Jellyfish have almost no skeletal structure because they are primarily composed of 95% water. Their soft and gelatinous bodies allow them to float and move easily in the water, without the need for bony support.
Unlike fish or marine mammals, jellyfish simply do not have any bones or rigid structure inside. Their body support depends solely on the pressure of the surrounding water, as well as a gelatinous substance called mesoglea, located between their outer and inner skin. This gel serves both as support and a soft shock absorber, allowing them to avoid the need for a solid and heavy skeleton. The result is a very flexible body that can easily change shape, making it ideal for floating and drifting gently with the rhythm of ocean currents.
The body of a jellyfish is made up of about 95% water, which explains why it appears so translucent and soft. This water, mixed with a gelatinous substance called mesoglea, gives the jellyfish its typical texture, both flexible and firm like jelly. Thanks to this balance between water and gel, the jellyfish can easily drift with the currents without getting too tired. This lightweight structure helps conserve energy while maintaining a simple yet effective shape for survival in the ocean.
Jellyfish live in an aquatic environment where a rigid skeleton would be rather cumbersome. A soft body allows for perfect buoyancy: they move fluidly, neither sinking nor surfacing too much. Thanks to this lightness, they glide through the water with the currents effortlessly. Their bell-shaped, very flexible form is ideal for being carried by the currents and quickly changing direction. This lack of solid structure is precisely what makes jellyfish so well adapted to a completely aquatic life.
The soft and gelatinous shape allows jellyfish to move effortlessly by being carried along by ocean currents. A simple rhythmic pulsation of their bell easily propels their light body through the water. This simplified method avoids the use of powerful muscles, allowing for a great energy conservation. Basically, they often just let themselves drift, thus saving their energy for essential activities like feeding and reproducing. No rigid skeleton, so it's lighter to move: convenient!
Having a simple body structure is a real advantage for jellyfish: less complex tissue means faster growth, easy cell renewal, and less energy required to maintain the body. This allows jellyfish to better manage their energy to survive in almost all the seas of the globe. Their simplicity also provides them with significant flexibility in the face of environmental changes. In short, being minimalist in terms of anatomy is quite clever from an evolutionary standpoint.
Jellyfish existed long before dinosaurs. They appeared in the oceans over 500 million years ago, making them one of the oldest creatures still present on Earth.
Some jellyfish, composed of about 95% water, can virtually disappear when they wash up on the beach due to their rapid evaporation.
The largest known specimen of jellyfish is the Cyanea capillata, also known as the 'lion's mane jellyfish.' It can reach up to 2 meters in diameter, and its tentacles can measure up to 30 meters long!
The venom of jellyfish is used in some promising medical research, particularly to develop treatments for cardiovascular diseases and cancer.
Most jellyfish have no rigid structure, but there are some related species such as hydromedusae or siphonophores that possess thin semi-rigid structures. However, even in these cases, they remain very different from the typical skeleton found in vertebrates, for example.
Jellyfish are primarily composed of water (about 95%) and lightweight gelatinous substances that allow them to float easily. Their density, which is very close to that of water, enables neutral buoyancy, thus eliminating the need for a rigid structure to maintain their shape or position.
Jellyfish use tentacles equipped with venomous cells called cnidocytes, which release paralyzing toxins to immobilize their prey. They then transport their prey to their internal cavity through rhythmic movements of their body.
Yes, some jellyfish can perform effective pulsatile movements thanks to their elastic gelatinous bodies. However, most jellyfish heavily rely on ocean currents to travel long distances, their active mobility being relatively limited.
Jellyfish do not have a centralized nervous system or a brain like more complex animals. Their very simple nerve net is more designed to respond to environmental stimuli than to feel pain as we know it.
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