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Cestum Veneris – A Mesmerizing Mystery of the Sea

Simone Jonker worked in NTD Inspired for two years. She wrote light articles and inspiring stories.
Published: March 28, 2022
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Cestum veneris. (Image: Team Aquatilis and @aquatilis_expedition)

The ocean is a restless and enigmatic place. Below its surface, the diaphanous comb jelly Cestum veneris or “Venus Girdle” (from the Greek goddess of love and the word “kestos” meaning girdle), may be found gliding slowly and gracefully in the world’s tropical oceans.

Cestum veneris is what underwater photographer Alexander Semenov sought when he dove into the water off Ponza Island, Italy, under the cover of night. Millions of creatures go down to the depths during the day and come up at night to feed on the surface waters that are rich in food. In that grand parade, Cestum veneris made its appearance. Semenov was there, waiting to capture its beauty.

Cestum veneris has roamed the seas for at least 500 million years. This unusual ctenophore consists of a long band of sylph-like jelly, averaging about 40 inches in length and 2 inches in width. Tentacles run along the oral borders, while tentillae drape across its body. 

Cestum veneris. (Image: Team Aquatilis and @aquatilis_expedition)

The entire creature is thin and transparent. Because Cestum is readily broken up by high waves, they are typically only seen intact in open waters of the mid-ocean.

Cestum veneris look like ghostly gliders, with a cockpit-like mouth in the middle and two ribbon-like wings on either side. These carnivores feed mainly on mollusks and tiny crustaceans called copepods. 

Its stomach and important nerves are located at the center of the body, which resembles a luminous spindle. Each wing is studded with a dense network of microscopic hair-like cilia that flap back and forth to drive the jelly forward in an undulating ribbon-like manner. When light strikes the tiny hairs they reflect exquisite prismatic hues.

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When they feed, the combs on their undulating wings generate micro whirlpools, believed to be instrumental in hunting. After confusing their prey, the comb jelly changes direction in a split second, creating barriers that the prey is forced to collide with. In addition to having sticky tentacles on each wing, they excrete an immobilizing substance that stuns the catch before it is brought to the central mouth for feeding.

Their unique capacity to convert themselves from transparent to milky in only a few minutes by pumping calcium across their cell membranes is a mystery to scientists. When the milky hue is in full force, beautiful bioluminescence is displayed along the length of its body, with its mesmerizing ciliary the only testament to its presence in the water. 

Due to the Venus Girdles’ serpentine movements, they are able to move multiple body lengths at breakneck speed. Abrupt changes in look and behavior are intended to shock or deceive potential predators. 

A sophisticated escape mechanism of coiling around itself protects its fragile center. Like many other comb jellies, cestum has strong regeneration abilities. As long as the mouth is not damaged, it can regrow and can regrow other damaged portions.

Cestum veneris produce both eggs and sperm, which they release into the water for fertilization and larval development. Unlike many jellyfish, they have no poisonous sting.

Flame jellyfish (Rhopilema esculentum) is an edible species enjoyed in Southeast Asia. (Image: Bill Abbott via Wikimedia Commons CC BY-SA 2.0)

Consuming jellyfish?

Humans have eaten jellyfish for at least 1700 years. Every year, fisheries in 15 nations catch 425,000 tons of jellyfish, most of which are consumed in Southeast Asia. While some jellyfish species are not edible, others are considered healthy fare, offering a variety of nutrients, protein, antioxidants, and minerals. The collagen present in jellyfish may help reduce blood pressure. 

The edible jellyfish Rhopilema esculentum, which is popular in Southeastern Asia, is one of at least 11 species suitable for human consumption. 

Depending on how it is prepared, jellyfish texture can range from crunchy to chewy. It is often desalted, making its flavor subtle enough to be influenced by added ingredients.

With growing concerns about ecological imbalances caused by overfishingwhen aquatic organisms are taken from the environment faster than they can replenish their numberswe may see increased consumption of jellyfish in the future, even if it is not currently a prevalent practice in the West.