Jellyfish Facts for Kids

Considering the clear appearance of jellyfish, no one can make out that some of these nearly transparent creatures can sting humans and at times, even cause death. Fortunately, not all jellyfish are venomous and/or dangerous to humans. The venom is injected for the purpose of paralyzing their prey before consumption. With more than 2000 identified species, studying facts about jellyfish is very important for avid marine biologists.

The jellyfish are grouped under the phylum Cnidaria, whose characteristic feature is the presence of gelatinous, non-living body embedded between epithelial layers. According to studies, this curious creature of the sea has evolved before the massive reptiles (dinosaurs) evolved on earth. Since then, they have survived in different marine water conditions, be it cold water or warm water, and shallow coastlines or deep sea water.

Based on the types of jellyfish, the color may be white, pink, yellow, orange, red, blue, green, or multicolored. Can you believe the biggest box jellyfish measures about 6 feet across? While some types of jellyfish are 1 inch in diameter, others can spread to about 4 meters. Likewise, the length of tentacles vary from one species to another, with some species having 100-feet long tentacles.

On the underside of the dome-shaped or bell-shaped body, lies the mouth of jellyfish that are surrounded by the tentacles. So, what do jellyfish eat? They are carnivores that feed on small marine organisms, zooplanktons, comb jellies, crustaceans, and at times, other jellyfish. After assimilation of useful nutrients, the waste products are expelled out from the mouth. The predators of jellyfish include sun fish, sea turtles, spade fish, and larger marine organisms.

The movement of jellyfish is largely dependent on the ocean currents, tides, and winds. Though they have less control over horizontal movement, jellyfish can control vertical movement by means of muscular contraction. Some of them are sensitive to light and move downwards during daytime. Jellyfish constantly need water in their surrounding for survival. Absence of water causes desiccation and death of these gelatinous marine creatures.

You might have seen jellyfish that have a cubic umbrella-like structure. They are none other than the box jellyfish. Some of these are known for their venomous and painful stings. A box jellyfish possesses several tentacles, each of which is equipped with approximately 500,000 of nematocysts. These specialized cells contain venom to sting predators that come in their way.

A type of box jellyfish, commonly known as sea wasp (scientific name Chironex fleckeri) is claimed to be the most venomous, causing the highest number of deaths. In Philippines, the number of fatalities caused by this deadly jellyfish is recorded to be 20-40 every year. Other poisonous types belonging to the same group are Malo kingi and Carukia barnesi.

Fortunately, the box jellyfish do not attack humans directly. But, anyone who accidentally comes too close to the venomous tentacles may get stung. To save the person's life, immediate treatment is essential. An effectual first-aid tip is to pour vinegar over the area. If left unattended, the venom can impair the heart functioning within a short time. The venom is neurotoxic, which can cause death of a child within 3 minutes.

Jellyfish is eaten in many parts of the world. The non-poisonous types are available in the international market for culinary uses. After being harvested, a treatment procedure is followed for 20-40 days, during which the mucous lining and gonads are removed. The remaining edible parts are processed with a salt and alum mixture. The final result sold in the market is salty in taste and crunchy in texture.

Moon jellyfish are quite interesting creatures. They do sting, but the effects are mild and short-term. These are small species and hardly survive in the natural habitat for 6 months. The causes of death after reproduction are lack of food, warm temperature, and disease.

Nevertheless, they live for many years in the controlled conditions of aquariums, where there are no predators and also, no competition for food.

So, aren't jellyfish facts interesting? Their transparent body and venomous tentacles, which swimmers and divers cannot see clearly may cause accidents. Accidentally, humans come in the way of jellyfish and within a fraction of seconds, the venomous jellyfish injects poisons from their tentacles. To avoid this, people should take precaution before diving in regions where venomous jellyfish are found in abundance.