Spotlight On Nature: Jellyfishes

Some are longer than a blue whale, others are barely larger than a grain of sand. Some release the world’s deadliest toxins, while others hold some of the greatest secrets behind major breakthroughs in biology. What creature could this possibly be? If you’ve read the title, then you must have gotten it right–yes, it is a jellyfish! (Well, technically, different species of jellyfishes.)

Size comparison between the largest species of jellyfish found (Lion’s Mane Jellyfish) and whales. (Source: Quora)

Their jelly bell is made out of a soft, delicate material called mesoglea. Sandwiched between two layers of skin, the mesoglea is more than 95% water, held together by protein fibres. What’s notable about jellyfishes is that they have no brains or spinal cords, but a neural net around the bell forms a rudimentary nervous system that can sense the ocean currents and the touch of other animals. Since they do not have a digestive system, they feed on planktons and other small sea creatures through a hole under their bell.

Anatomy of “true” jellyfish. (Source: Best Scuba Diving)

Despite having such simple features and systems in their body, it doesn’t seem to stop them from having remarkable abilities. Aequorea victoria, a common North American jellyfish species, produces a protein called green fluorescent protein (GFP), which enables the jellyfish to glow in the dark. Upon its discovery, GFP is now frequently used by researchers in molecular biology, as a reporter for gene expression.

Aequorea victoria, with visible GFP. (Source: Phil Blackburn)

Did you know that some jellyfish are practically immortal? There are essentially two stages to the life of a jellyfish: the stationary polyp stage and the mobile medusa stage. When we talk about jellyfishes, we are mostly referring to the medusa stage. One particularly interesting species, Turritopsis dohrnii, has earned the name of being “the immortal jellyfish” with its ability to revert to the polyp stage when under stress. This amazing discovery is closely related to the jellyfish’s ability to clone themselves. When a jellyfish is cut in half or wounded, it can regenerate and potentially create offspring. This finding has left many marine biologists awestruck. Current research is focused basic biological processes, such as aging, as well as pharmaceutical research.

The life cycle of Turritopsis dohrnii has both baffled and intrigued researchers in equal measures. (Source: How It Works)

While many marine animals are struggling to survive in warmer and more acidic ocean, jellyfish are thriving and getting even more numerous. Despite being such a creature that consists of 95% water, it has sophisticated and remarkable abilities. Perhaps, from now on, we should ask ourselves if calling someone “brainless” is an insult.


By Kelvin Wong

West Malaysian spirit of magniloquence, periphrasis and procrastination. I have half a mind...

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