian mimicry is fairly common. One of the most easily observed examples is members of the nudibranch family, Chromodoris – many of which have extremely distasteful flesh. Many members of this family share the same bright colours and similar markings, so any potential predators understand that they should avoid anything that looks similar.
What is Camouflage?
In biology, camouflage is where a species will try to blend into its environment to make it more difficult to spot. This could be the animal sharing a similar colour or pattern to its preferred environment, or it might be the animal has an unusual shape that helps it blend in more. Often, it is both. Camouflage can be found everywhere throughout the world, both above and underwater. Some species are even capable of changing their own skin colour and texture to aid camouflage, such as chameleons.
The underwater world is full of amazing examples of camouflage. Beautiful and tiny pygmy seahorses blend in perfectly with the sea fans they live on, and robust ghost pipefish look exactly like a blade of seagrass. Even animals that have no solid habitat to hide amongst make use of camouflage. Most pelagic fish are silver in colour, which helps them blend in the with open ocean, and juvenile species that are living in open waters tend to have transparent flesh so they are almost invisible.
By far the most impressive users of camouflage in the ocean – and probably the world – are cephalopods. Octopus and cuttlefish are well known for their ability to alter their colour to help them blend in with their environment. This is done via special skin cells known as chromatophores, and using these they can change their entire colour in a matter of milliseconds. These chromatophores are not always used to help them blend into their environment, but also to signal or warn others. The notoriously venomous blue-ringed octopus is normally quite dull looking, however the moment it moves or feels threatened, it will change its body colour to gold/yellow and flash bright blue rings to warn potential predators not to get too close.
To make their camouflage even more impressive, several species of cephalopods can alter their skin texture by tensing muscles in their skin. One moment they can have smooth, flat skin, and the next they are covered in what appears to be spikes. This can help them in two ways; by making themselves more jagged, they blend into many environments better, and they also appear larger, which may put off many predators. If the predator sees through the act and continues to act aggressively, they can simply disappear into a cloud of black ink.
Is Mimicry and Camouflage only for Defense?
Although mimicry and camouflage is primarily used by animals to avoid predation, others have adopted it to aid their hunting. Many ambush predators use mimicry and camouflage to their advantage, such as the slow and strange looking frogfish. They have evolved to look extremely similar to sponges, and will wait near one for any unsuspecting fish to get too close. They have even evolved a special “fishing” technique where they will dangle a lure in front of their mouth to attract their prey. Their camouflage is so incredible that sometimes other frogfish of the same species will be fooled by it, and subsequently get eaten.
Another example of an ambush predator that uses camouflage are members of the scorpionfish family. They are often a grey/brown colour and hide on top of rocks or in the sand waiting for their meal to come to them. It is important that you take care over sandy areas, and never rest on the bottom until you are 100% sure there is nothing below that can deliver a serious – and potentially fatal – sting.
Some predators will mimic other, less dangerous species so they can get closer before attacking. The cleaner wrasse is an extremely important part of most tropical reefs, and fish will allow them almost unlimited access to their delicate areas to remove any parasites they may have picked up. There are members of the blenny family who mimic these cleaner wrasse, and when they are close, they will rip a small amount of flesh off the unsuspecting fish.
Who is the King of Mimicry and Camouflage?
Although this question is up for debate, probably the best contender for this title is the mimic octopus. First discovered in Sulawesi, Indonesia, the mimic octopus is not the most inconspicuous critter, as its normal colour is brown and white stripes, although like all octopus, they can change their hues to blend in better. The most amazing thing about this animal, is its ability to mimic other species.
The mimic octopus has been known to mimic as many as 15 different species. When moving along the bottom, they can flatten their body and mimic the movements of a flounder. If it is detected, it can rush into a hole and then stick two arms out to make it look like an extremely venomous banded sea krait. Mimic octopus have also been observed mimicking jellyfish and lionfish to allow them safe passage through open waters.
Mimicry and camouflage are possibly the coolest survival methods utilised by marine species, and the best thing about it is that it happens all over the world!
We have only listed a handful of the countless different species that use mimicry and camouflage. Do you have a favourite? If so, let us know in the comments below.
Octopus and several other marine invertebrates have the ability to change their colors to blend in with their background, which can both aid hunting, and also avoid predation. Many other fish cannot change their colors, however have evolved color patterns and shapes that make them almost invisible against the correct background.
The highly poisonous Scorpion fish and stone fish look identical to algae covered rock, which means that unsuspecting SCUBA Divers could kneel on, or brush up against them while diving. This means you have to be extra cautious while looking for a nice sandy patch to kneel on to practice skills, especially while Night Diving.
Another fantastic example of camouflage is the incredibly beautiful Weedy & Leafy Sea Dragon that inhabits the waters of South Australia. Its leafy appendages and unusual shape allow it to blend in almost perfectly among the kelp forests. Even the way it moves is very similar to the way kelp moves in surge or currents.
Not just the hunted use mimicry however. Some hunters have developed the ability to mimic other, less dangerous reef fish. One species of Snapper, while still juvenile, can mimic certain species of Damsel fish, which are small schooling reef fish that live off a diet of zoo plankton, therefore ignored by other reef fish species. This allows the young Snapper to get in close and when it spots a small enough fish it can strike. The commonly known parasite picking cleaner wrasse is mimicked by certain Blenny species. When it looks the same as the Cleaner Wrasse other fish are more than willing to let it in close to help clean any parasites that they may have. At this point the Blenny darts in and rips off a scale or a piece of fin, which form a substantial amount of its diet.
Luckily as reefs worldwide have all evolved in slightly different ways there is almost no limits to the bizarre copycats around the world. So if you want to witness it first hand all you need to do is get into the water for a dive.
‘Mimicry and Camouflage’ was written by Mike