Subtidal area only
Both intertidal area and subtidal areas
Intertidal area only
On the beach
Strongylocentrotus
Purpuratus
Echinoderms
Animalia
Dome
Pentamerous
Toothpick
Porcupine
Mouth
Spine
Nose
Feet
Algae
Sea cucumbers
Small fish
Other sea urchins
Because sea urchins have large numbers of eggs
Because the eggs make great omlettes
Because sea urchins have large numbers of relatively big eggs
Because a sea urchin's egg is relatively big