Echinoderm
(Sea Urchins)
Vocabulary
Sea Urchin: Sea urchins are small marine invertebrates of the Echinodermata category of animals. They
are distinguished by having a globular body covered in multiple spines. There are approximately 700 different species of sea urchin which have adapted to many different environments, meaning that sea urchins are present in all of the world's oceans.
Purple sea urchin: The purple sea urchin, Strongylocentrotus purpuratus, lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico to British Columbia, Canada.
Heart urchins: Heart-shaped bodies. These creatures spend their lives burrowing under the sea floor and feed by filtering food particles out of the sand.
Pencil urchins: Have very thick, blunt spines shaped like pencils.
Rock-boring urchins: bore holes into rocks and live inside them. Some can burrow straight into steel walls.
are distinguished by having a globular body covered in multiple spines. There are approximately 700 different species of sea urchin which have adapted to many different environments, meaning that sea urchins are present in all of the world's oceans.
Purple sea urchin: The purple sea urchin, Strongylocentrotus purpuratus, lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico to British Columbia, Canada.
Heart urchins: Heart-shaped bodies. These creatures spend their lives burrowing under the sea floor and feed by filtering food particles out of the sand.
Pencil urchins: Have very thick, blunt spines shaped like pencils.
Rock-boring urchins: bore holes into rocks and live inside them. Some can burrow straight into steel walls.
Classification
Sea urchins are members of the phylum Echinodermata, which also includes sea stars, sea cucumbers, brittle stars, and crinoids. Like other echinoderms, they have fivefold symmetry (called pentamerism) and move by means of hundreds of tiny, transparent, adhesive "tube feet". The symmetry is not obvious in the living animal, but is easily visible in the dried test. Echinodermate means "spiny skin" in Greek.
Specifically, the term "sea urchin" refers to the "regular echinoids", which are symmetrical and globular. The term includes several different taxonomic groups: the order Echinoida, the order Cidaroida or "slate-pencil urchins", which have very thick, blunt spines, and others. Besides sea urchins, the class Echinoidea also includes three groups of "irregular" echinoids: flattened sand dollars, sea biscuits, and heart urchins.
Specifically, the term "sea urchin" refers to the "regular echinoids", which are symmetrical and globular. The term includes several different taxonomic groups: the order Echinoida, the order Cidaroida or "slate-pencil urchins", which have very thick, blunt spines, and others. Besides sea urchins, the class Echinoidea also includes three groups of "irregular" echinoids: flattened sand dollars, sea biscuits, and heart urchins.
Morphology
Gonads: The reproductive organs of the sea urchin. Like most other animals, sea urchins have a definite male and female of the species. Most urchins reproduce through spawning, with the males expelling sperm and female expelling eggs into the water.
Nerve Ring: Sea urchins so called 'brain'. They have a nerve ring near the hydraulic system that powers the tube feet.
Spines & Pericardia: The spines are the urchin's primary mode of defense against hungry predators. The spines are used by some species to burrow into rock by slowly scraping away an enclosure to further protect themselves. The spines are controlled by two rings of muscles and are covered with a layer of epithelium At the base of the sea urchin's spines are the pericardia which are small pinching appendages.
Water Vascular System: The system responsible for circulation, as well as the motor movement in echinoderms by pressuring the tube feet.
Digestive System: Along with the five gonads, the digestive tract takes up most of the internal space of the sea urchin. Urchins are most known for eating kelp, but will eat sponges and other invertebrates as well. Waste is expelled through the anus located at the top of the body.
Aristotle's Lantern: The mouth parts of the sea urchin. This consist of five bony plates used to scrape at the hold-fast of kelp and their other food sources.
Tube Feet: The tube feet are the primary means of locomotion for the sea urchin. Lateral movement is accomplished by means of paired muscles in the tube foot itself and extension and retraction by muscles in the hydraulic 'bulb' behind each tube foot. While each 'foot' may seems weak and ineffective, the large numbers of feet make up for their size.
Nerve Ring: Sea urchins so called 'brain'. They have a nerve ring near the hydraulic system that powers the tube feet.
Spines & Pericardia: The spines are the urchin's primary mode of defense against hungry predators. The spines are used by some species to burrow into rock by slowly scraping away an enclosure to further protect themselves. The spines are controlled by two rings of muscles and are covered with a layer of epithelium At the base of the sea urchin's spines are the pericardia which are small pinching appendages.
Water Vascular System: The system responsible for circulation, as well as the motor movement in echinoderms by pressuring the tube feet.
Digestive System: Along with the five gonads, the digestive tract takes up most of the internal space of the sea urchin. Urchins are most known for eating kelp, but will eat sponges and other invertebrates as well. Waste is expelled through the anus located at the top of the body.
Aristotle's Lantern: The mouth parts of the sea urchin. This consist of five bony plates used to scrape at the hold-fast of kelp and their other food sources.
Tube Feet: The tube feet are the primary means of locomotion for the sea urchin. Lateral movement is accomplished by means of paired muscles in the tube foot itself and extension and retraction by muscles in the hydraulic 'bulb' behind each tube foot. While each 'foot' may seems weak and ineffective, the large numbers of feet make up for their size.
Biology
To survive in the ocean, sea urchins always scurry away on their tube-like feet and hide in cracks and crevices.
Sea urchins live only in the ocean and cannot survive in fresh water.
Sea urchins live only in the ocean and cannot survive in fresh water.
Distribution Map
Importance
(Ecological, Economical)
Sea urchins are major components of marine communities. Their grazing limits algal biomass, and they are preyed upon by many predators. Purple sea urchins (Strongylocentrotus purpuratus) are among the best studied species. They live in environments that alternate between two stable states: luxuriant, species-rich kelp forests and sea urchin–dominated “barrens.” The transition from one state to the other can be initiated by several factors, including the abundance of algal food, predators, storm intensities, and incidence of disease. Purple sea urchins compete with other grazers, some of which are important fishery resources (such as abalones and red sea urchins), and they are harvested for scientific research. Revelations from their genome will lead to a better understanding of how they maintain their ecological importance, and may in turn enhance their economic potential.
Interesting facts on Sea urchins
-A sea urchin is a marine animal which belongs to the Echinodermata phylum, Echinoidea class and order Echinoida.
-Other family members include the sea cucumber, sea star and sand dollar.
-They are found all over the world.
-There are more than 200 varieties of sea urchins.
-They live in the deep parts of the ocean but are also found in the shallow parts.
-They prefer to live in coral reefs and areas that are more prone to tidal waves.