Sea urchins
Sea Urchins
Sea urchins (/siː ˈɜːrʃɪnz/), scientifically known as Echinoidea, are a class of marine animals that belong to the phylum Echinodermata. The term "sea urchin" is derived from the Old English 'yrihcin', meaning 'hedgehog', due to their spiny exterior.
Description
Sea urchins are characterized by their round, spiny bodies. They are typically small, ranging from 3 to 10 cm in diameter, but some species can grow up to 36 cm. Their bodies are covered in long, movable spines that serve as a defense mechanism against predators.
Anatomy
The body of a sea urchin, known as the test, is globular in shape and is covered with spines. The test is divided into five equal parts, each of which has two rows of tubercles to which the spines are attached. The mouth of the sea urchin, known as the Aristotle's lantern, is located on the underside of the body.
Habitat and Distribution
Sea urchins are found in oceans all over the world, from the tropics to the polar regions. They inhabit a variety of marine environments, including rocky shores, seagrass beds, and coral reefs.
Diet
Sea urchins are primarily herbivores, feeding on algae and seaweed. Some species are also known to eat invertebrates.
Reproduction
Sea urchins reproduce through a process known as broadcast spawning, where both males and females release their gametes into the water column.
Related Terms
- Echinodermata: The phylum to which sea urchins belong.
- Test: The hard shell of a sea urchin.
- Aristotle's lantern: The mouth of a sea urchin.
- Broadcast spawning: A method of reproduction used by sea urchins.
External links
- Medical encyclopedia article on Sea urchins
- Wikipedia's article - Sea urchins
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