In the azure ocean, there roam these beautiful and translucent creatures——jellyfish, shimmering with an ethereal glow as they gracefully glide through the water.

A jellyfish’s body resembles a transparent umbrella, with its bell-shaped diameter varying from a few centimeters to up to 2 meters in larger species. Along the edges of the bell-shaped body, there are tendrils, some of which can extend up to 20-30 meters.

The main component of a jellyfish's body is water, consisting of two layers: an inner and outer layer, separated by a thick middle layer called mesoglea, which is not only transparent but also provides buoyancy. Some jellyfish species also exhibit various colorful patterns on their bell-shaped bodies.

Jellyfish can be found in tropical and temperate waters, in shallow coastal areas, as well as depths of up to a hundred meters in the ocean, and even in freshwater environments. They have existed for over 650 million years, predating even the dinosaurs, with over 250 known species worldwide.

Jellyfish Movement:

Jellyfish move by contracting their bell-shaped bodies to expel water from their internal cavity, propelling themselves forward.

Muscular fibers extending from the top to the end of the bell-shaped body control the contraction and expansion of the internal cavity. As the cavity expands, water is slowly drawn in, filling the cavity, then rapidly contracting to expel the water, generating thrust to propel the jellyfish in the direction of its body axis.

When a jellyfish attempts to descend in the water, its tendrils extend upwards, appearing as long lines; when intending to ascend or move in a particular direction, the tips of its tendrils bend in the opposite direction of movement. Jellyfish effectively change their direction of movement using their tendrils. They are not adept swimmers and often rely on wind, waves, and currents to move.

Some jellyfish have specialized glands within their bell-shaped bodies that can emit carbon monoxide, causing the bell-shaped body to inflate. However, when facing danger or encountering severe storms, they automatically release the gas and sink to the seabed.

After the sea calms, they can reinflate themselves within minutes and float to the surface again. Additionally, some jellyfish have air sacs at the top of their bell-shaped bodies, allowing them to control the inflation of each sac and thus alter their movement direction.

Some jellyfish are bioluminescent, such as the comb jellyfish, emitting spherical blue light as they swim, with their long trailing tentacles shimmering with slender bands of light. As the comb jellyfish undulates and moves its body while swimming, the light display is diverse and captivating.

Interestingly, unlike other bioluminescent organisms that rely on luciferin and luciferase catalyzed by oxygen to emit light, jellyfish produce light through a remarkable protein called aequorin, which emits a strong blue light upon encountering calcium ions. Scientific research indicates that each jellyfish contains approximately 50 micrograms of luminescent protein, highlighting their reliance on this mechanism for bioluminescence.

Conclusion:

Jellyfish, with their mesmerizing beauty and unique mechanisms of movement and illumination, remain fascinating inhabitants of the world's oceans. Their presence, spanning millions of years, underscores their resilience and adaptability in various aquatic environments, adding to the rich tapestry of marine life.