A-z - Animals

sea urchin

This post may contain affiliate links to our partners such as Chewy, Amazon, etc. These purchases help us further AZ Animals' mission of educating the world's species.

Sea urchins are also called sea hedgehogs, sand dollars, and sea cakes.

Sea urchins are typically small, spiny, round animals. They live in all of Earth's oceans, at depths ranging from the tide line to 15,000 feet. Because they can't swim, they live under the sea. Their main defense against more agile predators such as eels and otters is their hard, spiny shell called a "test".

Sea urchin infographic

© AZ-Animals.com

3 Sea Urchin Facts

  • Secret weapon: Crabs use sea urchins as armor to fend off predators.
  • Five-fold symmetry: The body of a mature sea urchin contains five symmetrical parts, unlike mammals which have two.
  • Fear of the spotlight: They have no perceptible eyes, but experts suspect their entire bodies are light-sensitive compound eyes.

taxonomic name

What do sea urchins eat
The scientific name of the sea urchin is Echinoidia

Sea urchins belong to the phylum Echinodermata . The scientific name is Echinoidia , which is also their class name. They belong to the order Camarodonta and some belong to the family Echinidae . The family includes the genera Strongylocentrotus and Lytechinus .

history and origin

sea urchin
Sea urchins have been around for 465 million years.

© Brocken Inaglory/Creative Commons

Sea urchins form groups in the ocean for specific purposes. When they lay eggs, the male releases sperm and the female releases the eggs, which are then fertilized when they meet. This is why larger colonies are advantageous as they have a better chance of producing more embryos. Sea urchins have been around for a staggering 465 million years, constantly adapting to changing environments in order to survive. It is remarkable that such a brainless creature can live for so long.



Sea urchin fossils have been found dating back to the Middle Ordovician period, 465 million years ago. The tough calcite slabs of these creatures are well preserved in rocks from this period, and some specimens even have spines. Isolated spines are also commonly found as fossils. Some Cidaroida from the Jurassic and Cretaceous periods had very heavy club-like spines.

Paleozoic sea urchin fossils are often incomplete, consisting of spines and crushed individual fragments. Estonia is famous for its shallow water limestone formations featuring sea urchins from the Ordovician and Silurian periods. These ancient sea urchins likely lived in calmer waters because their thin shells could not withstand rougher waters like some modern species. During the Paleogene and Neogene periods, between 66 and 1.8 million years ago, sand dollars with flat shells and small spines emerged, adapted to living in shallow water or even under sand. These fossils are commonly found in limestone and sandstone in southern Europe.

Read more  volcano snail

species

Solo purple sea urchin on a reef
There are hundreds of species of sea urchins.

©Natalie Jean/Shutterstock.com

Some of the more interesting types among the 950 species include:

  • Strongylocentrotus purpuratus Pacific purple sea urchin is a key ingredient in uni sushi.
  • The pitch-black Diadema sea urchin helps keep Caribbean coral reefs healthy by inhibiting plant growth.
  • Toxopneustes pileolus, whose common name is flower sea urchin, is one of the most poisonous species. It inhabits the warm oceans of the western Indo-Pacific region.
  • The giant red sea urchin, or Mesocentrotus franciscanus, is the largest species, with an average test width of about 18 cm (7 in) and a spine length of 8 cm (3 in). It inhabits the waters off the Pacific coast of North America.
  • Heterocentrotus mamillatus, the slate pencil sea urchin, lives in the tropical Indo-Pacific. It has stubby spines with rounded ends and stripes that can pierce rocks.
  • Known by its common name of sand dollar, sea biscuit, or pansy shell, Echinarachnius parma is a flattened sea urchin with short spines called cilia that can burrow in the sand. It lives in oceans throughout the northern hemisphere.
  • The green sea urchin ( Strongylocentrotus droebachiensis ) is one of 18 edible species. Processors harvest the gonads, the glands inside the shell, which are mainly used in Japanese uni sushi. Green sea urchins live in North Atlantic waters.

appearance

sea urchin
Sea urchins are animals.

©JGA/Shutterstock.com

A sea urchin is a small sea animal with a spherical shell called a test, often covered with quills similar to porcupines. Spines with very small tubular feet help them move slowly along the ocean floor. They come in almost every color from black to white, red, orange, green, brown, purple, pink, yellow, blue and gray. They range in size from approximately 1" to 14" in diameter. On average, they weigh about a pound.

Since there are nearly a thousand species of sea urchins, the animals vary greatly in appearance. You can easily recognize most of them by their prickly appearance, but some, like sand dollars, have only short hairs all over their bodies. Others, like the pencil urchin, have round spines that are not as sharp as typical sea urchin spines.

Distribution, Population and Habitat

purple sea urchin
Sea urchins live in every ocean in the world.

©HotFlash/Shutterstock.com

Sea urchins live in oceans around the world. Arctic or tropical, coastlines or the deepest trenches, you can find them there. Because they can't swim, the ocean floor is their home. Some, like pebble sea urchins, live in the shallows near sunny beaches. Others, like those in the Pourtaleslidae family, live deep below the surface, where they are in total darkness.

Read more  Labrador Retriever Lifespan: How Long Do Labs Live?

Barren underwater areas have dense populations of these creatures, with populations closer to shore being by far the densest. Although they are found all over the world, they are most abundant in the shallows of temperate and tropical marine habitats to depths of up to 10 meters, where plants are abundant.

There are so many species and so wide a range of habitats that it's impossible to pin down. However, a recent marine study in Oregon estimated the number of purple species to be around 350 million on one coastal reef alone, a number that has grown 10,000-fold in just a few years, making them the least noticed protection class. The researchers attribute this exponential expansion of sea urchins along the Pacific coast to an unbalanced marine ecosystem.

Meanwhile, in the Mediterranean, purple sea urchin populations are currently endangered. Factors that contributed to the species' extinction included rising sea temperatures and invasive fish that fed on algae, depriving sea urchins of their staple food. Again, the root cause is an imbalance in the ecosystem.

However, food shortages don't necessarily mean the species is about to go extinct. Purple sea urchins can go dormant and survive for years without food. With such extraordinary perseverance, these populations may decrease, but they will also move.

predator and prey

sea urchin
Sea urchins are very susceptible to bacterial diseases.

©Damsea/Shutterstock.com

Despite their natural resilience, sea urchins are at risk from disease and predators. A bacterial disease in 1981 nearly wiped out the species Hemicentrotus pulcherimus and Pseudocentrotus depressus in Japan. Bald urchin disease, another bacterial disease that threatens some sea urchin populations, causes the animals to lose their spines, making them less able to defend themselves against predators.

What do sea urchins eat?

Shellfish such as crabs and lobsters are natural enemies of these creatures. Goldfish and wrasse are two types of fish that feed on them. Wolf eels are particularly well suited to prey on wolf eels in the northern hemisphere. Sea otters in places like British Columbia help maintain ecological balance by keeping sea urchins from becoming overpopulated.

Although they are slow-moving, sea urchins do have some ways of protecting themselves. Their sharp spines are often enough to deter some predators. Some sea urchin species are also poisonous.

What do sea urchins eat?

Sea urchins mainly eat marine plants such as seaweed and kelp. They also prey on sessile or immobile marine life such as corals and sea sponges.

Reproduction and Lifespan

sea urchin
Sea urchins eat sea vegetables.

© Lacen – Public Domain

Females of this species lay eggs. Most release these eggs into the sea to be fertilized by sperm released by the male. Females of some species deposit their eggs in their spines instead of letting them float free.

Read more  The 8 Largest Alligators in History

Once fertilization occurs, it only takes about 12 hours for the egg to become an embryo. Shortly thereafter, the embryo turns into a larva with cilia that gather tiny bits of food to nourish its growth. It takes several months for the larvae to turn into fully developed sea urchins. It will take a few more years to reach adulthood. Depending on the species, they can live for many years. For example, the life expectancy of purple species is about 20 years.

fishing and cooking

Purple and red sea urchins eat kelp.
Purple and red sea urchins eat kelp.

©Brandon B/Shutterstock.com

Gonad, or roe, is a delicacy in many international cuisines from Alaska to New Zealand. Typically, people eat it raw with lemon juice or olive oil. In other regions, chefs add roe to gourmet sauces, omelets, and soups.

Japanese love roe in uni sushi. They consume about 50,000 tonnes of sea urchin eggs per year, accounting for about 80 percent of the world's commercially processed supply.

950 kinds of sea urchins

Top 10 Shell Animals - Sea Urchins
Sea urchins use their spiny shells to protect themselves from predators.

©Damsea/Shutterstock.com

Scientific name of sea urchin
humic fungus
Strawberry waste archaea
Pseudabatus
Pseudabatus nimrodi
Agassiz abacus
Southern Abacus
Abaceae
Abacus
cavernous mouse
black flying squirrel
Abatus cavernosus
Abatus spongy variant. Bidens
chicken wings
elbow abacus
slender abacus
black duck
abacus
abacus
black salamander
Abacus
flying abacus
Philippine Abacus
Shackleton's Abacus
Abelida
Aspergillus flavus
Abetella
alberia
rape
S.cazzoni
Nereis
den's bug
Alberta florida
Goose caterpillar
havana moth
alberia
Ebberia miskielia
Palmeria
Abertella pirabensis
Arachnid
Absurdism
Astragalus
ridiculous meriani
Dianthus
Echinococcus
ratchet
Thorns
Echinococcus
Acanthus spinosa
spiny algae
spiny algae
spiny algae
Acanthidae
stickleback
Sester
anandala
bellflower
oval gooseberry
Echinacea
mustang
Weber's
gooseberry
Phoebe
Acerola kiwi
Acrieste
Amorpha
Hydrangea
Crocodile
Hydrangea
guava
locust
guava
Crocodile
Acrobatic troupe
Nymph
white cactus
black crown tree
Knotweed
Nymph
papilla coral
papilla coral
long handle branch
flat top branch
chain tree
triangular coral
violets
Echinococcus subfamily
cactus
Apiaceae
Octopus
Nymphalidae
Buckskin
Atlantic Robinia
Weed
Acrosalenia (Acrosalenia)
Acrosalenia (Milnia)
Fillet
Microbacteria
Phyllostachys flounder
Wintergreen
Duruma Betta
Gannan wintergreen
Wintergreen
Hexagonal bacteria
purple top grass
Hydrangea
Wintergreen
Stagweed
antler
wintergreen
Nymphalidae
small mouth coral
Acremonium mesophylla
prickly heat
Little wintergreen
Pentacoral
smelly catfish
Somali wintergreen
spines spines
antler
Willie Wintergreen
Miscellaneous fish
Miscellaneous fish
sky star
trotters
dung beetle
Anise worm
Actinomyces
tomato actinomycetes
Actinomycetes
Actinomycetes
Adcidaris
moray eel
moray eel
flounder
Begonia
Adetaster
new fish
Aerospace
rope
Pseudomonas red leaf
Long handle eggplant
Aërope rostrata
moth family
Ferns
Arabidopsis
long handle fern
Arabidopsis
Stomata
Agarose
Robinia
Robinia
Agassizia
Black locust (Agassizia) powersi
Agassizia (Anisaster)
Agassizia (Anisaster) Coffee
Agassizia (Anisaster) mossomi
Agassizia (Anisaster) wilmingtonica
Agassizia (Anisaster) wilmingtonica inflata
locust
locust
locust
locust
locust
locust
Cao Huai
Caribbean Robinia
Robinia Cyrene
ginkgo
Robinia Cyrene
Agassizia cyrenaica var. false clavicle
Agassizia cyrenaica var. pseudoinflammation
locust
Buckeye
locust
Sophora japonica
Guan Huai
locust
locust
Agassizia lamberti var. oligotail fish
locust
locust
Wang Huai
locust
locust
locust peach
locust
aguayoste
Aguayoaster aguayoi
Grouper
Elakia
Albert Chinus
Albertichinus Devonicus
albertecinos
alexander fish
Alexander port
alias
alastor
Ferrets
Henospora
Exotic Dragon
H. fragilis
prawns
Alomar
Aloma Karon
Almaty
Allotoxaster
catfish
catfish
Alomar
okra
Streptococcus
Stab each other
Double breast fish
mayfly fish
Roundbreast
light breast fish
Weak belly animals
Weak belly cow
oblique fin fish
Amblypneustes elevatus elevatus
Blunt-bellied Shrimp
blunt belly shrimp
Big blunt belly shrimp
gray blunt shrimp
gray blunt shrimp
gray blunt shrimp
Amblypneustes var. griseus. red
blunt belly shrimp
flat belly shrimp
White ball blunt shrimp
blunt belly shrimp eggs
Big blunt belly shrimp
blunt belly shrimp
blunt belly shrimp
blunt belly shrimp
Blunt-bellied Shrimp
pale blunt shrimp
Subspherical pale blunt shrimp
Amblypneustes pallidus var. subspheroidal muscle
Pentagonal blunt shrimp
blunt belly shrimp
Purple belly blunt shrimp
blunt belly shrimp
Weak belly shrimp
Textile Blunt Belly Shrimp
Three-sided Blunt Shrimp
Weak tail fish
Weaktail (Amblypygus)
Weaktail fish (Paramblypygus)
Blunttail (Paramblypygus) houphoueti
Cheki axolotl
tonsil
betta fish
axolotl
blunttail fish
blunttail fish
stray asteroid
Ammophiliae
Nereis
arachnids
Coarse sandworm
ringworm
Pinworms
Amorast
Black locust
sparrow
amphibians
amphibians
sandfly
Grouper
Momordica charantia
gibbon
kurtz amphibian
Nymphae
Grouper
Grouper
mediterranean nymph
Grouper
new zealand butterfly
Amphidetus novæ zelandiæ
Grouper
ovata
Nymph
Grouper
wild duck
amphibians
Grouper
safflower mayfly
amphibians
Amphibians (Tetrodiscus)
Amphibian (Tetrodiscus) auritus
Nymphaeus
Amphibians
Amphiope bioculata bentivegnae
long horned amphibians
Amphiope bioculata var. Bentivigne
Amphiope bioculata var. Escherichia coli
Horned butterfly
Nymph
dodlene amphibian
amphibian döderleini
amphibian doederleini
Fuchsia amphibian
amphibians
amphibians
Nymph
Nymph
Razor mayfly
amphibians
Bifido
short pectoral bifin
amphibians
Coriolis Diptera
Loriolia
kangaroo
Myronella
Striped Shrimp
Perch
similar amphibians
round belly crab
amphibians
Amphibians
plaster
Gypsum plaster
Bumblebee
oval pomegranate
heather
heather
anorexia
big mac
scarab
Anorexia sternum
Anachi Pie
Argentine swallowtail butterfly
Austrian swallowtail butterfly
Folliculitis
Antarctica
Ananchytes
tuberculosis grouper
Anapas
White-spined black-lined ape
long tailed ape
half colobus monkey
Anast
jellyfish
midge midge
Manasia jellyfish
insecticide
Pomegranate
Pomegranate
Octopus
animal world
Anise
Cumin
Heteroderidae
fennel
wasabi
fennel
goldenrod fennel
Cao Ben Fennel
star anise
oval fennel
star anise
Annocanus
Flammulina velutipes
Chimera
Clematis
jack
kiwi fruit
kiwi fruit
Clematis
kiwi fruit
Clematis
Clematis
Japanese clematis
Acanthus tenatum
Coral Branch
Ceratum
Arabidopsis
spiny stickleback
Singularity stickleback
yellow croaker
Texas longfoot
Xanthos
Anorthoscutum oregonense
Anorthoscutum oregonense quaylei
Bedbugs
Zanthoxylum
roses
Zanthoxylum
Sichuan peppercorn
thick prickly prickly ash
Sichuan peppercorn
Sichuan peppercorn
Violet Orchid
Antidote
day lily
seaweed
Antilaster bagmanovi
seaweed
short clam clam
day lily
Fusarium wilt
day lily
seaweed
Cancer
Antillaster Guvalais
sea anemone
Antillaster jaumei
seaweed
seaweed
Cordyceps
Formicidae
bloating
short pectoralis
kangaroo
Pelvic fish
prawns
antique
Cooperus
honeysuckle
antique fish
Ants
Wildebeest
Kangaroo Ant
back stink ant
Ant
Ant
tilapia
Micaridae
Arabidopsis
Highland sea cucumber
Arabidopsis
Arabidopsis thaliana
Arabidopsis
Arabidopsis
Arabidopsis
Cryptococcus
silver clematis
Cryptosporidium
Aphanopora echinobrissoides
Afilast
Rosewood
bamboo shoots
Aplodia dema
Apollo Rampas
prawns
steak
Antarctic bacteria
Ethania Steak
Arabidopsis fragilis
Suspected Arabidopsis
Mies Steak
Dianthus
purple flower tree
purple flower lotus
beetle
caledonian turtle
Arachnida
Ventral spider
Arachnoid
placental arachnoid
fine arachnoid
Zeeland Arachnida
New Zealand Arachnida
Spiders
Arachnida
ara olampas
atlantic coral
Red Coral
cyanobacteria
Red Coral
long handle guppy
air bag body
Aerocystis alternata
snout guppies
bread nematode
Bailey's
Didentate
Rhizoctonia brunii
Coral
leather geranium
leather geranium
Indian Brown Coral
Araeosoma coriaceum var. mark
brown algae
Fenestella
Pitella elongatum
Celiac fluke
Nematodes
Canny bodies
hawk moth
Trichoma morsoni
Aircystis austeni
Stomata austeni
A. bicolor
Naked air cysts
Stomata austeni
Araeosoma owstoni var. nude
Aircystoma clawus
less thorn geranium
Stomata hyaline
fire green algae
Achnatherum splendens
third air cyst
Checkered Geranium
Checkered Geranium
checkerboard nematode
Araeosoma tessellatum var. chicken feet
Air cysts
violets
Palm Branch
purslane
gum arabic
Gum Arabic (Echinocidaris)
Arbacia (Echinocidaris) substantia nigra
Honeysuckle (Echinocidaris) spatuligera
Arabian Raspberry (Tetrapygus)
Arbacia (Tetrapygus) substantia nigra
gum arabic
gum arabic
locust
Acacia
locust
locust
gum arabic
gum arabic
locust
Cut edge gum arabic
locust
African acacia
locust
black raspberry
locust
pustular raspberry
locust
gum arabic
honeysuckle
star gum arabic
gum arabic
Fungus
Nematodes
Arabidopsis
Arabidopsis
Arbaciidae incertae sedis bipatellis
Vertiform Arabidopsis
Globular Arabidopsis
Araucaria
white umbrella
Solanum nigrum
Burdock
Hu Gaizi
A. thaliana
umbrella hemp
Palm tree
Palm tree
Variation Masson Pine
Arabidopsis
Albia
Australopithecus
Archaea
Archaea
Oradouarcha
Paleocarididae
archaeal
Crawfish
Archaecidaris apheles
Pasteurella
Archaecidaris brownwoodensis
Coriella
Archaecidaris diadematoides
Australopithecus
ancient coral
Crawfish
Harvey's paleocoral
Crawfish semi spinosa
Crawfish
Manhattan mite
Archaea
Halal Australopithecus
Crawfish
Archaea
Archaea
Beech mite
Crawfish
Three Skewers of Crawfish
Archaea whitii
paleontology
paleontology
Hemingo
ancient nose fish
Gushi Cancer
ancient shrimp
Archaeopteryx
Archaeopteryx
Achia
old hungary tree
Violet laver
big ginkgo
Turtle Branch
Katydid
thorny butterfly
spiny butterfly
Nymph
glass nymph
pansies
Arnodast
Colombian lobster
South Sea Perilla
Aspera
Murray snake
head of snake
thorn snake
Tasmanian snake
Anthoptera
Arachnoid cyst
Aspidodiadema (Plesiodiadema)
Aspidodiadema (Plesiodiadema) microtuberculatum
Phyllocystis africana
annular leaf sheath
Spleenoptera
Ascocystis
Hawaiian spider mite
middle leaf sheath
Jacobus sp.
Tetranychus mejerei
spider web
Aspidodiadema meijerei var. Cairns
Sporangia
Black leaf sporozoa
Nicotine sporozoa
Nicotiana niba
Aspidodiadema nicobaricum var. Majore
spider web
tonsil cyst
Arachnid
Tetranychida
Seaweed
seaweed
Conch family
Starfish
Echinacea
star daisy
Granular star chrysanthemum
starfish algae
seaweed sauce
star chrysanthemum
asteroid
star chrysanthemum
Cockroach
starfish
star algae
Xingkou
Astragalus
Irregular Star Stomach
star chrysanthemum
Astragalus
Ringworm
Astrostomidae
interstellar animal
Soft tumor
Bailey Weak Fish
Bicolor
cortical molluscs
cortical molluscs
Bloat
nematode slender
grub weak nematode
Heterosexual Weakness
Firm body fluke
Ijimai Weak Fish
intermediate weak
weak fish
Glycyrrhizae elegans
Aspera austeni
Transparent weak body
Peripheral fine body
Software burning green
Raynaud's weak nematode
Renault Weak Bug
Soft nematode striatum
nematodes
nematodes
Weak bug
weak fish
Weak bug
Weak bug
weakened body tumor
Pelargonium
star coral
star coral
geranium
Cockroach
star coral
mango
Red Coral
Manny Star
Miaoli Star Coral
star coral
Alien star thorn
Yehliu Stars
star bamboo
High starry sky wood
ancient star wood
Astrodapsis altus var. antique
Star Roland
star bamboo
arnold star roland
Venus
Xingluotimu
black star wood
Beer Dragon
Bitter star wood
beer star algae
Little Star Wood
Astrodapsis brewerianus var. bitter vegetable
Astrodapsis brewerianus var. Emergency situations
Astrodapsis brewerianus var. primary
geranium
star wood
star wood
knife and fork star lotus
geranium
Desai Starry Wood
star bamboo
Superior Star Chrysanthemum
Astrodapsis diabloensis var. Predominant
star wood
British Star Bamboo
star wood
star wood
star wood
Fragile Starwood
Astrodapsis gregerseni var. fragile
Astrodapsis gregerseni var. variable
Variant of Star Roland
star wood
star wood
soybean star
Israel Star Bamboo
John's Star Bamboo
J&J Star Simile
star bamboo
Big Star Bamboo
Big Futaba Star Bamboo
Astrodapsis main variant. parents
Japanese star bamboo
Oval Star Bamboo
star wood
sumac
reed
Salt Starry Wood
geranium
Miranda Star Wood
Astrodapsis schencki var. Miranda
star wood
geranium
Astrodapsis schucherti var. affinity
star wood
Star Arowana
Yili Xinglong
star light
Beetle
squid
starfish
geranium
betta fish
Beetle
geranium
Japanese starfish
Big beetle
Big beetle
geranium
starfish
starfish
Astropyga pulvinata var. Venusta
radiant starfish
Thorny starfish
starfish
starfish
Nebula Dragon
Triceratops
Atatus
Grouper
Atelospatangus (half petal)
Atelospatangus (Semipetalion) anomon
giant turtle
Inarticulate order
Atlas star
Atlasaster Janetty
blue star
Turtle Branch
Grouper
yew
water chestnut
midge
Archaea
goldfish
gray seaweed
Auloclypeus
Toothless
Aureliaste
South Potato
Australian animal kingdom
Alexander australis
Australian prickly pear
Antarctic Dragon
Austrocidaris canaliculata var. Lori Ollie
Giant Arabidopsis
Nautilus
Australian spiny dragon
Arabidopsis
Antarctic Dragon
Erythrina australis
Australian Juniper
Seymour Antarctica
prickly pear
unicorn
Arabidopsis
Bahariya
Bahariya teetotumensis
lobster
Bakery Lobster
dragon head
lobster
shuttle lobster
Japanese Lobster
lobster
lobster
lobster
ticks
Golden thread lice
Banumia
red dates
Baronicinus
Pasteur Lobster
bass
sea bass
bathroom
seaweed
Bathyovulaster disjunctus
Batisania
Zinnia
Passion Herb
Batisana
anchovies
Pasteur grass
Grouper
geranium
monochrome patissania
baldone biggs
Paulia
angelica
Bouillonella
beceri sedaris
Ancaron
Biarritzella
double catapult stone
Bichordites monastiriensis
Bravester
Ecstasy
Argentine sleepers
pectoralis major
boletus
boletus
boletus
boletus
boletus
boletus
boletus
boletus
spotted boletus
boletus
boletus
boletus
Irradiated boletus
boletus
boletus
Bonaire Easter
Bonaireaster rutteni
Hedgehog
Nitraria
Trypanosoma
Spiny-tailed catfish
burr hedgehog
tiny lice
catfish
fire dragon
Superorder Stinger
Bosch
Nymph
Pleural effusion
arabica beans
Bessie pectoral fin fish
druma catfish
Beef Brisket Shrimp
Bothryopneustes swell
Kaufmann's chest mouse
Botrytis
Botox
jesus grape fly
Botrytis lamblia
broadleaf grass
Botrytis michaelii
New Botrytis
Botrytis ovale
poppy
goldfish
Botriopygus pappi kutassyi
petal grapes
flat petals
honeysuckle
lentils
Botrytis Sumatra
Botrytis Sumatra
Botrytis
Botrytis
Botulinum
Bobtail
short breast fish
Shortbreast Shrimp
brahmos
Brangoma
bellflower
Braunichnus
Breycia
Bacillus albus
Bregna
Brenia, Australia
Brenia, Australasia
Breynia australasiae var. arosis
Birch
Seashells
white flower crabapple
White Begonia
day lily
crabapple
crabapple
Breynia elegans
Chinese cabbage
cauliflower
Monstera
Bregna
Brenner
Brighton
white flower tree
Brisaster
Brisaster (Schizaster)
Brisaster (Schizaster) fragile
Antarctic Bristol

See all 289 animals that start with S

They primarily eat surrounding vegetation, including kelp, algae, and phytoplankton, which consist of microscopic plant matter. Sea urchins also eat zooplankton, which is made up of tiny animal life, as well as small non-mobile animals they can easily catch, such as sea sponges and periwinkles.

Sea urchins are small marine animals in the phylum Echinodermata that are spherical in shape and covered with spines or cilia. There are 950 species of sea urchins. Some are irregular, meaning they have a different appearance or anatomy than most species.

Sea urchins live in oceans around the world. They live on the seafloor from zero depth to the deepest trenches.

Of the 950 species of sea urchins, several are poisonous. Some have venom in their spines, while others have venom in their tubular feet. Sea urchins in tropical environments are more likely to be poisonous. When you step on a venomous sea urchin and the venom enters the piercing of the skin, you immediately feel the burning sensation. This can go on for hours. Other symptoms that may be caused by sea urchin stings include nausea, vomiting, difficulty breathing, and muscle weakness. However, the venom of even the most venomous species, the flower sea urchin, is rarely fatal.

Sea urchins belong to the animal kingdom.

Sea urchins belong to the phylum Echinodermata.

Sea urchins belong to the class Echinacea.

Sea urchins belong to the order Echinacea.

The sea urchin was covered in a plate.

Predators of sea urchins include fish, birds, crabs, and sea otters.

Sea urchins typically lay 2,000,000 eggs.

The scientific name of the sea urchin is Echinoidea.

Sea urchins can live between 15 and 200 years.

The optimum pH for sea urchins is between 6.0 and 9.0.

Sea urchins lay eggs.