Definition

Noun: A sea urchin is a small, round marine animal that lives on the ocean floor. It has a soft body enclosed in a hard, thin, and usually spiny spherical shell.

Usage

The word "sea urchin" is used to refer to the animal itself. It is a countable noun. - Scientists are studying the impact of warming oceans on sea urchin populations. - Be careful when walking on the rocks; you might step on a sea urchin.

Examples

• The diver carefully avoided the cluster of sea urchins clinging to the reef.
• In some cuisines, sea urchin roe is considered a delicacy.
• The aquarium has a tank dedicated to local species like starfish and sea urchins.

Advanced Usage

• Ecological Role: Sea urchins are often discussed in marine biology for their role as grazers, which can significantly affect kelp forest ecosystems.
  • An overpopulation of sea urchins can lead to the creation of "urchin barrens," areas devoid of kelp.

Variants and Related Words

• Urchin: In a historical or literary context, "urchin" alone could sometimes refer to a sea urchin, though it more commonly means a mischievous child. In modern biological contexts, "urchin" is typically understood as shorthand for "sea urchin."
• Echinoderm: This is the broader biological class (Echinodermata) to which sea urchins belong, along with starfish and sea cucumbers.

Synonyms

• Marine invertebrate: A general term for animals without backbones that live in the sea.
• Echinoid: The scientific term for a member of the class Echinoidea, which includes sea urchins.

Related Phrases/Idioms

There are no common idioms or phrasal verbs specifically using "sea urchin." The term is used literally in biological, culinary, and ecological contexts.

Noun

1. shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells