You may have wondered how creatures as delicate as jellyfishes manage to protect themselves with no spine or brain. While jellyfishes are known to sting defensively, could they also camouflage themselves to disguise their presence from predators?
Thanks to their gelatinous bodies, which are largely composited of water, jellyfishes can camouflage themselves by becoming very transparent. Jellyfishes have dense and acellular mesoglea. This means they efficiently transmit light, becoming colorless and harder for predators to differentiate these jellyfishes from their surroundings.
Transparent camouflages are just one of the several defensive adaptations jellyfishes pull off. You may be further curious: how specifically does the camouflage work? Can jellyfishes literally turn invisible? Also, do jellyfishes turn color?
These are some of the questions we answer in this guide.
How Do Jellyfish Camouflage Themselves?
In the aquatic ecosystem, there are three prominent camouflage mechanisms. These are counterillumination, reflectivity, and transparency.
The latter two are more prominent in sea creatures domiciled within the upper 100 meters of sea bodies (shallower water regions). Along with jellyfishes, plankton species and comb jellies demonstrate transparent camouflages.
The gelatinous nature of jellyfishes massively contributes to its capacity to camouflage itself as not all jellyfishes have the same refractive index as seawater.
For jellyfishes, their acellular mesogloea is dense and purely crystalline. Courtesy of such body type, jellyfishes enjoy enhanced buoyancy in shallower waters, with predators finding it harder to distinguish between jellyfishes and the water.
In the latter part of this guide, we will explore the chemical process behind the jellyfish’s transparent camouflage.
Can Jellyfish Turn Invisible?
Yes, jellyfishes can go out of sight. Typical of gelatinous planktonic organisms, jellyfishes have transparency ranging from 50%-90%.
50% transparency would suffice for jellyfishes in deeper water (say no deeper than 2,130 ft) to become invisible. However, with water depth reducing, the transparency of a jellyfish would need to increase for it to remain hidden.
This is especially because a predator’s vision is far more accurate with higher light intensity in shallower waters.
How Do Jellyfishes Protect Themselves?
Jellyfishes are some of the most delicate creatures in existence. They have no brain, spine, or even bone.
These marine organisms developed specialized defensive mechanisms to protect themselves from harm, given their physical vulnerability.
Their most potent defensive apparatus is their stinging cells. These stinging cells are positioned on their tentacles. Indeed, these cells can stun an invader to death.
Specifically, a jellyfish’s tentacles are kitted with barbed stingers. These stingers are incredibly small (but efficient), almost invisible to the bare eyes.
Each stinger on the tentacles is further kitted with a small bulb. This bulb is the depository of the venom while containing a pointed edge for penetrating victims.
An accidental crease of the jellyfish’s tentacles can automatically initiate stingers being shot at you.
These stingers can be deadly and can kill in minutes. This is especially in notoriously poisonous jellyfishes like box jellyfish (which is arguably the most venomous animal alive).
How Do Jellyfish Hide from Predators?
Jellyfishes, given their physical vulnerability (in that their body is mostly made of water), cannot outmuscle or outfight predators, so they hide.
Their transparent camouflage technique is very efficient in disguising their presence to predators.
Do Jellyfish Turn Colors?
Let us start by establishing that not all jellyfishes can change colors. Specifically, for a jellyfish to change color, it must contain unique micro-organisms called Zooxanthellae.
Zooxanthellae contain chlorophyll, producing visible pigmentation as they reside within the polyps’ tissues. In some cases, they are translucent, taking the color of light that passes through them.
These Zooxanthellae experience color mutations with time. It is this changing pigmentation that appears like the jellyfishes changing color.
Note that even jellyfishes with Zooxanthellae cannot instantaneously change their colors as a chameleon would.
What Adaptations Do Jellyfish Have?
To survive, the jellyfish develops several intelligent adaptations. This cuts through defensive adaptations, movement and feeding adaptations, and even adapting their brain and respiratory systems to their environment.
We have hit a lot on the defensive adaptations in jellyfishes. The stinging tentacles and transparent camouflages are some of jellyfishes’ most prominent defensive adaptations.
The arctic red jellyfish has a unique defensive adaptation. This jellyfish enters into a symbiotic contract with another fish.
This entails the partner fish staying close to the jellyfish’s tentacles and defending the jellyfish from bigger predators.
For such sentry duties, the jellyfish rewards this fish with small food pieces.
Talking about the feeding adaptations
The jellyfish – despite being pitiably delicate – is not the nicest guy you can find in the water.
To feed, it often has to sting its prey, stunning them into immobility before feeding on them.
Jellyfishes deploy their tentacles regularly in moving food into their mouths.
Adaptations to move
Left to its body shape, the jellyfish doesn’t have the aquatic equilibrium to move through water independently.
To make up for such deficiency, jellyfishes tap into the water current to propel them through water.
This is why most jellyfishes freely float when in water. Floating is relatively simplified for jellyfishes since their body is at least 90% water.
However, some jellyfishes further deploy their bells to facilitate movement. These bells are fitted with muscles.
By strategically contracting and relaxing these bell muscles, such jellyfishes can push themselves through water.
How Do Jellyfish Use Bioluminescence?
There is yet one defensive behavior jellyfishes demonstrate when they perceive danger. This is bioluminescence.
This involves the jellyfish ejecting brilliant light flashes to dazzle the attacking animal creature. Bioluminescence is more prevalent in jellyfish species like comb jellies.
Aside from jellyfishes, siphonophores display such a bioluminescent defense mechanism. Specifically, the latter releases a bulk of glowing particles to distract the predator.
Bioluminescence in jellyfishes arises from energy ejected when chemicals like luciferase and luciferin react together. This extensively differs from light emitted from a light bulb or solar rays.
The luciferin emits substantial energy (consequent to oxidation) after being acted upon by the luciferase catalyst.
The color of the light varies depending on the unique chemical structure of the luciferin and luciferase acting together in the chemical reaction.
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