Sea Urchins

Arbacia Sea Urchin

Arbacia stellata is a sea urchin recorded from the eastern Pacific.

Crown Sea Urchin

Astropyga pulvinata is an urchin with long spines and distinctive bright blue spots on parts of its body.

Mexican Long-spined Sea Urchin

Diadema mexicanum is an eastern Pacific urchin associated with rocky lower shores and underwater rocky habitat.

Pacific Flower Sea Urchin

Toxopneustes roseus is an eastern Pacific urchin called the flower sea urchin.

Pacific White Sea Urchin

Tripneustes depressus is an eastern Pacific sea urchin also known as the white sea urchin.

Pencil Sea Urchin

Eucidaris thouarsii is an eastern Pacific pencil urchin.

Nature Field Guide

Arbacia Sea Urchin

Spanish name: Erizo Arbacia
Scientific name: Arbacia stellata

What Do Pico & Tati Think?

Pico sees a spiny shape. Tati asks how many different kinds of urchin might share a coast.

Identification

Key Features of the Arbacia Sea Urchin

A rounded body covered with spines
Observe the proportions of the body and spines
Use a species reference to compare similar urchins

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.

Nature Field Guide

Crown Sea Urchin

Spanish name: Erizo corona
Scientific name: Astropyga pulvinata

Coastal Life · Marine Life · Sea Urchins Coastal Seafloor · Marine Reef

What Do Pico & Tati Think?

One spiny animal is interesting. A gathering of them raises even more questions. Pico and Tati watch without moving closer.

Identification

Key Features of the Crown Sea Urchin

Long slender spines
Small bright blue body spots may be visible
Observe without approaching the spines

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.

Nature Field Guide

Mexican Long-spined Sea Urchin

Spanish name: Erizo de espinas largas
Scientific name: Diadema mexicanum

Coastal Life · Marine Life · Sea Urchins Marine Reef · Rocky Shore

What Do Pico & Tati Think?

Long spines make a striking silhouette. Pico draws the shape from a distance while Tati notices the shelter around it.

Identification

Key Features of the Mexican Long-spined Sea Urchin

Long thin spines extending beyond the body
A shelter or opening among rocks may be nearby
A silhouette is a clue, not a complete species identification

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.

Nature Field Guide

Pacific Flower Sea Urchin

Spanish name: Erizo de flor del Pacífico
Scientific name: Toxopneustes roseus

Coastal Life · Marine Life · Sea Urchins Marine Reef

What Do Pico & Tati Think?

A name can sound delicate even when an animal needs plenty of space. Pico and Tati admire this urchin without touching it.

Identification

Key Features of the Pacific Flower Sea Urchin

A rounded urchin body
Flower-like surface structures may be visible in a verified photograph
Observe the complete animal without contact

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.

Nature Field Guide

Pacific White Sea Urchin

Spanish name: Erizo blanco del Pacífico
Scientific name: Tripneustes depressus

Coastal Life · Marine Life · Sea Urchins Marine Reef

What Do Pico & Tati Think?

Pico notices a rounded shape on the seabed. Tati wants to compare its small details with other urchins.

Identification

Key Features of the Pacific White Sea Urchin

A rounded body
Relatively short spines
Confirm the species with a correctly labeled reference image

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.

Nature Field Guide

Pencil Sea Urchin

Spanish name: Erizo lapicero
Scientific name: Eucidaris thouarsii

Coastal Life · Marine Life · Sea Urchins Marine Reef

What Do Pico & Tati Think?

Why do some spines look more like pencils than needles? Pico and Tati compare photographs before trying to name an urchin.

Identification

Key Features of the Pencil Sea Urchin

Thick pencil-like primary spines
A compact body among the spines
Compare with Eucidaris thouarsii, not an unlabeled aquarium photograph

Habitat & range

Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.

Conservation & care

Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.