Sea Urchin Facts and Worksheets

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A sea urchin is a ball-shaped invertebrate and echinoderm with long, pointy, and moveable spines all over its body. Sea urchins usually live on ocean seabeds and in rock pools. They are also known as sea hedgehogs. Not all species of sea urchins are poisonous, but those that are can be deadly.

See the fact file below for more information on the Sea Urchin or alternatively, you can download our 28-page Sea Urchin worksheet pack to utilise within the classroom or home environment.

Sea Urchin Facts & Information

Introducing the Fantastic Sea Urchin

• Sea urchins are echinoderms in the class Echinoidea
• They are hard-shelled, very spiky, globe-shaped creatures. 
• Sea urchins come in a variety of colors, including black, brown, dark purple, bright pink, green, and sand-colored.
• Sea urchins range in size from 1 – 4 in (3 – 10 cm), although the largest species can reach up to 14 in (36 cm.)
• There are more than 950 known species of sea urchins.

Etymology

• The term urchin is derived from “herichun” in Old French and “ericius” in Latin, which means hedgehog. It resembles a hedgehog, so it was named as such.

Physical Characteristics of Sea Urchins

• Sea urchins are invertebrates, which means they don’t have any bones. Instead, they have a hard outer shell made up of calcium.
• Urchins are radially symmetrical and can be divided into five equal parts. This is easy to see on their shells, but not when they’re covered in spikes.
• A sea urchin’s shell is also called a test.
• Sea urchins do not have a recognizable face, but they have an identifiable mouth and anus. 
• They don’t have eyes like other animals but are able to sense light and respond to it.
• Their shells are made of rigid, bony plates and serve as protection for their soft inner body parts.
• They have long and pointy spines all over their body.
• Some species have spines that are soft and poisonous.
• The spines are typically 1 to 2 mm thick and 1 to 3 cm long.
• Sea urchins’ spines are attached to ball-and-socket joints (the same joint as human hip joints) and can point in any direction.
• Scattered on their spines are claw-like structures called pedicellaria (plural: pedicellariae).
• Pedicellariae have three uses: 
  • gathering food 
  • defending themselves against predators
  • keeping their bodies clean.
• In most urchins, touch elicits a reaction from the spines.
• Sea urchins move slowly, crawling with their feet or propelling themselves with their spines.
• They have five rows of paired tube feet that act both as legs to push themselves across the ocean floor and also as suction to attach themselves to rocks or similar surfaces.
• A sea urchin’s mouth is dubbed “Aristotle’s Lantern” and is located on its underside.
• In a sea urchin’s mouth, there are five rigid teeth made of calcium carbonate and another structure acting as a tongue.
• A sea urchin does not have a brain.
• They have a water-vascular system that acts as their circulatory system by running water through their body.
• The average sea urchin is 3 to 10 centimeters in diameter.
• The biggest known sea urchin species is 36 centimeters in diameter.

Habitat, Diet, and Predators

• Colorful sea urchins can be found in all climates. They live in warm, tropical waters and also in the icy waters of the Antarctic.
• They inhabit all five of the world’s oceans and all the different levels of the ocean, from rock pools on the shore to kelp forests and coral reefs to the deep dark ocean. 
• Some species, such as Cidaris abyssicola, can live at depths of several kilometers.
• The greatest densities are found in shallow water. However, populations are generally found in deeper water if wave action is present.
• Storms cause sea urchins to seek protection in cracks and around underwater structures.
• Sea urchins feed mainly on algae making them primarily herbivores. 
• Their diet mainly consists of algae, plankton, and seaweed from nearby underwater rocks and corals.
• However, as sea urchins also feed on slow-moving animals and decomposing matter from fish, they are actually omnivores, meaning they eat both plants and the meat of animals.
• Sea urchins’ common predators are those that can claw through or break through a sea urchin’s protective spines. These include fish like triggerfish and also, wolf eels, sea otters, lobsters, crabs, sea birds, sun stars, and even humans.

Reproduction and Young

• Maturity in sea urchins varies depending on the species. 
• It mostly takes 2 – 5 years before a sea urchin can reproduce. 
• Sea urchins mate in the spring.
• A female sea urchin can produce up to twenty million eggs in one year. 
• To reproduce, males release sperm into floating plankton.
• The female urchins then release millions of eggs in the same area.
• Although females release millions of eggs at a time, only a small percentage of those are fertilized.
• Within 12 hours, the fertilized egg becomes an embryo.
• Fertilized eggs undergo the larval stage for several months before maturing into adults.
• In most species, the larva has 12 elongated arms lined with bands of cilia that capture food particles and transport them to the mouth.
• Larva sea urchins swim with many other small sea creatures. Together they form zooplankton.
• Adults reach their maximum size around five years of age.
• The lifespan of most sea urchin species can be up to 30 years.
• The red sea urchin can live up to 200 years in the wild which is the longest life span among earthly creatures. 

The Dangerous Flower Urchin

• The Flower Urchin is the most dangerous sea urchin because of its venomous spines.
• The Flower Urchin inhabits the Indo-West Pacific region.
• It has a symbiotic relationship with the clownfish.
• The poison of the Flower Urchin contains Contracting A and Peditoxin.
• Contracting A causes red blood cells to clump and body spasms.
• Peditoxin can cause convulsions, anaphylactic shock, and death.
• Species belonging to the Diadematidae and Echinothuriidae families are also venomous.

Treating Sea Urchin Puncture Wounds

• A puncture wound from a poisonous sea urchin looks swollen and red and must be treated immediately before it causes infection.
• Multiple puncture wounds may cause muscle paralysis, respiratory failure, and even death.
• The recommended treatment for a sea urchin puncture is to submerge the affected body part in hot water for an hour to break down the venom and relieve the pain.
• If there are spines stuck in the wound, they must be carefully removed.
• If it’s close to nerves or blood vessels, it might be too dangerous to remove it with tweezers, so it’s best to have a doctor remove it surgically.

Captivity and Uses

• Some species of sea urchin are listed as endangered.
• Major threats to sea urchins are overfishing and ocean pollution.
• Sea urchins do not reproduce well in captivity because certain conditions (such as ocean currents) must be present for breeding to occur.
• The gonads of both male and female sea urchins, alternatively called sea urchin roe or corals, are culinary delicacies in many parts of the world, most especially in Japan.
• In Japan, sea urchin roe (or eggs) are served as “uni” and can be eaten as raw sashimi or in sushi.
• One way to help protect the sea urchin population is to keep our oceans clean.

Sea Urchin Worksheets

This is a fantastic bundle which includes everything you need to know about Sea Urchin across 28 in-depth pages. These are ready-to-use Sea Urchin worksheets that are perfect for teaching students about a sea urchin which is a ball-shaped echinoderm with long, pointy, and moveable spines all over its body. Sea urchins usually live on ocean seabeds and warm waters. They are also known as sea hedgehogs. Not all species of sea urchins are poisonous, but those that are can be deadly.

Complete List Of Included Worksheets

• Sea Urchin Facts
• It’s A Sea Urchin!
• Body Terms
• Figure It Out
• Choosing One
• Typewriter
• 4 Pics, 1 Sea Creature
• Zooplankton Hunt
• Ouch! Help!
• Serving Urchins
• A Sea Story

Frequently Asked Questions

Can one keep sea urchins in a home aquarium?

Some species of sea urchins are sold in aquarium stores and effectively control algae. However, they are sensitive to water conditions and will quickly show signs of stress if conditions are not perfect.

Are sea urchins edible?

Only certain parts of the sea urchin are edible. These are the gonads or reproductive organs. Like many kinds of seafood, they are low in fat, calories, and carbs and are rich in proteins.

How big can sea urchins get?

Sea urchins typically range in size from 1 – 4 in (3 – 10 cm). However, bigger species easily reach 14 in (36 cm). The red sea urchin is the largest of the species measuring more than 7 in (18cm).

Are sea urchins used for medicine?

Yes, sea urchins have been used for medicine. Sea urchin has been used to produce a product used for a treatment in which damaged tissues can be replaced.

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Link will appear as Sea Urchin Facts and Worksheets: https://kidskonnect.com - KidsKonnect, November 22, 2018