Sea urchins are marine animals belonging to the phylum Echinodermata.

They have a round, spiny exoskeleton called a test, which encases their body.

Sea urchins are found in oceans worldwide, from shallow coastal waters to deep-sea environments.

The spines on sea urchins serve various purposes, including protection and movement.

Sea urchins have a water vascular system that helps in locomotion, feeding, and respiration.

They are radially symmetrical, with a five-fold symmetry, similar to other echinoderms.

Sea urchins are primarily herbivores, feeding on algae and other plant material.

Certain species of sea urchins, like the purple sea urchin, are used in ecological research.

Sea urchins are important grazers, controlling algal populations on coral reefs and rocky shores.

They have tube feet with suckers that aid in locomotion and capturing food.

Sea urchins can regenerate lost spines and even parts of their test.

Some sea urchins, like the flower urchin, have brightly colored spines for camouflage.

They are preyed upon by various marine animals, including sea otters, crabs, and certain fish.

Sea urchins play a role in nutrient cycling by recycling organic matter in marine ecosystems.

The mouth of sea urchins is located on the underside, surrounded by a structure called Aristotle's lantern.

Sea urchins are sensitive to changes in water temperature and quality.

Certain species of sea urchins are commercially harvested for their roe, a delicacy in some cuisines.

The roe of sea urchins is known as uni and is often used in sushi and seafood dishes.

Sea urchins have a unique feeding mechanism, using their specialized mouthparts to scrape algae from surfaces.

They are capable of both slow crawling and rapid movement using their tube feet.

Sea urchin embryos undergo a free-swimming larval stage before settling on the ocean floor.

The spines of sea urchins are covered in a thin epidermis and may contain venomous glands for defense.

Sea urchins have photoreceptor cells on their skin, allowing them to sense light and shadows.

They are important in maintaining the balance of kelp forest ecosystems by controlling algal growth.

Sea urchins have been used in developmental biology studies due to the transparency of their embryos.

Certain species of sea urchins, such as the collector urchin, use their spines to hold small objects and debris for camouflage.

Sea urchins are resilient to harsh environmental conditions and can tolerate fluctuations in salinity.

They are a diverse group, with about 950 recognized species of sea urchins.

Sea urchins have a well-developed sense of touch, helping them navigate and explore their surroundings.

Certain species of sea urchins, like the slate-pencil urchin, have thick, blunt spines for protection.

Sea urchins have been featured in various scientific studies exploring topics such as regeneration and immune response.

They are commonly found in intertidal zones, tide pools, and coral reefs.

Sea urchins are echinoderms, belonging to the same phylum as sea stars and sea cucumbers.

Efforts in marine conservation aim to protect sea urchin populations and their habitats.

Sea urchins are considered a delicacy in Mediterranean and Asian cuisines.

They have been used in traditional medicine in some cultures for their supposed health benefits.

Sea urchins are resilient to predation by some species of fish due to their protective spines.