Masters of Camouflage
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Many marine animals have evolved capabilities that have made them masters of camouflage. They have succeeded in making themselves elusive and almost invisible in the process. They mimic aspects of their environment to their own benefit with such success that they are rarely seen by the untrained and unaware eye, even at very close distance. Sometimes you’re looking right at one even without realising it’s right there in front of you!
Camouflage is at one end of two extreme visual survival strategies: at the one extreme you have deceptive coloration intended to conceal, at the other extreme advertising coloration intended to highlight the presence of (usually) poisonous characteristics such as the unappetising taste of the boldly coloured nudibranchs.
The most famous examples of marine camouflage (and of intelligence in marine creatures) must be the octopus and the cuttlefish. They can change both their body colour and texture in response to their environment and survival needs. The octopus’ ability to change its body colour and texture immediately to match whatever background it settles on commonly frustrates anyone hunting them in a rock pool. Encountering an animated cuttlefish on a night dive with waves of colour bands sweeping across their bodies is one of nature’s grand spectacles.
Special cells located in the outer skin layers contain colour pigments which the animal can alter by neural control (simply by thinking about it!). These chromatophores typically occur in red, yellow, brown, black and blue and each one can be expanded to display a large area of colour or contract to a tiny spec. Emotions trigger the nervous system to ‘paint’ the skin in a particular colour pattern, sometimes animated as in the cuttlefish.
But beyond these obvious masters of camouflage there are other commonly found marine creatures that exhibit great skill and specific strategies in this field. They are easy to observe because they typically do not move very quickly and rely particularly on the expert camouflage to escape predation.
The wily scorpionfish
The scorpionfish family Scorpaenidae is well represented on coral reefs world-wide and especially around Pemba in northern Mozambique (see photo 234). From the sea walls off the northern drop-offs to the rocky flats near shore the cryptic scorpionfish is found, its complex mottled coloration and a body covered in tiny hooked/spiked protuberances making it difficult to spot in amongst the varied life forms on the coral reef. Its body is covered by tiny colour cells (chromatophores) and reflecting cells (iridocytes) (see close-up photo of a scorpionfish eye in photo 142).
In the scorpionfish these changes in coloration appear to have less to do with behavioural conditions but rather to conceal themselves through imitating bottom objects such as sponges, sand or corals.
Many is the time that I have nearly put my hand one while steadying myself to photograph some other critter. It was only because the Scorpionfish saw my hand coming and darted away that has prevented a painful injury. If it had been up to me I would simply have recognised his presence too late. Even in juvenile scorpion fish the skill of blending with their background is evident. In photo 292 taken on Aliwal Shoal a tiny juvenile scorpion fish has selected a sponge to settle in that almost matches his coloration and the fish has possibly adapted slightly in order to match it almost completely! In photo 293 another (disruptive) camouflage strategy can be seen the way the fish has broken up the continuos orange colour so as not to appear quite like a contiguous fish on a somewhat differently coloured sponge. Apart from the fact that they are excellently adapted to escape detection in the coral environment they are also known to be able to adapt their coloration to the particular background on which they settle quite quickly - just to what degree I was about to discover.
I was prowling behind one particularly large and typically rusty orange individual following him in his slow deliberate ambulations around the reef. Suddenly he darted onto a large irregular patch of grey-white soft coral and momentarily I thought I had lost him. Then I realised that in a space of less than a second he had changed totally to mimic the colour of the soft coral quite closely - even though I knew he was there my mind could simply not discern the shape of his body, additionally disguised by the usual protuberances that now seemed perfectly suited for his new soft coral backdrop (see picture 230, perhaps contrast with 234. 230 really requires a line drawing as a ‘key’ to where the fish is perhaps outlining eyes and mouth).
Relatives of the scorpionfish include the paperfish and the stonefish. The paperfish Taenianotus triacanthus also has the same hook-shaped irregular protuberances covering it but it also employs another strategy to escape detection. The paperfish (photo 236) has a very flat compressed body shape and has evolved the tendency to wave in the currents just like a piece of paper! This, plus the ability to change colour, makes it very difficult to find.
The reputation of the deadly stonefish Synanceia sp. precedes it - it is literally the most venomous of all fishes. The tales of sudden painful death that emerge whenever the stonefish is mentioned are testimony to its success in the camouflage (and poison) stakes. This determined predator will remain still even when obviously threatened. It relies for survival on its camouflage and the deadly poisonous spines on its back. Even on close inspection it can be mistaken for an algae-covered rock or a bump in the sand - so perfect is its camouflage. Once detected (see photo 52) it has one of the most ugly countenances in the animal world - enough to inspire dread even though detected.
The cool klipfish
A local South African example of marine camouflage from Cape waters is the klipfish, a kind of blenny. Many of the species in this family are very cryptically coloured to match the immediate environment in which they live and hunt. The camouflage effect is so good that many times I have been watching a particular klipfish (most likely a lace klipfish Blennioclinus brachycephalus) amongst the swaying purple seaweed off the Cape south coast when he has suddenly disappeared in front of my eyes, only to reappear seconds later as the swaying seaweed once again created a pattern from which my eyes and mind could distinguish the vague outline of the fish once again. The ‘cool’ klipfish hadn’t moved at all (see photo 139 - again this needs a line drawing to enable reader to ‘see’ the eyes, mouth, fins etc.); its disguise was so perfect that as the seaweed swayed from side to side I couldn’t keep him in sight even from distance of 20 centimetres!!!!
The photograph illustrates the problem! See if you can see me before I can see you!
Another strategy: Take others for a ride
This unique hermit crab (see photo 60) illustrates another camouflage strategy. It seeks out small anemones to put onto its shell home and cultivates a relationship with them until eventually the shell is almost invisible. The anemones that cover it attract all the attention of potential predators while their stinging cells provide another level of protection. The anemones are literally along for the ride.
The sponge crab has taken the strategy of being a host for other animals to the extreme. These crabs are often so encrusted with the sponges that grow on their backs that they are truly ‘invisible’. It’s only when a ‘walking sponge’ is observed that the crab can be found underneath. (see photo 427).
The criss-cross patterns on the long-nosed hawkfish Oxycirrhitus typus and its tendency to sit absolutely still on the branches of the deep-sea coral fan that is its typical home are an example of the most simple kind of camouflage coloration. There is no attempt to change colour - it simply seeks out a quiet position on a coral fan and waits for unsuspecting prey to approach it. Then it strikes with a speed that is almost impossible for the human eye to detect. The prey simply appears to disappear and hawkfish now rests where the prey was!
At the other end of the camouflage spectrum is the dramatic advertising coloration so preferred by the nudibranchs. Nudibranchs are found in almost any rock pool and reef and many of them advertise their presence with bright colours. It is apparently exactly these bright colours that warn potential predators of their foul taste and poisonous bodies.
The striking and highly venomous firefish of the Pteroinae subfamily - also sometimes called the lionfish or turkeyfish - another relative of the scorpionfish, also advertises its presence dramatically. While floating in the water with its colourful poisonous spines spread as a protective armour, it is ready to pounce violently on any prey that comes too close (see picture 425 - and cover picture of a juvenile).
Camouflage strategies are many and varied, some apparently more successful than others. However, we must resist the temptation to judge the success of an animal’s attempt at camouflage by our own visual and perceptive capabilities. To be fair it must actually be judged from the perspective of the third party that the deception is intended for. If the third party has extremely poor visual capabilities then even a poor disguise is effective. Spectral sensitivity, sensitivity to movement and the way these are interpreted by the third party’s brain are vital to our understanding of the success of the camouflage.
Also, while we may easily be able to distinguish the patterns of a scorpionfish when illuminated by a camera’s flashlight, this may be quite difficult in the typical natural blue-hued light at a depth of say 20 metres.
In the marine world, camouflage - no matter how beautiful to us - is not a matter of fashion, it’s a matter of survival.