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The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian. Echinoderms are important both ecologically and geologically.
Tripneustes gratilla, the collector urchin or halloween urchin [1], is a species of sea urchin. Collector urchins are found at depths of 2 to 30 metres (7 to 100 ft) in the waters of the Indo-Pacific, Hawaii, the Red Sea, and The Bahamas. They can reach 10 to 15 centimetres (4 to 6 in) in size.
Sea urchins or urchins (/ ˈ ɜːr tʃ ɪ n z /) are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres (16,000 ft; 2,700 fathoms). [1]
Eleutherozoa is a subphylum of echinoderms. They are mobile animals with the mouth directed towards the substrate. They usually have a madreporite, tube feet, and moveable spines of some sort. It includes all living echinoderms except for crinoids. The monophyly of Eleutherozoa has been proven sufficiently well to be considered "uncontroversial ...
A brittle star, Ophionereis reticulata A sea cucumber from Malaysia Starfish exhibit a wide range of colours. This List of echinoderm orders concerns the various classes and orders into which taxonomists categorize the roughly 7000 extant species [1] as well as the extinct species of the exclusively marine phylum Echinodermata.
This echinoderm belongs to the family Echinometridae and it can reach a maximum diameter of 16–17 cm. [1] Kina populations throughout New Zealand have dramatically grown due to the effects of overfishing and climate change , resulting in over-grazing that significantly damages kelp forest ecosystems.
Their size is variable, averaging 76 mm with the world's largest found measuring 120 mm wide. [2] They have a dome shaped carapace varying in height to about 10 mm with a circular body or test. Their body is covered with fine, spiny tube-like feet with cilia, and like other echinoderms they have five-fold radial symmetry.
Brittle stars do not have a brain or eyes, but they do have a stomach, sex organs, and a mouth with five jaws. They have five long, thin, spiny arms made of calcium carbonate plates [ 2 ] connected by a central disc; the size of their disk ranges from 6-12mm disc diameter (d.d.), and their arms range from sizes greater than 4 times d.d. in length.