On the coral reef defense tactics can be highly visual and deceptive
Coral reefs are places of great beauty. But the tranquil appearance can be deceiving, as there are dangers everywhere for those who live among the corals. Reef communities are among the most densely populated environments on the planet. When predator and prey live so closely together, survival strategies become very important. Follow along for a few examples of the creative and bold defenses of some unique marine creatures found on Wakatobi’s reefs.
Adapt or perish
Fortunately, nature has bestowed a number of defense mechanisms, or adaptations, on marine life, helping them to escape predators. Those who are built for speed can often survive by remaining vigilant and ready to flee. But what about those who move more slowly, or not at all? They can’t spend their won lives in hiding. Instead, these reef dwellers have created a number of physical and behavioral adaptations that allow them to go about the business for acquiring nourishment and reproducing without becoming food for something else in the process.
Some of the most interesting adaptations are also some of the most visually captivating; bold statements to other marine creatures to “back off” or something bad might happen. The range and depth of some of these anti–predation tactics and defenses can be highly visual and exceedingly deceptive.
Look but don’t touch
Healthy coral reefs are like vibrantly colorful gardens. But these colors can mean “look, but don’t touch.” A mere brush of the wrong place, for divers and marine life alike, can teach a painful lesson in the dangers of contact. Cnidarians, which includes corals, hydroids, jellyfish, sea anemones and black corals, all possess stinging organelles called nematocysts, which they use for defensive purposes. While they are quite beautiful to look at, they can pack a sharp, and sometimes, deadly punch.
Sometimes a pretty package doesn’t necessarily mean an invitation. For example, one taste of a dorid nudibranch (Hypselodoris tryoni) is more than sufficient to teach a predator that it is a bitter mouthful to covet. Scientists believe that the natural toxins produced by reef invertebrates such as these may have future commercial or medicinal applications.
Some species of nudibranchs like the Cuthona are biological burglars; they will borrow the defense mechanism from one animal and use it for themselves. For example, nudibranchs that feed on hydroids can store the hydroids’ stinging cells (nematocysts) within their own body, primarily in the cerata (the wavy little appendages on their back). So if an unsuspecting fish were to attempt to eat these nudibranchs they would get a mouthful of stinging cells instead of a delectable treat. To advertise this trait, nudibranchs are among the most flamboyantly colored creatures on the reef – their way of waving the red warning flag, even if it should happen to be in Technicolor.
On the other hand, many soft corals have many microscopic stinging cell filaments or cnidoblasts, which give the phylum its name of “Cnidarian.” These cnidoblasts are located in the coral’s feathery tentacles, which are typically visually stunning. However, some can produce minute stinging capsules with a threadlike organ—effectively a mini harpoon—that can be shot out to either attack prey or ward off threats.
Coral reef fish are among the most elaborately ornamented animals on earth. But for marine creatures, their flashy exterior is not only for show.
A small octopus out in the open will make a nice meal for just about any predator on the reef, unless of course it happens to be a blue-ringed octopus. An individual blue-ringed octopus will use its dermal chromatophore cells to camouflage itself until it is provoked, at which point it quickly changes color, becoming bright yellow with blue rings or lines. This little beauty also packs a highly potent neurotoxin in its bite that can quickly neutralize anything up to a hundred times its size. To advertise this lethal feature, the blue-ringed octopus displays it’s unmistakable iridescent blue rings and lines, which glow stronger and brighter as the animal perceives a threat.
An individual blue-ringed octopus will use its dermal chromatophore cells to camouflage itself until it is provoked, at which point it quickly changes color, becoming bright yellow with blue rings or lines. Photo by Steve Rosenberg
When they’re young, bluespotted stingrays are covered with iridescent blue spots. Predators such as the hammerhead shark are known to frequently prey on the bluespotted stingray. But the ray’s coloration is an alert signal for its poisonous barb, so few animals attempt to overpower it. Borrowing the playbook from the blue-ringed octopus, their striking blue spots serve as a warning to other fish – don’t mess with me!
“Many marine creatures will use more than a single defensive measure and combine them for the most effective result.” Jennifer Gill
The red lionfish is one of the most beautiful fish on the coral reef, and perhaps the most widely recognized of all lionfish. Their vividly contrasting coloration is intended as a warning to other predators. Their “don’t care” attitude makes the red lionfish easily approachable for photography—just be sure to watch out for its venomous spines. While not as large as a red lionfish, the dwarf lionfish, or shortfin lionfish, is no less spectacular. Like other members of the Scorpaenidae family, the venomous spines are not only potent, but well advertised for the benefit of any attackers having the misguided intention of making this colorful morsel a meal.
Most members of the family Scorpaenidae, or scorpionfish, rely on camouflage as a means to hunt, but use weaponry that involves chemical warfare (toxins) for defense. As the name suggests, scorpionfish can sting with sharp spines coated with venomous mucus. The family is a large one, with hundreds of members, most of which are found in the Indo-Pacific. Once in a while you will find one that does not follow the basic earth tones for coloration but instead seems to say “Hey, look at me.”
The twinspot lionfish’s eyespots may serve to dissuade large fish-eating predators from messing with it, as well as its toxic dorsal spines might. Still scorpionfishes such as the twinspot, are sometimes eaten by sharks, morays, and even frogfishes. Photo by Dr. Richard Smith
But, there are also those who rely on false advertising by clearly stating they are something they are not. They achieve this by exhibiting bright and unusual color patterns intended to confuse predators into thinking they are warning signs that they are toxic. When it comes to butterflyfish we know better, but the good news is that many predators don’t. Some fish’s defenses are intertwined with their coloration, either in the form of color patterns that blend with their surroundings, or one that says out load “I am not the one to mess with.”
Some fish’s defenses are intertwined with their coloration, either in the form of color patterns that blend with their surroundings, or one that says out load “I am not the one to mess with,” like this Copperband butterflyfish. Photo by Steve Miller
Coral reefs and their creatures have found incredible ways to defend themselves, yet in this vastly serene, yet dangerous world, it appears it is not necessarily the strongest of the species that survives. In life, there are no guarantees for safety, but as we can see from some of our marine life friends, having a good insurance plan can even the odds.
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