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Unique Defenses in Marine Life

Submitted by admin on 2011-11-25

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It's a dogfish eat dogfish world out there and with some help from evolution. All species have developed their own unique ways to survive. As humans we tend to rely on our own to provide us with safety, while at the same time having our own species as our largest threat. Things in the animal world are a bit different though, with the constant threat of predators for almost all marine creatures, it was vital for their existence that they develop ways in either avoiding predators or managing to defend themselves from predators.

In the ocean the survival rates for many species are extremely low, turtles for example on average only have a 1/100 chance of reaching adulthood, meaning that only 1 or 2 turtles from a nest usually go on to reach adulthood.

Below is a list of some unique defense mechanisms found in sea creatures in the oceans. Many of the marine creatures listed will use more than a single defensive measure and combine them for the most effective result.


Echinoderms are able to use one of the most powerful self-preserving defense tactics around, they are able to regenerate missing parts.

Some star fish for example are able to drop their limbs and then regenerate them. This will leave the predator with only one of the star fish's limbs, and make survival far more likely for the starfish. What is even more remarkable is that these star fish can even regenerate completely from a small portion of the remaining body.

Some sea cucumbers also have a fascinating defense mechanism. These sea cucumbers can eject its internal organs from its body so that it can escape a predatory attack. They will excrete tubules of holothurians out of their digestive tract, these toxins are said to inhibit oxygen intake from the predator and as such usually results in the sea cucumber being dropped, where after it will attempt to escape and later regenerate the organs that were expelled.

Certain echinoderms are even able to deliberately split their bodies as to asexually reproduce.

Spikes and Spines

Sea Urchins have a blatantly visible physical defense of large spikes which extend out from most of its body. These sharp spikes keep it safe from majority of potential predators, but it does not stop the Triggerfish which has a hard beak-like mouth and the ingenuity to blow water at the urchin as to tip it over and expose it's less protected areas.

Porcupinefish also use the defense of spines. Their bodies may look fairly unthreatening by default, but when these fish feel threatened they swallow water and increase their size causing the spines on its body to stand erect and causing some serious problems for the predator in the situation.

Lionfish are easily recognizable and for a long time they were regarded as a pleasant sight, but for many in the Caribbean these days they are the enemy, and there is a reason for this. The Lionfish population is able to expand rapidly due to their intense defenses which leave them prey to few. The lionfish has large spines which extend outward in almost every direction, not only are these spines super sharp but they're also very venomous and do a great job in deterring predators.

Scorpionfish are somewhat similar to their Lionfish family members and also rely on venomous spines as a defense, though the scorpionfish is also one that relies heavily on camouflage. They will often lie on the sea floor, covering a lot of their body with sand, with only their spines and eyes exposed.


The mimic octopus has by far the most impressive camouflage technique. The mimic octopus will shape its body to mimic other marine creatures. There have been recordings and images taken of these octopuses shaping themselves as eels, sea snakes, lionfish and flounders. Other species of octopus can change the colours and textures of their bodies to become extremely camouflaged into their surroundings, making it even hard for humans to spot them.

As mentioned above the scorpionfish is another fish that relies heavily on camouflage, though camouflage can be found in hundreds of marine species.


Sea Hares have the ability to release an impressive amount of ink when threatened which can deter predators and is also known to be potentially toxic. The colour of the ink is dependent on the colour of the seaweed that they generally eat, their body colours are also dictated by the colour of their food source.

The octopus is well known for its ability to expel ink as a defense. It's an effective defense which allows the octopus to escape while the predator’s sight and sense of smell is disturbed. The ink is said to reduce olfactory organs which would make it exceptionally useful for escaping sharks. The ink that the octopus expels is black in colour and has the same main colouring agent as human hair and skin colour.

Venom and Stings

The Chironex (Box Jellyfish) possesses an extremely potent venom, which is contained in the numerous nematocysts on the tentacles. There is a reason why the box jellyfish is known as the 'sea wasp'. The box jellyfish's venom can kill a human and is extremely effective in working as a defensive element.

The Blue-Ringed Octopus is another sea creature with deadly venom. This octopus is packed with a neuromuscular paralyzing venom which can cause paralysis and death within a short period of time. They inject the venom with their mouths and in fact the venom itself is less of a defensive measure than their colour is. The blue-ringed octopus has bright, luminous blue rings (though they fluctuate in colour and intensity) around its body, warning predators of its venomous abilities.


Electric Rays are the most electro-sensitive animals in the world and pack up to 200 volts. The bioelectricity of these creatures is stored in hexagonal columns in their body. The effect of electrocution from these rays is similar to that of a hair dryer being dropped in a bath of water.

Electric Eels are another creature with the ability to shock off predators. These eels have stacked electrically stacked plates and some eels are capable of producing up to 500 volts, enough to potentially kill an adult human.


The Boxer Crab is a fascinating little crustacean which has a mutual living arrangement with small anemones. The anemones grow on the crab’s claws which the crab can then use as a form of self defense. The boxer crab is also called the pom-pom crab and it's easy to see why it has been named this.

Clownfish, also known as anemonefish are fairly small fish which are immune to the sting of certain large anemones, as such they use the anemones as protection from predators, being able to hide within the tentacles without fear of being stung.

Both the small blenny and the goby are known for their abilities in finding hiding in unique places. Blenny often house themselves in the old worm holes inside of corals and gobbies have a knack for finding small bottles or soda cans and making him inside of them. Octopuses too are known for seeking refuge in bottles, cans and other objects.


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