Jellyfish Facts & Worksheets

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Jellyfish are jelly-like aquatic creatures that existed even before the age of dinosaurs. They live in both cold and warm waters, as well as deep and shallow coastlines. Jellyfish may vary in color from transparent to blue, purple, or yellow, while many are bioluminescent.

See the fact file below for more information on the jellyfish or alternatively, you can download our 26-page Jellyfish worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

• Phylum: Cnidaria
• Class: Scyphozoa
• Classification: Invertebrate
• Lifespan: One year
• Average Weight: Up to 2 kg
• Body size: 2 cm to 2 m
• Diet: Shrimp, fish, crab, small plants
• Habitat: Oceans and freshwater lakes

Facts & Information About Jellyfish

• The scientific name for jellyfish is Scyphozoa.
• The informal common names are jellyfish and sea jellies.
• Jellyfish have been in existence for over 500 million years and possibly over 700 million years, making them the oldest multi-organ animal group.
• The name jellyfish has been in use since the eighteenth century.
• The term jellies or sea jellies are more recent. Public aquariums introduced it in an effort to avoid the use of the word “fish,” as it implies an animal with a backbone.
• The stinging cells used by jellyfish to subdue their prey can also injure humans. Thousands of swimmers worldwide are stung every year, with effects of stings ranging from mild discomfort to serious injury or even death. 

So What are Jellyfish?

• Most jellyfish are free-swimming marine animals.
• So most species of jellyfish are mobile, while some species are anchored to the seabed by stalks.
• Jellyfish have umbrella-shaped bells (bodies) and trailing tentacles. 
• The bell can pulsate to provide propulsion for highly efficient movement. 
• The tentacles are armed with stinging cells and are used to stun and capture prey and also to defend themselves against predators. 
• Some jellyfish are clear, but others are vibrant colors of pink, yellow, blue, and purple. 

What Do Jellyfish Look Like? 

Anatomy

• Jellyfish have a nearly transparent saucer-shaped body.
• The body is a hollow structure consisting of a mass of transparent jelly-like matter.
• Approximately 95% of their body is made up of water.
• Most jellyfish range from less than half an inch (1 cm) to about 16 inches (40 cm). 
• The smallest jellyfish (the peculiar creeping jellyfish) are tiny at just one millimeter wide, while the largest average around 1 m (3 ft) wide.
• The majority of jellyfish have four to eight tentacles hanging from their bell, but some species have hundreds.
• Tentacles are composed of stinging cells called cnidoblasts to stun and paralyze prey.
• Jellyfish have no brain, heart, limbs, bones, or senses like a nose or eyes. 
• They do, however, have a basic nervous system composed of receptors that help them detect light and vibrations under water.
• At the center of a jellyfish’s body is a small opening that serves as a primitive mouth, which both eats food and discards waste. 
• A jellyfish’s mouth and digestive tubes are surrounded by tiny oral or mouth arms.
• Jellyfish digest their food immediately so they can float in water and not sink.
• Most jellyfish have bioluminescent organs, which emit light. This feature helps them to attract prey. It also distracts predators, including sea turtles and other creatures.
• Jellyfish can regenerate body parts when injured.
• The weight of jellyfish depends on the species. Obviously, the tiny ones are very light, and the giant ones are extremely heavy.

Habitat and Diet

Habitat

• Jellyfish are found all over the world, from freshwater lakes and surface waters to deep oceans. 
• Jellyfish of all sizes and colors are especially common in coastal zones worldwide.
• Scyphozoans (the “true jellyfish”) are exclusively marine jellyfish.
• Freshwater jellyfish can be found in lakes, quarries, and reservoirs.
• The peach blossom jellyfish (Craspedacusta sowerbii) is a species of freshwater jellyfish.

Diet

• Most jellyfish are passive carnivores.
• They feed on plankton, crustaceans (like shrimp and crab), fish eggs, small fish, and sometimes other jellyfish that float into them.

Reproduction

• Jellyfish have a complex life cycle that includes both sexual and asexual phases.
• The four main stages of the jelly life cycle are
  • Eggs and Sperm 
  • Planula Larvae, Polyps 
  • Polyp Colonies 
  • Ephyra, and Medusa
• Upon reaching adult size, jellyfish spawn regularly, provided there is a sufficient supply of food.
• Most jellyfish are usually either male or female (some species are hermaphrodites).
• The adults release sperm and eggs simultaneously into the surrounding water.
• Depending on the species, either the unprotected eggs are fertilized and develop into larvae, or the sperm swim into the female’s mouth, fertilizing the eggs within her body, where they remain during early development stages. 
• In the next stage of the cycle, they become planula larva, which is a free-swimming larval form.
• Once the free-swimming larva finds something to attach to, usually on the sea bed, it starts the next phase, which is becoming a polyp.
• Polyps are extremely tiny, and the polyp stage can last over a year as they feed and grow.
• The polyps then bud into ephyrae (free-swimming jellyfish) before transforming into fully grown medusa (adult jellyfish).
• Polyps can reproduce asexually by budding, while medusae spawn eggs and sperm to reproduce sexually.
• The medusae of most species are fast-growing, mature within a few months, and die soon after breeding.

Predators

• The common predators of jellyfish are sharks, tuna, sea turtles, and sea anemones.
• Some species of jellyfish are caught and eaten by humans. 
• In some Asian countries, they are considered a delicacy, where some species are pressed, then salted, and eaten either raw or cooked.
• In Japan, cured jellyfish are rinsed, cut into strips, and served with vinegar as an appetizer.
• Australian researchers have described jellyfish as both a sustainable and protein-rich food.

Jellyfish Sting Symptoms, Causes, and Prevention

• These are some common signs and symptoms of a jellyfish sting.
  • Prickling, burning, and stinging pain.
  • Red, brown, and purplish streak of tentacles on the skin.
  • Swelling and itching.
• When jellyfish stings are severe, a person may feel the following:
  • Abdominal pain, vomiting, and nausea.
  • Headache with muscle pains and spasms.
  • Drowsiness and fainting.
  • Difficulty in breathing.
• Jellyfish tentacles are equipped with microscopic barbed stingers with bulbs that hold venom. These serve as their main defense mechanism against predators and danger.
• When a tentacle contacts human skin, it releases a stinger which penetrates the skin and releases venom. It affects the skin on contact and may possibly enter the bloodstream.
• Among the most harmful to humans are box jellyfish, Portuguese man-o-war, sea nettle, and lion’s mane jellyfish.
• In order to avoid being stung by jellyfish, people should wear protective suits like skin suits and stinger suits and avoid swimming and diving in jellyfish-infested areas.
• The box jellyfish is a unique type of jellyfish with 24 eyes, 60 anal regions, and four parallel brains. Its venom is considered one of the deadliest in the world as it attacks the nervous system. They are also called sea wasps and marine stingers, which are normally found in the waters of Northern Australia and the Indo-Pacific.
• Due to frequent stinging incidents in Australia, scientists have developed an antivenom for box jellyfish stings.

Did You Know?

• An adult jellyfish is called Medusa after the Greek monster Medusa who had snakes for hair.
• There are over 2,000 different types of jellyfish, but only about 70 can hurt people.
• That being said, over 150 million people around the world are reported stung by jellyfish every year.
• In 2002, an American tourist died after being stung by an Irukandji jellyfish (an extremely venomous species of box jellyfish) in the waters of Australia’s Great Barrier Reef.
• Natural collagen is made from harvested jellyfish.
• A group of jellyfish is called a swarm, smack, or bloom.
• The largest jellyfish on earth is probably the lion’s mane jellyfish (Cyanea capillata). A specimen of this jellyfish was recorded as 36.5 m (120 ft) from its bell-top to the bottom of its tentacles. That is huge!

Jellyfish Worksheets

This is a fantastic bundle that includes everything you need to know about jellyfish across 26 in-depth pages. These are ready-to-use Jellyfish worksheets that are perfect for teaching students about jellyfish, which are jelly-like aquatic creatures that existed even before the age of dinosaurs. They live in both cold and warm waters, as well as deep and shallow coastlines. Jellyfish may vary in color from transparent to blue, purple, or yellow, while many are bioluminescent.

Complete List Of Included Worksheets

• Jellyfish Facts
• Types of Jellyfish
• Jellyfish Anatomy
• Jellyfish Life Cycle
• Venomous Jellyfish
• Largest Jellyfish
• All About Sea Jellies
• Fill In
• Scientific Classification
• Sting Symptoms
• Treating Jellies

Frequently Asked Questions

Can one have a jellyfish as a pet?

The Moon Jellyfish (Aurelia aurita) is the most common species kept as a pet jellyfish. Provided they are kept in a suitable aquarium environment, jellyfish can live for about a year.

What do pet jellyfish eat?

Jellyfish love to be fed live baby brine shrimp or frozen baby brine shrimp. In the wild, brine shrimp are freely available and form a large part of a jellyfish’s diet.

Are jellyfish harmful?

Jellyfish stings are often painful, but most are not usually harmful. They can cause pain in the sting area as well as red marks, itching, numbness, or tingling.However, the sting from some species, like the Sea Wasp or Box Jellyfish can be deadly.

Do jellyfish have predators?

Jellyfish do have predators. Their predators include turtles (especially the leatherback sea turtle), the ocean sunfish, some seabirds (such as the fulmars), the whale shark, some crabs, and some whales. These predators are often the victims of eating plastic floating in the ocean because it resembles jellyfish.

How long do jellyfish live?

Domestic jellyfish in aquariums live from one to three years. Species in the wild live from a few days to decades. It is said that one species, dubbed the ‘Immortal Jellyfish’ (Turritopsis dohrnii), may actually live forever!

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Link will appear as Jellyfish Facts & Worksheets: https://kidskonnect.com - KidsKonnect, June 25, 2018