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